A New More Potent Analogue of LH-RH

Effects of 8-Arginine Vasotocin on Plasma Prolactin and Follicle-Stimulating Hormone Surges in the Proestrous Rat

“…2), for which the timing, duration, and magnitude in our studies were similar to those previously reported (5)(6)(7)(8). Neither lengthening the administration time of AVT nor increasing the dosage (up to eight times the amount that inhibited the prolactin surge) caused suppression of the endogenously elevated levels.…”

“…In diestrous rats, AVT did not affect tonic blood levels of LH, nor did it alter the elevated blood L H patterns in rats used 2, 14, or 30 days after ovariectomy. We undertook the present study to determine if AVT is capable of suppressing the endogenous increases in levels of plasma prolactin (3)(4)(5)(6) and follicle-stimulating hormone (FSH) (4)(5)(6)(7)(8) that occur on the afternoon of proestrous.…”

“…The endogenous increase of plasma prolactin commences between 1300 and 1600 hr on the day of proestrus (3)(4)(5)(6), and, accordingly, the 250-pl samples of blood were drawn hourly from 1200 through 1800 hr. The 93 rats in the prolactin experiments included 29 saline controls; the remainder were divided into groups for each compound, with 1-pg injections being administered at various times between 1300 and 1600 hr (see Table I).…”

“…The increase in plasma FSH occurring on proestrus is initiated at approximately 1400-1600 hr and remains elevated until late afternoon the following day (5)(6)(7)(8). Blood samples of 600 pl were obtained every 3 hr either from 0900 to 2100 hr or from 1500 to 2400 hr on the day of proestrus and at 0500 and 1200 hr the following day.…”