title: (3H)-muscimol, (3H)-nipecotic acid and (3H)-isoguvacine as autoradiographic markers for GABA neurotransmission.
abstract: Retinas from rabbit, goldfish and guinea-pig were exposed to (3H) GABA, (3H)-nipecotic acid and (3H)-isoguvacine either by intravitreal injection in vivo or by incubations in a balanced salt solution and the distribution of radioactivity was then studied with autoradiography. All substances labelled a similar set of presumed amacrine cells. Incubating at 0 degrees C, in 10-(5)M ouabain, or in 10-(3)M GABA inhibited the labelling by (3H)-muscimol whereas bicuculline (10-(4)M), and glycine (10-(3)M) were less efficient blockers. The result is interpreted as a neuronal uptake of (3H)-muscimol rather than as a GABA receptor binding. All the substances except (3H)-isoguvacine also labelled glia to such a degree that neuronal labelling was often disguised in rabbits and goldfish. Glial labelling by muscimol was less pronounced in guinea-pig. (3H)-isoguvacine (tested only in rabbits) gave a strong labelling of cells with the distribution of GABA neurons and only little glial labelling.
mesh_terms: D000818:Animals; D001345:Autoradiography / Q000379:methods*; D006054:Goldfish; D006168:Guinea Pigs; D007539:Isonicotinic Acids / Q000378:metabolism*; D009118:Muscimol / Q000378:metabolism*; D009457:Neuroglia / Q000378:metabolism; D009474:Neurons / Q000378:metabolism; D009557:Nipecotic Acids / Q000378:metabolism*; D010080:Oxazoles / Q000378:metabolism*; D011817:Rabbits; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011963:Receptors, GABA-A; D012160:Retina / Q000378:metabolism; D009435:Synaptic Transmission; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D007539:Isonicotinic Acids; D009557:Nipecotic Acids; D010080:Oxazoles; D011956:Receptors, Cell Surface; D011963:Receptors, GABA-A; D009118:Muscimol; D005680:gamma-Aminobutyric Acid; C015300:isoguvacine