Functional properties of GABAA receptors in two rat lines selected for high and low alcohol sensitivity.

The effects of lorazepam and sodium barbital on GABAA receptor function were evaluated in rat lines selected for differential sensitivity to the motor-impairing effects of ethanol [alcohol-insensitive (AT) and alcohol-sensitive (ANT) lines]. The effect of GABA on [3H]flunitrazepam and [3H]Ro 15-4513 binding and the effects of lorazepam and sodium barbital on [3H]muscimol binding were measured in cerebellar, cerebrocortical, and hippocampal membrane preparations. The effects of lorazepam and sodium barbital on muscimol-stimulated 36Cl- influx were measured using membrane vesicle suspensions from the same brain areas. No differences were found between the rat lines in the GABA-induced stimulation of [3H]flunitrazepam binding or in the lorazepam and sodium barbital-induced enhancement of either [3]muscimol binding or muscimol-stimulated 36Cl- flux. Neither was desensitization of the 36Cl- flux affected differently by ethanol, lorazepam, and barbital in vitro between the lines. The affinity of cerebellar diazepam-insensitive (DZ-IS) [3H]Ro 15-4513-binding sites for benzodiazepine agonists has been shown to be much greater in the ANT than the AT rats. In the present study, at 0 degrees C, GABA decreased [3H]Ro 15-4513 binding in the presence of diazepam only in ANT rats. Similarly, GABA decreased this binding at 37 degrees C in ANT rats having a high affinity for diazepam, whereas it enhanced the binding in all AT samples in those ANT samples where diazepam had a poor AT-like affinity. The decrease in binding in ANT samples is apparently caused by the enhancing effect of GABA on diazepam binding to DZ-IS [3H]Ro 15-4513-binding sites.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cerebellar GABAA receptors in two rat lines selected for high and low sensitivity to moderate alcohol doses: pharmacological and genetic studies.

Alcohol-sensitive (ANT) rat line produced by selective outbreeding for high acute sensitivity to the motor-impairing effects of ethanol, displays unusual cerebellar GABAA receptor pharmacology. The ANT rats have enhanced benzodiazepine agonist affinity at their binding sites for an imidazobenzodiazepine, [3H]Ro 15-4513, normally not affected by agonists at all, and reduced GABAA agonist, [3H]muscimol, binding, when compared to the alcohol-insensitive (AT) rat line. In the present study, the benzodiazepine receptor difference was localized to the cerebellar granule cell layer. This receptor difference was not found in ex vivo binding studies after lorazepam administration, although brain lorazepam concentrations in both rat lines similarly exceeded 1 microM. An indication for differential binding in vivo between the lines was, however, observed, as pretreatment with lorazepam accentuated the relative accumulation of radioactivity only in the cerebellum of the AT rat line after an intravenous injection of a trace amount of [3H]Ro 15-4513, thus revealing benzodiazepine insensitivity for a portion of the cerebellar [3H]Ro 15-4513 binding in the AT but not in the ANT rats. In the second generation of AT/ANT cross-breeding, there was no clear association of alcohol sensitivity and cerebellar receptor binding. There was, however, a significant positive correlation between the [3H]muscimol binding and the diazepam-insensitive [3H]Ro 15-4513 binding in the cerebellum. In conclusion, the receptor defect in the cerebellar granular cell layer of the alcohol-sensitive ANT rats was also detectable in vivo, but it may not explain the enhanced alcohol sensitivity of these rats.     

Cation modulation of GABA(A) receptors in brain sections of AT and ANT rats.

