T. Onaga et al., CHOLECYSTOKININ DOES NOT ACT ON THE EFFERENT PATHWAY OF CHOLINERGIC AND ADRENERGIC-NERVES TO INHIBIT RUMINAL CONTRACTIONS IN SHEEP (OVIS-ARIES), Comparative biochemistry and physiology. Part A, Physiology, 111(1), 1995, pp. 51-58
The effect of exogenous cholecystokinin-octapeptide (CCK-8) on ruminal
contractions and the role of efferent pathways of cholinergic and adr
energic nerves on the effect were studied in sheep. Intravenous infusi
on of CCK-8 at 11.4 and 45.6 pmol/kg/min significantly inhibited the f
requency and amplitude of ruminal contractions in conscious sheep. Aft
er bilateral cervical vagotomy, intravenous infusion of CCK-8 at 45.6
mol/kg/min had no detectable effect on amplitude of ruminal contractio
ns 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. T
he amplitude of contractile responses of ovine ruminal muscle strips t
o acetylcholine at 5 x 10(-5) M was not inhibited by CCK-8 applied sim
ultaneously at 1 x 10(-9) M. Intravenous infusion of phentolamine at 5
3.0 nmol/kg/min, propranolol at 101.4 nmol/kg/min, or their combined i
nfusion did not alter the inhibitory action of CCK-8 at either dose on
ruminal contractions in conscious sheep. These results suggest that C
CK-8, which does not act on the efferent pathway of cholinergic and ad
renergic nerves, may reflexively inhibit reticuloruminal contractions
via vagal afferent fibers in sheep.