Effects of extrinsic denervation on net water transport and motility of the feline gallbladder in vivo

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The influence on the concentrating ability of the gallbladder after extrinsic denervation was studied in anesthetized cats, previously subjected to truncal vagotomy, and/or celiacectomy, and compared with sham-operated controls. Net water absorption was studied by perfusion techniques. Acute experiments were performed under basal conditions and α-adrenoceptor stimulation (iv infusion of norepinephrine (NE), 1 μg/kg · min). Gallbladder biopsies were studied by fluorescence microscopy to visualize and quantitate catecholamines. Three weeks after celiacectomy basal absorption had decreased significantly. In the short-term vagotomy group no changes were demonstrated. However, in the long-term vagotomy group there was a fourfold increase in absorptive capacity, which decreased to control levels after α-adrenoceptor blockade (phentolamine 1 mg/kg iv). Long-term vagotomy with subsequent celiacectomy caused no significant changes. Infusion of NE increased net water absorption by 70 ± 16% in all experimental groups except in long-term vagotomized animals, where the high basal absorption was not further augmented. One hour after NE infusion controls returned to basal absorption rate, while denervated cats remained at stimulated levels. In long-term vagotomized gallbladders there were morphological signs of adrenergic proliferation (increased total number of nerve terminals, sprouting, and elevated levels of intraneuronal NE). In conclusion these results suggest that the adrenergic nervous system is important for full absorptive capacity of the gallbladder. The increased absorption after long-term vagotomy, abolished after α-adrenoceptor blockade, might well be explained by the parallel adrenergic proliferation. This hypothesis was further corroborated in animals with long-term vagotomy, where subsequent surgical adrenergic denervation restored basal absorption to control levels. There was no motility response to NE in controls or short-term vagotomy animals, but after previous celiacectomy a short relaxation was seen indicating denervation supersensitivity of β-adrenoceptors. After long-term vagotomy there was a contractile response indicating activation of α-adrenoceptors as outlined in the absorption study.