Changes in magnesium ion (Mg(2+)) concentration may be implicated in alcohol-related behaviors through modulation of neuronal excitability by actions on ligand-gated ion channels. To study whether putative Mg(2+)-binding sites differ between two rat lines, alcohol-insensitive (AT) and alcohol-sensitive (ANT) rats, selectively outbred for differential sensitivity to the motor-impairing effect of ethanol, we compared the effect of Mg(2+) on [35S]tert-butylbicyclophosphorothionate ([35S]TBPS) binding to GABA(A) receptors with the use of ligand autoradiographic analyses of brain sections from these rats. There were some slight differences between the rat lines in modulation of the binding in the forebrain. A low concentration of Mg(2+) (0.1 mM) inhibited basal [35S]TBPS binding more efficiently in the central gray matter and hippocampus in the ANT rats than in the AT rats. In the presence of gamma-aminobutyric acid, the effect of a low concentration of Mg(2+) was higher in the caudate-putamen and inner layer of the cerebral cortex in the AT rats than in the ANT rats. No difference between the rat lines was found at a higher (3 mM) Mg(2+) concentration. Furosemide, a GABA(A) antagonist selective for cerebellar granule cell-specific alpha6beta2/3 subunit-containing receptors, was less efficient in antagonizing the Mg(2+)-induced inhibition of [35S]TBPS binding in the ANT rats than in the AT rats. Another divalent cation, zinc ion, was less efficient in displacing [35S]TBPS binding from the cerebellar granule cell layer in the ANT rats than in the AT rats, whereas a trivalent cation, lanthanum ion, produced identical modulation of the binding in the two rat lines. The results indicate that the alcohol-sensitive ANT rats have altered cerebellar granule cell--specific alpha6 subunit--containing GABA(A) receptors and seem to indicate that these receptors might be implicated in the sensitivity difference of the rat lines to ethanol and sedative drugs.     

Ethanol-induced alterations in the function of cerebral GABAA receptor complex: effect on GABA-dependent 36Cl- influx into cerebral membrane vesicles.

Effect of addition in vitro of ethanol on the functions of the GABAA receptor complex was investigated using synaptic membrane preparation obtained from mouse brain. Ethanol (50-200 mM) had no significant effect on the specific bindings of [3H]muscimol to GABAA receptor and [3H]flunitrazepam to benzodiazepine receptor in cerebral particulate preparations. However, ethanol induced an inhibition of [3H]TBOB binding to Cl- channel and a suppression of flunitrazepam-induced enhancement of [3H]muscimol binding and of salsolinol-induced accentuation of [3H]flunitrazepam binding to cerebral particulate fraction. In contrast, ethanol facilitated GABA-dependent 36Cl- influx but eliminated the stimulatory effects of flunitrazepam and salsolinol on GABA-dependent 36Cl- influx into cerebral membrane vesicles. These results suggest that ethanol may facilitate the function of GABA-gated chloride channel in spite of inducing deteriorations of antagonist binding capacity of chloride channel as well as of the functional coupling between GABAA receptor and benzodiazepine receptor in the brain.     

Furosemide action on cerebellar GABA(A) receptors in alcohol-sensitive ANT rats.

Furosemide increases the basal tert-[35S]butylbicyclophosphorothionate ([35S]TBPS) binding and reverses the inhibition of the binding by gamma-aminobutyric acid (GABA) in the cerebellar GABA(A) receptors containing the alpha6 and beta2/beta3 subunits. These effects are less pronounced in the alcohol-sensitive (ANT) than in the alcohol-insensitive (AT) rat line. The difference between the rat lines in the increase of basal [35S]TBPS binding was removed after a longer preincubation with ethylendiaminetetraacetic acid (EDTA) containing buffer, but long preincubation did not reduce the GABA content of the incubation fluid or remove the difference in GABA antagonism by furosemide. The GABA sensitivity of the [35S]TBPS binding did not differ between the rat lines. There was no nucleotide sequence difference in the beta2 or beta3 subunits between the rat lines and similar beta2/3 subunit-dependent agonistic actions by methyl-6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (DMCM) in the rat lines were detected. The data suggest that there are still unknown structural alterations in the cerebellar GABA(A) receptors between the AT and ANT rat lines, possibly associated with differential alcohol sensitivity.     

Synaptosomal sodium channels in rat lines selected for alcohol-related behaviors

Alcohol has been shown to inhibit veratridine- and batrachotoxin-stimulated sodium flux in rodent brain synaptosomes. In this study, binding of [3H]batrachotoxinin A 20-alpha-benzoate ([3H]BTX-B) and uptake of [14C]guanidine in cerebrocortical synaptosomes were measured in naive rats belonging to lines with high or low acute sensitivity to ethanol (ANT, Alcohol Non-Tolerant, vs. AT, Alcohol Tolerant, lines) and to lines with high or low voluntary alcohol consumption (AA, Alko Alcohol, vs. ANA, Alko Non-Alcohol, lines). Our rat line pairs did not differ in the equilibrium binding characteristics of [3H]BTX-B nor in the properties of [14C]guanidine uptake, suggesting that the genetic selection has not modulated the genes or the expression of the genes associated with the voltage-sensitive sodium channels.     

