bluuebunny/crossref_metadata_2025 huggingface dataset:
CNS signal transduction in the pathophysiology and pharmacotherapy of affective disorders and schizophrenia
Authors: Hudson Craig J. , Young L. Trevor , Li Peter P. , Warsh Jerry J.
Published: December 2004

Until recently, research on the neurochemical basis of affective disorders (AD) and schizophrenia (SCZ) focused on detecting postulated disturbances in presynaptic neurotransmitter release and metabolism, or postsynaptic receptor function. New insights into the molecular mechanisms involved in the propagation of neurotransmitter signals across biological membranes and in the regulation of neuronal responses have allowed the development of novel hypotheses, which may explain the altered postsynaptic neuroreceptor responsivity thought to be integral to the pathophysiology of these disorders. In this review we evaluate evidence from both basic science and clinical research implicating disturbances in postreceptor signal transduction in the pathophysiology and pharmacotherapy of AD and SCZ. Specific findings regarding potential postreceptor sites of pathophysiology are highlighted in each of these disorders, together with the growing body of data on the possible postreceptor loci of psychotropic drug action, especially lithium and antidepressants. © 1993 Wiley‐Liss, Inc.
Locomotor activity following intra‐accumbens microinjections of dopamine D1 agonist SK&F 38393 in rats
Authors: Meyer Merle E. , van Hartesveldt Carol , Potter Thomas J.
Published: December 2004

The present study examined the effects of the dopamine D1 receptor subtypes agonist SK&F 38393 on locomotor activities after bilateral microinjection (0.00, 0.01, 0.1, 10.0 μg) into the nucleus accumbens (Acb). The dose of 0.1 μg elicited the highest response rate across measures of locomotion, rearing and stereotypy behavior. On the other hand, the largest dose of 10.0 μg was associated with significant increase in center time behaviors. The data were supportive of the hypothesis that dose‐related locomotor activities elicited by microinjections of SK&F 38393 into the Acb are independently mediated by D1 receptors. © 1993 Wiley‐Liss, Inc.
Glutamate effects on calcium homeostasis in cerebellar granule cells in primary cultures grown under depolarizing and nondepolarizing conditions
Authors: Zhao Zhong , Peng Liang
Published: December 2004

Cerebellar granule cell culture are normally grown under partly depolarizing conditions (in a medium with ∼25 mMK+), but these cultures can also be grown at a normal potassium concentration (5.4 mM k+), although some of their characteristics are altered. In this study, intracellular free calcium concentration and 45Ca uptake were measured in cerebellar granule cell cultures grown at either 25 or 5.4 mM extracellular potassium in the presence of glutamate, and/or some of its subtype‐specific agonists and antagonists. Granule cells in cultures grown at 25mM K+ responded to glutamate, but not to quisqualate, with an increase in free cytosolic calcium concentration and in 45Ca uptake. This increase in free cytosolic calcium concentration was dependent on extracellular calcium and it was antagonized by AP5 and Ketamine, NMDA receptor antagonists. In contrast, granule cells in cultures grown at 5.4 mM K+ responded to both glutamate and quisqualate, and these responses were independent of extracellular calcium and not sensitive to AP5 and ketamine. In agreement with this, 45Ca uptake was not affected by glutamate. Neither of the two culture types responded to kainate with an increase in calcium concentration or uptake. These observations indicate that calcium uptake in granule cells in cultures grown at 25mM K+ reflect NMDA activation of calcium influx, whereas the cells in cultures grown at 5 mM K+ increase cytosolic calcium concentration on account of intracellular release of bound calcium, caused by activation of the metabotropic receptor. The two types of cultures may constitute valuable experimental tools for investigation of physiological and pathological effects of calcium releas from intracellular stores induced by glutamate via the metabotropic receptors and of calcium uptake induced by NMDA. © 1993 Wiley‐Liss, Inc.
Serotonin‐induced increase in cAMP in ganglia isolated from the myenteric plexus of the guinea pig small intestine: Mediation by a novel 5‐HT receptor
Authors: Fiorica‐Howells Elena , Wade Paul R. , Gershon Michael D.
Published: December 2004

Serotonin (5‐HT) is a mediator (through 5‐HT1P receptors) of slow EPSPs in myenteric ganglia of the small intestine. The effect of 5‐HT can be mimicked by elevating cAMP; therefore, we tested the hypothesis that the slow EPSP‐like response to 5‐HT is cAMP‐mediated. Guinea pig gut was enzymatically dissociated; myenteric ganglia remained intact and were collected by filtration. Neurons in the isolated ganglia retained their ability to manifest the slow EPSP‐like response to 5‐HT. Exposure to 5‐HT raised the ganglionic level of cAMP (ED50 0.3 μM). This effect was not antagonized by the 5‐HT1P antagonist, N‐acetyl‐5‐hydroxytryptophyl‐5‐hydroxytryptophan amide (100.0 μM), or mimicked by the 5‐HT1P agonist, 5‐hydroxyindalpine (10.0 μM). Increases in cAMP were also evoked by the 5‐HT1 agonist, 5‐carboxyamidotryptamine (10.0 μM), the 5‐HT2 agonist, (±)‐1‐(2,5‐dimethoxy‐4‐iodophenyl)‐2‐aminopropane (DOI; 1.0–10.0 μM), and by the 5‐HT4 agonists, renzapride (1.0–10.0 μM) and 5‐methoxytryptamine (1.0–10.0 μM); however, neither the 5‐HT1/5‐HT2 antagonists, spiperone, methysergide, and methiothepin, nor the 5‐HT4 antagonist, tropisetron (ICS 205–930; 10.0 μM), were able to inhibit the rise in cAMP evoked by these compounds or by 5‐HT (0.1–10.0 μM). The 5‐HT‐evoked elevation of cAMP was antagonized by ketanserin (10.0 μM), which also blocked the effects of 5‐methoxytryptamine and DOI, but not those of renzapride. The effective concentration of DOI, however, was higher than that needed for activation of 5‐HT2 receptors, and Northern analysis using a cDNA probe encoding the rat 5‐HT2 receptor failed to reveal the presence of 5‐HT2 mRNA in myenteric ganglia, although it hybridizes with mRNA of the right size in the guinea pig brain. Compounds that failed to change levels of cAMP or to antagonize the action of 5‐HT included 8‐hydroxy‐di‐n‐propylamino tetralin, R58639, R88226, and sumatriptan. It is concluded that the receptor responsible for the 5‐HT‐induced rise in cAMP in ganglia isolated from the guinea pig myenteric plexus is not a known subtype of 5‐HT receptor. Since the pharmacology of this novel receptor is different from that of the slow EPSP‐like response to 5‐HT, the receptor probably does not mediate the slow EPSP. © 1993 Wiley‐Liss, Inc.
Striatal binding of the PET ligand 11C‐raclopride is altered by drugs that modify synaptic dopamine levels
Authors: Dewey Stephen L. , Smith Gwenn S. , Logan Jean , Brodie Jonathan D. , Fowler Joanna S. , Wolf Alfred P.
Published: December 2004

