Fig. 5.

Effects of estrogen, estrogen plus the M2 receptor antagonist BIBN 99, or BIBN 99 alone on NMDA-displaceable [³H]glutamate binding in CA1. Ovariectomized rats received one of the following treatments: control treatment (C), two injections of estradiol benzoate (10 μg) delivered 48 and 72 hr before death (E), two injections of estradiol benzoate plus injections of BIBN 99 (0.05 mg/kg, delivered every 4 hr; E + B), or injections of BIBN 99 alone (B). After death, NMDA receptor binding was determined via in vitro quantitative receptor autoradiography. Values reported are total [³H]glutamate binding minus [³H]glutamate binding in the presence of NMDA (in pmol/mg protein ± SEM). Data were collected from 12 consecutive sections of the dorsal hippocampus between 2.56 and 2.80 mm posterior to bregma (*p < 0.05 vs C, E + B; Newman–Keuls).