bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence for Neurotensin Autoreceptors and Relationship of Neurotensin and its Receptors with Tyrosine Hydroxylase‐positive Neurons in Rat Primary Hypothalamic CuItures
Authors: Bachelet Claude‐Marie , Scarcériaux Valerie , Rostène William , Pélaprat Didier
Published: April 2006

Neurotensin is present in high quantity in the hypothalamus, where it regulates pituitary hormone secretion. A relationship between dopaminergic and neurotensinergic systems has been suggested in the hypothalamus in studies showing an effect of neurotensin on tuberoinfundibular dopaminergic neurons. In order to determine the anatomical basis of such interactions, primary cultures of rat hypothalamic neurons were used. Tyrosine hydroxylase and neurotensin containing cells were identified by immunocytochemistry and neurotensin binding sites by [125I]Tyr3‐neurotensin autoradiography. Colocalization studies showed that neurotensin immunoreactivity was present in 16% of tyrosine hydroxylase‐positive cells, and that these neurotensinhyrosine hydroxylase neurons represented more than half (58%) of the neurotensinergic population. Five percent of the tyrosine hydroxylase‐positive cells had neurotensin binding sites, suggesting that only a restricted number of hypothalamic dopaminergic neurons is responsive to neurotensin. Neurotensin binding sites were also found on some neurotensin‐positive cells, demonstrating for the first time the presence of autoreceptors for this peptide on neurons. These results in primary cultures provide a cellular basis for direct effects of neurotensin on a subpopulation of hypothalamic dopaminergic cells, and support the possibility of an autocrine action of neurotensin in the hypothalamus.
Peroxynitrite and Nitric Oxide Donors Induce Neuronal Apoptosis by Eliciting Autocrine Excitotoxicity
Authors: Leist Marcel , Fava Eugenio , Montecucco Cesare , Nicotera Pierluigi
Published: April 2006

Endogenous generation of nitric oxide and its congeners, including peroxynitrite (ONOO‐), has been implicated in the mechanism of neuron loss in neurodegenerative diseases. Accordingly, nitric oxide donors and ONOO‐can elicit both apoptosis and necrosis in neuron cultures. Here we show that nitric oxide donors and ONOO‐ are each able to trigger apoptosis of mouse cerebellar granule cells by an excitotoxic mechanism requiring exocytosis and NMDA receptor‐mediated intracellular Ca2+ overload. This conclusion is supported by the following findings. Apoptosis was induced by various nitric oxide donors or by direct addition of ONOO‐ to differentiated cerebellar granule cell cultures that were sensitive to NMDA toxicity, but not in cerebellar granule cells that did not display NMDA‐induced cell death (i.e. early days in culture) or in various glial cell populations. Donors of ONOO‐ or nitric oxide stimulated a sustained increase in intracellular Ca2+, which was prevented by inhibitors of NMDA receptors, such as MK‐801 and 5‐phospho‐aminovaleric acid, or by dampening neuronal electrical activity with high concentrations of extracellular Mg2+. Moreover, these treatments and the exposure of cerebellar granule cells in nominally Ca2+‐free media prevented apoptotic cell death. Both the intracellular Ca2+ increase and apoptosis elicited by ONOO‐ or the nitric oxide donors were prevented by blocking exocytosis with tetanus toxin or botulinum neurotoxin C.
Neurons in the Rat Occipital Cortex Co‐expressing the Substance P‐Receptor and GABA: a Comparison Between In Vivo and Organotypic Cultures
Authors: Echevarría D. , Matute C. , Albus K.
Published: April 2006

The morphology and the distribution of neurons expressing the NK1‐receptor (NK1R) and the co‐expression of γ‐aminobutyric acid (GABA) in these neurons were studied in the rat occipital cortex and in organotypic cultures (OTCs) derived from this structure. By employing immunohistochemistry, we demonstrate that the NK1R‐expressing neurons are non‐pyramidal neurons and co‐express GABA. Some differences were noted between in vivo and OTCs. NK1 R‐expressing neurons in OTCs had larger somata and longer dendrites and the proportion stained with an anti‐GABA‐antibody (∼50%) was smaller than in vivo (90%). The preferential location of NK1 R‐expressing neurons in layers II/III and VI, seen in vivo is not present in OTCs where these neurons distribute rather homogeneously through layers Il‐VI. Our findings imply that in contrast to the cat and monkey, in the rat occipital cortex the effects of substance P are almost exclusively mediated via inhibitory interneurons.
Hypothyroidism Alters the Expression of Prostaglandin D2 Synthase/β‐ Trace in Specific Areas of the Developing Rat Brain
Authors: García‐Femández Luis F. , Rausell Estrella , Urade Yoshihiro , Hayaishi Osamu , Bernal Juan , Muñoz Alberto
Published: April 2006

