Nervous Regulation of Islet Functions

Abstract

Despite a recent surge in interest, the neural regulation of the endocrine pancreas is poorly understood. Possibly, islet innervation is important for the pulsatile release of islet hormones. Pulsatile release of hormones, as opposed to tonic delivery, may have advantages such as increased efficiency at target organs (thus “saving” hormone), or prevention of receptor desensitization (for literature see Weigle et al. 1984; Samols et al. 1986). Another function of islet innervation may be an overriding control in the integration of islet responses. The vast majority of new data on islet innervation, which comes from studies in mammals, already reveals considerable inter- and intraspecific differences (Gerich and Lorenzi 1978; Woods and Porte 1978; R. E. Miller 1981; Smith and Madson 1981; Palmer and Porte 1983; Porte and Woods 1983; Rohner-Jeanrenaud et al. 1983; Smith and Davis 1983; Steffens and Strubbe 1983; Luiten et al. 1984; Jeanrenaud 1985). Although comparative studies are in their infancy, the available information shows that it is beforehand impossible to identify phylogenetic or functional patterns of islet innervation (Epple et al. 1980; Buchan 1984). Perhaps the extremes are best illustrated by the cyclostomes which totally lack an islet innervation and the teleosts in which islet cells show particularly intimate contacts with neurons (Epple and Brinn 1975).