Expression Of GABAA Receptor Subunit mRNAs Research Articles

Hemisphere-dependent Changes in mRNA Expression of GABAA Receptor Subunits and BDNF after Intra-prefrontal Cortex Allopregnanolone Infusion in Rats

Allopregnanolone is a neurosteroid implicated in mood disorders such as depression and anxiety. It acts as a GABAA receptor (GABAAR)-positive allosteric modulator and changes the expression of GABAAR subunits and of brain-derived neurotrophic factor (BDNF) in different brain regions. It has been demonstrated that such neurochemical changes may have an asymmetrical pattern regarding brain hemispheres. The aim of this study was to verify the behavioral and hemisphere-specific neurochemical effects of the bilateral intra-prefrontal cortex (intra-PFC) infusion of allopregnanolone in rats. Rats were exposed to the forced swim test and to the grooming microstructure test, followed by the right and left hemisphere-specific quantification of mRNA expression by Real-Time PCR of δ and γ2 GABAAR subunits and BDNF in the PFC and in the hippocampus. Though we did not observe any significant effects in the behavioral tests, intra-PFC allopregnanolone infusion bilaterally increased the mRNA expression of the δ subunit in the same area and of BDNF in the hippocampus. Both mRNA expressions of the γ2 subunit and BDNF were higher in the right than in the left PFC of control animals, and the hemisphere differences were not seen after allopregnanolone infusion. Overall hippocampal BDNF expression was also higher in the right hemisphere, but this asymmetry was not normalized by allopregnanolone. No asymmetries or changes were observed in the hippocampal mRNA expression of GABAAR subunits. These results point to a hemisphere-dependent regulation of GABAAR subunits and BDNF that can be modulated by intra-PFC allopregnanolone infusion, even in the absence of associated behavioral effects.

Zolpidem withdrawal induced uncoupling of GABA<sub>A</sub> receptors in vitro associated with altered GABA<sub>A</sub> receptor subunit mRNA expression

Hypnotic zolpidem produces its effects via the benzodiazepine binding site in α1-containing GABAA receptors. The aim of the study was to assess the influence of duration of zolpidem treatment and its withdrawal, as well as the role of alpha1-containing GABAA receptors in the development of physical dependence and tolerance. Namely, recombinant receptors can be used to characterize mechanisms involved in different processes in the brain and to delineate the contribution of specific receptor subtypes. To address the influence of chronic zolpidem treatment we exposed HEK293 cells stably expressing alpha1beta2gamma2S recombinant GABAA receptors for seven consecutive days, while withdrawal periods lasted for 24, 48, 72 and 96 hours. Using radioligand binding studies we determined that chronic zolpidem treatment did not induce changes in either GABAA receptor number or in the expression of subunit mRNAs. We observed the enhancement of binding sites and upregulated expression of subunit mRNAs only following 96-hour withdrawal. Moreover, zolpidem treatment and its withdrawal (All time points) induced functional uncoupling between GABA and benzodiazepine binding sites in the GABAA receptor complex. Accordingly, it might be assumed that zolpidem withdrawal-induced uncoupling of GABAA receptors is associated with altered GABAA receptor subunit mRNA expression. The results presented here provide an insight into molecular and cellular mechanisms probably underlying adaptive changes of GABAA receptor function in response to chronic usage and withdrawal of zolpidem and perhaps the observed molecular changes could be linked to the tolerance and dependence produced upon prolonged treatment with other GABAergic drugs.