Lipocalin‐type prostaglandin D2 synthase is the enzyme responsible for the synthesis of prostaglandin D2, a major prostaglandin in the central nervous system. We analysed the effects of thyroid hormone deprivation on prostaglandin D2 synthase gene expression in the developing rat brain. By in situ hybridization, the strongest prostaglandin D2 synthase mRNA signal was detected in the leptomeninges and choroid plexus. The signal was greatly reduced in the cerebellar interlaminar meninges of hypothyroid rats aged 15 and 25 days. lmmunohistochemical studies defined changes in the location of the prostaglandin D2 synthase protein. In control but not in hypothyroid animals, Cajal‐Retzius neurons of cortical layer 1, and pyramidal cortical plate neurons were intensely stained on postnatal day 5. Conversely, prostaglandin D2 synthase protein levels were higher in neurons of the CA1 and CA3 regions and the dentate gyrus of the hippocampus of hypothyroid animals on postnatal days 5, 15 and 25, and also in subplate neurons on postnatal days 15 and 25. In agreement with the in situ hybridization and northern blotting data, the major difference was found in the cerebellar interlaminar meninges of hypothyroid animals, where the protein was clearly down‐regulated on postnatal days 15 and 25. These results show that hypothyroidism causes both age‐ and region‐specific alterations in the expression and location of the prostaglandin D2 synthase during postnatal brain development, probably reflecting a cell‐specific regulatory effect of thyroid hormone on the prostaglandin D2 synthase.
Elimination of Motor Nerve Terminals in Neonatal Mice Expressing a Gene for Slow Wallerian Degeneration (C57Bl/Wlds)
Authors: Parson Simon H. , Mackintosh Claire L. , Ribchester Richard R.
Published: April 2006

Degeneration of motor terminals after nerve section occurs much more slowly than normal in young adult mice of the C57BI/WldS strain. This observation prompted us to re‐examine the possible role of degeneration and intrinsic axon withdrawal during neonatal synapse elimination. Polyneuronal innervation was assayed by two methods: intracellular recording of end‐plate potentials in cut‐muscle fibre preparations of isolated hemidiaphragm and soleus muscles; and in silver‐stained preparations of triangularis sterni and transversus abdominis muscle fibres. No differences in the rate of synapse elimination were detected in unoperated Wlds compared with CBA, C3H/HE and BALB/c mice. At 3 days of age, >80% of fibres were polyneuronally innervated. By 7 days this declined to ∼20% of hemidiaphragm, 50% of triangularis sterni and 60% of soleus fibres. Nearly all fibres were mononeuronally innervated by 15 days. The mean number of terminals per triangularis sterni muscle fibre 7 days after birth was 1.55 ± 0.07 in Wlds and 1.56 ± 0.09 in wild‐type mice. Three to 4 days after sciatic nerve section, near‐normal numbers of motor units were evident in isometric tension recordings of the soleus muscle, and intracellular recordings revealed many polyneuronally innervated fibres. Mononeuronally and polyneuronally innervated fibres were also observed in silver‐stained preparations of soleus and transversus abdominis muscles made 3–4 days after sciatic or intercostal nerve section. We conclude (i) that the Wlds gene has no direct impact on the normal rate of postnatal synapse elimination, (ii) that Wallerian degeneration and synapse elimination must occur by distinct and different mechanisms, and (iii) that muscle fibres are able to sustain polyneuronal synaptic inputs even after motor axons have become disconnected from their cell bodies.
Learning‐induced Changes in Rat Piriform Cortex Activity Mapped Using Multisite Recording With Voltage Sensitive Dye
Authors: Litaudon Philippe , Mouly Anne‐Marie , Sullivan Regina , Gervais Remi , Cattarelli Martine
Published: April 2006

The piriform cortex (PCx) has a potential role in storage and recall of olfactory information. This study is a first extensive investigation of the spatiotemporal distribution of activity in the PCx induced by learned sensory inputs following conditioning. In a conditioned group, rats chronically implanted with four electrodes in the olfactory bulb were trained to associate the electrical stimulation of a given bulbar electrode with a positive reinforcement, while stimulation of a different electrode predicted a negative reinforcement. In a familiarized group, rats received the same protocol of daily electrical stimulation with no associated reinforcement. At the end of the conditioning or familiarization episode, activity evoked in the PCx was optically mapped using a 144 photodiode array. In the anaesthetized rats, PCx maps were recorded in response to stimulation of each of the four bulbar electrodes using either high (0.5–1 mA) or low (0.1 mA) test current intensities. Low intensity stimulation revealed that conditioning selectively enhanced the probability of occurrence of a signal composed of a single late (56–73 ms) component which occurred almost simultaneously on a large PCx area. In the conditioned group, high intensity stimulation through either of the four electrodes revealed a potentiation of the early (17–30 ms) disynaptic component of the PCx response in the most posterior part of the PCx as well as a homogeneous increase of the late (39–52 ms) component spread over the PCx areas. These data suggest that learning induces synaptic changes at different nodes of the PCx circuitry.
Short‐ and Long‐term Plasticity of the Hippocampus to Nucleus Accumbens and Prefrontal Cortex Pathways in the Rat, In Vivo
Authors: Mulder A. B. , Arts M. P. M. , da Silva F. H. Lopes
Published: April 2006

The pathways from the hippocampal formation to the nucleus accumbens and the prefrontal cortex are likely to play a role in several aspects of learning and memory. In the present study we addressed the question of how plastic changes in these structures may occur simultaneously. This question can be studied in an appropriate way in the hippocampaVfornix‐fimbria to prefrontal cortexhucleus accumbens system, since electrical stimulation of the fornix‐fimbria fibre bundle evokes characteristic field potentials in the two target areas simultaneously. First, we examined the termination field in the nucleus accumbens (medial shell and core region with an extension into the ventro‐medial caudate‐putamen) and the prefrontal cortex (deeper layers of the ventral prelimbic and ventral infralimbic areas) by recording single unit activity evoked by stimulation of fornix‐fimbria fibres in halothane anaesthetized rats. Second, we studied short‐term plasticity, namely paired pulse facilitation, in these two areas upon stimulation of the fornix‐fimbria fibres. In the nucleus accumbens, paired pulse facilitation was encountered for double pulse intervals between 25 and 500 ms, peaking around 100 ms. In the medial prefrontal cortex it was confined to intervals between 25 and 200 ms, with a peak around 75 ms. Third, we investigated whether LTP could be elicited simultaneously in the two target structures by a single tetanic stimulation (50 Hz, 2 s) of the fornix‐fimbria fibres. LTP that was sustained for more than 90 min in the medial prefrontal cortex, reached levels of 130% of control values. In the nucleus accumbens, however, only a transient form of potentiation was found which lasted no more than 60 min. These data show that synaptic weights can be changed in several target structures of the hippocampal formation, simultaneously, in a distributed way.
Sensory‐induced Plasticity of Motor Pattern Selection in the Lobster Stomatogastric Nervous System
Authors: Nargeot R. , Moulins M.
Published: April 2006

