A Met-enkephalin releaser (kyotorphin)-induced release of plasma membrane-bound Ca2+ from rat brain synaptosomes.

The neuropeptide kyotorphin (Tyr-Arg) released 45Ca2+ from synaptosomal membrane preparations of the rat lower brainstem. This dipeptide also decreased plasma membrane-bound Ca2+ ([Ca2+]m), determined using chlorotetracycline, in the slice and synaptosome of the rat lower brainstem. Taken together with other data indicating that kyotorphin induces an increase in synaptosomal intracellular Ca2+ ([Ca2+]i) in a Ca2+ channel-independent manner, it is suggested that kyotorphin may mobilize the [Ca2+]m and thus increase the [Ca2+]i in the nerve terminals of the rat lower brainstem.