Characterization of alpha(1)-adrenoceptor subtypes in rat spinal cord

The a, adrenoceptor subtypes in ventral and dorsal horns of rat lumbar spinal cord were studied. High concentrations of the alpha(1D)-adrenoceptor antagonist, BMY 7378 (8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]-ethyl]-8-azaspiro[4.5]decane-7,9-dione dihydrochloride), displaced bound [H-3]prazosin in a single-site manner and the binding affinity was close to those for alpha(1A)- and alpha(1B)-adrenoceptor binding sites. 5-Methyl-urapidil displaced bound [H-3]prazosin in a two-site manner and the high and low affinities were close to those of alpha(1A)- and alpha(1B)-adrenoceptor binding sites, respectively. The alpha(1)-adrenoceptor subtype populations of ventral and dorsal horns did not differ. The alpha(1A)- and alpha(1B)-adrenoceptor populations comprised 70% and 30%, respectively, of the total and very few alpha(1D)-adrenoceptors and a were detected.