In a previous study, a bilateral sensory input pathway to the crustacean stomatogastric nervous system was reported to induce the functional switching of an identified motor neuron (VD) from one rhythm generating neural network (the pyloric circuit) to another (the cardiac sac network). In the present in vitro study on the spiny lobster, Palinurus vulgaris, we have shown that under certain conditions, repetitive trains of phasic stimulation (1 s; 40 Hz) of one of these sensory nerves elicits either an increase or a decrease in efficacy of the VD switching response. In preparations showing no previous sign either of increase or decrease in VD switching, either response can be induced by prior conditioning stimulation. The increasing effect can be induced by unpaired conditioning stimulation of the contralateral sensory nerve. Conversely, the decrease in switching efficacy is obtained by pairing stimulation of the sensory‐motor pathway with that applied to its contralateral partner. Both the experimentally induced increase and decrease in VD switching are long‐lasting, remaining observable for at least 20 min and in some cases up to 3 h after the original conditioning procedure. Our results suggest that this system provides a suitable ‘simple’ model for the analysis of experience‐related plasticity of the switching of a neuron from one network to another.
Differential Developmental Expression of the Two Rat Brain Glutamate Transporter Proteins GLAST and GLT
Authors: Ullensvang K. , Lehre K. P. , Storm‐Mathisen J. , Danbolt N. C.
Published: April 2006

The extracellular concentration of the excitatory neurotransmitter glutamate is kept low by the action of glutamate transporters in the plasma membranes of both neurons and glial cells. These transporters may play important roles, not only in the adult brain, but also in the developing brain, as glutamate is thought to modulate the formation and elimination of synapses as well as neuronal migration, proliferation and apoptosis. Here we demonstrate the developmental changes in the expression of two glutamate transporters, GLAST and GLT, by quantitative immunoblotting and by light and electron microscopic immunocytochemistry. At birth, GLT is not detectable, but GLAST is present at significant concentrations both in the forebrain and in the cerebellum. GLT is first detected in the forebrain and cerebellum in the second and third week, respectively. Both transporters reach adult levels by postnatal week 5. The development of the total glutamate uptake activity in the forebrain, as determined by solubilization and reconstitution of the transporters in liposomes, parallels that of GLT, in agreement with the observation that GLT is the predominant transporter in the adult brain. The regional distributions of both GLAST and GLT in the tissue are similar in young and adult rats. Only GLAST is detectable in the external germinal layer of the cerebellar cortex. Electron microscopical investigation demonstrated GLAST and GLT exclusively in glial cells in young as well as in adult animals.
Male Faces and Odours Evoke Differential Patterns of Neurochemical Release in the Mediobasal Hypothalamus of the Ewe During Oestrus: An Insight Into Sexual Motivation?
Authors: Fabre‐Nys Claude , Ohkura Satoshi , Kendrick Keith M.
Published: April 2006

During behavioural oestrus female sheep, like females of many species, become both attracted to and sexually receptive towards males, whereas at other times they will avoid them. The mediobasal hypothalamus is the main site for the feedback action of sex steroids to induce sexual behaviour in the sheep and in previous studies we have shown that noradrenaline and serotonin are released in this region during sexual interactions with males. The current study investigated whether such changes are specific to interactions with males and if visual or olfactory cues or somatosensory stimulation during mating are critical. In vivo microdialysis sampling was carried out in the mediobasal hypothalamus of ovariectomized ewes submitted to artificial oestrous cycles. Release of monoamines and amino acid transmitters was first measured in animals during and after oestrus when they were exposed to interactions with either males or females or presentation of food. Noradrenaline concentrations only increased significantly when the females were in oestrus and interacted with males irrespective of whether intromissions were permitted. Females were then exposed to visual (faces) or odour (a home pen) cues from males or to the males themselves. Slide images of male faces increased concentrations of amines, glutamate and GABA during early oestrus, when females spent most time looking at them. During late oestrus noradrenaline, glutamate and GABA concentrations also increased in response to the male faces but no transmitter changes were seen during the luteal phase or at any time where the females were exposed to female faces, or inverted male faces. Exposure to male odour produced a lower increase in noradrenaline concentrations when females were in early oestrus but marked increases 20 and 30 min after exposure to male odours in late oestrus. No other transmitters were affected. Exposure to a male and mating with him when females were in early or late oestrus produced increased noradrenaline concentrations similar to those seen with face stimuli alone although other neurotransmitters were unaffected. These results show that noradrenaline, and to a lesser extent dopamine, serotonin, glutamate and GABA release in the mediobasal hypothalamus, can be modulated specifically in the oestrous female by sensory information coming from the male during oestrus. The differential effects of male cues during early and late oestrus suggest their involvement in (i) proceptive or anticipatory sexual responses shown by the female to male cues, and (ii) receptive sexual responses, and suggest that the mediobasal hypothalamus plays a key role in the integration of hormonal action on sexual motivation and processing of sensory information during oestrus.
Bone Morphogenetic Proteins: Neurotrophic Roles for Midbrain Dopaminergic Neurons and Implications of Astroglial Cells
Authors: Jordan Jens , Böttner Martina , Schluesener Hermann J. , Unsicker Klaus , Krieglstein Kerstin
Published: April 2006

