Electrophysiological evidence for a rapid membrane action of the gonadal steroid, 17β-estradiol, on CA1 pyramidal neurons of the rat hippocampus

The rapid electrophysiological effects of 17β-estradiol on CA1 pyramidal neurons(n = 86) were investigated utilizing intracellular recording from the rat hippocampal slice preparation. Bath application of 17β-estradiol, but not 17α-estradiol, caused a reversible depolarization and increased input resistance with a latency of less than 1 min in 19.8% of CA1 neurons tested. There was no significant difference in the percentage of estradiol-responsive cells between male and female rats. Estradiol-responsive cells were identified from prepubertal female rats, as well as females in all stages of the estrous cycle. 17β-estradiol had no effect on the slow afterhyperpolarization or accommodative properties of CA1 neurons. In 2 out of 4 cells tested, the specific antiestrogen, tamoxifen, blocked the excitatory response to 17β-estradiol.