Intra-hippocampal estradiol infusion enhances memory in ovariectomized rats

OVARIECTOMIZED adult Long-Evans rats received an eight-trial training session in a hippocampal-dependent hidden platform water maze task. Following trial 8, rats received an intra-hippocampal injection of estradiol in a water soluble cyclodextrin inclusion complex (1.0, 2.0 or 5.0 mu g/0.5 mu l), or saline. Twenty-four hours later, the retention test escape latencies of rats administered post-training intra-hippocampal injections of estradiol (5.0 mu g) were significantly lower than those of saline treated rats, indicating a memory-enhancing effect of estradiol. Injections of estradiol (5.0 mu g) given 2 h post-training had no effect on retention, indicating a time-dependent effect of estradiol on memory storage processes.