Role of the strychnine insensitive glycine binding site in the nucleus accumbens and anterodorsal striatum in sensorimotor gating: A behavioral and microdialysis study

This study examined the role of the strych-nine-insensitive glycine binding site of the NMDA receptor in prepulse inhibition (PPI) of the acoustic startle response (ASR) in rats. PPI is an operational measure of gating processes which normally lead to a diminished ASR when a startling stimulus is preceded by a weak prepulse. PPI is impaired in schizophrenics and, therefore, experimentally induced PPI deficits in rats can be regarded as a model for gating deficits in schizophrenia. Local administration of 7-chloro-kynurenate (7-CLKYN), an antagonist of the strych-nine-insensitive glycine site of the NMDA receptor into the nucleus accumbens reduced PPI. This sensorimotor gating deficit was antagonized by systemic pretreatment of the rats with the glycine site agonist D-cycloserine, indicating that the effect of 7-CLKYN was due to a blockade of the NMDA receptor associated glycine binding site. A similar deficit in PPI was observed after intra-accumbal administration of the competitive NMDA receptor antagonist AP-5. PPI was normal after injecting these drugs into the anterodorsal striatum. The hypothesis that the PPI deficit is accompanied by a change in dopamine release was tested by a neurochemical analysis of the effects of local injection of 7-CLKYN. Microdialysis data showed no increase of accumbal and striatal dopamine release after blockade of the glycine site with 7-CLKYN. Our data demonstrate that the glycine/NMDA receptor in the nucleus accumbens plays a important role in sensorimotor information processing that depends not on a hyperactive dopamine system.