EFFECTS OF THE NEUROLEPTIC ALPHA-FLUPENTIXOL ON LATENT INHIBITION IN AVERSIVELY-MOTIVATED AND APPETITIVELY-MOTIVATED PARADIGMS - EVIDENCE FOR DOPAMINE-REINFORCER INTERACTIONS

Three experiments examined the influence of the dopamine (DA) D-1/D-2 receptor antagonist alpha-flupenthixol on the latent inhibition (LI) e ffect. LI is a phenomenon which is manifest when non-reinforced pre-ex posure to a stimulus retards subsequent conditioning to that stimulus, and has been proposed as an animal model of the selective attentional processes that are disrupted in acute schizophrenia. Experiment 1 ext ended previous findings that neuroleptics enhance the LI effect in con ditioned suppression paradigms in rats to a-flupenthixol (0.23 mg/kg). Experiment 2 demonstrated that this enhancement of the LI effect was also seen in a parallel appetitively-motivated conditioning paradigm a t the same dose. In both Experiment 1 and Experiment 2, the enhancemen t of the LI effect by alpha-flupenthixol appeared to be accompanied by a decrease in the impact of the reinforcer (be it appetitive or avers ive). Experiment 3 investigated the possible role of the reinforcer in the effect of alpha-flupenthixol on the LI effect in the aversive, co nditioned suppression paradigm by increasing the intensity of footshoc k in rats treated with alpha-flupenthixol. Increasing the intensity of the footshock completely abolished the enhancement of LI found follow ing injection of alpha-flupenthixol, a result which could not be attri buted to a floor effect. The results provide no support for interpreta tions of the influence of DA manipulations on the LI effect that draw parallels with deficits in selective attention observed in acute schiz ophrenia.