ABSTRACT
The idea that 5–HT neurones mediate the effects of punishment on behaviour was first suggested by Wise, Berger and Stein (1970) and fostered by subsequent reports that 5–HT depletion with PCPA or treatment with non–selective 5–HT receptor antagonists releases punished responding in the conflict paradigm (Geller & Blum, 1970; Graeff, 1974). Tye, Everritt & Iverson, (1977) showed that 5,7–dihydroxytryptamine (5,7–DHT) lesions of ascending 5–HT pathways in rats released bar pressing for food reward from inhibition by contingent foot shock. This was perhaps the clearest demonstration that ascending 5–HT pathways are involved in shock–induced suppression of behaviour. One criticism of 5–HT punishment theories is that they are vaguely formulated and do not take into account the various behavioural effects of punishment nor do they ascribe differential behavioural functions to the different 5–HT projections.
