bluuebunny/crossref_metadata_2025 huggingface dataset:
Differential influence of electrical blocking agents on embryonic acetylcholine receptor mRNA levels in long‐term cultures of aneural mammalian myotubes
Authors: Carlson C. George , Adkins Steven D. , Blake Michael J. , Hasan Abul K. Q. , Loyland Stacy
Published: December 2004

The influence of spontaneous muscle activity on acetylcholine receptor (AChR) expression was examined by exposing long‐term cultures of mammalian myotubes to two pharmacological agents that have similar effects on the rate of spontaneous contractile activity but pharmacologically distinct actions on voltage gated Na+ channels. Previous studies by other investigators have shown that tetrodotoxin upregulates and that veratridine downregulates surface AChR expression in short‐term mammalian muscle cultures. In order to determine whether these drugs have disparate actions on AChR mRNA levels, myotubes were exposed to either tetrodotoxin or veratridine for a period of 10 days, and measurements of the relative levels of embryonic AChR subunit mRNAs (alpha, beta, gamma, delta) were obtained during and following the period of drug exposure. Veratridine produced a substantial decrease (between 33% and 50% reduction), while tetrodotoxin produced a relatively small increase (between 17% and 23%), in each of the AChR subunit mRNAs after 6 days of drug exposure. At 23 days in culture, spontaneously active myotubes exhibited a decrease in the relative levels of each of the AChR subunit mRNAs. Myotubes previously exposed to either veratridine or tetrodotoxin exhibited elevated levels of beta, gamma, and delta AChR subunit mRNAs 6 days after cessation of drug treatment, thus suggesting that a period of muscle inactivity can induce sustained influences on some AChR mRNA levels. These results indicate that the disparate effects of veratridine and tetrodotoxin on surface AChR expression are partly mediated by opposing alterations in AChR subunit mRNA levels, and suggest that changes in the resting influx of sodium and/or calcium ions that are independent of spontaneous electrical or contractile activity can modulate intracellular levels of AChR subunit mRNAs. © 1994 Wiley‐Liss, Inc.
In vivo biogenic amine efflux in medial prefiontal cortex with imipramine, fluoxetine, and fluvoxamine
Authors: Jordan Shaun , Kramer Gerald L. , Zukas Paul K. , Moeller Melissa , Petty Frederick
Published: December 2004

In vivo brain microdialysis was used to determine the effects of the standard tricyclic antidepressant imipramine and the two selective serotonin reuptake inhibitors (SSRIs) antidepressants, fluoxetine and fluvoxamine, on extracellular levels of norepinephrine (NE), dopamine (DA), and serotonin (5‐HT) in rat medial prefrontal cortex. When given intraperitoneally (IP), imipramine increased NE in the microdialysis perfusate, and elevated DA and 5‐HT to a lesser extent. Similar dose‐dependent increases in DA and 5‐HT were detected after IP fluoxetine, although NE was less affected. In contrast, IP fluvoxamine produced no change in basal NE nor DA, although a large increase in 5‐HT occurred at an intermediate dose. When administered directly into cortex, all three antidepressants increased 5‐HT by the same amount in a dose‐dependent fashion. Intracortical imipramine and fluoxetine increased NE, and fluoxetine and fluvoxamine both increased DA, with fluoxetine doing so at a lower concentration. These data suggest that the SSRIs are not entirely selective for serotonin in vivo. © 1994 Wiley‐Liss, Inc.
Further characteristics of long‐term potentiation in piriform cortex
Authors: Jung Min Whan , Larson John
Published: December 2004

Mechanisms for the induction and expression of long‐term potentiation (LTP) were studied in slices of piriform cortex. Cooperativity among afferent inputs as a controlling factor for induction of LTP was tested by pairing stimulation of one input that normally does not induce LTP with stimulation of another input. Combined stimulation, given either to two weak inputs with simultaneous bursts or by pairing single pulses with bursts, did effectively induce LTP. Tests for expression of LTP by NMDA vs. non‐NMDA receptors indicated that non‐NMDA receptor‐mediated responses expressed much greater LTP than NMDA receptor‐mediated responses. Ratios for paired‐pulse facilitation and depression were not altered after induction of LTP. These characteristics are comparable to those exhibited by synapses in the CA1 field of hippocampus. © 1994 Wiley‐Liss, Inc.
Anesthetics block morphine‐induced increases in serotonin release in rat CNS
Authors: Tao Rui , Auerbach Sidney B.
Published: December 2004

The effect of morphine on serotonin (5‐HT) was examined by microdialysis in unanesthetized and anesthetized rats. In unanesthetized rats, morphine (10 mg/kg, s. c.) produced increases in extracellular 5‐HT in nucleus accumbens (n. accumbens) and dorsal raphe nucleus (DRN), but not in the dorsal hippocampus. Similarly, extracellular 5‐HT in the n. accumbens, but not the dorsal hippocampus, was increased after morphine (1 μM) was infused for 60 min by reverse dialysis into the DRN. Chloral hydrate, pentobarbital, and ketamine anesthesia had different effects on 5‐HT in the n. accumbens. Chloral hydrate induced a transient increase and ketamine a sustained increase in extracellular 5‐HT. Pentobarbital caused a sustained decrease. The effects of systemic and intraraphe administration of morphine were abolished by all three anesthetics. Infusion of muscimol, a GABAA receptor agonist, into the DRN also induced a decrease in 5‐HT and abolished the effects of morphine on 5‐HT in the DRN and n. accumbens. These results are consistent with other evidence suggesting that morphineinduced increases in monoamine neurotransmission are a disinhibitory effect resulting from opioid‐mediated inhibition of GABA release. More conclusively, it is apparent that anesthetized animals are inappropriate for testing the effect of morphine on 5‐HT neurotransmission. © 1994 Wiley‐Liss, Inc.
Quantal analysis of presynaptic inhibition, low [Ca2+]0, and high pressure interactions at crustacean excitatory synapses
Authors: Golan Hava , Moore Homer J. , Grossman Yoram
Published: December 2004