The effect of intra-nucleus accumbens administration of allopregnanolone on δ and γ2 GABAA receptor subunit mRNA expression in the hippocampus and on depressive-like and grooming behaviors in rats

Alterations in GABAA receptor expression have been associated with the allopregnanolone (3α-hydroxy-5α-pregnan-20-one; 3α,5α-THP) antidepressant-like effect in rats. The present study aimed to verify the effect of bilateral, intra-nucleus accumbens core (intra-AcbC) administration of the neurosteroid allopregnanolone on behaviors in the forced swim and grooming microstructure tests and in the δ and γ2 GABAA receptor subunit mRNA expression in right and left hippocampus of rats. The results of this study showed that bilateral, intra-AcbC allopregnanolone administration (5μg/rat) presented antidepressant‐like activity in the forced swim test concomitant with an increase in climbing. Allopregnanolone at doses of 1.25 and 5μg/rat also decreased the percentage of correct transitions in the grooming microstructure test. Both δ and γ2 GABAA subunit expressions increased in the rat hippocampus after allopregnanolone intra-AcbC treatment. Our findings point to asymmetrical GABAA receptor expression changes in the hippocampus of animals treated with allopregnanolone. Further investigation should evaluate the antidepressant-like effect of allopregnanolone not only in other directly infused regions but also with respect to changes in other brain areas of the limbic system to understand allopregnanolone's mechanism of action.

Stressor exposure of male and female juvenile mice influences later responses to stressors: Modulation of GABAA receptor subunit mRNA expression

Stressors encountered during the juvenile period may have persistent effects on later behavioral and neurochemical functioning and may influence later responses to stressors. In the current investigation, we evaluated the influence of stressor exposure applied during the juvenile period (26–28days of age) on anxiety-related behavior, plasma corticosterone and on GABAA α2, α3, α5 and γ2 mRNA expression within the prefrontal cortex (PFC) and amygdala measured during adulthood. These changes were monitored in the absence of a further challenge, as well as in response to either a social or a non-social psychogenic stressor administered during adulthood. Exposure to an acute adult stressor elicited anxiety in females and was still more pronounced among females that had also experienced the juvenile stressor. Among males, arousal and impulsivity predominated so that anxiety responses were less notable. Furthermore, experiencing the stressor as a juvenile influenced adult GABAA subunit expression, as did the adult stressor experience. These changes were differentially expressed in males and females. Moreover, these subunit variations were further moderated among mice that stressed as juveniles and were again exposed to an adult stressor. Interestingly, under conditions in which the juvenile stressor increased the expression of a particular subunit, exposure to a further stressor in adulthood resulted in the γ-aminobutyric acid (GABA) subunit variations being attenuated in both sexes. The current results suggest that juvenile and adult stressor experiences elicit variations of GABAA receptor subunit expression that are region-specific as well as sexually-dimorphic. Stressful events during the juvenile period may have pronounced proactive effects on anxiety-related behaviors, but linking these to specific GABAA subunits is made difficult by the diversity of GABA changes that are evident as well as the dimorphic nature of these variations. Nevertheless, these GABAA sex-specific subunit variations may be tied to the differences in anxiety in males and females.

GABA system changes in methylphenidate sensitized female rats

Methylphenidate (MPD) is a psychostimulant that is prescribed to treat attention-deficit/hyperactivity disorder (ADHD) and has been used as a recreational drug. In animal models, repetitive exposure to methylphenidate can induce a behavioral sensitization. Stimulants are able to change neuronal circuits in the mesolimbic pathway, and the GABA system is one of the most involved neurotransmitter systems in this process. Women represent a risk group for psychostimulant abuse because they respond more strongly, which is probably due to the influence of sex hormones. The objective of the present study was to investigate the influence of sex hormones on behavioral sentsitization and changes to glutamic acid decarboxylase (GDA65 and GDA67) isoenzymes and α2 GABAA receptor subunit mRNA expression in the prefrontal cortex and the striatum of rats, as induced by methylphenidate administration (2.5mg/kg, i.p.). Female rats were divided into 2 hormonal conditions: ovariectomized and intact group. Repeated methylphenidate treatment led to behavioral sensitization, which was stronger in females with circulating hormones (intact group). The analysis of mRNA levels in the striatum, in both groups, showed a decline in GAD65, but not GAD67, transcription after repeated methylphenidate treatment. In the prefrontal cortex, both GAD65 and GAD67 showed an increase in transcription with repeated methylphenidate treatment. There was no change in the transcription level of α2 GABAA receptor subunits. In conclusion, it was shown that sex hormones were able to modify behavioral sensitization to methylphenidate and the drug affected the GABA system in brain areas known to be involved in the development of drug dependence.

