Effects of 2-deoxyglucose on plasma catecholamines in adult and aged rats

To examine the effects of aging on the responsiveness of the sympathetic-adrenal medullary system, I have measured plasma levels of norepinephrine (NE) and epinephrine (EPI) in adult (6 months old) and aged (24 months old) Fischer 344 male rats. Two days prior to testing, rats were surgically prepared with chronic tail artery catheters to permit remote sampling of blood in conscious, unrestrained animals. Following collection of basal blood samples, each rat received a single injection of 2-deoxyglucose (2-DG, 250 or 500 mg/kg, IP) and additional blood samples were collected 1, 2 and 4 hours later. 2-DG, a glucose analogue, stimulates a centrally mediated activation of the adrenal medulla and to a lesser extent the postganglionic sympathetic neurons. For purposes of analysis, data were excluded from animals which died within 4 hours after injection. Basal plasma levels of both catecholamines were similar in adult and aged rats. Administration of 2-DG was attended by significant and sustained increases in plasma NE and EPI in rats of both ages. A greater proportion of aged rats died following administration of 2-DG compared to adult rats. At the higher dose of 2-DG, plasma levels of NE were significantly higher in 6 month old rats at 1 and 2 hours post-injection. In contrast, plasma levels of EPI were significantly higher in 24 month old rats at 1 and 2 hours after administration of 250 mg/kg 2-DG and at 1 hour after administration of 500 mg/kg 2-DG.(ABSTRACT TRUNCATED AT 250 WORDS)