The cellular mechanisms underlying the effects of high pressure, GABAergic presynaptic inhibition, and low [Ca2+]0 on glutamatergic excitatory synaptic transmission were studied in the opener muscle of the lobster walking leg. Excitatory postsynaptic currents (EPSCs) were recorded with or without prior stimulation of the inhibitor using a loose macropatch clamp technique at atmospheric pressure and at 6.9 MPA helium pressure. High pressure reduced the mean EPSC amplitude and variance, decreased the quantal content (m), but did not affect the quantum current (q). Pressure shifted the median of the amplitude histogram to the left by 1–2 q. Under normal pressure conditions, presynaptic inhibition and low [Ca 2+]0 induced similar effects. However, quantal analysis using a binomial frequency distribution model revealed that high pressure and low [Ca 2+]0 diminished n (available active zones) and slightly increased p (probability of release), but presynaptic inhibition reduced p and slightly increased n. At high pressure, presynaptic inhibition was reduced, at which time the major contributor to the inhibitory process appeared to be reduction in n and not p. The similarity of the alterations in quantal parameters of release at high pressure, low [Ca 2+]0, and in some conditions of presynaptic inhibition is consistent with the hypothesis that pressure reduces Ca2+ inflow into the presynaptic nerve terminals to affect the Ca2+‐dependent quantal release parameters n and p. © 1994 Wiley‐Liss, Inc.

This article is a US Government work and, as such, is in the public domain in the United States of America.
In situ hybridization evidence for the synthesis of 5‐HT1B receptor in serotoninergic neurons of anterior raphe nuclei in the rat brain
Authors: Doucet Edith , Pohl Michel , Fattaccini Claude‐Michelle , Adrien Joëlle , Mestikawy Salah El , Hamon Michel
Published: December 2004

The regional distribution of the mRNA encoding the serotonin 5‐HT1B receptor was studied in the central nervous system of the rat by in situ hybridization histochemistry and Northern blot analysis. A 180 base pair probe, corresponding to a highly selective portion of the third intracellular loop of the rat 5‐HT1B receptor, was used. In most regions, a single 5 kb message was found by Northern blot analysis. However, two additional bands (2.5 and 4 kb) were detected in the striatum. The rank order of 5‐HT1B mRNA abundance was striatum ≥ septum = ventral tegmentum _‐ colliculi = hypothalamus = hippocampus > brain stem a cerebellum _‐ dorsal horn of the spinal cord > cerebral cortex a ventral horn of the spinal cord > olfactory tubercle. This distribution was confirmed by in situ hybridization, which further revealed that the 5‐HT1B mRNA was present in dorsal root ganglia, the layer IV of the cerebral cortex, the Purkinje cell layer of the cerebellum, the pyramidal neurons in the CAl area of the hippocampus, and the dorsal and median raphe nuclei. In situ hybridization was also performed in nomifensine (10 mg/kg/ i.p.)‐pretreated rats whose serotoninergic neurons were extensively and selectively lesioned by microinjection of 5,7‐dihydroxytryptamine (8 μg/1 μl) directly into the anteroventral vicinity of anterior raphe nuclei 3 weeks before sacrifice. In lesioned rats, 5‐HT1B mRNA was present in the same areas and at the same levels as in control rats, except in the dorsal and median raphe nuclei, where a marked decrease (–75%) in its local concentration was observed. These data provide the first demonstration of the synthesis of 5‐HT1B receptor within serotoninergic neurons, as expected of their presynaptic autoreceptor function at the level of serotoninergic terminals. ©1995 Wiley‐Liss, Inc.
Cellular colocalization of dopamine D1 and D2 receptors in rat medial prefrontal cortex
Authors: Vincent Stephen L. , Khan Yusuf , Benes Francine M.
Published: December 2004

In a recent study in rat medial prefrontal cortex (mPFC), a fluorescently coupled, high‐affinity ligand for the D1 receptor subtype was localized to nonpyramidal neurons, while a ligand selective for the D2 subtype was found on neurons with a size distribution overlapping with both small pyramidal and large nonpyramidal cells. These observations raised the possibility that a subpopulation of cortical neurons with an intermediate size range may coexpress both the D1 and D2 receptor subtypes. In the present study, the D1 and D2 receptor subtypes have been simultaneously localized in layer VI of rat mPFC using 20 nM SCH 23390‐Bodipy and 20 nM N‐(p‐aminophenethyl) spiperone‐Texas red, respectively, in the presence of 100 nM mianserin (5‐HT2 receptor antagonist). The localization of receptor binding fluorescence was assessed in paired images using fluoresceiN isothiocyanate (FITC) and rhodamine dichroic filters for the D1 and D2 subtypes, respectively. Under the conditions employed here, most cell bodies showed either Dl‐like or D2‐like receptor binding fluorescence, while a colocalization of both fluoroprobes was observed on only 25% of the labeled cells. When the size of each single‐labeled cell body was measured using the respective FITC (D1‐probe) and rhodamine (D2‐probe) epifluorescence filters, the distribution of cells showing only D1‐like receptor binding fluorescence was similar to nonpyramidal neurons (68.6 ± 1.8 μm2), while that for cells showing only D2‐like receptor binding fluorescence was similar to that of both large interneurons and small pyramidal cells (106.9 ± 2.4 μm2). Cells showing both D1‐ and D2‐like receptor binding fluorescence were found to overlap in size only with nonpyramidal cells when either fluorescent filter was used. These findings are consistent with the hypothesis that the D1 and D2 receptor subtypes are most often found on different populations of neurons in mPFC, although approximately 25% of all such cells appear to be nonpyramidal neurons having both D1 and D2 receptor binding activity. These findings suggest that the dopamine projections to rat cortex probably engage in a complex interplay with intrinsic cortical neurons and their respective neurotransmitter systems. © 1995 Wiley‐Liss, Inc.
Different mechanisms may be required for maintenance, of NMDA receptor‐dependent and independent forms of long‐term potentiation
Authors: Grover Lawrence M. , Teyler Timothy J.
Published: December 2004