Bone morphogenetic proteins (BMPs) are members of the transforming growth factor β (TGF‐β) superfamily that have been implicated in tissue growth and remodelling. Recent evidence suggests that several BMPs are expressed in the developing and adult brain. Specifically, we show that BMP 2 and BMP 6 are expressed in the developing midbrain floor of the rat. We studied potential neurotrophic effects of BMPs on the in vitro survival, transmitter uptake and protection against MPP+ toxicity of mesencephalic dopaminergic neurons cultured from the embryonic midbrain floor at embryonic day (E) 14. At 10 ng/ml and under serum‐free conditions, most BMPs promoted the survival of dopaminergic neurons visualized by tyrosine hydroxylase immunocytochemistry during an 8‐day culture period, but to varying extents (relative potencies: BMP 6 = 12 > 2, 4, 7). BMPs 6 and 12 were as effective as fibroblast growth factor‐2 (FGF‐2) and glial cell line‐derived neurotrophic factor, promoting survival 1.7‐fold compared with controls. BMPs 9 and 11 were not effective. Dose‐response curves revealed an EC50 for BMPs 2, 6 and 12 of 2 ng/ml. BMPs 2, 4, 6, 7, 9 and 12 also promoted DNA synthesis and astroglial cell differentiation, visualized by 5‐bromodeoxyuridine (BrdU) incorporation and glial fibrillary acidic protein (GFAP) immunocytochemistry respectively. Suppression of cell proliferation and subsequent maturation of GFAP‐positive cells by 5‐fluorodeoxyuridine or aminoadipic acid abolished the neuron survival‐promoting effect of BMP 2. This suggests that BMPs, like other non‐TGF‐β factors affecting dopaminergic neuron survival, act indirectly, probably by stimulating the synthesis and/or release of glial‐derived trophic factors. BMP 6 and BMP 7 also increased the uptake of [3H]dopamine without affecting the uptake of [3H]5‐hydroxytryptamine and [3H]GABA, underscoring the specificity of the trophic effect. We conclude that several BMPs share a neurotrophic capacity for dopaminergic midbrain neurons with other members of the TGF‐β superfamily, but act indirectly, possibly through glial cells.
Electrophysiological Evidence for Multiple Glycinergic Inputs to Neonatal Rat Sympathetic Preganglionic Neurons In Vitro
Authors: Krupp Johannes , Bordey Angélique , Feltz Paul
Published: April 2006

The time pattern of glycinergic inhibitory postsynaptic currents (IPSCs) in sympathetic preganglionic neurons was studied in thin transverse spinal cord slices of neonatal (1–10 days postnatal) rats by means of the patch‐clamp technique. Three time patterns could be distinguished: (i) large events [mostly >400 pA (30–36°C)] occurring at regular intervals, (ii) small events occurring at irregular intervals, and (iii) small events occurring in transient (1.5–10 s), high‐frequency (>15 Hz) bursts of synaptic activity. The large regular events had uniform kinetics which was consistent with the idea of a proximal site of origin for all of these events. They were reversibly inhibited in amplitude and frequency by extracellular application of a high concentration of acetylcholine (200 μM) or the specific nicotinic acetylcholine receptor agonist dimethylphenylpiperazinium iodide (DMPP; 1 mM), but unaffected by glutamate (100 μM). IPSCs occurring in bursts had slower and less uniform kinetics, suggesting a more diverse site of origin. The frequency of events decreased during a burst. Similar bursts could be induced by extracellular application of glutamate receptor agonists. These results indicate that sympathetic preganglionic neurons in a thin, transverse spinal cord slice receive at least two different glycinergic inputs.
Involvement of Activation of Dopamineraic Neuronal System in Learning and Memory Deficits Associated with Experimental Mild Traumatic Brain Injury
Authors: Tang Ya‐Ping , Noda Yukihiro , Nabeshima Toshitaka
Published: April 2006

Much evidence has indicated that a disturbance in dopamine neurotransmission following mild to moderate traumatic brain injury is involved in the development of post traumatic memory deficits. In the present study we examined the effects of a dopamine receptor agonist and some antagonists on latent learning and memory deficits associated with a concussive traumatic brain injury in mice. Anaesthetized animals were subjected to mild traumatic brain injury by dropping a weight onto the head, and a single‐dose injection of apomorphine (0.3–3.0 mg/kg) or haloperidol (0.3–3.0 mg/kg) was made i.p. 15 min after the trauma. One week later, a water‐finding task consisting of an acquisition trial, a retention test and a retest was employed to assess learning and memory functions. Mice that had received a traumatic brain injury were impaired in task performance, with prolonged latencies for finding and drinking in the retention test and retest. Administration of haloperidol but not of apomorphine significantly shortened the prolonged latency in both of the tests, indicating that antagonism of dopamine receptors is beneficial for the recovery of post traumatic memory deficits. In order to evaluate which receptor subtype plays the major role in this model, we examined the effects of SCH‐23390 (0.03–0.3 mg/kg), a D1 receptor antagonist, and sulpiride (3.0–30 mg/kg), a D2 receptor antagonist, in the same experimental paradigm. The results showed that administration of sulpiride but not of SCH‐23390 significantly improved the deficits in task performance, indicating that D2 receptors are the major site of action. However, combined treatment with SCH‐23390 (0.03–0.3 mg/kg) and sulpiride (3.0 mg/kg) at doses that had no effect when the antagonists were given alone exerted a significant additive effect in improving these deficits, indicating that interaction between D1 and D2 receptors is involved in these processes. The present results suggest that a dopaminergic mechanism contributes to the memory dysfunction associated with traumatic brain injury.
A Thalamic Contribution to Arousal‐induced, Non‐photic Entrainment of the Circadian Clock of the Syrian Hamster
Authors: Maywood Elizabeth S. , Smith Emma , Hall Stephanie J. , Hastings Michael H.
Published: April 2006

