Autoradiographic studies of central alpha(2A)- and alpha(2C)-adrenoceptors in the rat using [H-3]MK912 and subtype-selective drugs

In the present study we examined the distribution of alpha(2A)- and alpha(2C)-adrenoceptors in tissue slices from the rat cervical spinal cord and from brain slices collected at the level of the striatum. To differentiate between alpha(2A)- and alpha(2C)-adrenoceptors, the slices were incubated with [H-3]MK912 in the presence of graded concentrations of the alpha(2A)-selective drug, BRL44408, or the alpha(2C)-selective drug, spiroxatrine. Computer analysis of the autoradiograms indicated that 0.4 nM [H-3]MK912 plus 185 nM BRL44408 selectively labeled alpha(2C)-adrenoceptors, while 0.4 nM [H-3]MK912 plus 220 nM spiroxatrine selectively labeled alpha(2A)-adrenoceptors. Using this approach, alpha(2C)-adrenoceptors were detected in the striatum, while alpha(2A)-adrenoceptors predominated in the cortical layers 1-4, the spinal cord distal dorsal horn, the septum and the endopiriform nucleus. (C) 1997 Elsevier Science B.V.