In hippocampal area CA1, long‐term potentiation (LTP) is induced by tetanic stimulation protocols that activate N‐methyl‐D‐aspartate (NMDA) receptors. In addition, some stimulation protocols can induce LTP during NMDA receptor blockade. An initial signal in both NMDA receptor‐dependent and independent LTPs is increased intracellular Ca2+ concentration in postsynaptic neurons. It therefore seems possible that subsequent steps leading to expression and maintenance of potentiation are shared whether or not LTP is induced through NMDA receptor activation. We tested this hypothesis by applying a broad spectrum protein kinase, inhibitor, previously shown to inhibit NMDA receptor‐dependent LTP. In agreement with earlier reports, we found that H‐7 inhibited NMDA receptor‐dependent LTP when applied either during tetanic stimulation, or beginning 30 min following tetanic stimulation. In contrast, NMDA receptorindependent LTP was not inhibited by H‐7 applied during or following tetanic stimulation. We also tested for mutual occlusion between NMDA receptor‐dependent and independent LTPs. Although induction of NMDA receptor‐independent LTP did not occlude later induction of NMDA receptor‐dependent LTP, induction of NMDA receptordependent LTP did occlude NMDA receptor‐independent LTP. While the kinase inhibitor experiment showed a clear difference between NMDA receptor‐dependent and independent LTPs, the occlusion experiments suggest an interaction between the signalling pathways for the two LTPs. © 1995 Wiley‐Liss, Inc.
How can exocytosis account for the actual properties of miniature synaptic signals?
Authors: Vautrin Jean , Barker Jeffery L.
Published: December 2004

It is broadly accepted that a postsynaptic “miniature” is the most elementary chemically transmitted signal and results from the all‐or‐none release of transmitter packaged in a single presynaptic vesicle. Hitherto, it has not been possible to directly verify this renowned representation, although it is consistent with evidence of vesicle traffic and, following an intense period of release, vesicle depletion. However, vesicle traffic involving molecular components similar to those implicated in transmitter release has been attributed to other functions including membrane repair. Furthermore, as a number of investigators have recently proposed, miniature signals recorded at peripheral and central synapses may actually reflect several rather than a single discharge of transmitter. It is not clear whether such putative multiple‐discharge miniatures represent near‐synchronous exocytoses of several vesicles or a burst of openings in a pore that couples a vesicle with the outer membrane. In any case, despite the popularity of the vesicular hypothesis, the molecular mechanism involved in synchronizing fast elementary secretion has not yet been elucidated. Interdependencies among subminiature discharges composing a miniature have suggested that the underlying process is a regenerative signal restricted to a presynaptic terminal unit, confirming Fatt and Katz's first speculation on miniatures, which was not vesicular exocytosis [Fatt and Katz (1952), J. Physiol., 117:109–128]. Here we discuss the possibility that this regenerative signal might be a localized cytosolic Ca2+ transient and attempt to reconcile this hypothesis with the exocytotic models proposed to explain fast transmitter release. © 1995 Wiley‐Liss, Inc.
Neuropeptide Y and dynorphin‐immunoreactive large dense‐core vesicles are strategically localized for presynaptic modulation in the hippocampal formation and substantia nigra
Authors: Pickel Virginia M. , Chan June , Veznedaroglu Erol , Milner Teresa A.
Published: December 2004

Neuropeptide Y (NPY) and dynorphin elicit regionally selective presynaptic modulation in the hippocampal formation and the pars reticulata of the substantia nigra, respectively. We examined potential anatomical substrates for their presynaptic modulation by determining the distribution and size of large (80–120 nm) dense‐core vesicles (DCVs), organelles previously shown to be immunoreactive for each peptide. Throughout the hippocampal formation, NPY‐immunoreactive DCVs were located primarily in axon terminals and were more sparingly distributed in dendrites. In comparison with other portions of the hippocampal formation, NPY‐labeled DCVs were most abundant in axons and terminals of the CA1 region. The DCVs in the CA1 region of the hippocampus also more frequently had larger mean cross‐sectional diameters when located along portions of the terminal in contact with unlabeled axons. In both the CA1 region of the hippocampus and the dentate gyrus, NPY‐labeled DCVs in contact with portions of the axonal membrane apposed to astrocytes also were larger than those located more centrally in the axon terminal. Dynorphin‐immunoreactive DCVs in axon terminals 'of the substantia nigra were significantly larger when found near portions of the axonal membrane in contact not only with other axons and astrocytic processes, but also occasionally with postsynaptic dendrites. The parallels between diameters of DCVs and known selectivity of NPY for presynaptic modulation in the CA1 region of the hippocampus suggest a direct correlation between the size and distribution of immunoreactive DCVs and their sites of exocytotic release. By analogy, we can conclude that dynorphin in the pars reticulata of the substantia nigra is also principally a presynaptic modulator, but may additionally elicit functional changes through interactions with receptive sites on astrocytes or postsynaptic neurons. © 1995 Wiley‐Liss, Inc.
Pet imaging studies of dopamine D2 receptors: Comparison of [18F]N‐Methylspiperone; and the benzamide analogues [18F]MABN and [18F]MBP in baboon brain
Authors: Mach Robert H. , Ehrenkaufer Richard L. E. , Greenberg Joel H. , Shao Lingxiong , Morton Thomas E. , Evora Paul H. , Nowak Peggy A. , Luedtke Robert R. , Cohen David , Reivich Martin
Published: December 2004

