Induced inhibition of reticulo-rumen motility via central opioid mechanisms in sheep

Abstract

In conscious sheep, β-casomorphin 1–4 (BCM), administered into the third cerebral ventricle, caused no significant changes of the amplitude of the first rumen contraction, appearing just after the end of infusion. Average amplitude of primary contractions and contraction frequency were noted for the smaller dose (10 μg kg −1 BW) and significant inhibitory effects on these amplitudes and reticulo-rumen contractions for the larger dose (20 μg kg −1 BW). Both doses of BCM administered by intracerebroventricular (i.c.v.) infusion caused increased tone of the stomach muscle wall within approximately 9.3 min. Nalorphine infused i.c.v. (10 μg kg −1 BW) 15 min prior to the i.c.v. infusion of BCM (20 μg kg −1 BW), proved its inhibitory action on the reticulo-rumen motility. BCM alone infused i.c.v. (10 and 20 μg) caused general psychosedative effects, 5–10 min after the end of infusion. These results suggest that a central inhibitory opioid system is involved in the BCM-induced inhibition of forestomach motility and general behaviour in sheep and confirmed the physiological role of BCM in important functions of small ruminants.