[Effect of melatonin on L-leucine aminopeptidase in the hypothalamus and cerebral cortex of the normal and ovariectomized rat].

The effect of melatonin (500 micrograms/kg weight s.c. for 15 consecutive days) on the L-leucine amino peptidase (LAP) activity of the hypothalamus and brain cortex is studied on castrated and nan castrated rats. There was a significant increase in the LAP activity of hypothalamus (p less than 0.001 v.s. saline group) in the non castrated group, however, no changes were observed in the brain cortex. In the ovariectomized group injected from the 15th to 30th after castration, a very big decrease was recorded in the LAP activity in both the hypothalamus and brain cortex which was not modified by melatonin. This data is studied in relationship to the antigonadotrophic effect of melatonin on the non castrated animals since the changes of this activity in the hypothalamus are inversely related to the gonadotrophin secretion, specially luteinizing hormone.