A series of positron emission tomography (PET) imaging studies was conducted in a baboon with the benzamide derivatives [18F]2,3‐dimethoxy N‐9‐(4‐fluorobenzyl)‐9‐azabicyclo[3.3.1]nonan‐3β‐yl]benzamide ([18F]MABN) and [18F]2,3‐dimethoxy‐N‐[1‐(4‐fluorobenzyl)piperidin‐4‐yl]benzamide ([18F]MBP). Studies were also conducted with the butyrophenone [18F]N‐methylspiperone (NMSP) for comparison. Tissue‐time activity curves of [18F]MABN are similar to those of [18F]NMSP since both compounds displayed approximately the same uptake in the basal ganglia and displayed irreversible binding kinetics in vivo. However, the rapid rate of clearance from the cerebellum and high basal ganglia: cerebellum ratio of [18F]MABN indicate that this compound has a much lower amount of nonspecific binding than [18F]NMSP. [18F]MBP displayed a higher uptake in the basal ganglia relative to [18F]NMSP and [18F]MABN and exhibited reversible binding kinetics in vivo. This property of [18F]MBP is desirable since the uptake of radioactivity in D2‐rich ligands is less likely to be influenced by changes in cerebral blood flow. The current data suggest that both [18F]MABN and [18F]MBP are promising ligands for studying dopamine D2 receptors with PET. © 1995 Wiley‐Liss, Inc.
Long‐lasting inhibition of in vivo cocaine binding to dopamine transporters by 3β‐(4‐Iodophenyl)Tropane‐2‐Carboxylic acid Methyl Ester: RTI‐55 or βCIT
Authors: Volkow N. D. , Gatley S. J. , Fowler J. S. , Chen R. , Logan J. , Dewey S. L. , Ding Y.‐S. , Pappas N. , King P. , Gregor R. R. Mac , Kuhar M. J. , Carroll F. I. , Wolf A. P.
Published: December 2004

Cocaine analogs such as 3β‐(4‐iodophenyl)tropane‐2β‐carboxylic acid methyl ester (RTI‐55 or βCIT) with a higher affinity for the dopamine transporter (DAT) may be potentially useful in interfering with cocaine's actions in brain. This study evaluates the time course of the effects of RTI‐55 on cocaine binding in baboon brain using PET and [11C]cocaine. [11C]Cocaine binding was measured prior to, and 90 minutes, 24 hours, 4–5 days and 11–13 days after RTI‐55 (0.3 mg/kg i.v.). Parallel studies with [3H]cocaine and RTI‐55 (0.5 mg/kg i.v. or 2 mg/kg i.p.) were performed in the mouse. RTI‐55 significalitly inhibited [11C]cocaine binding at 90 minutes and 24 hours after administration.The half‐life for the clearance of RTI‐55 from the DAT was estimated to be 2 to 3 days in the baboon brain. In the mouse brain, RTI‐55 significantly inhibited [3H]cocaine binding at 60 and 180 minutes after administration and recovery was observed at 12 hours. These results document long‐lasting inhibition of cocaine binding by RTI‐55 and corroborate that binding kinetics of RTI‐55 in striatum observed in imaging studies with [123I]RTI‐55 represents binding to DATs. © 1995 Wiley‐Liss, Inc.
Brain transcription factor gene expression, neurotransmitter levels, and novelty response behaviors: Alterations during rat amphetamine withdrawal and following chronic injection stress
Authors: Persico Antonio M. , Schindler Charles W. , Zaczek Robert , Brannock Michael T. , Uhl George R.
Published: December 2004

Transcription factors are known to act as gene expression regulators, possibly linking extracellular stimuli to long‐term modifications at the neuronal level. Such modifications may potentially ‐underlie chronic psychostimulant‐ and stress‐induced behavioral alterations. This study illustrates how a 2 week, twice daily 7.5 mg/kg d‐amphetamine or saline regimen alters rat brain regional expression of transcription factor genes, including c fos, fos‐B, jun‐B, c jun, and zif268, and seeks potential correlations between those changes and alterations in neurotransmitter levels and behavioral novelty responses.

Amphetamine withdrawal‐induced decreases in transcription factor mRNA levels, assessed using Northern blot analysis, appear most prominent in prefrontal cortex, begin approximately 12 h after the last injection, and largely recover to control levels by 54 h. Prefrontal cortical and striatal dopamine content, assessed using HPLC, decrease and recover over a similar time course. Behavioral “stereotypy time” manifest by animals exposed to a novel environment, a measure sensitive to psychostimulant withdrawal, also decreases beginning 12 h after the last injection, is still significantly reduced at 54 h, and recovers at 72 h.

Chronic saline injections are followed by a consistent decrease in transcription factor gene expression, observed 6 h after the last injection, followed by a “rebound” increase at 12 h. These changes are accompanied by dramatic, mostly biphasic alterations in prefrontal cortical biogenic amines and by a short‐lived increase in striatal dopamine turnover. At the same time, rats display much longer‐lasting decreases in locomotor responses when exposed to a novel environment, with recovery occurring only 54 h after the last injection.

