Enhancement of prepulse inhibition after blockade of GABA activity within the superior colliculus

The present study examined the effects of local microinjections of the GABA chloride channel blocker Picrotoxin into the superior colliculus (SC) on p repulse inhibition (PPI) of the acoustic startle response (ASR) in rats. PP I is a useful model for the investigation of the neuronal basis of sensorim otor gating which is deficient in some psychiatric disorders, such as schiz ophrenia. Blockade of GABA activity within the SC by Picrotoxin injections (leading to a moderate stimulation of the SC) significantly enhanced PPI wi thout affecting the ASR baseline amplitude or the spontaneous motor activit y. Based on these results we discuss the role of the SC in a hypothetical n euronal circuit mediating PPI of the ASR. (C) 1999 Elsevier Science B.V. Al l rights reserved.