PREPULSE INHIBITION OF ACOUSTIC OR TRIGEMINAL STARTLE OF RATS BY UNILATERAL ELECTRICAL-STIMULATION OF THE INFERIOR COLLICULUS

Transient electrical stimulation of the inferior colliculus (IC) of ad ult male rats had a strong and long-lasting inhibitory effect on start le responses elicited by either intense noise bursts or unilateral ele ctrical stimulation of the principal trigeminal nucleus. Startle elici ted by noise bursts was inhibited over a wide range of interstimulus i ntervals (ISIs) with the maximum inhibition at ISIs between 15 and 30 ms. Startle elicited by trigeminal stimulation was inhibited more shar ply than acoustic startle, with the maximum inhibition at ISIs between 20 and 35 ms. These data support the view that the IC is a critical p art of the pathway mediating prepulse inhibition (D. S. Leitner & M. E . Cohen, 1985). More important, the data reveal the time course of the inhibitory influence of the IC on startle and indicate that the inhib itory effects of IC stimulation have higher temporal resolution on tri geminal startle than on acoustic startle.