GABA receptors are increased in brains of alcoholics

gamma-Aminobutyric acid (GABA) receptor binding was increased in postmortem brain samples of chronic alcoholic patients compared to control patients. Numbers of binding sites were augmented in alcoholic brain, with no change in affinity. Muscarinic cholinergic and benzodiazepine receptors did not differ between controls and alcoholic brains, while a modest reduction in beta-adrenergic receptors may have been related to postmortem receptor changes. The results suggest that GABAergic mechanisms might play a role in chronic alcoholism.

Histidine decarboxylase. Purification from fetal rat liver, immunologic properties, and histochemical localization in brain and stomach

Histidine decarboxylase from fetal rat liver was purified to near-homogeneity. The purified enzyme has a molecular weight of 210,000, and appears to contain two subunits with molecular weights of 145,000 and 66,000, respectively. The enzyme is inhibited by heavy metals such as Hg2+ and Zn2+ and sulfhydryl-reactive compounds such as 5,5'-dithiobis-2-nitrobenzoic acid. The enzyme is partially dependent on exogenous pyridoxal phosphate. Extensive dialysis results in 50% loss of enzyme activity which can be fully recovered by adding pyridoxal phosphate. Affinity of pyridoxal phosphate for the apoenzyme is 0.1 microM at pH 6.8. Antibody against purified histidine decarboxylase was raised in rabbits. The antibody has been employed in immunohistochemical studies to visualize histidine decarboxylase containing cells and neuronal processes in rat stomach and brain, respectively. Immunologic studies indicate that histidine decarboxylase from brain, gastric mucosa, and fetal rat liver share common antigenic properties.

Histamine H1-receptors labeled in vivo: antidepressant and antihistamine interactions

3H-Mepyramine labels specific histamine H1-receptors in brains of mice after intravenous injection. The potencies of H1-antihistamines in reducing 3H-mepyramine binding in vivo correspond to their pharmacological activities and show parallels with their affinities for 3H-mepyramine binding sites in isolated brain membranes. Several antidepressants are potent in competing for 3H-mepyramine binding in vivo as well as in vitro.

Neurotransmitter receptor localizations: brain lesion induced alterations in benzodiazepine, GABA, beta-adrenergic and histamine H1-receptor binding

Selective neuronal lesions have been utilized in efforts to localize binding sites in rat brain for beta-adrenergic, gamma-aminobutyric acid (GABA), histamine H1 and benzodiazepine receptors. The various receptors respond differentially to lesions both in extent of change and in time course. After kainate lesions in the corpus striatum, benzodiazepine receptors are depleted up to 45% at 45--78 days but are unaffected after 7 days. By contrast striatal GABA receptors are increased at 7 days but depleted at later times. Thus both striatal benzodiazepine and GABA receptors appear to be associated at least in part with intrinsic neurons. In the cerebellum both benzodiazepine and GABA receptors are reduced in kainate treated rats and in Nervous mice, mutants which lack Purkinje cells. The most pronounced dissimilarity between benzodiazepine and GABA receptors occurs in Weaver mice, which selectively lack granule cells and display a 60% reduction in GABA receptors but a 40% augmentation in benzodiazepine receptors. A major portion of cerebellar GABA receptors, therefore, appear to be localized to granule cells. Striatal beta-adrenergic receptors are reduced following intrastriatal kainate injections but are unaffected by cerebral cortex ablation, suggesting an association with intrinsic neurons but not with axon terminals of the corticostriate pathway. While intraventricular injections of 6-hydroxydopamine enhance [3H]dihydroalprenolol binding to beta-adrenergic receptors in the cerebral cortex and hippocampus, such binding is not augmented in the corpus striatum, brain stem, midbrain or thalamus-hypothalamus by this treatment. Moreover, medial forebrain bundle lesions, which destroy ascending adrenergic neurons, fail to alter cerebral cortical or striatal beta-adrenergic receptors. Thus denervation-elicited increases in beta-adrenergic receptors vary with brain region and the type of denervating lesion. Histamine H1-receptors are the most resistant of all to neuronal lesions. In the corpus striatum [3H]mepyramine binding is unaffected by cerebral cortex ablation, nigral injections of 6-hydroxydopamine or brain stem hemisection. In the hippocampus, medial forebrain bundle lesions, intrahippocampal kainate injection, and fimbria and fornix transection largely fail to alter [3H]mepyramine binding. Accordingly, a major portion of these receptors may be associated with nonneuronal elements such as glia or blood vessels.

Characteristics of histamine H1-receptors in peripheral tissues labeled with [3H]mepyramine

Specific binding of [3H]mepyramine to membranes of various peripheral tissues of different species has been demonstrated. Drug specificity indicates an association with histamine H1-receptors. Of all the tissues examined brain contains the highest numbers of binding sites, while substantial levels of specific [3H]mepyramine binding are also demonstrable in some species in heart, lung, adrenal and ileum. Negligible specific [3H]mepyramine binding is observed in the liver, stomach and uterus of several species. The lesser bronchoconstricting response of the rat than of other species to histamine is paralleled by a lower number of [3H]mepyramine binding sites in rat lung than in other species. However, similar numbers or [3H]mepyramine binding sites occur in ileal membranes of rat, guinea pig and rabbit, although contractile effects of histamine vary in these species. In the quinea-pig ileum, [3H]mepyramine binding is most concentrated in the longitudinal muscle itself where histamine exerts its predominant contractile effects. In the bovine adrenal gland, [3H]mepyramine binding is more abundant and has higher affinity for drugs in the medulla than in the cortex.

Penetration of cefoxitin into cerebrospinal fluid of dogs with and without experimental meningitis

The penetration of cefoxitin into the cerebrospinal fluid (CSF) after slow intravenous infusion of 50-100 mg/kg over 1 hr was studied in normal dogs and in dogs with meningitis experimentally induced by intrathecal injection of 10(9) Staphylococcus aureus. With healthy dogs the peak CSF concentration of 1 microgram of cefoxitin/ml was found to correspond with a serum level of 120 micrograms/ml. With administration of probenecid the CSF level was 1.5 micrograms of cefoxitin/ml. Doubling the dose from 50 to 100 mg/kg resulted in a CSF concentration of 2 micrograms of cefoxitin/ml. In the CSF of animals with meningitis, a peak concentration of 10 micrograms of cefoxitin/ml was obtained 90 min after the start of the infusion, and 5 micrograms/ml was still present at 240 min. The peak level in CSF of animals with meningitis was about 10% of the simultaneous level in serum.

Histamine H1 receptors identified in mammalian brain membranes with [3H]mepyramine

The antihistamine [3H]mepyramine binds to H1 histamine receptors in mammalian brain membranes. Potencies of H1 antihistamines at the binding sites correlate with their pharmacological antihistamine effects in the guinea pig ileum. Specific [3H]mepyramine binding is saturable with a dissociation constant of about 4 nM in both equilibrium and kinetic experiments and a density of 10 pmol per gram of whole kinetic experiments and a density of 10 pmol per gram of whole brain. Some tricyclic antidepressants are potent inhibitors of specific [3H]mepyramine binding. Regional variations of [3H]mepyramine binding do not correlate with variations in endogeneous histamine and histidine decarboxylase activity.