Transient change in GABAA receptor subunit mRNA expression in Lurchercerebellar nuclei during Purkinje cell degeneration

BackgroundLurcher mice suffer from a complete Purkinje cell (PC) loss in the first four postnatal weeks. Parallel to this degeneration, GABAergic synapses in the deep cerebellar nuclei (DCN), the major recipient of the inhibitory PC projection, increase synaptic conductance. Here, we further investigated this phenomenon, using real-time RT-PCR to assess GABAA receptor subunit gene expression during PC degeneration.ResultsWe observed a specific reduction in γ2 subunit gene expression, while α1–5, β1–2, γ1,3 and δ subunits were unaffected. We made two further specific findings. First, the difference in gene expression was shown in tissue from DCN only. Neither the hippocampus nor coronal sections through the forebrain showed such effects. Furthermore, the involvement of different levels of corticosterone, a possible humeral trigger for differences in gene expression, could be excluded. Second, like the known potentiation of GABAergic synapses, the γ2 down-regulation was present only after the onset of degeneration at p14. The difference in γ2 mRNA expression, however, appeared transient, since it was no longer detectable in adult Lurcher mice.ConclusionIn conclusion, the down-regulation of γ2 subunits may be related to differences in synaptic efficacy and, as such, may reflect the initial phase of adaptive responses of DCN tissue to massive GABAergic deafferentation. Its transient course, however, does not support the idea that modulations in GABAergic transmission are at the basis of the well-known DCN-based functional benefit of Lurcher mice present throughout their life.

In situ hybridization histochemistry as a method to assess GABA(A) receptor subunit mRNA expression following chronic alprazolam administration.

Previous work in our laboratory has demonstrated region-specific effects for chronic alprazolam on binding and function at the GABA(A) receptor. The present study evaluated regional changes in mRNA expression of several subunits of the GABA(A) receptor following chronic alprazolam administration that might underlie these effects. Mice received alprazolam (2 mg/kg/day) or vehicle via subcutaneously implanted osmotic pumps for 1, 7, 14 or 28 days. In situ hybridization histochemistry was performed on tissue sections using [35S]dATP oligonucleotide probes corresponding to the alpha1 and gamma2 subunits of the GABA(A) receptor. Specific hybridization was clearly demonstrated and alpha1 subunit mRNA expression in frontoparietal cortex (layers II-IV) on day 1 of infusion was reduced in animals receiving alprazolam compared to vehicle. On subsequent days, there were no alterations in the levels of alpha1 subunit mRNA in the frontoparietal cortex, hippocampus or dentate gyrus. Expression of gamma2 subunit mRNA was increased on day 1 in the frontoparietal cortex (layer VI), hippocampus and dentate gyrus. mRNA expression was also increased in the dentate gyrus on day 28 of infusion. Comparison of the present study with the results of chronic treatment with other benzodiazepines clearly demonstrates that the pattern of mRNA subunit alterations obtained is both treatment- and region-specific. This makes a definitive conclusion regarding benzodiazepines and their interactions with GABA(A) receptors difficult at best.

Regulation of GABAA receptor subunit mRNA expression by the pesticide dieldrin in embryonic brainstem cultures: A quantitative, competitive reverse transcription‐polymerase chain reaction study