The cerebellar GABAAR α6-R100Q polymorphism alters ligand binding in outbred Sprague–Dawley rats in a similar manner as in selectively bred AT and ANT rats

The alcohol-tolerant AT and alcohol-nontolerant ANT rat lines have been selectively bred for innate sensitivity to ethanol-induced motor impairment. The cerebellar GABA_A receptor (GABA_AR) α6 subunit alleles α6-100R and α6-100Q are segregated in the AT and ANT rats, respectively. This α6 polymorphism might explain various differences in pharmacological properties and density of GABA_ARs between the rat lines. In the present study, we have used nonselected outbred Sprague–Dawley rats homozygous for the α6-100RR (RR) and α6-100QQ (QQ) genotypes to show that these RR and QQ rats display similar differences between genotypes as AT and ANT rat lines. The genotypes differed in their affinity for [³H]Ro 15-4513 and classic benzodiazepines (BZs) to cerebellar “diazepam-insensitive” (DZ-IS) binding sites, in density of cerebellar [³H]muscimol binding and in the antagonizing effect of furosemide on GABA-induced inhibition of [³H]EBOB binding. The results suggest the involvement of α6-R100Q polymorphism in these line differences and in the differences previously found between AT and ANT rats. In addition, the α6-R100Q polymorphism induces striking differences in [³H]Ro 15-4513 binding kinetics to recombinant α6β3γ2s receptors and cerebellar DZ-IS sites. Association of [³H]Ro 15-4513 binding was ∼10-fold faster and dissociation was ∼3–4-fold faster in DZ-IS α6βγ2 receptors containing the α6-100Q allele, with a resulting change of ∼2.5-fold in equilibrium dissociation constant (K_D). The results indicate that in addition to the central role of the homologous α6-100R/Q (α1-101H) residue in BZ binding and efficacy, this critical BZ binding site residue has a major impact on BZ binding kinetics.     

Effect of ethanol on brain catecholamines in rat lines developed for differential ethanol-induced motor impairment

The importance of the central catecholamines, with the emphasis on the noradrenergic neurons in the differential sensitivity to ethanol between the AT (alcohol-tolerant) rats selected for low and the ANT (alcohol-nontolerant) rats selected for high sensitivity to ethanol-induced (2 g/kg) motor impairment, was clarified by studying the effects of ethanol (2 and 4 g/kg, IP) on the utilization of norepinephrine (NA) and dopamine (DA), and on the metabolism of NA. The utilization of the catecholamines was estimated from the disappearance of the amines after inhibition of the brain tyrosine hydroxylase by alpha-methyl-p-tyrosine (200 mg/kg, IP), given 15 min after the administration of ethanol. The formation of 3-methoxy-4-hydroxy-phenylglycol (MHPG) was used as an estimate of NA metabolism, and was measured 30 min after the administration of ethanol. The basal utilization rate of NA and DA was similar between the two rat lines, but the increased formation of MHPG suggested that the naive AT rats had a higher noradrenergic activity in the limbic forebrain, hypothalamus, and cerebellum than did ANT rats. In the brain of both lines, ethanol accelerated the utilization and metabolism of NA in the same manner. Ethanol also increased the utilization of DA in the limbic forebrain of the AT and ANT rats. The higher sensitivity of the ANT rats' DA neurons to ethanol in the limbic forebrain and striatum was revealed by the significant rat line X ethanol interaction. The present findings suggest that the AT and ANT rats differ in the dopaminergic, but not in the noradrenergic responses to ethanol.     

Effects of in utero ethanol exposure on cortical 5-HT2 binding sites

Previous studies by this laboratory found that in utero ethanol exposure results in a decrease of several presynaptic components of serotonin (5-HT) containing neurons in the cerebral cortex and cortical regions. The present study examined whether in utero ethanol exposure similarly affects the development of the cortical targets of serotonergic projections. Specifically, we examined the influence of in utero ethanol exposure on 5-HT2 binding sites in the motor and somatosensory cortices of the offspring of rats that consumed a control or 6.6% (v/v) ethanol liquid diet on a chronic basis prior to parturition. These studies demonstrated that neither the Kd nor Bmax for the binding of [3H]-ketanserin to membranes from the motor and somatosensory cortices of 19- and 35-day-old rats were significantly altered by in utero ethanol exposure. These results suggest that the development of the postsynaptic target areas of cortical serotonergic projections are more resistant to the effects of in utero ethanol exposure than the presynaptic components of these projections.     

