CNS effects of circulating CCK8: involvement of brainstem neurones responding to gastric distension

Abstract Cholecystokinin octapeptide (CCK8) given i.v. or i.p. produces a variety ofbehavioural and CNS effects; these actions are probably exerted at a peripheral site but the neuronal pathways involved are uncertain. We show here that i.v. CCK8 acts on neurones in the n. tractus solitarius with an input from the stomach; cells are either or depressed by CCK8 and gastric distension, and responses to the two stimuli are always in the same direction. The responses to closearterial injection of CCK8 indicate a site of action within the splanchnic bed, and most probably a direct action on the vagal afferents mediating gastric mechanoreceptor discharge.