THE CCKB ANTAGONIST, L-365,260, ATTENUATES FEAR-POTENTIATED STARTLE

The neuropeptide cholecystokinin (CCK), via the CCKB receptor, increas es 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 amplit ude of the acoustic startle response is potentiated if preceded by a s timulus 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 no t affect baseline acoustic startle amplitudes, but dose-dependently de creased fear-potentiated startle. These results indicate that the spec ific attenuation of fear-potentiated startle induced by L-365,260 was not due to a general decrease in motor responsivity. The present findi ngs are consistent with the effects of CCKB antagonists in other tests measuring anxiety in animals.