The delayed recovery of behavioral responses to novelty is consistent with potential involvement of changes in transcription factor‐mediated gene expression in neurochem‐ ical mechanisms underlying psychostimulant withdrawal and chronic injection stress‐ induced behavioral alterations. © 1995 Wiley‐Liss, Inc.
Biological mechanisms and perinatal exposure to abused drugs
Authors: Thadani Pushpa V.
Published: December 2004

Use of illicit and licit drugs during pregnancy is a major public health concern, as it can have adverse effects on the developing fetus. Infants born of women addicted to narcotics, cocaine, alcohol, or polydrugs often undergo a characteristic withdrawal syndrome and may have physical, behavioral, and/or neurological abnormalities. As it is not feasible to ascertain whether these functional changes in human infants are produced by abused substance(s) per se or by a combination of complex socioeconomic factors and polydrug use, researchers in recent years have developed and utilized various innovative animal models to assess drug‐induced alterations and their biological mechanisms during the developmental period under a controlled environment. To promote interdisciplinary communications as well as to assess the progress and the future needs in this area, the National Institute on Drug Abuse (NIDA) held a technical review at which biomedical researchers discussed their current findings in various physiological systems. This report summarizes the major findings and the methodological and experimental issues discussed at the conference. The meeting was held in Washington, DC, on May 25 and 26, 1994. © 1995 Wiley‐Liss, Inc.
Modulation of dopamine D1‐mediated turning behavior and striatal c‐fos expression by the substantia nigra
Authors: Fenu S. , Carta A. , Morelli M.
Published: December 2004

In order to study the possible contribution of the substantia nigra (SN) in the positive interaction between dopamine D1 receptor agonists and glutamate antagonists in unilaterally 6‐hydroxydopamine (6‐OHDA) lesioned rats, the effect of the D1 agonist, SKF 38393, was studied in combination with intranigral infusions of glutamate antagonists of the NMDA (MK 801, CPP) or AMPA (NBQX) type of receptor. Local infusion into the SN of the 6‐OHDA lesioned side of MK 801, CPP or NBQX at doses inducing no or minimal behavioral effects significantly increased the turning behavior and the expression of c‐fos induced, in the lesioned caudate‐putamen (CPu), by a parenteral administration of SKF 38393. The same result was obtained after intra‐SN infusion of the GABA agonist, muscimol. High doses of MK 801, CPP or muscimol infused into the SN produced intense contralateral turning per se and induced a sparse c‐fos expression in the lesioned CPu which was antagonized by parenteral administration of MK 801. The results indicate that a depression of SN pars reticulata efferent neurons potentiates D1‐mediated responses and suggest that this area may play a role in the positive interaction between glutamate antagonists and D1 receptor agonists. © 1995 Wiley‐Liss, Inc.
Effects of the σ receptor ligand SR 31742A on neurotensin biosynthesis in rat basal ganglia
Authors: Labie Christophe , Saubusse Patricia , Keane Peter E. , Fur Gérard Le , Soubrié Philippe
Published: December 2004

The effects of SR 31742A, a specific σ ligand, were investigated on neurotensin (NT) biosynthesis in the basal ganglia of the rat. Both single and repeated treatments with either SR 31742A (20 mg/kg i.p.) or haloperidol (1 mg/kg i.p.) increased the concentration of NT‐like immunoreactivity (NT‐1i) in the nucleus accumbens. In contrast to haloperidol, the administration of SR 31742A failed to increase the concentration of NT‐li in the caudate‐putamen. We have further investigated drug‐induced variations in NT biosynthesis by studying NT/neuromedin N (NT/NN) mRNA levels in the nucleus accumbens and the ventral tegmental area of the rat following SR 31742A administration. The NT/NN mRNA levels in the ventral tegmental area were increased by a maximum of fifteen fold (7 h at 20 mg/kg i.p.). A lower increase in NTINN mRNA levels was elicited in the nucleus accumbens. These results suggest that the increase in NT‐li observed after SR 31742A treatment, like that produced by haloperidol, may result from an increase of NT biosynthesis. Furthermore, the effects of SR 31742A on NT metabolism are similar to those of atypical antipsychotics, since they appear to be selective for the limbic system. © 1995 Wiley‐Lies, Inc.
Synaptic reorganisation in the rat striatum after dopaminergic deafferentation: An ultrastructural study using glutamate decarboxylase immunocytochemistry
Authors: Nitsch Cordula , Riesenberg Rainer
Published: December 2004

The ultrastructure of GABAergic and non‐GABAergic synapses in the adult rat neostriatum was examined 6‐8 months after unilateral removal of the nigrostriatal dopaminergic pathway by 6‐hydroxydopamine injection into the medial forebrain bundle. GABAergic profiles were identified by preembedding glutamate decarboxylase (GAD) immunocytochemistry performed on parasagittal vibratome sections. In three representative fields of the striatum, the nature and number of boutons and their postsynaptic partners were determined and the differences between the striata ipsi‐ and contralateral to the lesion analyzed. The percentage of GAD‐immunoreactive boutons was increased from 23% on the intact side to 28% on the lesioned side. In addition, the GABAergic boutons underwent significantly more multiple contacts with several independent postsynaptic profiles, preferentially with dendritic spines. This could reflect a lesion‐induced sprouting of local GABAergic axon terminals. On the other hand, although the vast majority of GABAergic boutons underwent synaptic contacts with dendrites (77% vs. 80%), the number of boutons per dendrite or per dendritic circumference remained unchanged. Thus, the higher frequency of GABAergic boutons may simply reflect the loss of the dopaminergic nerve endings, without a heterosynaptic replacement by GABAergic boutons. The deafferentation also induced structural changes of the postsynaptic profiles. Some dendritic spines had a shortened neck; others were completely integrated in the dendrite which now contained a spine apparatus and was contacted by boutons with the features of axospinous synapses. The spine retraction resulted in a quantitative decrease in the number of spines. Analysis of the synaptic curvature revealed that only spines with a flat contact zone were lost. Concurrently, the number of dendrites was increased, of the GAD‐containing in particular, suggesting that the denrites of GABAergic interzeurons tend to elongate and/or arborize. Taken together, the results of the present study show that the dopaminergic denervation caused a remodeling of the postsynaptic neurons. The relative increase of the number of GABAergic boutons and their synaptic contacts suggests that an altered wiring of the intrinsic GABAergic system contributes to the changes in the striatal output activity. © 1995 Wiley‐Liss, Inc.
Chronic corticosterone treatment maintains synaptic activity of CA1 hippocampal pyramidal cells: Acute high corticosterone administration increases action potential number
Authors: Birnstiel Susanne , List Troy J. , Beck Sheryl G.
Published: December 2004

