Characterization of Neurotransmitter Receptors in the Rat Hippocampal Formation

Publisher Website
Google Scholar
Abstract
The hippocampal formation has been extensively researched in terms of its putative neurotransmitters, anatomical connections and behavioral relevance. An aspect of related importance is the assessment of apparent neurotransmitter receptors by using receptor binding assays. In the present study, such assays were done in vitro to investigate .alpha.1-adrenergic, .alpha.2-adrenergic, .beta.-adrenergic, muscarinic cholinergic, benzodiazepine and opiate receptors in the rat hippocampal formation. The corresponding radioligands for these receptors were [3H]prazosin, [3H]p-aminoclonidine, [3H]dihydroalprenolol, [3H]quinuclidinyl benzilate, [3H]flunitrazepam, and [3H]naloxone. An analysis of the binding parameters for the ligands indicated saturable binding of a high affinity and the following rank order of maximal capacities: [3H]flunitrazepam > [3H]quinuclidinyl benzilate > [3H]naloxone > [3H]p-aminoclonidine > [3H]prazosin > [3H]dihydroalprenolol. Competition experiments with pharmacologic agonist and antagonists confirmed the specificity of each ligand. The results are integrated with information on other types of receptors and with neurotransmitter concentrations, and discussed in terms of hippocampal function.