Bilatera decreases in striatal 11C‐raclopride binding were observed in adult female baboons with high resolution PET following administration of drugs that act centrally on dopaminergic neurons. At baseline and following administration of d‐amphetamine (a dopamine‐releasing drug), GBR‐12909 (a potent dopamine reuptake inhibitor), or tetrabenazine (a biogenic amine depleting drug) PET scans of 11C‐raclopride binding were obtained in a CTI 931 positron tomograph. In all studies, the ratio of the distribution volumes for the striatum to the cerebellum for 11C‐raclopride binding decreased significantly by an average of 16.2% for d‐amphetamine, 22.1% for GBR‐12909, and 28.3% for tetrabenazine while there were no significant changes observed in the cerebellum or in the rate of systemic metabolism of the radiotracer. These decreases exceed the test/retest variability of striatal 11C‐raclopride binding measured in the same animals under identical experimental conditions (Dewey et al., 1992b). Together these studies demonstrate that PET measurements of striatal 11C‐raclopride binding can be used to indirectly and non‐invasively monitor changes in synaptic dopamine concentrations that result from a variety of neurophysiologic mechanisms. © 1993 Wiley‐Liss, Inc.
Further studies concerning the role of nitric oxide in LTP induction and maintenance
Authors: Musleh Wael Y. , Shahi Kavian , Baudry Michel
Published: December 2004

Nitric oxide (NO) has recently been proposed to act as a retrograde messenger to produce long‐term potentiation (LTP) in hippocampal area CA1. This notion is based largely on the absence of LTP when hippocampal slices are incubated in the presence of inhibitors of NO synthase (NOS) or of NO scavengers. In the present study, we tested the effects of such compounds on both the induction and maintenance of LTP in field CA1 of hippocampal slices. Incubation of slices in the presence of N‐methyl‐L‐arginine (MLA) or L‐nitroarginine (LNA), two inhibitors of NOS, or in the presence of hemoglobin (Hb), a NO scavenger, produced a large reduction in the magnitude of LTP induced by a theta burst stimulation (TBS) paradigm. These compounds had no effect on the degree of paired‐pulse facilitation but produced a significant reduction of the facilitation of postsynaptic responses occuring during TBS. On the other hand, MLA did not prevent the potentiation induced by application of tetraethylammonium (TEA). These results suggest that the inhibition of LTP produced by these agents could be due to an effect on a physiological mechanism that triggers LTP and not necessarily on an event that follows the triggering step. © 1993 Wiley‐Liss, Inc.
Withdrawal following cocaine self‐administration decreases regional cerebral metabolic rate in critical brain reward regions
Authors: Hammer R. P. , Pires W. S. , Markou A. , Koob G. F.
Published: December 2004

The quantitative [14C]‐2‐deoxyglucose autoradiographic method was utilized to assess regional cerebral metabolic rate for glucose (rCMRglc) in rat brain during withdrawal from cocaine self‐administration. RCMRglc was determined in 62 regions from brains of naïve rats which were placed into an empty operant chamber for 12 hr continuously, and rats trained to self‐administer cocaine during 3 hr training sessions and subsequently placed into the operant chamber for 12 hr continuously with or without access to cocaine. Animals placed into the chamber without access to cocaine were examined 6 hr later, while animals allowed access to the 12 hr cocaine binge were examined either 6 or 72 hr post‐cocaine. Metabolic activity was reduced during withdrawal in the nucleus accumbens, olfactory tubercle, islands of Calleja region, basolateral and central amygdaloid nuclei, medial septum, piriform and cingulate cortices, rostral caudatoputamen, entopeduncular nucleus and the adjacent lateral hypothalamus, somatosensory, auditory, and motor cortices compared to the naïve state. These effects were usually more severe at 72 than at 6 hr after binge exposure, with intermediate values observed in cocaine trained animals without binge exposure. The response was negatively correlated with the amount of cocaine consumed during binge exposure in the striatum, olfactory tubercle, piriform, cingulate, somatosensory, and motor cortices. Thus, the amount of cocaine consumed can affect the extent of metabolic depression after sustained drug exposure. The pattern of regional effects suggests that mesolimbic and rostral extrapyramidal dopamine terminal regions and certain of their efferent pathways are preferentially affected during cocaine withdrawal. The reduction of basal metabolic rate observed in these brain regions during cocaine withdrawal may become more severe with time despite the apparent recovery of certain behavioral‐motivational responses. © Wiley‐Liss, Inc.
Cocaine actions on rat prefrontal cortical and hippocampal dentate granule neurons in vitro
Authors: Jahromi Shokrollah S. , Schertzer Stephen , Carlen Peter L.
Published: December 2004