The hypothalamic‐pituitary‐adrenocortical (HPA) axis controls the levels of plasma corticosterone (CT) in the rat and the levels of cortisol in man. CT is important in maintaining homeostasis and regulating energy production. Homeostasis is maintained by basal activation of the hippocampal‐HPA axis. In response to stress CT secretion is increased. CT activation of receptors in the hippocampus provides feedback inhibition of the HPA axis to return the system to basal activity. There are two types of CT receptors: the mineralocorticoid receptor (MR) and the glucocorticoid receptor (GR). CT has a 10‐fold higher affinity for MR than GR. Normal basal levels of CT occupy the majority of the MR. During the diurnal surge of CT and following the presentation of a stressful stimulus, the MR and GR are both maximally occupied. To begin to understand how CT influences the hippocampal‐HPA axis, intracellular recording techniques in the hippocampal brain slice preparation were used to determine how high concentrations of CT may alter cell characteristics and/or evoked synaptic activity. Two treatment groups were used, i.e., adrenalectomized (ADX) and ADX with CT pellet replacement (ADX + CT) that produced plasma blood levels equal to that seen in a normal rat in the morning. Acute administration of 100 nM CT decreased action potential threshold and the number of action potentials elicited by a depolarizing current pulse in cells from both the ADX and ADX + CT treated rats. The amplitude of the evoked excitatory postsynaptic potentials (EPSP) or inhibitory postsynaptic potentials (IPSP) declined in cells recorded from ADX animals and ADX rats acutely treated with high concentrations of CT (ADWCT). The EPSPs and IPSPs were stable in cells from ADX + CT rats exposed to high CT concentrations. We conclude from these data that chronic CT treatment is necessary to maintain EPSP and IPSP amplitude. Also, acute administration of a high concentration of CT alters the output of the CA1 hippocampal pyramidal cells by increasing the number of action potentials elicited by a depolarizing current pulse but does not alter the amplitude of subthreshold EPSPs and IPSPs. © 1995 Wiley‐Liss, Inc.
Neonatal excitotoxic ventral hippocampal damage alters dopamine response to mild repeated stress and to chronic haloperidol
Authors: Lipska Barbara K. , Chrapusta Stanislaw J. , Egan Michael F. , Weinberger Daniel R.
Published: December 2004

The effects of neonatal excitotoxic ventral hippocampus (VH)lesions on dopamine release in response to repeated stress (saline injections) and to chronic haloperidol treatment were investigated in Sprague‐Dawley rats infused with ibotenic acid or vehicle into the VH on day 7 of postnatal life (PD7). Beginning on PD35, lesioned and sham‐operated rats were injected i.p. with saline (INJ) once daily for 3 weeks or were not treated (NO INJ). Another cohort of rats was given haloperidol (HAL, 0.4 mg/kg, i.p.) or vehicle beginning on PD35 and thereafter once daily for 3 weeks. 3‐Methoxytyramine (3‐MT) was measured by combined gas chromatography/mass spectrometry in the frontal cortex (FC), nucleus accumbens (NAcc), and striatum (STR) at PD56 following MA0 inhibition with pargyline. At baseline (NO INJ), 3‐MT was reduced in STR of lesioned rats. Repeated saline injections resulted in a further 3‐MT reduction in STR, FC, and NAcc of lesioned animals, but had no effect in sham rats. Chronic HAL, compared with vehicle, suppressed locomotor activity, and increased 3‐MT accumulation in the FC, NAcc, and STR in sham and lesioned rats. This increase was enhanced in the FC of lesioned rats. These data show that mild repeated stress attenuates dopamine release in FC, NAcc, and STR of lesioned rats, while chronic HAL augments it in FC of lesioned animals versus controls. We conclude that the neonatal excitotoxic lesion of VH alters the functioning of midbrain dopamine systems during environmental and pharmacological challenge. © 1995 Wiley‐Liss, Inc.
Sensitivity of striatal [11C]cocaine binding to decreases in synaptic dopamine
Authors: Gatley S. John , Volkow Nora D. , Fowler Joanna S. , Dewey Stephen L. , Logan Jean
Published: December 2004