It is well established that the circadian clock of the suprachiasmatic nuclei (SCN) is entrained by light. More recently, the potent effects of arousing, non‐photic cues on the clock have been recognized. The neural mediators of non‐photic entrainment are yet to be identified. To examine the contribution of the thalamic intergeniculate leaflet (IGL) and its NPY‐immunopositive projection, the geniculo‐hypothalamic tract to non‐photic entrainment by arousal, male Syrian hamsters received lesions of the IGL (IGLX) which ablated NPY‐immunoreactivity in the SCN. Their circadian responses to both photic and non‐photic cues were then tested. Lesions resulted in a delay in the timing of activity onset following lights out, but had no effect on the behavioural or cellular circadian responses to phase‐advancing light pulses presented at circadian time (CT) CT19 (where CT12 represents the time of activity onset). Injection with a benzodiazepine (chlordiazepoxide, 100 mg/kg) at CT6 suppressed wheel‐running, increased general locomotion of intact controls and induced large phase advances of the circadian rhythm of wheel‐running. Chlordiazepoxide also inhibited wheel‐running in lesioned animals, but there was no significant increase in general locomotion and the lesioned animals did not phase advance. Serial arousal by injection of saline at intervals of 23.5 h for 6 days entrained the circadian rhythm of wheel‐running of intact hamsters and was associated with an increase in general locomotor activity. Entrainment by serial arousal was abolished by IGLX. However, the lesioned animals did show a clear behavioural response to every presentation of the non‐photic cue. These results show that the IGL is a necessary component of the neural pathways mediating both arousal‐ and benzodiazepine‐induced non‐photic entrainment.
Glycosaminoglycan Supplementation Promotes Nerve Regeneration and Muscle Reinnervation
Authors: Gorio A. , Lesma E. , Vergani L. , Di Giulio A. M.
Published: April 2006

This study shows that treatment of rats with exogenous glycosaminoglycans stimulates peripheral nerve regeneration, increases the abundance of mRNAs for myelin proteins and promotes muscle reinnervation. After the sciatic nerve had been crushed the number of regenerating axons in the distal stump was markedly and highly significantly increased by glycosaminoglycan treatment throughout the experimental period. The increased number of axons was correlated with increased axon and fibre (axon + myelin) diameter. The abundance of mRNAs for Po protein and myelin basic protein of regenerating nerves was also affected by treatment with glycosaminoglycans. The increase in mRNA was also observed in the contralateral unlesioned nerve. Such a phenomenon did not occur in saline‐treated rats. Glycosaminoglycan treatment markedly increased the number of muscle fibres reinnervated and accelerated the restoration of muscle twitch tension elicited by nerve stimulation. The effect was particularly evident during the early stages (16 and 21 days after nerve crush) of muscle reinnervation.
Development of Orientation Preference Maps in Area 18 of Kitten Visual Cortex
Authors: Gödecke Lmke , Kim Dae‐Shik , Bonhoeffer Tobias , Singer Wolf
Published: April 2006

We investigated the development of orientation preference maps in the visual cortex of kittens by repeated optical imaging from the same animal. Orientation maps became detectable for the first time around postnatal day (P) 17 and improved continuously in strength until P30, the time at which their appearance became adult‐like. During this developmental period the overall geometry of the maps remained unchanged, suggesting that the layout of the orientation map is specified prior to P17. Hence, before the visual cortex becomes susceptible to experience‐dependent modifications its functional architecture is largely specified. This suggests that the initial development and layout of orientation preference maps are determined by intrinsic processes that are independent of visual experience. This conclusion is further supported by the result that orientation maps were well expressed at P24 in binocularly deprived kittens. Because the appearance of the first orientation‐selective neurons and the subsequent development of orientation preference maps correlated well with the time course of the expression and refinement of clustered horizontal connections, we propose that these connections might contribute to the specification of orientation preference maps.
Up‐regulation of Bax Protein in Degenerating Retinal Ganglion Cells Precedes Apoptotic Cell Death after Optic Nerve Lesion in the Rat
Authors: Isenmann Stefan , Wahl Claudia , Krajewski Stanislaw , Reed John C. , Bähr Mathias
Published: April 2006

