RESUMEN
OBJECTIVE: Progesterone is a sex hormone and its receptors are expressed throughout the hippocampus. This study was aimed at evaluating the effects of different doses of progesterone on memory. METHODS: Male rats were arbitrarily assigned to nine groups, namely Group I: control, Group II: control-cannula, Group III received 0.5 µl of saline by cannula, Groups IV , V, VI, VII and VIII received progesterone in doses of 0.5, 1, 1.5, 2, and 3 µg/ 0.5 µl by cannula, respectively. Group IX received 0.5 µl almond oil by cannula. Memory performance was tested in form of passive avoidance task. RESULTS: Our results indicated that progesterone at doses of 1.5 and 2 µg (p < 0.05) significantly increased the memory performance while at a dose of 3 µg (p < 0.05), it significantly decreased memory as compared to the control group. CONCLUSION: The current study revealed that the influence of progesterone on memory is related to its dose (Fig. 1, Ref. 25).