We have previously shown that tracer concentrations of [11C]cocaine binding to the dopamine transporter (DAT) in human and baboon striatum can be visualized using positron emission tomography (PET). To determine whether the concentration of dopamine normally present in the synaptic cleft can compete with [11C]cocaine for transporter binding sites, we conducted baboon PET studies with drugs (sodium 4‐hydroxybutyrate, four studies, 200 mg/kg gamma‐vinylGABA, three studies, 300 mg/kg and citalopram, three studies, 2 mgkg) expected to decrease synaptic dopamine. Each study involved two [11C]cocaine injections and PET scans separated by 2‐4 h, with drug administration after the first injection, and without movement of the subject between scans. Time‐activity data from striatum and from cerebellum were used with the arterial plasma input function to determine graphically by Logan plotting [11C]cocaine distribution volumes for the brain regions. Specific binding of [11C]cocaine to DAT in striatum was calculated as the distribution volume ratio (DVR) for striatum and cerebellum. In nine of the ten studies drug treatment produced a small increase in DVR (range, 1‐ll%), and in seven of these studies the increase was >7%. The mean increase was 6.2 ± 4.1%. The reproducibility of the DVR measure was assessed by comparing [11C]cocaine studies conducted without pharmacological treatments using individual baboons on separate days, and thus involving possible repositioning errors, as well as long‐term changes in the state of the striatal dopamine system. For four individual baboons with three or four studies per animal the mean (±s.d.) values of DVR were 1.73 ± 0.03, 1.39 ± 0.03, 1.53 ± 0.06, and 1.54 ± 0.12. The maximum differences between baseline DVRs, expressed as percentage of the lowest value, were 5%, 5%, 9%, and 20%. For two other baboons with two studies each, the between study differences were 1% and 9%. Thus within‐subject variability was quite low, even with repositioning. The results suggest that [11C]cocaine binding to the DAT is sensitive to pharmacological alterations in the concentration of synaptic dopamine. However, the sensitivity of [11C]cocaine to dopamine‐depletion is less than that of the D2 receptor radioligand [11C]raclopride, in agreement with literature in vitro binding studies, and is unlikely to be a serious issue in PET evaluations of DAT density. © 1995 Wiley‐Liss, Inc.
Distribution of GABAAreceptor alpha 1 subunit‐like immunoreactivity in comparision with that of enkephalin and substance P in the rat forebrain
Authors: Marksteiner J. , Lassnig E. , Humpel C. , Sieghart W. , Kaufmann W. , Saria A.
Published: December 2004

The γ‐aminobutyric acid‐A receptor consists of several subunits. In this immunohistochemical study we investigated the regional distribution of the α1 subunit with an antibody directed against a specific amino acid sequence (1‐9) of the α1 subunit. We compared the distribution pattern of the α1 subunit‐like immunoreactivity with that of substance P‐ and enkephalin‐like immunoreactivities in adjacent sections of the rat forebrain. α1 subunit‐like immunoreactivity appeared in the form of varicosities and fibers. A band‐like terminal staining pattern (woolly fibers) that has been shown by others for substance P‐ and enkephalin‐like immunoreactivity is also observed for α1 subunit‐like immunoreactivity. In contrast to substance P and enkephalin, numerous α1 subunit‐like immunoreactive perikarya were found. The highest density of α1 subunit‐like immunoreactive fibers and perikarya was found in the pallidal areas and the substantia nigra pars reticulata whereas the nucleus accumbens and the caudate putamen displayed a low density. α1 subunit‐like immunoreactive neurons resembled typical pallidal neurons. Some of these neurons were pericellularly stained with enkephalin‐like immunoreactive varicosities in the dorsal pallidum.

The distribution pattern of α1 subunit‐like immunoreactivity reflects a partial overlap with the substance P and enkephalin system although a differential distribution to each of these peptides was observed for cell bodies, fibers, and axon terminals. © 1995 Wiley‐Liss, Inc.
Effects of local connectivity on striatal function: Simulation and analysis of a model
Authors: Wickens J. R. , Kotter R. , Alexander M. E.
Published: December 2004

Neuronal population activity was investigated by computer simulation of a network model based on the neostriatum. Three network topologies were studied, based on different assumptions about the synaptic connectivity among medium spiny neurons. In all networks neurons were interconnected by inhibitory synapses. The connectivity was either symmetric, in which case all connections between cells were reciprocal and equal in strength; or asymmetric. Simulations showed that networks with symmetric connectivity receiving randomly distributed afferent excitation produced stationary spatial activity patterns. In contrast, asymmetric connectivity in homogeneous networks produced slow travelling‐wave activity across the network. We suggest that the shape of the medium spiny neurons is an important determinant of synaptic connectivity and that changes in the shape of these neurons caused by Huntington's disease would result in asymmetric connectivity. Slow travelling‐wave activity produced by asymmetric connectivity in the neostriatum could explain some aspects of the choreic movement and some electromyographic features seen in Huntington's patients. © 1995 Wiley‐Liss, Inc.
IPT: A novel iodinated ligand for the CNS dopamine transporter
Authors: Kung Mei‐Ping , Essman William D. , Frederick Dana , Meegalla Sanath , Goodman Mark , Mu Mu , Lucki Irwin , Kung Hank F.
Published: December 2004

An iodinated cocaine derivative, N‐(3′‐iodopropen‐2′‐yl)‐2β‐carbomethoxy‐3β‐(4‐chlorophenyl)tropane (IPT), was evaluated as a probe for in vitro and in vivo labeling of dopamine (DA) and serotonin (5‐HT) transporters in Sprague‐Dawley rat brain. Saturation analysis of [125I]IPT in rat striatal homogenates, in two different buffer solutions, Tris‐HCl and phosphate, demonstrated a one‐site binding with affinities (Kd) of 0.25 ± 0.02 and 0.16 ± 0.02 nM and densities (Bmax) of 939 ± 161 and 1,982 ± 137 fmol/mg protein, respectively. Competition by known DA transporter ligands showed a rank order of RTI‐55 > IPT > GBR12909 > mazindol > (−)cocaine. Binding to 5‐HT transporter sites was evaluated in rat cortical homogenates. Saturation experiment results showed a single site with a Kd value of 1.2 ± 0.2 nM and a Bmax value of 100 ± 20 fmol/mg protein. The rank order of potency of several monoamine uptake inhibitors (paroxetine > fluoxetine > mazindol > R‐nisoxetine > GBR12909) suggests that [l25I] IPT labels 5‐HT transporters in rat cortical homogenates. Both ex vivo and in vitro autoradiographic studies revealed high densities of [125I]IPT binding sites in the caudate nucleus, putamen, olfactory tubercle and nucleus accumbens, areas known to be rich in dopaminergic innervation. Moderate accumulation of activity was also observed in the substantia nigra. The dorsal raphe, a region with a high density of 5‐HT innervation, was labeled using in vitro autoradiography with [125I]IPT, but the labeling using ex vivo autoradiography was less prominent at 30 min postinjection and not noticeable at 60 min postinjection. Furthermore, systemic administration of IPT to rats increased the locomotor activity, a behavioral effect consistent with the in vitro and in vivo characteristics of compounds acting at dopaminergic sites. These results demonstrate that [125I]IPT is a useful ligand for in vitro labeling of DA and 5‐HT transporters and a ligand selective for labeling of DA transport sites in vivo. When labeled with I‐123,[123I]IPT holds promise as a SPECT imaging agent for studies of neuropsychiatric disorders that involve DA transporters. © 1995 Wiley‐Liss, Inc.
D3 and D2 dopamine receptors: Visualization of cellular expression patterns in motor and limbic structures
Authors: Larson Eric R. , Ariano Marjorie A.
Published: December 2004

