The effects of peripheral serotonin2 (5-HT2) and serotonin3 (5-HT3) receptor agonists on blood glucose levels in rats.

The involvement of the peripheral serotonin2A (5-HT2A) receptor in alpha-methyl-5-HT-induced hyperglycemia was examined in rats. The 5-HT2A receptor antagonist, ketanserin, significantly inhibited alpha-methyl-5-HT-elicited hyperglycemia. Taken together with a previous report that 5-HT-induced hyperglycemia was prevented by ketanserin, it is suggested that the peripheral 5-HT2A receptor participates in glucose regulation. As alpha-methyl-5-HT increased serum insulin but did not affect glucagon levels, it is indicated that these pancreatic hormones are probably not related to alpha-methyl-5-HT-induced hyperglycemia. Moreover, the peripheral 5-HT3 receptor agonist, 2-methyl-5-HT, did not affect blood glucose, insulin or glucagon levels. Our results therefore suggest that the peripheral 5-HT3 receptor is not involved in glucose regulation.