Position Paper Central α-Adrenoceptors Involved in Cardiovascular Regulation

Summary: It appears to be established that the central α-adrenoceptors involved in the control oreardiovascular function belong to the α2-subtype. They are stimulated hy eatecholamines. clonidine. and other imidazoline derivatives but also by eompounds of rather hetcrogenons strnetiire. Activation of these central α2-adrenoceptors results in an increase ol cardiac vagal tone as well as in decreases of sympathetic nervons activity. blood pressure. and heart rate. α2-Adrenoeeptors in the nncleus of the solitary traet appear to be the main site of action of elonidine. followed. in deereasing order of likelihood. by those in the interniediolateral ccII column of the spinal cord and the anterior hypothalainus. The location of the α2-adrenoceptors relative to synapses is controversial. Two possibilitics have so fur been discussed: a location at the terminals ofadrenergic neurons (presynaptic) oron the cell bodies ordendrites of not vet identified neurons innervated by adrenergic neurons (postsynaptie). In this paper, attention is drawn to another possihility suggesting a location at the terminals of nonadrenergic neurons.