EVIDENCE FOR SEXUAL DIFFERENCES IN THE PREOPTIC AREA REGULATION OF BLOOD-GLUCOSE IN RATS

The effect of noradrenaline (NA) injection (20 or 40 nmol) into the pr eoptic area (POA) on plasma glucose and insulin was studied in male an d female rats. The rats were implanted with chronic jugular catheters for blood sampling and unilateral intracerebral cannulas placed just a bove the POA. Blood samples were taken before and at 5, 10, 15, 30 and 60 min after NA injection. As early as 5 min after NA injection, plas ma glucose levels rose rapidly in both male and female rats, reaching a peak at 15 min poststimulus. NA injection into the POA caused a dose -dependent hyperglycemic response in both male and female rats, althou gh the response was more intense and longer lasting in females than in males. However, NA injection into the POA induced an increase in plas ma insulin concentration in male but not in female rats. In addition, the increase in plasma glucose induced by 40 nmol NA injection in male s preceded that of insulin. Plasma levels of glucose after POA injecti on of NA were already significantly elevated (p < 0.01) within the fir st experimental interval (5 min), whereas a plasma insulin increase we re first detected 15 min post injection. We conclude that, when admini stered locally into the POA, NA can activate the sympathetic outflow e xpressed by a neurally mediated hyperglycemia which is more intense in females than in males. These data demonstrate that the POA has a sexu ally differentiated function in the regulation of glycemia.