Chick brain cholinergic receptors studied by antagonist labelling: distribution, ontogeny & function

John Christopher Coulter
1988
By means of an in vitro labelling technique and methods of light microscope autoradiography the distribution of/muscarinic cholinergic receptor, labelled L by the tritiated antagonists I-Quinuclidinyl benzilate or Propylbenzilylcholine mustard, and the distribution of the nicotinic cholinergic receptor, labelled by a-Bungarotoxin, was shown in thin tissue sections of the young post hatch chick brain. The distribution of muscarinic cholinergic receptor in the chick brain was found to be
more » ... d. The highest density concentrations of muscarinic receptors, for example in the paleostriatum augmentatum and hyperstriatum ventrale of the forebrain, thalamic and mesencephalic relay nuclei, optic tectum and brain stem nuclei, were found to be highly regionally localised. In contrast, nicotinic receptors were found to be concentrated to mesencephalic and diencephalic regions of the brain, in particular to colliculi and the principal optic relay nuclei of the diencephalon. The density of nicotinic receptor in the forebrain, apart from the olfactory lobe, was found to be very low. The concentration of muscarinic receptor throughout the brain was found to be at least one order of magnitude greater than the concentration of nicotinic cholinergic receptor. Without exception, all regions populated by substantial concentrations: of nicotinic receptor were also populated by substantial concentrations of muscarinic receptor. On the other hand, a number of brain regions populated by high densities of muscarinic receptor were found to be almost devoid of specific a-bungarotoxin labelled nicotinic cholinergic receptor, eg. the hyperstriatum ventrale. H antagonist labelled muscarinic and nicotinic cholinergic receptors in chick brain tissue slices were shown to be similar to values given by other reports for alternative tissue preparations. The great majority of H muscarinic antagonist binding sites were shown to be specific, ie. atropine 'sensitive' or displaced. Evidence has been given which suggests that muscarinic antagonists ar [...]
doi:10.21954/ou.ro.0000f7d3 fatcat:pxgxd4erzbfsfmdukxvh5uq7aq