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The relation between drive state and general level of activity has been a frequent topic of investigation in psychology since Richter's first systematic experiments on the activity of the rat in 1922. Most of the studies in this area, designed to support the notion of an "energizing" function of drive, have reported a regular increase in activity with moderate food deprivation (Siegel and Steinberg, 1949;Finger, 1951; Dashiell, 1925, as cited in Alderstein and Fehrer, 1955). In recent years this relation has come to be taken so for granted that some current textbooks have used it as the basis for defining the term "drive", viz., " ... a theoretical conception" associated with " ... a condition in which the animal is impelled to persistent activity until equilibrium is restored" (Hebb, 1958, p.l55), and "A term implying impetus to behavior" (Morgan, 1956, p.629). [...]

One way in which a better understanding may be gained of the processes underlying human alcoholism is through experimental research using lower animals as subjects, an approach that has already received much experimental attention. The purpose of this kind of research is not to extrapolate directly from animal to human behavior, but instead to investigate the kinds of factors that may be important to the initiation, development, and maintenance of the disorder. [...]

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It is well established that the neurotransmitter serotonin participates in the control of sexual behaviour in the male rat. Recently, it has been found that serotonergic activity may either inhibit or facilitate sexual behaviour, depending on the subtypes of serotonin receptors involved. However, the participation of 5-HT2 receptors in the control of male rat copulation has received little experimental attention, and the published data are equivocal. In Experiments 1-4, it was established that the 5- HT2/1C agonist DCI inhibits sexual behaviour in male rats; this inhibition is effectively reversed by the antagonists ritanserin, pirenperone, and ketanserin. Comparison of these effects , with reference to the binding profiles of each drug, provided strong evidence that 5-HT2/1C receptors mediate an inhibitory influence on sexual behaviour in male rats. In addition, a tentative claim may be made that the effects of these drugs may be more attributable to 5-HT2 activity than 5-UT1C activity. ‘Wet dog shake’ behaviour in rats is known to be 5-HT2- dependent. Experiments 5—7 evaluated the novel proposition that the incidence of spontaneous wet dog shaking (WDS) by male rats in mating tests may provide a behavioural assay of concurrent 5—HT2 activity. WDS was found to be associated with copulatory inhibition in noncopulating males, compared to normal copulators, and this relationship was specific to mating situations. Activating 5-HT2/1C receptors with DOl simultaneously induced WDS and inhibited copulation. Thus, the incidence of spontaneous WDS in untreated males may reflect the function of a 5—HT2—mediated neural mechanism that tonically inhibits copulation in male rats. In Experiment 8, DOl microinjection in the nucleus raphe obscurus/inferior olivary complex also induced WDS and inhibited copulation. This suggests that the hypothesized 5- flT2-dependent inhibitory mechanism is vested in the ventromedial brainstem. Recent anatomical findings support this suggestion: cells in this region have bifurcating axons, projecting collaterally to both the medial preoptic area (implicated in sexual behaviour) and to the ventral cervical spinal cord (implicated in WDS). Overall, the results of the eight experiments provide strong evidence that 5-HT2 receptors mediate some of the inhibitory effects of serotonin on male rat sexual behaviour.

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