The electrophysiological actions of cocaine hydrochloride (COC) on medial prefrontal cortical (mpfc) and hippocampal dentate granule (DG) neurons were investigated in rat brain slices with intracellular recording techniques. The following parameters were measured: resting membrane potential (RMP), spike threshold, spike firing adaptation, postspike train afterhyperpolarization (AHP), excitatory postsynaptic potentials (EPSPs), and inhibitory postsynaptic potentials (IPSPs). In the mpfc, COC appeared to have both inhibitory and excitatory effects. In the majority of cells examined, the EPSP amplitude was attenuated by COC (200 nM–20 μM), whereas the amplitude of the postspike train afterhyperpolarization (AHP) was reduced (an excitatory effect). In DG neurons, 1 μM COC caused a small depolarization. COC potentiated the EPSPs at 1 μM but attenuated EPSPs and IPSPs at 10–100 μM. The amplitude of antidromically evoked EPSPs was also increased by 20 μM COC. At concentrations of 10 μM and greater, COC increased spike threshold. It is concluded that COC actions on mpfc and DG neurons are both excitatory and inhibitory and that these effects may be mediated by multiple neurotransmitters/modulators. © 1993 Wiley‐Liss, Inc.
Quantitative autoradiographic analysis of [3H]carfentanil binding to mu opiate receptors in the rat brain
Authors: Fitzgerald Lawrence W. , Teitler Milt
Published: December 2004

Fentanyl and its derivatives are considered among the most potent opiate analgesic/euphoriants. The pharmacological literature generally supports a μ opiate receptor site of action for the fentanyl derivatives, but some observations suggest that other sites of action may be involved in producing the extremely potent fentanyl effects. In order to investigate the mechanism of action of fentanyl‐like drugs further, [3H]carfentanil was used as a radioligand to image high‐affinity carfentanil binding sites in slidemounted sections of the rat brain (receptor autoradiography). In parallel studies the prototypical μ opiate agonist radioligand [3H]DAMGO ([D‐Ala2‐MePhe4‐Glyol5]enkephalin) was also used. The working hypothesis was that if carfentanil was acting through another high‐affinity site besides the μ opiate receptor, the distribution pattern of the autoradiographic image produced by [3H]carfentanil should be significantly different than the autoradiographic image produced by [3H]carfentanil should be significantly different than the autoradiographic pattern displayed by the well‐characterized and selective μ opiate [3H]DAMGO. Thirty‐five brain regions were examined for specific [3H]carfentanil and [3H]DAMGO binding. The absolute and relative densities of the sites were essentially identical. The highest levels of binding were observed in the “patch” areas of the striatum (131 ± 5 fmol/mg T. E. for [3H]carfentanil; 162 ± 13 fmol/mg T. E. for [3H]DAMGO). The lowest levels were observed in the cerebellum where no specific binding of either radioligand was observed. The overall distribution pattern of the two radioligands produced a correlation coefficient of 0.95; the distribution pattern was prototypical for the μ opiate receptor as reported previously by other groups. Despite the nearly identical distribution patterns, an intriguing difference in the interaction of DAMGO and carfentanil with the μ opiate receptor was observed. The biologically active nonhydrolyzable analog of GTP, GTPγS, was able to completely abolish or greatly diminish specific [3H]DAMGO binding depending on brain region; GTPγS had little or no effect on specific [3H]carfentanil binding. This latter difference in the molecular interaction of DAMGO and carfentanil with the μ opiate receptor may indicate that some of the observed differences in the effects of fentanyl‐like opiates may be due to a difference in the intrinsic activity of the fentanyl derivatives at the μ opiate receptor. © 1993 Wiley‐Liss, Inc.
Identification of tryptamine and tryptamine‐serotonin neurons in the rat dorsal raphe nuclei using specific antibodies
Authors: Dabadie Henry , Geffard Michel
Published: December 2004

Previous studies have shown that tryptamine (T) is closely associated with the serotonergic system but have failed to determine whether neurons containing only T exist in the raphe nuclei (RN) and/or if T colocalizes with serotonin (5‐HT). The use of rabbit‐conjugated T antisera (TAS) and rat‐conjugated 5‐HT antisera (5‐HTAS) in a double‐labelling technique has made the study of the colocalization of T and 5‐HT in neurons of the rat dorsal RN (DR) possible. Slices taken from the same zone of the DR were treated following four different procedures of double‐immunolabelling: DAB coloration for the rabbit TAS and DAB‐nickel coloration for the rat 5‐HTAS either first or second; or DAB coloration for the 5‐HTAS and DAB‐nickel coloration for the TAS first or second. Control sections were treated according to a single immunoperoxidase staining in the same zone. The immunolabelled neurons were computed using the Biocom 200 program at the same magnification. The results of this double‐immunolabelling show that three different cell types exist in the rat DR: (1) T‐only‐containing neurons, (2) 5‐HT‐only‐containing neurons displaying either homogeneous DAB or homogeneous DAB‐nickel, and (3) neurons where T colocalizes with 5‐HT (T‐positive/5‐HT‐positive neurons) displaying heterogeneous DAB‐nickel coloration. The results were identical whatever the procedure performed or the order of the DAB‐nickel revelation. In contrast, the single immunolabelling method failed to stain T‐only‐containing neurons (or 5‐HT‐only‐containing neurons); T‐immunoreactive cells (or 5‐HT‐immunoreactive cells) correspond in fact to neurons containing either T (or 5‐HT) or T and 5‐HT. © 1993 Wiley‐Liss, Inc.
Localization of 5‐HT1A receptors to astroglial cells in adult rats: Implications for neuronal‐glial interactions and psychoactive drug mechanism of action
Authors: Whitaker‐Azmitia Patricia M. , Clarke Colin , Azmitia Efrain C.
Published: December 2004

Although tissue culture studies have shown a variety of neurotransmitter receptors on astroglial cells, verifying these observations in adult animals has been difficult and rarely accomplished. In the current study we have used double immunocytochemistry to localize 5‐HT1A receptors to astroglial cells in fixed sections of adult rat brain. The astroglial cells were identified using an antibody raised against the astroglialspecific protein glial fibrillary acidic protein (GFAP). To label the 5‐HT1a receptor, we used an antibody we recently raised against a unique peptide sequence occurring in the second extracellular loop of the receptor.