Cyclodiene organochlorine pesticides, such as dieldrin, inhibit γ-aminobutyric acid (GABA)ergic neurotransmission by blocking the Cl− channel of GABAA receptors. This action may make the developing nervous system especially vulnerable to these neurotoxins, which could interfere with the trophic actions of GABA on developing neurons and alter expression of GABAA receptors. We have used an in vitro model to determine whether exposure to dieldrin alters developmental expression of GABAA receptor subunit mRNA transcripts. Dissociated cell cultures were prepared from embryonic day 14 (E14) brainstem and cultured in serum-containing medium for 1 day in vitro (DIV), then treated for 2 DIV with 10 μM dieldrin in serum-free medium. This dose was based on preliminary experiments and previous studies (Nagata et al.: Brain Res 645:19–26, 1994; Pomes et al.: J Pharmacol Exp Ther 271:1616–1623, 1994). Absolute amounts of α1, β3, γ1, γ2S and γ2L mRNA transcripts were quantified in these cultures by quantitative, competitive reverse transcription–polymerase chain reaction (RT-PCR) using subunit-selective internal standards. The most abundant GABAA subunit transcript was β3, which was much more highly expressed than γ2S, γ1, γ2L, or α1 subunit mRNAs. Dieldrin differentially regulated expression of these transcripts. Levels of β3 subunit transcripts were significantly increased (by 300%) by dieldrin, whereas expression of γ2S and γ2L transcripts were decreased (by 50% and 40%, respectively). However, dieldrin did not alter the ratio of γ2S to γ2L transcripts, indicating that it did not affect alternative splicing of γ2 transcripts. Dieldrin appeared to increase expression of α1 subunit transcripts, but this effect was not statistically significant. Dieldrin did not significantly alter expression of γ1 subunit transcripts. These results support the hypothesis that in utero exposure to cyclodiene pesticides could pose a risk to the developing brain by virtue of their ability to alter gene expression of GABAA receptor subunits, which could produce GABAA receptors with altered functional properties. J. Neurosci. Res. 49:645–653, 1997. © 1997 Wiley-Liss, Inc.

Regulation of GABAA receptor subunit mRNA expression by the pesticide dieldrin in embryonic brainstem cultures: A quantitative, competitive reverse transcription-polymerase chain reaction study

Cyclodiene organochlorine pesticides, such as dieldrin, inhibit gamma-aminobutyric acid (GABA)ergic neurotransmission by blocking the Cl- channel of GABA(A) receptors. This action may make the developing nervous system especially vulnerable to these neurotoxins, which could interfere with the trophic actions of GABA on developing neurons and alter expression of GABA(A) receptors. We have used an in vitro model to determine whether exposure to dieldrin alters developmental expression of GABA(A) receptor subunit mRNA transcripts. Dissociated cell cultures were prepared from embryonic day 14 (E14) brainstem and cultured in serum-containing medium for 1 day in vitro (DIV), then treated for 2 DIV with 10 microM dieldrin in serum-free medium. This dose was based on preliminary experiments and previous studies (Nagata et al.: Brain Res 645:19-26, 1994; Pomes et al.: J Pharmacol Exp Ther 271:1616-1623, 1994). Absolute amounts of alpha1, beta3, gamma1, gamma2S and gamma2L mRNA transcripts were quantified in these cultures by quantitative, competitive reverse transcription-polymerase chain reaction (RT-PCR) using subunit-selective internal standards. The most abundant GABA(A) subunit transcript was beta3, which was much more highly expressed than gamma2S, gamma1, gamma2L, or alpha1 subunit mRNAs. Dieldrin differentially regulated expression of these transcripts. Levels of beta3 subunit transcripts were significantly increased (by 300%) by dieldrin, whereas expression of gamma2S and gamma2L transcripts were decreased (by 50% and 40%, respectively). However, dieldrin did not alter the ratio of gamma2S to gamma2L transcripts, indicating that it did not affect alternative splicing of gamma2 transcripts. Dieldrin appeared to increase expression of alpha1 subunit transcripts, but this effect was not statistically significant. Dieldrin did not significantly alter expression of gamma1 subunit transcripts. These results support the hypothesis that in utero exposure to cyclodiene pesticides could pose a risk to the developing brain by virtue of their ability to alter gene expression of GABA(A) receptor subunits, which could produce GABA(A) receptors with altered functional properties.

GABA and epileptogenesis.

GABA and epileptogenesis.

