Neonatal diethylstilbestrol (DES) exposure diminishes pituitary responsiveness to GnRH in castrated postpubertal rats 4 h after placement of intra-atrial cannulae under ketamine anesthesia. Ketamine anesthesia has been reported to blunt the preovulatory LH surge in female rats and to decrease baseline LH levels in males immediately following administration, although its effect lasted less than 2 h. It is not known what impact ketamine has on baseline LH levels or on GnRH-stimulated LH release in estrogen-exposed castrated rats. This study was designed to determine 1) whether the changes in GnRH-induced LH secretion in DES-exposed castrated rats are partially attributable to a direct effect of ketamine; 2) the gender-specific effects of ketamine on LH secretion; and 3) the DES-dependent effects of ketamine on LH secretion. In this experiment we ascertained the effect of ketamine anesthesia for right heart cannulation on LH levels in male and female 42-day-old castrated rats that were exposed to either corn oil or DES (0.1 microgram/day) on Days 1 through 10 of life. LH secretion in DES-exposed animals increased, in contrast to that in control animals, immediately (< 10 min) after anesthesia and cannulation. Mean LH levels in DES-exposed females were lower than in controls before GnRH administration and were blunted following GnRH. While ketamine and catheterization were associated with decreased LH titer in males, the extent of that decrease was not dependent on exposure to DES. Both sexes and exposure groups achieved baseline catheter LH values by 4 h.(ABSTRACT TRUNCATED AT 250 WORDS)