Effect of 1-amino-5-bromouracil on brain monoamine metabolism in rats

Effects of nucleotides on learning and memory in a Morris water maze test in normal and basal forebrain-lesioned rats

The effects of nucleotides on learning and memory were studied in normal and basal forebrain-lesioned rats using a Morris water maze test. Chronic oral administration of a nucleotide mixture (500 mg/kg), containing an equal weight of the disodium salts of adenosine 5'-monophosphate, guanosine 5'-monophosphate, inosine 5'-monophosphate, cytidine 5'-monophosphate, and uridine 5'-monophosphate facilitated learning acquisition in normal rats. In basal forebrain-lesioned rats, administration of the nucleotide mixture showed a tendency to improve learning acquisition and memory retrieval. In the biochemical studies, no significant changes were observed in brain choline and acetylcholine levels by treatment with the nucleotide mixture at the doses tested in both normal and basal forebrain-lesioned rats. The nucleotides did not affect the monoaminergic systems in normal rats, but did cause some changes in these systems in basal forebrain-lesioned rats. The present studies indicate that nucleotides ameliorate learning and memory processes in normal rats, but not in basal forebrain-lesioned rats, and they also modulate the activity of the central monoaminergic systems under certain conditions.

Effects of clobenpropit (VUF-9153), a histamine H3-receptor antagonist, on learning and memory, and on cholinergic and monoaminergic systems in mice

The effects of clobenpropit (VUF-9153), a potent histamine H3-receptor antagonist, on a scopolamine-induced learning deficit in the step-through passive avoidance test was studied in mice. Clobenpropit (10 and 20 mg/kg) alone showed a tendency to ameliorate the scopolamine-induced learning deficit, and clobenpropit (10 mg/kg) in combination with zolantidine (20 mg/kg), a histamine H2-receptor antagonist, ameliorated the scopolamine-induced effect. This ameliorating effect was antagonized by (R)-alpha-methylhistamine (20 mg/kg), a histamine H3-receptor agonist and pyrilamine (20 mg/kg), a histamine H1-receptor antagonist, suggesting that clobenpropit in combination with zolantidine showed the ameliorating effect via histamine H3 receptors and/or histamine H1 receptors. We also studied the effects of clobenpropit on cholinergic and monoaminergic systems. Clobenpropit did not show any significant effect on these neuronal systems except the activation of noradrenergic system. The present results suggest that the effect of clobenpropit might be partially involved with the activation of noradrenergic system, and the histaminergic system may play certain important roles in learning and memory.

Effects of 1-amino-5-bromouracil on the benzodiazepine-GABAA receptor complex

We investigated the effects of 1-amino-5-bromouracil on the benzodiazepine-gamma-aminobutyric acid (GABA)A receptor complex to elucidate its central action. 1-Amino-5-bromouracil neither displaced nor enhanced [3H]muscimol, [35S]t-butylbicyclophosphorothionate (TBPS), or [3H]dehydroepiandrosterone sulfate binding to the rat brain synaptosomal membranes. The anesthesia induced by 1-amino-5-bromouracil was potentiated by diazepam, pentobarbital, and muscimol, and was antagonized by picrotoxin but not by bicuculline. 1-Amino-5-bromouracil protected mice from picrotoxin-induced seizure and slightly ameliorated TBPS-induced seizure, but did not antagonize bicuculline-induced seizure. Diazepam antagonized both the bicuculline- and the picrotoxin-induced seizure, and pentobarbital antagonized the picrotoxin- and the TBPS-induced seizure. Our in vivo studies suggest that part of the central action of 1-amino-5-bromouracil is concerned with the benzodiazepine-GABAA receptor complex including the chloride channel.