Changes in pineal sympathetic innervation are not significant in the hyperproliferative effects of pinealectomy on the intestinal crypts.

OBJECTIVES To observe the effect of changes in the pineal sympathetic innervation on the crypt cell proliferation rate in the rat small intestine, and compare these with the effect of pinealectomy to determine the role of the sympathetic innervation in the effect of pinealectomy. METHODS The effect of bilateral ablation of the superior cervical ganglion, and that of pinealectomy on the crypt cell proliferation rate in the rat small intestine was determined, using a stathmokinetic technique. RESULTS Pinealectomy was associated with a considerably increased crypt cell proliferation rate, whereas superior cervical ganglionectomy was associated with a slightly decreased rate. CONCLUSIONS It appears likely that changes in pineal melatonin production cannot be correlated directly with the effects of pinealectomy on the crypts, although melatonin production was not measured in this case. The role of loss of the non-adrenergic innervation of the pineal in the effect of pinealectomy needs to be examined. There is also other experimental evidence that melatonin-free extracts of the pineal, containing as yet unidentified substances, can influence mitotic activity in some tissues, so the possible role of these substances in the effects of pinealectomy should also be considered. Furthermore, the superior cervical ganglion itself has an extra-pineal role. Changes in pineal sympathetic innervation are not significant in the hyperproliferative effects of pinealectomy on the intestinal crypts.