We have examined the capacity of calcitonin gene-related peptide (CGRP) to exert two biological actions in the central nervous system (CNS): modulation of GH release and alteration of food intake. These effects were compared with those of calcitonin (CT). Intracerebroventricular administration of both rat (r) CGRP (10 micrograms/10 microliter) and salmon (s) CT (250 ng/10 microliter) to chronically cannulated freely-moving rats reduced the frequency and amplitude of spontaneous GH secretory pulses; however, the suppressive effect was of longer duration with sCT than with rCGRP. Both peptides also significantly reduced spontaneous food intake over a 6-h period when administered centrally, although the decrease with sCT was again more extensive than that with rCGRP. The results demonstrate that CGRP can simulate two of the effects of CT in brain. Furthermore, the findings suggest that CGRP may function as an endogenous ligand for CT receptors in the CNS, and participate centrally in the modulation of GH release and the control of satiety.