Retrograde degeneration of retinal ganglion cells as a consequence of optic nerve lesion has been shown to fulfil the criteria of apoptosis. In the present study, we investigated the time course of ganglion cell apoptosis following intraorbital crushing of the optic nerve in adult rats using morphological criteria and applying a terminal transferase technique (TUNEL) for in situ detection of DNA strand breaks. In addition, we examined expression patterns of the anti‐apoptotic proteins Bcl‐2 and Bcl‐X and the cell death‐promoting protein Bax in retinae after crushing the optic nerve. Apoptotic nuclei were detected in the ganglion cell layer in the first 3 weeks after optic nerve crush, with a peak after 6 days. Bcl‐2 and Bcl‐X proteins were expressed in ganglion cells at low levels. Expression of Bcl‐2 decreased further during the days following crush. Bcl‐X expression was initially increased, followed by a decline over the following days. In contrast, Bax protein, which was expressed in most ganglion cells at moderate baseline levels, was sharply increased as early as 30 min after crush, reached peak levels after 3 days, and remained up‐regulated for at least 1 week thereafter. Double labelling for Bax and TUNEL in retinal sections, however, did not reveal colocalization of the two signals in individual retinal ganglion cells, consistent with the idea that increases in Bax precede apoptosis after optic nerve lesion. Thus, retinal ganglion cell death might be prevented by ablation of Bax protein in these cells, or by up‐regulation of Bax‐antagonists such as Bcl‐2 or Bcl‐X.
Chronic Loss of Glucocorticoids Following Adrenalectomy Down‐regulates the Expression of Glucocorticoid Receptor mRNA in the Rat Forebrain
Authors: Hu Zhongting , Yuri Kazunari , Morimoto Masafumi , Ozawa Hitoshi , Kawata Mitsuhiro
Published: April 2006

In the negative feedback model, loss of endogenous glucocorticoids up‐regulates the expression of glucocorticoid receptor mRNA. To elucidate further the effect of chronic lack of glucocorticoids on the expression of glucocorticoid receptor mRNA and protein, in situ hybridization and immunohistochemical methods were used to examine the long‐term alteration of glucocorticoid receptor mRNA and its immunoreactivity in the forebrain of adrenalectomized rats. Constant lack of glucocorticoids resulted in marked decrease in the expression of glucocorticoid receptor mRNA and disappearance of glucocorticoid receptor immunoreactivity in many forebrain structures. In particular, in the suprapyramidal blade of the hippocampal granule cell layer and cerebral cortex, many cells showed almost no glucocorticoid receptor mRNA signals. These results suggest that long‐term loss of endogenous glucocorticoids down‐regulates the levels of glucocorticoid receptor mRNA, leading to reduction in the synthesis of glucocorticoid receptors in the rat forebrain. Therefore, the presence of endogenous glucocorticoids is vital to the continued expression of glucocorticoid receptor mRNA.
Spatial View Cells in the Primate Hippocampus
Authors: Rolls Edmund T. , Robertson Robert G. , Georges‐François Pierre
Published: April 2006

Hippocampal function was analysed by making recordings in rhesus monkeys actively walking in the laboratory. In a sample of 352 cells recorded in the hippocampus and parahippocampal cortex, a population of ‘spatial view’ cells was found to respond when the monkey looked at a part of the environment. The responses of these hippocampal neurons (i) occur to a view of space ‘out there’, not to the place where the monkey is, (ii) depend on where the monkey is looking, as shown by measuring eye position, (iii) do not encode head direction, and (iv) provide a spatial representation that is allocentric, i.e. in world coordinates. This representation of space ‘out there’ would be an appropriate part of a primate memory system involved in memories of where in an environment an object was seen, and more generally in the memory of particular events or episodes, for which a spatial component normally provides part of the context.
Critical Role for M3 Muscarinic Receptors in Paradoxical Sleep Generation in the Cat
Authors: Sakai Kazuya , Onoe Hirotaka
Published: April 2006

In the cat, microdialysis application of 200 μM carbachol to the peri‐locus coeruleus a (peri‐LCα) of the mediodorsal pontine tegmentum produced a marked (≤5–fold) increase in paradoxical sleep. This effect was blocked by 5–50 μM 4–diphenylacetoxy‐N‐methylpiperidine methiodide (4–DAMP), an M1/M3‐selective muscarinic receptor antagonist. In contrast, the effect was not reversed by methoctramine, an M2‐selective antagonist, or pirenzepine, an M1‐selective antagonist, even at concentrations as high as 500 μM. In addition, unilateral application of 5 μM 4–DAMP alone to the peri‐LCa induced both a >60% decrease in paradoxical sleep and a state of paradoxical sleep without atonia, whereas 50 μM pirenzepine and 500 μM methoctramine had no effect. Our findings are further evidence for the important role played by the peri‐LCα and demonstrate a critical role for M3 muscarinic cholinergic receptors in the generation of paradoxical sleep.
Persistent Excitability Changes in the Piriform Cortex of the Isolated Guinea‐pig Brain after Transient Exposure to Bicuculline
Authors: Forti Matteo , Biella Gerardo , Caccia Silvio , de Curtis Marco
Published: April 2006

