Effects of the neuroleptic α-flupenthixol on latent inhibition in aversively- and appetitively-motivated paradigms: evidence for dopamine-reinforcer interactions
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Three experiments examined the influence of the dopamine (DA) D1/D2 receptor antagonist α-flupenthixol on the latent inhibition (LI) effect. LI is a phenomenon which is manifest when non-reinforced pre-exposure 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 extended previous findings that neuroleptics enhance the LI effect in conditioned suppression paradigms in rats to α-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 at the same dose. In both Experiment 1 and Experiment 2, the enhancement of the LI effect by α-flupenthixol appeared to be accompanied by a decrease in the impact of the reinforcer (be it appetitive or aversive). Experiment 3 investigated the possible role of the reinforcer in the effect of α-flupenthixol on the LI effect in the aversive, conditioned suppression paradigm by increasing the intensity of footshock in rats treated with α-flupenthixol. Increasing the intensity of the footshock completely abolished the enhancement of LI found following injection of α-flupenthixol, a result which could not be attributed to a floor effect. The results provide no support for interpretations of the influence of DA manipulations on the LI effect that draw parallels with deficits in selective attention observed in acute schizophrenia.
Key wordsDopamine Latent inhibition Schizophrenia α-Flupenthixol Neuroleptic Conditioning Attention
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