In vivo regulation of specific GABAA receptor subunit messenger rnas by increased gaba concentrations in rat brain

This study has examined whether changes in endogenous GABA concentrations influence GABAA receptor subunit mRNA expression in vivo. Increased GABA concentrations were achieved by treating female rats with gamma-vinyl-GABA (15 mg/100 g), an irreversible inhibitor of the GABA transaminase, daily for three days. High performance liquid chromatography analysis of brain punches from specific brain regions showed that gamma-vinyl-GABA treatment resulted in approximately two-fold increases in brain GABA content. Using in situ hybridization techniques with specific 35S-labelled oligonucleotides, the mRNA expression of the alpha 1, alpha 2, beta 2, beta 3, gamma 1 and/or gamma 2 subunits of the GABAA receptor was quantified in various brain regions including the medial preoptic nucleus, bed nucleus of the stria terminalis, bed nucleus of the anterior commissure, supraoptic and paraventricular nuclei of the hypothalamus, globus pallidus and cingulate cortex. Silver grain density analysis showed that gamma-vinyl-GABA treatment induced a significant 35 and 49% decrease in gamma 1 mRNA expression in the medial preoptic nucleus and the principle encapsulated nucleus of the bed nucleus of the stria terminalis respectively, and a significant 20% decrease in alpha 2 mRNA expression in the cingulate cortex. Expression of alpha 2 and beta 3 in the former areas was unchanged as was alpha 1, beta 2, beta 3 and gamma 2 subunit expression in the cingulate cortex. Elevation of brain GABA levels also resulted in a specific and significant 17% increase in gamma 2 mRNA expression in the supraoptic nucleus. In the globus pallidus, gamma-vinyl-GABA treatment induced a significant 29% increase in alpha 1 mRNA expression combined with 19 and 30% decreases in beta 2 and gamma 2 mRNA expression, respectively. Levels of GABAA receptor subunits expressed in the bed nucleus of the anterior commissure (alpha 2, beta 3, gamma 1) and paraventricular nucleus (alpha 1, alpha 2, beta 2, gamma 2) were not changed by gamma-vinyl-GABA treatment. These results provide in vivo evidence for a region- and subunit-specific regulation of GABAA receptor subunit mRNA levels following the elevation of brain GABA concentrations and suggest that endogenous GABA levels influence GABAA receptor subunit mRNA expression.

Reversible Modification of GABAA Receptor Subunit mRNA Expression During Tolerance to Diazepam-induced Cognition Dysfunction

Benzodiazepines (BZs) that are endowed with full positive allosteric modulatory (FAM) activity on GABAA receptors cause anterograde amnesia in both animals and humans. In rats subjected to a delayed object recognition test, diazepam, endowed with FAM activity, exerted an amnesic action, whereas BZs endowed with partial allosteric modulatory (PAM) activity on GABAA receptors, such as imidazenil, failed to induce amnesia, even if administered at doses five times higher than those equipotent to a standard anticonvulsant dose of diazepam (17.6 μmol/kg/os). After discontinuation of 14 days' treatment with vehicle, diazepam, or imidazenil (three times daily with increasing doses starting from 17.6 μmol/kg/os for diazepam and 2.5 μmol/kg/os for imidazenil), we compared the persistence of tolerance to the amnesic effect of diazepam with the persistence of the changes in the content of four (α1, α5, γ2L, γ2S) GABAA receptor subunit mRNAs in the fronto-parietal motor (FrPaM) cortex and the hippocampus. Rats receiving the long-term treatment with diazepam developed a tolerance to the amnesic effect of this drug and showed a decrease (30–50%) in the expression of mRNAs encoding for α1, γ2L, γ2S GABAA receptor subunits, an increase, by approximately 30%, of the expression of mRNA of the α5 subunit in the FrPaM cortex and a decrease, by approximately 25%, in the expression of mRNA, of the α1 subunit in the hippocampus. These changes of subunit mRNA expression and the tolerance to the amnesic effect of diazepam returned to control values 72 hr after termination of the long-term treatment with diazepam. No tolerance to the amnesic effect of diazepam and no changes in GABAA receptor subunit mRNA expression were found in rats undergoing long-term treatment with imidazenil. Copyright © 1996 Elsevier Science Ltd

