The importance of muscarinic receptors in proliferation of different cell types and in insulin secretion from pancreatic beta cells has been extensively studied. However, the role of pancreatic muscarinic receptors during pancreatic regeneration has not yet been studied. For the first time, the functional status of the muscarinic M1 and M3 receptors in regeneration of the pancreas is investigated here. It is observed that the number and affinity of high-affinity muscarinic M3 receptors increased at the time of regeneration. The low-affinity M3 receptors also showed a similar trend. In the case of muscarinic M1 receptors, the receptor number increased with a decrease in affinity. We also observed an increase in the circulating insulin levels at the time of active regeneration. The in vitro studies confirmed that muscarinic receptors are stimulatory to insulin secretion. Our results suggest that the increased muscarinic M1 and M3 receptor subtypes stimulate insulin secretion and islet cell proliferation during the regeneration of pancreas.

The purpose of this study was to investigate the role of brain alpha1-adrenergic receptor binding in the rat model of pancreatic regeneration using 60-70% pancreatectomy. The alpha1-adrenergic receptors kinetics was studied in the cerebral cortex and brain stem of sham operated, 72 h pancreatectomised and 7 days pancreatectomised rats. Scatchard analysis with [3H]prazosin in cerebral cortex and brain stem showed a significant decrease (P < 0.01), (P < 0.05) in maximal binding (Bmax) with a significant decrease (P < 0.001), (P < 0.01) in the Kd in 72 h pancreatectomised rats compared with sham respectively. Competition analysis in cerebral cortex and brain stem showed a shift in affinity during pancreatic regeneration. The sympathetic activity was decreased as indicated by the significantly decreased norepinephrine level in the plasma (P < 0.001), cerebral cortex (P < 0.01) and brain stem (P < 0.001) of 72 h pancreatectomised rats compared to sham. Thus, from our results it is suggested that the central alpha1-adrenergic receptors have a functional role in the pancreatic regeneration mediated through the sympathetic pathway.