Involvement of adrenergic mechanism in hyperglycemia due to SCN stimulation.

Previously we found that in rats, electrical stimulation of the suprachiasmatic nucleus (SCN) of the hypothalamus elicited hyperglycemia associated with hyperglucagonemia without immediate hyperinsulinemia. To clarify the mechanism of these responses, we examined the effects of blockers of the autonomic nervous system on these responses. Hexamethonium, a ganglion blocker, suppressed the hyperglycemic and hyperglucagonemic responses to electrical stimulation of the SCN. Both bunazosin, an alpha 1-adrenergic blocker, and yohimbin, an alpha 2-adrenergic blocker, increased the level of insulin before stimulation, but only the latter suppressed the hyperglycemic and hyperglucagonemic responses. Propranolol, a beta-adrenergic blocker, partially inhibited the responses. These findings suggest that alpha 2- and beta-adrenergic mechanisms are involved in the hyperglycemic and hyperglucagonemic responses to SCN stimulation.