GABAA receptor subunit mRNA expression in the weaver cerebellum: modulation by cell-cell interactions

Recent studies have suggested that the developmental expression of GABA A receptor subunit mRNAs in cerebellar Purkinje neurons is modulated by cell-cell interacactions. In this population, the levels of mRNAs encoding the α1, β2, and γ2 subunits increase simultaneously during the second week of postnatal ontogeny, a period temporally coincident with cerebellar maturation and synapse formation. To determine the importance of cell-cell interactions in modulating receptor gene expression, the levels of GABA A receptor subunit mRNAs in Purkinje neurons of weaver mice and littermate controls were examined by quantitative in situ hybridization histochemistry. In the weaver mutant most granule neurons die early in postnatal development, thus eliminating the major source of excitatory input to Purkinje cells. Despite this loss, the three subunit mRNAs were expressed in all Purkinje neurons. However, the levels of expression were generally lower in the mutants than in the littermate controls. These results suggest that the onset of GABAA receptor gene expression in cerebellar Purkinje neurons occurs in the absence of extensive synapse formation by mechanisms which may be intrinsic to the neurons. In contrast, the absolute level of transcript expression attained appears to be modulated by cell-cell interactions or by other extrinsic cues present in the cerebellar environment.

Estrogen regulation of GABAA receptor subunit mRNA expression in preoptic area and bed nucleus of the stria terminalis of female rat brain

This study has examined whether circulating estrogens are involved in regulating gamma-aminobutyric acid (GABA)A receptor mRNA expression in regions of the female rat brain known to contain estrogen receptors (ERs). In situ hybridization experiments using 35S-labeled oligonucleotides specific for alpha 2, beta 3, and gamma 1 subunit mRNAs of the GABAA receptor demonstrated that all three mRNAs were abundant in only the medial preoptic nucleus (MPN), where they were expressed by the vast majority of cells, and specific regions of the bed nucleus of the stria terminalis including the principle encapsulated nucleus (PrN-BNST) and bed nucleus of the anterior commissure (BNAC). Estrogen treatment of ovariectomized rats for 7 d resulted in significant 30-60% increases in alpha 2 and gamma 1, but not beta 3, subunit mRNA expression in the MPN and PrN-BNST. Estrogen treatment for 24 hr resulted in levels of mRNA expression intermediate between those of controls and animals treated with estrogen for 7 d. No changes in subunit mRNA expression were detected for any subunit in the BNAC or cingulate cortex. Double-labeling immunocytochemistry experiments using antibodies directed against the alpha 2 subunit of the GABAA receptor and the ER, revealed that 67 +/- 3% of alpha 2 subunit-immunoreactive cells in the MPN also contained ER immunoreactivity. Cells expressing alpha 2 subunits in the PrN-BNST were also found to possess ERs while those in the BNAC and cingulate cortex did not. These findings suggest the possibility that ER-containing cells in the MPN and PrN-BNST express an alpha 2 beta 3 gamma 1 isoform of the GABAA receptor that has its alpha 2 and gamma 1 subunits regulated by circulating estrogen concentrations. Together, our observations indicate that estrogen may regulate GABAA receptor mRNA expression at a transcriptional level and that this is only likely to occur within regions of the rat brain possessing ERs.

Rapid decline of GABAA receptor subunit mRNA expression in hippocampus following transient cerebral ischemia in the gerbil.