Our results show that the 5‐HT1a receptor occurs in relatively high abundance on astroglial cells. There is regional specificity, the receptor being much more commonly found is septum and hippocampus than striatum. There are also intraregional differences in that even within a single brain region one astrocyte may have very high levels of the receptor while an adjacent cell has none.

We propose that the cellular localization of this receptor could have significance in understanding the mechanism of action of 5‐HT1a receptor active drugs in alleviating anxiety and depression. The mechanism may be through the release of a neurotrophic agent, S‐100β, from astrocytes. This factor may then cause regeneration or sprouting of neuronal terminals which have been lost due to a disease process. © 1993 Wiley‐Liss, Inc.
Spontaneous activity and recurrent inhibition in cultured hippocampal networks
Authors: Siebler Mario , Köller Hubertus , Stichel Christine C. , Müller Hans Werner , Freund Hans‐Joachim
Published: December 2004

As a model for an integrated neuronal network based on the concept of modular units, we have investigated the occurrence of spontaneous activity and the formation of synaptic circuits in primary cultures of dissociated hippocampal neurons from the embryonic rat. Sodium‐dependent action potentials (APs) could be elicited after 1 day in vitro (DIV), whereas spontaneous postsynaptic potentials (PSPs), “miniature” PSPs and APs appeared after 3‐6 DIV. The number of cells with spontaneous APs and the rate of APs increased during development of the neuritic network. In addition to a stochastic spike interval distribution, pyramid‐shaped neurons could be identified after 10‐12 DIV, which fired preferentially at interspike intervals between 20‐120 ms and 190‐400 ms. This distinctive bimodal interspike interval pattern was sensitive to GABA‐A antagonists. Simultaneous recordings of pairs of neurons demonstrated recurrent inhibitory, GABA‐ergic synaptic circuits. In addition, a subpopulation of GABAergic neurons could be visualized by immunocytochemistry. These results are discussed in relation to the hypothesis that spontaneous firing of connected neurons is networkdriven, based on synaptic “noise” and patterned by recurrent inhibition. © 1993 Wiley‐Liss, Inc.
Depression of glutamatergic and gabaergic synaptic responses in striatal spiny neurons by stimulation of presynaptic GABAB receptors
Authors: Nisenbaum Eric S. , Berger Theodore W. , Grace Anthony A.
Published: December 2004

The influence of γ‐aminobutyric acidB (GABAB) receptor stimulation on the excitatory and inhibitory synaptic potentials and membrane properties of identified striatal spiny neurons was examined in a corticostriatal slice preparation. Stimulation of the subcortical white matter evoked a monosynaptic, excitatory postsynaptic potential (EPSP) and a polysynaptic, inhibitory postsynaptic potential (IPSP) in spiny neurons. The EPSP had two components: a large amplitude response which could be blocked by the kainate/quisqualate receptor antagonist, 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX, 10μM), and a small amplitue, long‐duration depolarization which could be blocked by the N‐methyl‐D‐aspartate receptor antagonist, d‐(‐)‐2‐amino‐5‐phosphonovaleric acid (APV, 100 μM). The IPSP was observed as a membrane depolarization when recorded from neurons at resting membrane potential. However, when neurons were injected with the Na+‐channel blocker, QX‐314, allowing cells to be depolarized above their spike thresholds, a prominent hyperpolarizing IPSP was readily observed which could be blocked by the GABAA antagonist, bicuculline (10‐50 μM). This bicuculline‐sensitive IPSP was responsible for the inhibition of EPSP amplitude and probability of spike discharge revealed using paired stimulation of the subcortical white matter. The amplitude of both the EPSP and the IPSP were depressed by the GABAB receptor agonist, p‐chlorophenyl‐GABA (baclofen, 0.5‐100 μM) in a concentration‐dependent manner. Baclofen also blocked paired stimulus inhibition of spike discharge. These effects of baclofen persisted in slices in which the cortex was removed and were reversed by the GABAB receptor antagonist, 3‐amino‐3‐hydroxy‐2‐(4‐chlorophenyl)‐propanesulphonic acid (saclofen, 100‐500 μM). In contrast to its profound influence on synaptic input, baclofen did not alter resting membrane potential, input resistance, membrane current‐voltage relationship, or spike threshold of the cells recorded, and therefore did not appear to exert direct postsynaptic effects on the striatal spiny neurons.

Taken together, these data indicate that the depressant effects of baclofen on EPSPs are mediated through GABAB receptors located on the terminals of glutamatergic afferents within the striatum. Moreover, the results suggest that the actions of baclofen on IPSPs and paired stimulus inhibition are produced by activation of GABAB receptors within the striatum at a site presynaptic to spiny neurons, either on the terminals of GABAergic afferents or on an interposed non‐spiny GABAergic cell. Thus, GABAB hetero‐ and auto‐receptors have the capacity to provide a negative feedback mechanism through which the major excitatory and inhibitory inputs to striatal spiny neurons are regulated. © 1993 Wiley‐Liss, Inc.
Electrophysiological evidence for a large receptor reserve for inhibition of dorsal raphe neuronal firing by 5‐HT1A agonists
Authors: Cox Richard F. , Meller Emanuel , Waszczak Barbara L.
Published: December 2004

