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Phillips, Gavin (1990) Dopamine and reward : effects of dopamine antagonist drugs on operant and consummatory behaviours. Doctoral thesis, City of London Polytechnic.
The Herrnstein matching law was used to dissociate motoric from motivational drug-induced performance changes. The effects of neuroleptic drugs were compatible with, at low doses, a reduction in reinforcer efficacy, and at higher doses, an additional motor impairment However, the Herrnstein matching law was found to be prone to artifactual error; in particular, under reinforcement-lean conditions reductions in reinforcer efficacy were time-dependent These problems compromised the use of the Herrnstein law to assess drug-induced performance changes.
Raclopride-induced time-dependent reductions in response rate occurred in the absence of both primary and secondary reinforcement. Within-session decrements in both operant and consummatory behaviour were observed following administration of sulpiride to the anterodorsal striatum, but not following administration of sulpiride to the nucleus accumbens. The implications of this finding are discussed in relation to the internal organisation of behaviour, and Parkinson's disease.
Consumption of sucrose and operant responding maintained by sucrose pellets follows an inverted-U-shaped concentration-intake function. Systemic administration of raclopride shifted the curve to the right. It is argued that this curve shift reflects an impairment in the primary reward process. Effects of intracranial administration of sulpiride on sucrose consumption were restricted to the nucleus accumbens at a low concentration of sucrose, but were also observed within the anterodorsal striatum and basolateral amygdala at higher concentrations. These findings are discussed in relation to the neuroanatomical substrates for the guidance of behaviour by external cues, and for reward processes.
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