Some observations on the anorectic activity of prostaglandin F2alpha.

1 Intracerebroventricular injection of prostanglandin F2alpha (10-40 microgram) decreases food intake in a dose-dependent manner in rats trained to consume their daily total food intake in a 2 h period. 2 This anorexia is also observed in satiated rats, which had ad libitum access to food. 3 The anorectic activity of prostaglandin F2alpha is not modified by changes in the internal environment of the body after food intake, such as increased blood glucose and insulin levels and decreased fatty acid levels, or by the presence or absence of food in the stomach, as is evident from the anorectic activity of prostaglandin F2alpha in partially satiated rats. 4 The anorexia is not due to pain or irritative properties of prostaglandin F2alpha since induction of comparable pain with 3% acetic acid does not affect food intake in rats deprived of food for 22 hours. 5 Anorectic doses of prostaglandin F2alpha when injected intraperitoneally cause hypothermia. 6 The results suggest that the inhibitory activity of prostaglandin F2alpha on food intake is at both peripheral and central sites. 7 Prostaglandin F2alpha-induced anorexia is associated with the behavioural tranquilization that is seen after the ingestion of food.