The development of long‐lasting excitability changes after a single intracerebral injection1 of bicuculline (1 mM) in a restricted region of the anterior piriform cortex was studied by means of simultaneous, intra‐ and extracellular recordings in the isolated guinea‐pig brain preparation maintained in vitro by arterial perfusion. The transitory disinhibition induced by bicuculline revealed transient afterdischarges that were followed˜ by the activation of a synaptic potential mediated by the recurrent propagation of the focal epileptiform activity along cortico‐cortical associative fibres. The epileptiform associative potential persisted for the duration of the1 experiment. Both the induction and the long‐term expression of the epileptiform associative potential were dependent on the activation of glutamatergic receptors of the NMDA type, as demonstrated by perfusion with the NMDA receptor antagonist 2–aminopentanoic acid (AP5) (100 μM). After bicuculline washout, piriform cortex neurons responded to afferent stimulation with a burst discharge superimposed on a paroxysmal depolarizing potential. The early component of the burst was mediated by a Ca2+‐dependent, non‐synaptic potential located at the proiimal apical dendrites and soma of layer 11–111 cells, since (i) it was abolished by membrane hyperpolarization, (ii) it was not affected by AP5, (iii) it was correlated with a current sink in layer II, as demonstrated by current source density analysis of field potential laminar profiles, and (iv) it was abolished by cadmium (2–5 mM) applied lbcally in layer II. The late component of the burst response (i) coincided in time with the extracellular epileptiform hssociative potential, (ii) increased linearly in amplitude during membrane hyperpolarization, (iii) was blocked by AP5, and (iv) was correlated with an extracellular sink in layer Ib, where the associative fibres contact the distal apical dendrites of piriform cortex neurons. The results presented here indicate that a transient focal disinhibition promotes persistent intrinsic and synaptic excitability changes in piriform cortex neurons. These changes may be responsible for the propagation of epileptiform activity and for the induction of secondary epileptogenesis.
An Evolutionarily Conserved Region in the Second lntron of the Human Nestin Gene Directs Gene Exmession to CNS Progenitor Cells and to Early Neural Ciest Cells
Authors: Lothian Carina , Lendahl Urban
Published: April 2006

Central nervous system (CNS) progenitor cells transiently proliferate in the embryonic neural tube and give rise to neurons and glial cells. A characteristic feature of the CNS progenitor cells is expression of the intermediate filament nestin and it was previously shown that the rat nestin second intron functions as an enhancer, directing gene expression to CNS progenitor cells. In this report we characterize the nestin enhancer in further detail. Cloning and sequence analysis of the rat and human nestin second introns revealed local domains of high sequence similarity in the 3′ portion of the introns. Transgenic mice were generated with the most conserved 714 bp in the 3′ portion of the intron, or with the complete, 1852 bp, human second intron, coupled to the reporter gene lacZ. The two constructs gave a very similar nestin‐like expression pattern, indicating that the important control elements reside in the 714 bp element. Expression was observed starting in embryonic day (E)7.5 neural plate, and at E10.5 CNS progenitor cells throughout the neural tube expressed lacZ. At E12.5, lacZ expression was more restricted and confined to proliferating regions in the neural tube. An interesting difference, compared to the rat nestin second intron, was that the human intron at E10.5 mediated lacZ expression also in early migrating neural crest cells, which is a site of endogenous nestin expression. In conclusion, these data show that a relatively short, evolutionarily conserved region is sufficient to control gene expression in CNS progenitor cells, but that the same region differs between rodents and primates in its capacity to control expression in neural crest cells.
Neuronal GDNF Expression in the Adult Rat Nervous System Identified By In Situ Hybridization
Authors: Pochon N. A.‐M. , Menoud A. , Tseng J. L. , Zurn A. D. , Aebischer P.
Published: April 2006

Glial cell line‐derived neurotrophic factor (GDNF) is a potent neurotrophic factor which has been purified on the basis of its ability to promote the survival of dopaminergic neurons in vitro. GDNF has subsequently been cloned and its sequence shown to be distantly related to transforming growth factor‐β (TGF‐β). To identify GDNF expressing cells in the adult rat brain, in situ hybridization using a digoxygenin (DIG)‐labelled riboprobe has been performed. Our results show that GDNF mRNA is mainly expressed in neurons and that its synthesis is not restricted to dopaminergic areas. It is widely expressed in the cortex, the hippocampus, the striatum, the substantia nigra, the thalamus, the cerebellum and the spinal cord. Neuronal GDNF expression varies among brain regions as determined by the intensity of the in situ signal. Double labelling of the substantia nigra using tyrosine hydroxylase immunohistochemistry, associated with GDNF in situ hybridization, show that the majority of dopaminergic neurons express GDNF. The widespread expression of GDNF throughout the adult brain suggests that its administration in Parkinson's disease should be restricted to the altered structures, in order to avoid possible deleterious side effects.
Increased Presynaptic Protein Kinase C Activity and Glutamate Release in Rats with a Prenatally Induced Hippocampal Lesion
Authors: Di Luca M. , Caputi A. , Cattabeni F. , De Graan P. N. E. , Gispen W. H. , Raiteri M. , Fassio A. , Schmid G. , Bonanno G.
Published: April 2006

We have previously shown that protein kinase C (PKC) activity is up‐regulated in nerve terminals of animals that have been subjected to targeted cellular ablation of cortical and hippocampal neurons by treatment with methylazoxymethanol (MAM), which results in impaired long‐term potentiation (LTP) and cognitive deficit. In this study we investigated the consequences of increased membrane‐bound PKC in the regulation of release of glutamate, the major excitatory transmitter involved in LTP. We show that nerve terminals of MAM‐treated rats show higher PKC activity, as monitored by the in situ phosphorylation of B‐50/GAP‐43, in both basal and phorbol ester‐stimulated conditions. In these animals, hippocampal nerve endings release a greater amount of glutamate than those of controls, both in basal conditions and when synaptosomes are stimulated with KCI or 3,4–diaminopyridine. The potentiation observed in MAM‐treated rats was counteracted by the PKC blocker H‐7 and the clostridial tetanus toxin. On the contrary, GABA release was not significantly up‐regulated, either in basal or in depolarization‐evoked conditions. Therefore our data show that the increase in synaptosomal PKC activity is paralleled by increased glutamate but not GABA release in this animal model. Whether this reflects specific up‐regulation of membrane PKC activity in glutamatergic terminals or an alteration in the regulation of glutamate release remains to be determined.
Tenascin‐C Synthesis and Influence on Axonal Growth During Rat Cortical Development
Authors: Götz Magdalena , Bolz Jürgen , Joester Angret , Faissner Andreas
Published: April 2006