Inhibitory neurotransmission may play an important role in neuronal degeneration following transient cerebral ischemia. We studied the effect of transient forebrain ischemia on the GABAA receptor system in the gerbil hippocampus. Gerbils were subjected to 5 minutes of bilateral carotid occlusion and were sacrificed at various times over 4 days following reperfusion. There was a substantial loss of pyramidal cells in the CA1 area of the hippocampus 4 days following ischemia. No cell loss was detected in CA3 pyramidal cells of the hippocampus, granule cell layer of the dentate gyrus, and ventroposterior medial and ventroposterior lateral nuclei of the thalamus at any time following ischemia. Examination of brain slices by in situ hybridization histochemistry revealed that a change in expression of the GABAA receptor alpha 1 and beta 2 subunit mRNAs occurred in two phases following onset of reperfusion. The early phase (rapid) occurred within the first 4 hours following reperfusion. The expression of mRNAs significantly decreased (up to 25%) within 1 hour after occlusion in CA1 and CA3 pyramidal cell layers of the hippocampus and in the granule cell layer of the dentate gyrus. The expression of the mRNAs in these regions continued to decrease for 4 hours (up to 43%). In the second phase, which began between 4 and 12 hours following reperfusion, mRNA expression started to return to control levels in CA3 hippocampus and in the dentate. However, expression of both mRNAs continued to decline slowly in the CA1 pyramidal cell layer (up to 85%) over the next 3 days, concomitantly with degeneration of the CA1 pyramidal cells. Expression of mRNAs in the ventroposterior medial or ventroposterior lateral nuclei of the thalamus was similar to control values. To determine if a change in GABAA receptor distribution paralleled changes in receptor subunit mRNA expression, we also measured the binding of [35S]t-butylbicyclophosphorothionate to GABAA receptor chloride channels. The t-butylbicyclophosphorothionate [35S] binding decreased between 1 and 4 days after reperfusion in the dendritic fields of CA1 pyramidal cells (strata oriens, radiatum, and lacunosum-moleculare) but not in the pyramidal cell body layer. These results indicate that expression of GABAA receptor subunit mRNAs decrease well before CA1 pyramidal cell degeneration and loss of GABAA receptors. At present, it is not clear if an early loss of mRNA expression after an ischemic insult leads to a functional defect in GABAA receptors. If so, a loss of GABA neurotransmission may contribute to the development of neuronal degeneration following cerebral ischemia.(ABSTRACT TRUNCATED AT 400 WORDS)

Developmental cues modulate GABAA receptor subunit mRNA expression in cultured cerebellar granule neurons

The developmental expression of mRNAs encoding the GABAA receptor was analyzed in the rat cerebellar cortex and in cultured cerebellar granule neurons. Our studies in vivo reveal that the alpha 1-, beta 2-, and gamma 2-subunit mRNA levels in the cerebellar cortex rise dramatically during the second post-natal week, a period temporally correlated with extensive cerebellar maturation. To determine if these increases were preprogrammed or dependent on extrinsic factors, we examined subunit mRNA expression in granule cell cultures prepared at embryonic day 19 (E19) and postnatal day 10 (P10), immature and mature stages of cerebellar development, respectively. In E19 cultures, the alpha 1, beta 2, and gamma 2 GABAA receptor subunit mRNAs were present and their levels remained constant over the 21 d culture period. These results suggest that GABAA receptor gene expression is not intrinsic to the immature granule cells. A different pattern was found in P10 cultures where the three subunit mRNAs were initially present at levels approximately sixfold higher than those found at E19. The beta 2- and gamma 2-subunit mRNAs remained constant for 4 d and then increased sixfold between 4 and 7 d in culture. The magnitude and time course of these increases were similar to the developmental changes that occurred in vivo. Thus, our findings raise the possibility that signals encountered during development are necessary to induce GABAA receptor subunit mRNA expression. Moreover, these cues have been received by granule neurons prior to P10.(ABSTRACT TRUNCATED AT 250 WORDS)

Discontinuation of alprazolam treatment in panic patients.

Alprazolam treatment was tapered in 17 panic patients at a rate of 10% of the starting dose every 3 days. Only four subjects completed withdrawal on schedule (4-5 weeks); four additional subjects discontinued treatment in 7-13 weeks. During withdrawal 15 patients had recurrent or increased panic attacks and nine had significant new withdrawal symptoms. Most common among the latter were malaise, weakness, insomnia, tachycardia, lightheadedness, and dizziness. None had seizures, psychosis, or significant neurological or EEG abnormalities. Results indicate that relapse and withdrawal are important considerations in the choice of alprazolam treatment for panic attacks.