Previous studies [Meller et al. (1990) Mol. Pharmacol., 37:231‐237] have shown that a large receptor reserve exists for the inhibition of serotonin synthesis in rat cortex and hippocampus by the 5‐HT1A agonist 8‐hydroxy‐2(di‐n‐propylamino)tetralin (8‐OH‐DPAT), whereas little or no reserve exists for the lower efficacy agonists ipsapirone and BMY 7378. The current studies were undertaken to determine if the above drugs exhibit similar relative efficacies and receptor reserves in an electrophysiological model of 5‐HT1A receptor activation, i. e., the inhibition of dorsal raphe cell firing. Intravenous dose‐response curves were constructed in untreated control rats, or in rats which received an injection of the irreversible receptor inactivator N‐ethoxycarbonyl‐2‐ethoxy‐1, 2‐dihydroquinoline (EEDQ, 6 mg/kg, s. c.) 24 hours before recording. All three drugs fully inhibited dorsal raphe cell firing in control rats (ED50's: 1.5 μg/kg, 8‐OH‐DPAT; 30.0 μg/kg, ipsapirone; 17.5 μg/kg, BMY 7378). However, unlike effects on serotonin synthesis, EEDQ treatments caused no depression of the maximal inhibitory response for any of the agonists, although all dose‐response curves were shifted to the right (ED50's: 10.1 μg/kg, 6.7‐fold shift, 8‐OH‐DPAT; 139.9 μg/kg, 4.7‐fold shift, ipsapirone; 53.8 μg/kg, 3.1‐fold shift, BMY 7378). Although the order of agonist efficacies was similar for both inhibition of serotonin synthesis and dorsal raphe cell firing (8‐OH‐DPAT > ipsapirone > BMY 7378), a large (>50%) receptor reserve was estimated for all three drugs in this electrophysiological system. This suggests that 5‐HT1A receptor populations mediating the inhibition of transmitter synthesis and neuronal firing may be differently regulated or have different receptor‐effector coupling characteristics (G‐proteins, effectors, and/or transduction efficiencies). © 1993 Wiley‐Liss, Inc.
Chronic fluoxetine treatment upregulates 5‐HT uptake sites and 5‐HT2 receptors in rat brain: An autoradiographic study
Authors: Hrdina Pavel D. , Vu Thu B.
Published: December 2004

This study was undertaken to investigate the effect of chronic treatment with fluoxetine, a selective serotonin uptake inhibitor used widely in the treatment of depression, on the distribution and density of 5‐HT uptake sites, 5‐HT2 receptors, and vesicular amine uptake sites in rat brain. Fluoxetine (10 mg/kg i. p.) was administered daily for 21 days. The density of 5‐HT uptake sites labelled by [3H]paroxetine, 5‐HT2 receptors labelled by [3H]ketanserin in presence of tetrabenazine and vesicular amine uptake sites labelled by [3H]ketanserin in the presence of mianserin were measured by quantitative autoradiography in 22 areas of rat brain, using coronal tissue sections. Chronic administration of fluoxetine produced significant increases in the density of 5‐HT uptake sites in layers of frontoparietal cortex (by 32–43%), of striate cortex (by 55%), in CA1 field of hippocampus (by 111%) and in superior colliculus (by 20%). Fluoxetine treatment also resulted in upregulation of 5‐HT2 receptors in layers of frontparietal cortex (31–38%) and in CA2‐3 fields of hippocampus (by 39%). The density of tetrabenazine‐sensitive vesicular amine uptake sites in the caudate‐putamen was also significantly increased (by 66%). The observed alterations in 5‐HT uptake site and 5‐HT2 receptor densities are likely a part of adaptive neuronal changes that occur after chronic administration of fluoxetine and may be related to the antidepressant effect of the drug. © 1993 Wiley‐Liss, Inc.
Gender disparity in the academic pipeline: Women in neuroscience
Authors: Smith Dean O.
Published: December 2004

The percentages of females at critical steps in the academic career ladder were examined for one specific field, neuroscience. There was a slight attrition among females completing the Ph. D. However, the major drop‐off occurred when qualified post‐doctorates did not apply for faculty positions. Remedial actions should focus on not only the graduate school environment but also on the more critical postdoctoral experience. © 1993 Wiley‐Liss, Inc.
Evidence for the cholinergic nature of C‐terminals associated with subsurface cisterns in α‐Motoneurons of rat
Authors: Nagy J. I. , Yamamoto T. , Jordan L. M.
Published: December 2004

C‐terminals can be distinguished at the ultrastructural level from other types of nerve endings on motoneurons by their prominent and regularly occurring postsynaptic specializations termed subsurface cisterns (SSC). We have previously shown (Yamamoto et al., 1991) that an antibody directed against a sequence within the gap junction protein connexin 32 immunolabels these motoneuronal SSCs and can therefore serve as a immunohistochemical tool to visualize indirectly the location of C‐terminals on motoneurons at the light microscope level. Here we have used this anti‐SSC antibody in combination with antibodies against choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) to determine whether C‐terminals on motoneurons contain these cholinergic enzyme; markers. In sections at all major spinal cord levels and in several cranial motor nuclei examined, motoneuronal cell bodies and their proximal dendrites were studded with large ChAT‐immunoreactive (ChAT‐IR) boutons. Boutons having a similar distribution and appearance on motoneurons were also immunolabelled for AChE. In addition, motoneurons were surrounded by a dense plexus of AChE‐immunoreactive (AChE‐IR) varicose fibers and fine preterminal axons. In double‐labeled sections, AChE‐IR boutons corresponded to those immunolabeled for ChAT. In sections processed for simultaneous immunofluorescence detection of ChAT and SSCs, ChAT‐IR boutons were very often found in apposition to immunolabeled SSCs. In sections processed for simultaneous labeling of AChE and SSCs, AChE‐IR boutons were again frequently seen abutting labeled SSCs. These results provide the first strong evidence at the LM level that a large proportion, if not the entirety, of C‐terminals are cholinergic and show that these terminals consist in part of relatively large varicosities along highly varicose axons that form en passant type contacts on motoneurons. At the same time, our results substantially narrow possibilities regarding the as yet undetermined source of C‐terminals, which can now be considered to originate from cholinergic neurons, such as those located in the brainstem and/or the spinal cord. © 1993 Wiley‐Liss, Inc.
Chronic repeated cocaine administration alters basal and opioid‐regulated adenylyl cyclase activity
Authors: Unterwald Ellen M. , Cox Brian M. , Kreek Mary Jeanne , Cote Thomas E. , Izenwasser Sari
Published: December 2004

