Antecedent Hypoglycemia, Catecholamine Depletion, and Subsequent Sympathetic Neural Responses

Antecedent hypoglycemia is well known to impair sympathetic responses to subsequent hypoglycemia. However, it is less clear whether this occurs through altered sympathetic neural traffic or through decreased adrenal catecholamine release per se. It is also not clear whether antecedent hypoglycemia impairs sympathetic responsiveness to subsequent nonhypoglycemic sympathetic stimuli. We exposed rats to two episodes of insulin-induced hypoglycemia or sham hypoglycemia (n = 15 per group) on d −2 and −1 before exposure to transient (10 min) hypotension on d 0. Adrenal sympathetic nerve activity (SNA) was directly recorded in the conscious state and plasma catecholamine concentrations were assessed. We also examined the effect of antecedent hypoglycemia on phosphorylated and nonphosphorylated tyrosine hydroxylase (TH) protein expression as well as the expression of phenylethanolamine N-methyltransferase. Adrenal SNA was not significantly altered by antecedent hypoglycemia either at baseline of d 0 (before hypot...