ASYMMETRICAL CHANGES IN THE CHOLINE-ACETYLTRANSFERASE ACTIVITY IN THEPREOPTIC-ANTERIOR HYPOTHALAMIC AREA DURING THE ESTROUS-CYCLE OF THE RAT

THERE is evidence that the cholinergic system modulates, in a circadia n and asymmetric way, the neural activity involved in the regulation o f ovulation. In the present study we measured choline acetyltransferas e (ChAT) activity during the oestrous cycle in both sides of the preop tic-anterior hypothalamic area (POA-AHA) of the rat. The right side of POA-AHA showed significant changes in ChAT activity during the oestro us cycle. The activity of the enzyme was higher in the right side on t he day of oestrous (47.3 +/- 3.2 nmol mg(-1) protein 1 h(-1) vs 25.8 /- 2.4, p < 0.05), whilst on the second day of dioestrous the activity was higher in the left one (30.6 +/- 3.4 us 20.0 +/- 1.5). The differ ences in the activity of ChAT observed support the idea of the existen ce of asymmetry in the POA-AHA cholinergic system which varies during the oestrous cycle.