Prenatal ethanol exposure during the last third of gestation in rat reduces hippocampal NMDA agonist binding site density in 45-day-old offspring.

The effect of ethanol exposure during different periods of prenatal or postnatal development on hippocampal N-methyl-D-aspartate (NMDA) receptor binding was studied in rat. Fetal rat pups were exposed to ethanol for different periods of time during gestation via maternal consumption of a 3.35% ethanol liquid diet. In a separate experiment, neonatal pups were fed 2.51 g ethanol/kg body weight/day from Postnatal Day (PD) 4 to PD 10 via intragastric feeding tube. These two ethanol administration paradigms produced average peak maternal and pup blood ethanol concentrations of 39 mg/dl and 57 mg/dl, respectively. At 45 days of age, offspring from each treatment group were sacrificed for measurements of hippocampal NMDA-sensitive [3H]-glutamate binding site density using in vitro radiohistochemical techniques. As observed previously, prenatal ethanol exposure throughout gestation resulted in NMDA-sensitive [3H]-glutamate binding site reductions in the apical dendritic field regions of dentate gyrus, hippocampal CA1 and subiculum of dorsal hippocampal formation compared to the ad lib or pair-fed control groups. NMDA-sensitive [3H]-glutamate binding was not different than control in rats exposed to ethanol during the first half of gestation only. Prenatal ethanol exposure during the last half or the last third of gestation resulted in NMDA-sensitive [3H]-glutamate binding site reductions comparable to the binding site reductions observed in rats exposed to ethanol throughout gestation. Hippocampal NMDA-sensitive [3H]-glutamate binding site density in postnatal ethanol-exposed rats was not different than the suckling or gastrostomy control groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Brain neurotensin receptors in mice bred for differences in sensitivity to ethanol

The hypothesis that some of ethanol's acute effects are mediated via neurotensinergic systems was investigated by characterizing neurotensin (NT) receptors in mice (LS and SS) selectively bred for differences in sensitivity to ethanol. [3H]Neurotensin binding in brain membranes from both mouse lines was specific, saturable, reversible, and linear with protein concentrations. Subcellular localization studies showed specific NT binding to be concentrated in the microsomal/synaptosomal fractions. Scatchard analyses of [3H]NT binding indicated similar KD values for membranes from various brain regions of LS and SS mice. However, Bmax values in frontal cortex, cerebellum, and striatum were greater in SS than in LS mice. In competitive binding studies IC50 values were lower for NT8-13 than for NT1-13, and IC50 values for NT1-8, NT1-11, D-Trp11-NT, and D-Tyr11-NT were greater than 1000 nM. Association and dissociation rate constants for [3H]NT and resulting KD values (0.8 nM) were similar for LS and SS brain membranes. Ethanol, in vitro, had no effect on NT binding characteristics, but as expected various cations markedly increased KD values.     

Chronic ethanol exposure alters MK-801 binding sites in the cerebral cortex of the near-term fetal guinea pig.

The mechanism of ethanol central nervous system (CNS) teratogenesis, resulting from chronic maternal ingestion of high-dose ethanol during pregnancy, is not clearly understood. One of the target sites for ethanol-induced damage in the developing brain is the cerebral cortex. It has been proposed that chronic prenatal ethanol exposure alters NMDA receptors in the developing cerebral cortex. To test this hypothesis, timed pregnant guinea pigs were administered one of the following oral treatments throughout gestation: 4 g ethanol/kg maternal body weight/day; isocaloric sucrose/pair-feeding; water; or no treatment (ad lib). Near-term fetuses were studied at gestational day (GD) 63 (term, about GD 68). This ethanol regimen produced a maternal blood ethanol concentration of 66+/-4 mM (304+/-19 mg/dl) at 1 h after the daily dose on GD 58. The chronic ethanol regimen decreased near-term fetal body weight (12-26% decrease), brain weight (23% decrease), and cerebral cortical weight (21% decrease), compared with the isocaloric sucrose/pair-feeding, and combined water/ad lib experimental groups. Saturation analysis of near-term fetal cerebral cortical membranes using a [3H]MK-801 radioligand binding assay demonstrated a decreased affinity and increased number of MK-801 binding sites for the chronic ethanol regimen compared with the control treatments. These data support the suggestion that upregulation of NMDA receptors in the cerebral cortex after chronic prenatal ethanol exposure could lead to NMDA receptor-mediated excitotoxicity in this brain region.     

