Cholecystokinin does not act on the efferent pathway of cholinergic and adrenergic nerves to inhibit ruminal contractions in sheep (Ovis aries).
The effect of exogenous cholecystokinin-octapeptide (CCK-8) on ruminal contractions and the role of efferent pathways of cholinergic and adrenergic nerves on the effect were studied in sheep. Intravenous infusion of CCK-8 at 11.4 and 45.6 pmol/kg/min significantly inhibited the frequency and amplitude of ruminal contractions in conscious sheep. After bilateral cervical vagotomy, intravenous infusion of CCK-8 at 45.6 mol/kg/min had no detectable effect on amplitude of ruminal contractions induced by electric stimulation to the cervical vagus nerve (1 msec, 20 Hz, 5 mA, for 10 sec at 1-min intervals) in anesthetized sheep. The amplitude of contractile responses of ovine ruminal muscle strips to acetylcholine at 5 x 10(-5) M was not inhibited by CCK-8 applied simultaneously at 1 x 10(-9) M. Intravenous infusion of phentolamine at 53.0 nmol/kg/min, propranolol at 101.4 nmol/kg/min, or their combined infusion did not alter the inhibitory action of CCK-8 at either dose on ruminal contractions in conscious sheep. These results suggest that CCK-8, which does not act on the efferent pathway of cholinergic and adrenergic nerves, may reflexively inhibit reticuloruminal contractions via vagal afferent fibers in sheep.
Onaga
T
T
Department of Veterinary Medicine, Rakuno Gakuen University, Hokkaido, Japan.
Onodera
T
T
Mineo
H
H
Kato
S
S
D000109:Acetylcholine / Q000494:pharmacology; D000320:Adrenergic Fibers / Q000502:physiology*; D000818:Animals; D002766:Cholecystokinin / Q000502:physiology*; D002799:Cholinergic Fibers / Q000502:physiology*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000502:physiology; D010646:Phentolamine / Q000494:pharmacology; D012159:Reticulum / Q000187:drug effects / Q000502:physiology; D012417:Rumen / Q000187:drug effects / Q000502:physiology*; D012756:Sheep / Q000502:physiology*; D012844:Sincalide / Q000494:pharmacology; D014628:Vagotomy; D014630:Vagus Nerve / Q000502:physiology
D002766:Cholecystokinin; D012844:Sincalide; D000109:Acetylcholine; D010646:Phentolamine