Self-stimulation in the sheep: interactions with ingestive behaviour and light cycle.

Self-stimulation was obtained in 5 adult male sheep using a movable electrode system. The effects on response rate of increases in current, food deprivation and satiation were determined. Interactions between feeding, drinking and self-stimulation over longer periods (5 days) were studied in experiments in which individual sheep lived in an isolated continuously illuminated pen. Experimental conditions were as follows:--(1) Food + water available on operant (FR 30); (2) Operant food and water + self-stimulation; (3) Bowl feeding, ad lib water + self-stimulation; (4) As for condition '3' but with 12:12 light/dark cycle. Finally, sheep were tested for stimulation-bound feeding and drinking. The results obtained in these experiments with the sheep, a ruminant, are compared with those previously found for the pig.