乐果90 d染毒对大鼠大脑皮质GABA系统的影响

[目的]研究乐果[O,O-二甲基-S-(N-甲基氨基甲酰甲基)二硫化磷酸酯]90d染毒对大鼠大脑皮质γ-氨基丁酸(GABA)系统的影响。[方法]48只健康雄性SD大鼠分成4组,剂量分别为O(生理盐水)、5、10、20mg/kg,灌胃给药,每周染毒5d(次),实验周期90d,每天称重1次,每3天记录动物饲料消耗量,定期测定全血乙酰胆碱酯酶(AChE)活性,实验结束时全部动物断头处死,测定延髓AChE活性,反相高效液相色谱荧光法测定大脑皮质GABA含量,放射性配体受体结合法测定大脑皮质GABA_A受体的活性。[结果]实验期间,各染毒组动物全血AChE活性明显抑制,实验后期有所恢复。实验结束时,低、中、高染毒组延髓AChE活性分别约为对照组的78%、63%、42%。与对照组相比,中、高剂量组大脑皮质GABA含量明显降低(P<0.01);GABA_A受体的最大结合容量(maximum binding capacity,Bmax)低剂量组升高(P<0.05),中剂量组降低(P<0.05);各剂量组GABA_A受体的平衡解离常数(equilibrium dissociation constant,Kd)比对照组均有降低,但仅低、中剂量组差异有统计学意义(P<0.05)。[结论]乐果90d染毒过程中大脑皮质GABA含量、GABA_A受体功能都有所改变,可能参与了乐果慢性中毒过程中的非胆碱能机制。     

Chronic maternal ethanol consumption results in decreased serotonergic 5-HT1 sites in cerebral cortical regions from offspring

This laboratory previously demonstrated that chronic maternal ethanol consumption results in a marked deficiency of cortical serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) and of 5-HT uptake sites in the 19- and 35-day-old offspring. In order to determine whether in utero exposure to ethanol similarly affects other components of the serotonergic system we examined the influence of chronic maternal ethanol consumption on cortical, serotonergic 5-HT1 binding sites in developing offspring. Female Sprague-Dawley rats were pair-fed, using control or 6.6% (v/v) ethanol liquid diets on a chronic basis prior to parturition. Serotonergic 5-HT1 sites were measured in synaptosomal membranes from whole cortex and cortical regions from developing offspring. Serotonergic 5-HT1 sites were assessed by measuring the binding of [3H]-5-HT to synaptosomal membranes in the presence and absence of nonradioactive 5-HT. Serotonergic 5-HT2 sites were blocked by including 100 nM spiperone in the assay buffer. The results demonstrated that the 19- and 37-day-old offspring of ethanol-fed rats had a significant (approximately 10-40%) reduction in the Bmax for serotonergic 5-HT1 binding sites on synaptosomal membranes from whole cortex (p less than 0.025), motor cortex (p less than 0.01), and somatosensory cortex (p less than 0.025). However, the binding affinity (Kd) for serotonin was not significantly altered (p greater than 0.05). These results emphasize the sensitivity of the developing cortical serotonergic system to prenatal ethanol exposure.     

Ethanol sensitivity and consumption in F2 hybrid crosses of ANT and AT rats

ANT rats that are highly sensitive to the motor-impairing effects of moderate ethanol doses voluntarily drink less ethanol in a free-choice test between 10% (v/v) ethanol solution and water than the ethanol-insensitive AT rats, suggesting the possibility that ethanol drinking is affected by initial ethanol sensitivity. However, in the F₂ hybrid crosses of ANT and AT rats, voluntary ethanol drinking did not correlate with sensitivity to the motor-impairing effects of ethanol in the tilting plane test. Therefore, initial ethanol sensitivity does not appear to be a major factor in explaining variation in voluntary ethanol drinking.     

Alcohol modulation of benzodiazepine receptors

The effects of ethanol-feeding and in vitro ethanol addition on the binding of ³H-diazepam and ³H-flunitrazepam in synaptosomal membrane preparations from rat cerebral cortex were investigated. Long-term ethanol-feeding (liquid-diet, 14 g/kg/day, pair-feeding, 35 days) significantly increased the diazepam dissociation constant (from 3.80 to 4.62 nM at 4°C and from 29.3 to 35.2 nM at 37°C). Similarly, the flunitrazepam dissociation constant was also increased (from 0.80 to 0.98 nM at 4°C and from 6.52 to 8.90 nM at 37°C). However, there was no significant difference in the number of receptors after ethanol feeding. γ-Aminobutyric acid (GABA) and pentobarbital increased the binding affinity by the same magnitude in control and ethanol-fed rats. Alcohol, in vitro (100 mM), did not have a significant effect on the binding parameters under most conditions. These findings suggest that long-term ethanol-feeding reduced the binding affinity of benzodiazepines without alteration of other properties of the receptors or their number.     

