EFFECTS OF FEEDING AND INSULIN ON EXTRACELLULAR ACETYLCHOLINE IN THE AMYGDALA OF FREELY MOVING RATS

Extracellular levels of acetylcholine (ACh) were measured in the centr al nucleus of the amygdala using microdialysis in 20-min intervals bef ore, during, and after 1 h feeding in food-deprived rats. The results were compared to the effects of peripheral injections of glucose or 'l ow' (200 mU) and 'high' (1 U) doses of insulin. Feeding caused a 40% i ncrease in extracellular ACh in the amygdala during the hour-long meal . Acetylcholine returned to baseline 1 h after food was removed. Syste mic injections of either glucose or insulin in ad Libitum fed rats als o resulted in an increase in ACh levels (+50-60%), but with a differen t time course. Glucose elevated ACh to a plateau within 20 min for an hour's duration; whereas both doses of insulin caused a peak in ACh re lease in the first 20 min followed by gradual return to baseline. The 'low' and 'high' doses of insulin had similar effects on ACh release e ven though they had different hypoglycemic potency as measured in bloo d samples. These results suggest that ACh in the AMY is involved in fe eding and the response to glucose utilization. (C) 1998 Elsevier Scien ce B.V.