Inhibition of fear potentiated startle in rats following peripheral administration of secretin.

Abstract

Previous results indicate that peripheral administration of secretin leads to robust Fos protein expression in the central nucleus of the rat amygdala. The implications of this observation on rat brain function, if any, remain unclear. We examined the effect of systemic secretin administration on the expression of fear-potentiated startle in rats, a behavioral response known to require an intact, functional central nucleus of the amygdala. Rats were trained to associate a neutral light conditioned stimulus (CS) with footshock, a fear-inducing unconditioned stimulus (US). Twenty-four hours later, rats were administered secretin or vehicle and were tested immediately for their startle response to a loud noise in the presence or absence of the light. Within a dose range relevant to its clinical use in autistic children, secretin dose-dependently decreased the magnitude of fear-potentiated startle in rats. This investigation provides additional evidence that systemically administered secretin can influence a neural network implicated in the acquisition and expression of emotional behaviors, including fear and anxiety.