The CCKB antagonist, L-365,260, attenuates fear-potentiated startle.

The neuropeptide cholecystokinin (CCK), via the CCKB receptor, increases behaviors associated with anxiety in laboratory animals and humans. The present experiment assessed the role of endogenous CCKB function in fear-potentiated startle, a test of "anxiety" in rats. The amplitude of the acoustic startle response is potentiated if preceded by a stimulus that has been previously paired with shock. Pretreatment with the CCKB antagonist L-365,260 (0, 0.1, 1.0, and 10.0 mg/kg, IP) did not affect baseline acoustic startle amplitudes, but dose-dependently decreased fear-potentiated startle. These results indicate that the specific attenuation of fear-potentiated startle induced by L-365,260 was not due to a general decrease in motor responsivity. The present findings are consistent with the effects of CCKB antagonists in other tests measuring anxiety in animals.