Cholecystokinin enhances the acoustic startle response in rats.

The present study examined the effects of the neuropeptide cholecystokinin (CCK) on neurones of the caudal pontine reticular nucleus (PnC), which mediates the acoustic startle response (ASR) in rats. Electrophysiological experiments revealed an excitatory effect of CCK on acoustically responsive neurones in the PnC. On the behavioural level, CCK also enhanced the ASR. Since the PnC is not only an obligatory relay station of the brain circuit mediating the ASR, but also receives modulatory input from brain areas involved in the expression of fear and anxiety, the enhancement of the ASR by CCK could be interpreted as an anxiogenic-like effect of this peptide.