Repeated daily cocaine injections have been shown to alter μ‐opioid receptor densities in the caudate putamen and nucleus accumbens of rat brain (Unterwald et al., 1991, 1992). Addenylyl cyclase activity was measured in rat rostral caudate putamen and nucleus accumbens following repeated cocaine administration to determine the functional consequences of cocaine‐induced opioid receptor changes. Male Fischer rats were injected daily for 14 days with saline or cocaine HC1 (30 or 45 mg/kg/day, i.p.) in three equal doses at 1‐hr intervals. Basal adenylyl cyclase activity and the effects of the selective μ‐ and δ‐opioid agonists [D‐Ala2, N‐Me‐Phe4, Gly‐ol5]enkephalin (DAMGO) and [D‐penicillamine2, D‐Penicillamine5]enkephalin (DPDPE), respectively, on arenylyl cy‐clase activity were examined 30 min after the last injection using a cAMP radioligand binding assay in crude membrane preparations. Basal adenylyl cyclase activity was 49% and 34% lower in the caudate putamen of animals treated with 30 and 45 mg/kg/day of cocaine, respectively, as compared to those receiving saline injections. Basal adenylyl cyclase activity was unchanged in the nucleus accumbens following cocaine treatment. DAMGO and DPDPE each maximally inhibited approximately 25% and 30%, respectively, of basal adenylyl cyclase in the caudate putamen and nucleus accumbens of saline‐injected animals. Administration of cocaine attenuated the ability of DPDPE to inhibit adenylyl cyclase in both brain regions, but had no effect on the efficacy or potency of DAMGO for inhibiting adenylyl cyclase activity. These results suggest that chronic, repeated cocaine administration results in a selective impairment of δ‐opioid receptor‐mediated effector function in the caudate putamen and nucleus accumbens. © 1993 Wiley‐Liss, Inc.
Failure of the three compartment model to describe the pharmacokinetics in brain of a high affinity substituted benzamide
Authors: Votaw John R. , Kessler Robert M. , de Paulis Tomas
Published: December 2004

The applicability of using the standard 3‐compartment model to describe the neuropharmacokinetics of a high affinity substituted benzamide was investigated. We performed the following experiments using the [18F]‐5‐(3‐fluoropropyl) analog of epidepride ([18F]5‐FPrEpid), a potent dopamine D2 receptor antagonist: constant left ventricular infusion, first‐pass clearance, varying ligand specific activity, and displacing bound ligand with varying amounts of unlabelled ligand. Taken together, the information from these experiments rigorously tests the standard 3‐compartment model. The obtained data and predictions from the model of the kinetic behavior of the ligand are inconsistent. The measured and model predicted dissociation rate (measured Koff = 0.065 min−1, model prediction Koff = 0.007 min−1) and the equilibrium dissociation constant (measured KD = 0.14 nM, model prediction KD = 2.2 nM) differ by an order of magnitude. Furthermore, the model cannot be used to accurately estimate the receptor density. We postulate that the synapse geometry and physical relationship between receptors are necessary components of a model that describes the pharmacokinetics of [18F]5‐FPrEpid. © 1993 Wiley‐Liss, Inc.
Prenatal methamphetamine attenuates serotonin mediated renin secretion in male and female rat progeny: Evidence for selective long‐term dysfunction of serotonin pathways in brain
Authors: Cabrera Theresa M. , Levy Andrew D. , Li Qian , Van De Kar Louis D. , Battaglia George
Published: December 2004

In adult rats, methamphetamine produces biochemical alterations in brain serotonin (5‐HT) neurons. Since 5‐HT is critical to the development of fetal 5‐HT neurons and target tissues, we hypothesized that in utero exposure to methamphetamine could result in long‐term alterations in postnatal 5‐HT systems. Pregnant Sprague‐Dawley rats, administred either saline or (±)methamphetamine (5 mg/kg, s.c., b.i.d.) from gestational day 13 to 20, were divided into three treatment groups: Saline‐injected/Ad Lib Fed (VEH); Saline‐injected/Pair Fed (PF); and methamphetamine injected (METH). Prenatal methamphetamine exposure did not alter litter size, gender number, or progeny birth weights. Functional alterations in serotonergic systems were determined in postnatal day (PD) 70 male progeny and in PD 30 female progeny by measuring changes in 5‐HT mediated increases in plasma hormones following a single injection of the 5‐HT releaser p‐chloroamphetamine (PCA; 8 mg/kg). Prenatal metham‐phetamine produced long‐term marked (−30 to −62%) attenuation of plasma renin responses to PCA in male and female progeny. In contrast, no alterations were observed in the ACTH, corticosterone, or prolactin responses to PCA in male and female progeny. Prenatal methamphetamine did not alter basal levels of any hormones measured regardless of gender. No significant differences were observed in the density of cortical or hypothalamic 5‐HT uptake sites, or in the density of cortical 5‐HT1 or 5‐HT2 receptors in male progeny. The lack of significant differences in cortical 5‐HT uptake sites observed between PF and METH treated dams 2 days post‐parturition indicates that methamphet‐amine was not neurotoxic to the pregnant dams. These data, which demonstrate long‐term postnatal deficits in 5‐HT mediated renin secretion, suggest selective functional alterations of brain 5‐HT systems in male and female progeny exposed in utero to methamphetamine. © 1993 Wiley‐Liss, Inc.
Kainic acid seizures cause enhanced expression of cholecystokinin‐octapeptide in the cortex and hippocampus of the rat
Authors: Gruber Bernhard , Greber Susanne , Sperk Günther
Published: December 2004

