Interactive effects of brain catecholamines and variations in sexual and non-sexual arousal on copulatory behavior of male rats.

In pargyline pretreated male rats, an intraventricular 6-hydroxydopamine procedure which resulted in subtotal brain catecholamine (CA) depletion produced a mild defict in copulatory behavior followed by rapid recovery. Challenges employed to study the behavioral capacities of these 'recovered' animals revealed: (1) a heightened sensitivity to acute treatment with the CA synthesis inhibitor alpha-methyl tyrosine (AMT) as reflected in a reinstatement and exaggeration of the original copulation deficit; (2) a greater dependence on the sexual eliciting properties of the female, since abolishing her soliciting behavior also reinstated and exaggerated the sexual dysfunction; and (3) a pattern of behavioral impairment indicating increased difficulty in both initiating sexual activity and maintaining copulatory performance. Furthermore, in males not copulating after 6-OHDA/AMT treatment, copulation could easily be induced by the simple application of a non-specific activating stimulus. On the basis of these data and parallel findings reported for other behaviors, we have concluded that: (1) both the initiation and maintenance of copulatory behavior in the male rat is the part dependent on normal functioning in one or more of the brain CA-containing systems; and (2) this copulatory deficit is symptomatic of a broader functional impairment reflecting reduced behavioral responsiveness to stimuli that normally elict appetitive or approach responses but not to stimuli requiring more automatic, inhibitory responses.