The distribution of the D3 and D2 dopamine receptor subtypes in forebrain regions of the basal ganglia and mesocorticolimbic system was determined. This was assessed through combined fluorescent visualization of subtype selective anti‐peptide antibodies for these cloned receptors and detection of their ligand recognition sites using the D2 subfamily antagonist, N‐(p‐aminophenethyl) spiperone (NAPS fluoroprobe). The double‐labeling technique enabled direct comparison of the cloned receptor proteins and NAPS fluoroprobe binding in vitro. The application of these two methods together produced results comparable to single‐labeling paradigms. Functional D3 receptors, defined as the coincident fluorescence of the D3 receptor antisera and fluoroprobe binding, were detected in the core region of the nucleus accumbens and exhibited a laminated expression pattern in the frontal cortex. D3 receptor protein was expressed robustly in neurons of the dorsolateral striatum, but showed an intense neuropil reaction in the globus pallidus. Functional D2 receptors, defined as the coincident fluorescence of the D2 receptor antisera and fluoroprobe binding, were detected in the frontal cortex and the medial shell of the nucleus accumbens. Thus, heterogeneities occurred in the cellular expression of functional D3 and D2 receptors in forebrain dopaminoceptive areas. D3 appears more related to basal ganglia and structures involved with motoric behavior, while D2 was associated with regions associated with cognitive/affective functions. © 1995 Wiley‐Liss, Inc.
The road to tranquility: The search for selective anti‐anxiety agents
Authors: Estes J. Worth
Published: December 2004

The earliest treatments of anxiety included cathartics and emetics, which were used to remove the excess of black bile (hence our word melancholia) thought to be responsible for the patient's demeanor. By the 1700s, physicians were prescribing drugs that are more selective for the CNS, chiefly opium and strengthening tonics. In the 1860s cardioactive drugs such as atropine, aconite, and digitalis were assumed to counteract anxiety because it could be associated with tachycardia andlor melancholia. A little later, the emergence of laboratory animal models, culminating in the conditioned avoidance response, and also Freudian psychiatry, permitted the evolution of new definitions of anxiety, as well as the introduction of sedative agents such as KBr, chloral hydrate, and barbiturates for its treatment. The first somewhat selective anxiolytics, reserpine, meprobamate, and chlorpromazine, appe ared in the early 1950s, while in 1959 the benzodiazepines were the first to prove more selective than all the others in a systematic battery of screening tests. © 1995 Wiley‐Liss, Inc.
In vivo‐synthesized radioactively labelled α‐methyl serotonin as a selective tracer for visualization of brain serotonin neurons
Authors: Cohen Z. , Tsuiki K. , Takada A. , Beaudet A. , Ddiksic M. , Hamel E.
Published: December 2004

To investigate the use of α‐[3H]methyl tryptophan (α‐[3H]MTrp) as a tracer for the in vivo study of brain serotonergic neurons, we examined whether α‐[3H]MTrp and its metabolite α‐[3H]methyl serotonin (α‐[3H]M5‐HT) selectively label serotonergic neurons and whether once accumulated in these neurons, the radioactive metabolite behaves like endogenous serotonin. Rats received a systemic injection of 1–5 mCi of α‐[3H]MTrp and 24 h later their brains were immediately removed or fixed by perfusion before removal. Tissue sections in which serotonergic neurons had been immunostained for 5‐HT or its synthesizing enzyme, tryptophan hydroxylase, were processed for radioautography at the light and electron microscopic level. In another group of rats, the release of radioactivity from different brain areas was studied both under basal and depolarizing conditions. In the dorsal raphe nucleus, the light microscopic examination revealed almost complete colocalization between serotonergic neurons and those that accumulated radioactivity, with a heterogeneity in the content of α‐[3H]M5‐HT among the various cells. At the ultrastructural level, immunoidentified serotonergic perikarya and dendritic processes in the dorsal raphe nucleus, as well as nerve terminals in the cerebral cortex were also found to contain α‐[3H]M5‐HT. Under basal conditions, radioactivity was released from the brainstem raphe region and from projection areas such as the striatum and hippocampus. The basal output of α‐[3H]M5‐HT increased approximately twofold after a depolarizing 50 mM KCl solution was added to the perfusion fluid. These findings suggest that newly synthesized α‐[3H]M5‐HT can be released both at somatodendritic and terminal sites. In sum, the present results demonstrate the selectivity of α‐[3H]MTrp as a tracer for serotonergic cells, and further suggest that α‐[3H]MTrp radiolabelling provides for a direct assessment of the in vivo dynamics of brain serotonergic neurons at the cellular level. © 1995 Wiley‐Liss, Inc.