Immunocytochemistry and in situ hybridization techniques were used for investigating changes in cholecystokinin immunoreactivity and mRNA in the cerebral cortex and hippocampus after kainic acid‐induced limbic seizures in the rat. Marked increases in cholecystokinin mRNA concentrations were observed in layers II/III and V/VI of the cerebral cortex, in CA1 pyramidal neurons of the hippocampus, and in presumptive basket cells of the dentate gyrus 1 and 2 days after the acute seizures. Whereas cholecystokinin mRNA contents returned to normal in the cerebral cortex and the CA1 sector at later intervals, high concentrations were observed in basket cells even 2 months after the initial seizures. Accordingly, cholecystokinin‐like immunoreactivity was intensified in the cerebral cortex, CA1 sector and in presumed basket cells of the hippocampus 30 days after kainic acid. Besides its high content in basket cells, cholecystokinin‐like immunoreactivity was primarily present in neuronal fibers or diffusely distributed in the respective brain area. In the hippocampus, strongly enhanced staining for cholecystokinin was also observed in the alveus, the stratum lacunosum moleculare, and in the inner molecular layer, suggesting increased concentrations of the peptide in afferent and efferent fibers of the hippocampus.

The present experiments suggest a strong activation of cholecystokinin systems in the brain after kainic acid‐induced limbic seizures in the rat. This is indicated by pronounced increases in cholecystokinin mRNA in the cortex and individual cell types of the hippocampus (basket cells, granule cells, and CA1 pyramidal neurons). The subsequent increases in cholecystokin immunoreactivity even surpass those in mRNA. The observed changes may be part of the self‐defense mechanisms that protect the animals during subsequent epileptic episodes. © 1993 Wiley‐Liss, Inc.
Long‐term action of lithium: A role for transcriptional and posttranscriptional factors regulated by protein kinase C
Authors: Manji Husseini K. , Lenox Robert H.
Published: December 2004

Lithium, a simple monovalent cation, represents one of psychiatry's most important treatments and is the most effective treatment for reducing both the frequency and severity of recurrent affective episodes. Despite extensive research, the underlying biologic basis for the therapeutic efficacy this drug remains unknown, and in recent years, research has focused on signal transduction pathways to explain lithium's efficacy in treating both poles of manic‐depressive illness. Critical to attributions of therapeutic relevance to any observed biochemical effect, however, is the observation that the characteristic prophylactic action of lithium in stabilizing the profound mood cycling of bipolar disorder requires a lag period for onset and is not immediately reversed upon discontinuation of treatment. Biochemical changes requiring such prolonged administration of a drug suggest alterations at the genomic level but, until recently, little has been known about the transcriptional and posttranscriptional factors regulated by chronic drug treatment, although long‐term changes in neuronal synaptic function are known to be dependent upon the selective regulation of gene expression. In this paper, we will present evidence to show that chronic lithium exerts significant transcriptional and posttranscriptional effects, and that these actions of lithium may be mediated via protein kinase C (PKC)‐induced alterations in nuclear transcription regulatory factors responsible for modulating the expression of proteins involved in long‐term neural plasticity and cellular response. Such target sites for chronic lithium may help unravel the processes by which a, simple monovalent cation can produce a long‐term stabilization of mood in individuals vulnerable to bipolar illness. © 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.
Systemic nicotine‐induced dopamine release in the rat nucleus accumbens is regulated by nicotinic receptors in the ventral tegmental area
Authors: Nisell Magnus , Nomikos George G. , Svensson Torgny H.
Published: December 2004

Stimulation of the mesolimbic dopamine (DA) system is considered of major importance for the rewarding and dependence producing properties of nicotine (NIC). To identify the site of this stimulatory action, simultaneous microdialysis was performed in the ventral tegmental area (VTA) and the ipsilateral nucleus accumbens (NAC) of awake rats. Extracellular concentrations of DA and its metabolites were measured in the NAC. NIC (0.5 mg/kg, s.c.) increased DA and its metabolites by ∼50%.Concomitant infusion of the nicotinic receptor antagonist mecamylamine (MEC, 100 μ) through the VTA probe, starting 40 min before NIC injection, antagonized the NIC induced increases of DA and its metabolites. In contrast, similar MEC pretreatment (40 or 140 min) in the NAC did not affect DA or metabolite responses to systemic NIC. Infusion of NIC (1,000 μ) in the NAC or the VTA increased DA release by 49% and 48%, respectively, whereas only the VTA infusion increased metabolite concentrations by ‐25%. MEC infusion (1–1,000 μ) in the VTA did not affect DA or its metabolites, whereas the 1,000 μ concentration infused in the NAC increased DA by 77%. These results suggest that nicotinic receptors in the somatodendritic region may be of greater importance than those located in the terminal area for the stimulatory action of systemic NIC on the mesolimbic DA system. Furthermore, our findings support the notion that the mesolimbic dopaminergic system is phasically rather than tonically regulated by nicotinic receptor activation within the VTA. © 1994 Wiley‐Liss, Inc.
“Strong” and “weak” synaptic differentiation in the crayfish opener muscle: Structural correlates
Authors: Govind C. K. , Pearce J. , Wojtowicz J. M. , Atwood H. L.
Published: December 2004

