Vagal influences on the jejunal 'minute rhythm' in the anaesthetized ferret.

Abstract

Spontaneous jejunal motility in the urethane-anaesthetized ferret shows a cyclical pattern of contraction bursts alternating with quiescent periods described as 'minute rhythm' in conscious animals. Cooling the cervical vagi to below 4 degrees C or acute vagotomy abolished this pattern of motility. On re-warming the vagi there was a return to cyclical motility after a latency which depended upon the contractile state at the time vagal conduction was restored. Electrical vagal stimulation produced bursts of contractions at the same frequency as the spontaneous motility. Longer periods of stimulation gave rise to bursts of contractions interrupted by periods of relative quiescence, mimicking the spontaneous motility, despite the continuous stimulation. Following atropinization all spontaneous motility was abolished, but electrical stimulation of the vagi revealed a non-cholinergic, non-adrenergic response whose characteristics differed from that of the cholinergic response. It is concluded that the vagus plays a permissive role in regulating the jejunal 'minute rhythm' via a cholinergic pathway and that there is a second excitatory vagal pathway which innervates non-cholinergic post-ganglionic neurones whose functional significance and transmitter mechanism is unknown.