Loss of muscarinic and benzodiazepine neuroreceptors from hippocampus of alcohol abusers

Thiamine deficiency (Wernicke-Korsakoff's disease) may not be the only mechanism whereby chronic alcohol abuse affects the brain and not all alcohol-related changes may be evident morphologically. The purpose of this study was to determine if alcohol abuse affects muscarinic cholinergic and benzodiazepine receptors in the hippocampus of histologically normal brains obtained at autopsy in a general hospital population. Because patients were excluded who had significant brain atrophy and/or dementia severe enough to require institutionalization, the reported findings are presumed to be early changes in the development of an alcohol encephalopathy. In addition, patients were excluded from this study if they had clinical brain diseases (including Wernicke's disease), died in coma, had liver disease, or received medications that could potentially alter receptor binding. The reported changes in receptor binding were therefore presumed to be related to alcohol abuse per se and not an alcohol-associated condition. We found that muscarinic cholinergic synaptic receptor density determined with 3[H] quinuclidinyl benzilate was decreased by 30% in homogenates of the hippocampus of 25 alcohol abusers compared with 25 matched nonalcoholic controls. Similarly, densities of benzodiazepine receptors determined with 3[H] flunitrazepam were also decreased by approximately 30% in alcohol abusers. The affinities of both receptor types were not affected by alcohol abuse. Age and death-autopsy time interval had no significant effects on either wet tissue protein concentrations, yields of protein after centrifugation, or receptor binding. The contributions of age and time interval were each less than 2% of the total variance of protein concentrations and receptor binding.(ABSTRACT TRUNCATED AT 250 WORDS)     

Prenatal ethanol exposure decreases hippocampal NMDA-sensitive [3H]-glutamate binding site density in 45-day-old rats.

The effect of prenatal ethanol exposure on N-methyl-D-aspartate (NMDA)-sensitive [3H]-glutamate receptor binding site density was studied in rat brain. Pregnant Sprague-Dawley rats were fed a liquid diet containing 3.35% ethanol throughout gestation. This diet produced maternal peak blood ethanol levels of about 39 mg/dl eight hours after the administration of the liquid diet. Pair-fed dams received an isocalorically matched liquid diet and an ad lib lab chow group served as control for the paired feeding technique. At 45 days of age, offspring from each of the three diet groups were sacrificed and brain NMDA-sensitive [3H]-glutamate binding site density measured using in vitro radiohistochemical techniques. NMDA-sensitive [3H]-glutamate binding site density was reduced significantly by 19 to 29% in the apical dendritic field regions of dentate gyrus, hippocampal CA1 and subiculum of dorsal hippocampal formation of fetal alcohol rats compared to pair-fed and ad lib controls. NMDA-sensitive [3H]-glutamate binding site density was not significantly different among the three groups in the ventral hippocampal formation, posterior neocortex, lateral entorhinal cortex or cerebellum. These results are consistent with our previous observations of a reduction in total [3H]-glutamate receptor binding site density in the dorsal hippocampal formation of fetal alcohol rats, as well as more recent electrophysiological observations of a decrease in the sensitivity of fetal alcohol hippocampal slices to NMDA.     

Imidazo[2,1-b]thiazepines: synthesis, structure and evaluation of benzodiazepine receptor binding

As a continuation of our search for new ligands acting on benzodiazepine receptors among the fused 2-thiohydantoin derivatives, a series of 5-substituted imidazo[2,1-b]thiazepines was synthesized and investigated in radioligand binding studies at the benzodiazepine binding site of GABA(A) receptors in rat brain cortical membranes. Among ortho-substituted 5-arylidene-imidazo[2,1-b]thiazepines compounds could be identified which exhibit affinity for the benzodiazepine binding site at low micromolar concentrations. X-ray structure analyses for two compounds (6ae and 6ag) have been performed. In order to analyze the structure-activity relationships, 3D models of all compounds have been completed (using X-ray data). Physicochemical properties calculated (log P and log D) as well as experimental thin layer chromatography data were examined.