CHARACTERIZATION OF ALPHA(2) ADRENOCEPTORS AND OTHER ADRENOCEPTORS INMEMBRANES ISOLATED FROM DOG MESENTERIC NERVE AXONS

The axonal membranes from dog mesenteric nerves were isolated and char acterized. They had a high density of [H-3]saxitoxin, [H-3]rauwolscine and [I-125]iodocyanopindolol binding sites, but low densities of [I-1 25]omega-conotoxin (GVIA) and [H-3]prazosin binding sites. The microso mal membranes had one of the higher densities of [H-3]rauwolscine bind ing sites in centrifugation fractions. These sites were characterized by saturation, kinetic and competition studies. in competition with ox ymetazoline, WE 4101, prazosin, ARC-239, SK&F 104078 and SK&F 104856, these rauwolscine binding sites were alpha(2A)-like. Chloroethylclonid ine pretreatment did not affect the ability of SK&F 104078 or SK&F 104 856 to compete with rauwolscine binding sites on axonal membranes. B-m ax values were unchanged by chloroethylclonidine under conditions that also failed to reduce B-max values of rauwolscine binding to membrane s from human platelets. These receptors appear to be alpha(2A) adrenoc eptors and may represent sites of prejunctional control of neurotransm itter release in the dog. This membrane preparation may be useful in b iochemical studies of prejunctional neural receptors.