Adaptation of the mechanisms controlling gastric motility following chronic vagotomy in the ferret

Abstract

Changes in gastric motility were studied in the urethane-anaesthetized ferret following acute or chronic (3 weeks) vagotomy. The stomach was divided into the corpus and antrum and the effects of vagotomy on tone, frequency and contraction amplitude were investigated separately in the two gastric regions. In the corpus tone is kept at low levels by vagal activation of nonadrenergic, non-cholinergic (NANC) inhibitory neurones and also tonic sympathetic inhibition of intramural cholinergic activity. Frequency of contractions is also low due to tonic inhibition of cholinergic neurones by the vagus but not the sympathetic nervous system. There appears to be little vagal involvement in contraction amplitude but there is sympathetic inhibition of this parameter again via inhibition of cholinergic neurones. In the antrum there is no vagally driven inhibition of tone but a sympathetic inhibition of cholinergic neurones tends to reduce tone in the intact animal. Frequency of contractions does not appear to be extrinsically modulated. The vagus is tonically excitatory with regard to contraction amplitude in the antrum whereas the sympathetic nervous system is inhibitory, again via inhibition of cholinergic neurones. After chronic vagotomy some adaptation appears to take place within the surviving control systems in both the corpus and the antrum. Changes in cholinergic function have been suggested previously and are corroborated in this study. In addition novel alterations in intrinsic NANC systems and the remaining sympathetic innervation have been demonstrated in both regions of the stomach which tended to reduce the effects of vagotomy and return values for the parameters measured toward those observed in intact animals. The contribution of the cholinergic, adrenergic and NANC neurotransmitter systems to the post-vagotomy motility patterns differed in the corpus and antrum.