Relative potencies of alpha-1 and alpha-2 antagonists in the locus ceruleus, dorsal raphe and dorsal lateral geniculate nuclei: an electrophysiological study.

The actions of some adrenoceptor antagonists were examined in single unit studies at alpha-1 adrenoceptors of the dorsal raphe nucleus and the dorsal lateral geniculate nucleus and alpha-2 adrenoceptors of the nucleus locus ceruleus. Prazosin, WB-4101 and corynanthine were found to be effective central alpha-1 adrenoceptor antagonists and piperoxane, yohimbine and rauwolscine were found to be effective central alpha-2 adrenoceptor antagonists. Prazosin, WB-4101 and corynanthine had no activity at alpha-2 adrenoceptors. However, piperoxane, yohimbine and rauwolscine in addition to their alpha-2 adrenoceptor actions, also displayed significant alpha-1 adrenoceptor antagonist properties. Thus, the latter drugs are not as selective for central alpha-2 adrenoceptors as in some other systems. This supports the suggestion that alpha adrenoceptor subtypes are not identical across all species and tissues.