The single excitor motoneuron to the limb opener muscle in the crayfish Procambarus clarkii provides multiterminal innervation to individual muscle fibers. At low impulse frequencies, these neuromuscular synapses generate a threefold larger junctional potential in fibers of the proximal region of the muscle compared to those in the central region. Focal extracellular recording from synapse‐bearing “boutons” showed more quantal release at low frequencies in the proximal region. Structural correlates for the physiological differences were sought. Fluorescence microscopy of surface innervation stained with a vital fluorescent dye, 4‐Di‐2‐Asp, showed that density of innervation was not greater in the proximal region and thus could not account for the overall differences in synaptic strength. Freeze fracture studies showed that the intramembrane organization of excitatory synapses and their active zones was qualitatively similar in proximal and central sites. Serial section electron microscopy of several innervation sites in proximal and central regions showed homogeneity in number and size of synapses. However, presynaptic dense bars (at release sites, or active zones) were longer and occurred at a higher density in proximal than in central synapses. The differences in number and length of presynaptic dense bars correlate positively with the differences in synaptic strength represented by junctional potential amplitudes and quantal contents of individual surface recording sites. Since many individual proximal synapses have multiple dense bars, co‐operativity among these may serve to enhance transmitter output. It is concluded that occurrence of dense bars is a significant pre synaptic correlate of synaptic strength in this neuron. © 1994 Wiley‐Liss, Inc.
RTI‐4793‐14, a new ligand with high affinity and selectivity for the (+)‐MK801‐insensitive [3H]1‐[1‐(2 thienyl)cyclohexyl]piperidine binding site (PCP site 2) of guinea pig brain
Authors: Goodman Carl B. , Thomas D. Nigel , Pert Agu , Emilien Betsey , Cadet Jean L. , Carroll F. Ivy , Blough Bruce E. , Mascarella S. Wayne , Rogawski Michael A. , Subramaniam Swaminathan , Rothman Richard B.
Published: December 2004

[3H]TCP, an analog of the dissociative anesthetic phencyclidine (PCP), binds with high affinity to two sites in guinea pig brain membranes, one that is MK‐801 sensitive and one that is not. The MK‐801‐sensitive site (PCP site 1) is associated with NMDA receptors, whereas the MK‐801‐insensitive site (PCP site 2) may be associated with biogenic amine transporters (BAT). Although several “BAT ligands” are known that bind selectively to PCP site 2 and not to PCP site 1 (such as indatraline), these compounds have low affinity for site 2 (Ki values > 1 μ). Here we demonstrate that the novel pyrrole RTI‐4793‐14 is a selective, high affinity ligand for PCP site 2. We determined the IC50 values of RTI‐4793‐14 and several reference compounds [PCP, (+)‐MK801 and indatraline] for PCP site 1 (assayed with [3H](+)‐MK801), PCP site 2 (assayed with [3H]TCP in the presence of 500 nM (+)‐MK801) and a variety of BAT‐related measures ([3H]CFT binding to the DA transporter, [3H]nisoxetine binding to the norepinephrine transporter, [3H]dopamine uptake, [3H]serotonin uptake). In addition, we determined the ability of RTI‐4793‐14 to block NMDA responses in cultured hippocampal neurons under voltage clamp. (+)‐MK801 had high affinity for PCP site 1 (4.6 nM) and potently inhibited NMDA‐induced responses, but was much less potent in the BAT‐related measures (IC50s > 10 μ). PCP had high affinity at PCP site 1 (IC50 = 92 nM) and PCP site 2 (IC50 = 117 nM), and was moderately potent in all BAT‐related measures except [3H]nisoxetine binding. Indatraline was potent in BAT‐related measures (IC50s, 2 to 5 nM), but weak in other measures (IC50s > 1 μ). In contrast, RTI‐4793‐14 had high affinity for PCP site 2 (38 nM), low affinity for PCP site 1 (> 36 μ), moderate IC50s for all BAT‐related measures, and negligible activity at NMDA receptors. Viewed collectively, these data indicate that RTI‐4793‐14 binds with high affinity and selectivity to PCP site 2 and provide further support for an association between PCP site 2 and the BATs. © 1994 Wiley‐Liss, Inc.
Activation of NMDA receptors in hippocampal area CA1 by low and high frequency orthodromic stimulation and their contribution to induction of long‐term potentiation
Authors: Grover Lawrence M. , Teyler Timothy J.
Published: December 2004

N‐methyl‐D‐aspartate (NMDA) receptors are important in many instances of synaptic plasticity. In hippocampal area CA1, long‐term potentiation (LTP) can be induced by both NMDA receptor‐dependent and ‐independent mechanisms. Using intracellular recordings and single‐electrode voltage clamp, we isolated and characterized NMDA receptor‐mediated synaptic responses. NMDA receptor‐mediated responses evoked by low frequency orthodromic stimulation were inhibited in a dose‐dependent manner by the competitive antagonist D,L‐2‐amino‐5‐phosphonovaleric acid (APV). High frequency (tetanic) stimulation, which facilitates synaptic release of glutamate, failed to overcome the blockade of NMDA receptors by APV. Using extracellular recordings of field potentials, we studied the contribution of NMDA receptors to LTP induced by different patterns of tetanic stimulation. LTP was inhibited in a dose‐dependent manner by APV, but was more sensitive to APV than were NMDA receptor‐mediated synaptic responses. This most likely reflects a threshold for NMDA receptor activation in LTP induction. A component of LTP that resisted blockade by APV was induced by high (200 Hz), but not low (25 Hz), frequency tetanization. This NMDA receptor‐independent component of LTP persisted for > 4 hours and accounted for approximately half the potentiation induced by 200 Hz tetanization. Procedures necessary to induce LTP at the Schaffer collateral/ commissural synapses in area CA1 by both NMDA receptor‐dependent and ‐independent mechanisms are now well characterized. Using the same neuronal population, it will be possible to ask if processes involved in the maintenance of LTP are shared even when LTP is induced through two different mechanisms. © 1994 Wiley‐Liss, Inc.