Several putative guidance molecules are restricted to the marginal and subplate zones, the major fibre tracts in the developing cortex. It is presently unknown how their distribution is achieved and how these molecules affect neurite extension. Tenascin‐C is of particular interest in this context, because it may either promote or deflect growing axons depending on its mode of presentation. Therefore, the cellular origin of tenascin‐C in the developing rat cortex and its effects on the extension of cortical afferents and efferents were examined. Tenascin‐C protein is first restricted to the marginal and subplate zones and spreads later into the developing grey matter, in close correlation with afferent innervation. In situ hybridization showed that tenascin‐C mRNA is first confined to the ventricular zone, at some distance from the location of the protein, while at later stages tenascin‐C‐synthesizing cells become scattered throughout the cortical thickness, concomitant with the spread of the protein. In order to assess its function, monoclonal antibodies directed against different domains of tenascin‐C were used in quantitative axonal outgrowth assay. These perturbation experiments suggested that distinct tenascin‐C fibronectin type 111 repeats sustain the growth of thalamic and cortical axons on cortical membrane carpets, whereas the EGF‐type repeats are not involved. The combination of different antibodies revealed that separate fibronectin‐type III repeats exert cooperative effects. These results suggest that ventricular zone cells regulate the establishment of thalamic and cortical axonal projections through locally restricted deposition of tenascin‐C.
Anatomical Gradients in Proliferation and Differentiation of Embryonic Rat CNS Accessed by Buoyant Density Fractionation: α3, β3 and γ2 GABAA Receptor Subunit Co‐expression by Post‐mitotic Neocortical Neurons Correlates Directly with Cell Buoyancy
Authors: Maric Dragan , Maric Irina , Ma Wu , Lahojuji Fatiha , Somogyi Roland , Wen Xiling , Sieghart Werner , Fritschy Jean‐Marc , Barker Jeffery L.
Published: April 2006

Development of the CNS occurs as complex cascade of pre‐programmed events involving distinct phases of cell proliferation and differentiation. Here we show these phases correlate with cells of specific buoyant densities which can be readily accessed by density gradient fractionation. Sprague‐Dawley dams were pulse‐labelled with bromodeoxyuridine (BrdU) and selected regions of embryonic (E) CNS tissues at El1–22 dissociated with papain into single‐cell suspensions. Proliferative cell populations were assessed by anti‐BrdU and propidium iodide staining using flow cytometry. Cell differentiation was evaluated using molecular and immunocytochemical probes against mRNAs and antigens differentiating the neuroepithelial, neuronal and glial cell lineages. The results show the emergence of distinctive spatiotemporal changes in BrdU+ populations throughout the CNS during embryonic development, which were followed by corresponding changes in the cellular distributions of antigens distinguishing specific cell types. Fractionation of neocortical cells using discontinuous Percoll gradients revealed that an increasing number of cells increase their buoyancy during corticogenesis. Immunocytochemical and molecular characterization showed that the proliferative and progenitor cell populations are for the most part associated with lower buoyancy or higher specific buoyant densities (> 1.056 g/ml) whereas the post‐mitotic, differentiated neurons generally separated into fractions of higher buoyancy or lower specific buoyant densities (<1.043 g/ml). Immunostaining with antibodies against several GABAA receptor subunits (α3, β3, γ2) revealed that the highest percent (70–90%) of immunopositive cells could be identified in the most buoyant, differentiating neurons found in the cortical plate/subplate regions, with the lowest percent of the immunopositive cells found in the least buoyant, proliferative and progenitor cell populations originating from the ventricular/subventricular zones. Taken together, these results indicate that buoyant density is distinguishing characteristic of embryonic CNS cells transforming from primarily proliferative to mainly differentiating, and that fractionation of these cells according to their buoyant densities provides rapid access to the properties of specific cell lineages during the prenatal period of CNS development.
Dendritic Localization of Rat Vasopressin mRNA: Ultrastructural Analysis and Mapping of Targeting Elements
Authors: Prakash Nilima , Fehr Susanne , Mohr Evita , Richter Dietmar
Published: April 2006

Transcripts encoding the vasopressin precursor are located in axons and dendrites of rat hypothalamic magnocellular neurons. While the axonal vasopressin mRNA has been extensively characterized both at the biochemical and morphological level, little is known about those transcripts residing in dendrites of magnocellular neurons. As revealed by in situ hybridization at the electron microscopic level, the mRNA is located in proximal and distal dendritic segments and is exclusively confined to regions containing rough endoplasmic reticulum. These results suggest that dendrites of hypothalamic neurons may be capable of local precursor synthesis independent of that occurring in the cell somata. A heterologous system has been employed to define cis‐acting elements within the vasopressin mRNA which may be involved in dendritic compartmentalization. Expression vector constructs consisting of the cytomegalovirus promoter coupled to the rat vasopressin cDNA have been injected into the cell nuclei of cultured neurons derived from embryonic rat superior cervical ganglia. Vector‐encoded vasopressin transcripts were also sorted to dendrites of these neurons indicating that the molecular determinants of dendritic mRNA transport are not cell specific. Mapping of the targeting elements revealed two segments within the vasopressin mRNA that are able to confer dendritic compartmentalization to α‐tubulin mRNA which is normally confined to the cell body.