Use of adult male bonnet monkeys (Macaca radiata) for testing the biological activity of gonadotropin releasing hormone and its analogues.

The effect of injecting agonistic and antagonistic analogues of gonadotropin releasing hormone analogues on serum testosterone levels was checked in adult and immature male bonnet monkeys. Of the agonistic analogues Buserelin, Ovurelin and D-Phe6 Gln8 GnRH were found to be most potent in increasing serum testosterone levels in the adult male bonnet monkeys. While 27-month-old monkeys responded well to des Gly10 GnRH, only marginal response was observed in the case of 15-month-old monkeys. Studies carried out with Ovurelin indicated that it was not effective in causing desensitization in adult monkeys. The antagonistic analogue was effective in blocking nocturnal surge of serum testosterone. Based on these studies it is suggested the adult male bonnet monkeys can be effectively used for testing the activity of GnRH analogues.

Effect of constant infusion of gonadotropin releasing hormone (GnRH) agonist buserelin and antagonist CDB 2085 A using osmotic minipumps on testicular function in adult male bonnet monkey (Macaca radiata).

The effect of chronic infusion of gonadotropic hormone agonist Buserelin or antagonist CDB 2085 A for 15 weeks via alzet minipumps in adult male bonnet monkeys was studied. Infusion of Buserelin resulted in a decrease in the difference between serum testosterone values at 22.00 hours and 10.00 hours, decrease in responsiveness to injected Buserelin as judged by change in serum testosterone values from pre-injection values and decrease in sperm counts. Infusion of antagonist resulted in a decrease in the difference between serum testosterone values at 22.00 hours and 10.00 hours.

Effect of suppression of prolactin on gonadal function in immature male hamsters.

The effect of chronic suppression of serum prolactin levels in immature male hamsters has been studied by injecting 15 micrograms of bromoergocryptine (EBC) for 20 days. A statistically significant decrease in serum testosterone, responsiveness to injected human chronic gonadotropin as judged by increase in serum testosterone and binding of 125I hCG in EBC treated animals was noticed. However there was no statistically significant decrease in testicular weight and serum prolactin was decreased only by 31% compared to the controls.

Effect of LHRH agonists and antagonists in male and female bonnet monkeys (Macaca radiata).

A few analogues of LHRH have been tested in the adult bonnet monkeys using change in serum testosterone following LHRH injection as a parameter of response to LHRH. Of the four analogues tested in male monkeys, Buserelin was found to be the most potent one in increasing serum testosterone levels. Injection of the LHRH antagonist at 1600 h resulted in the abolition of the characteristic nocturnal surge of testosterone observed in adult bonnet monkeys maintained under regulated light conditions. Following administration of LHRH a/s during early pregnancy, serum chorionic gonadotropin levels decreased though the course of pregnancy was not affected. These results suggest that bonnet monkey can be successfully employed to test LHRH analogues.

Effect of intranasal administration of norethisterone and progesterone on pituitary and gonadal function in adult male and female bonnet monkeys (Macaca radiata).

The effect of intranasal spray of norethisterone (NET) and progesterone (P) on serum testosterone (T) and total sperm count in adult male bonnet monkeys and the effect of NET spray on the menstrual cycle in female monkeys has been studied. Whereas NET spray resulted in a drastic decrease in serum T levels and sperm count, P spray caused a decrease in total sperm count only. Intranasal spray of NET in adult cycling female monkeys between days 5 and 14 resulted in shortening of the menstrual cycle; this could be ascribed to a decrease in serum follicle-stimulating hormone, luteinizing hormone, 17 beta-estradiol, and P levels. Nasal spray of only solvent in male or female monkeys, however, had no effect on any of the parameters tested.

Serum concentrations of chorionic gonadotrophin, oestradiol-17 beta and progesterone during early pregnancy in the south Indian bonnet monkey (Macaca radiata).

Serum concentrations of chorionic gonadotrophin (CG) during early pregnancy in the bonnet monkey (Macaca radiata), were determined by a radioimmunoassay validated for measuring monkey chorionic gonadotrophin. The earliest time at which CG could be detected was on the 28th day of a fertile cycle and it could not be detected beyond the 50th day. During a fertile cycle, mean values of oestradiol-17 beta, in addition to exhibiting a preovulatory peak around Days 9-10 of cycle, exhibited a secondary peak around Day 30 of the cycle. Serum progesterone levels remained elevated throughout the period of study from Day 18 to Day 50 and at no time did the levels fall below 2 ng/ml.

Serum testosterone levels during the menstrual cycle and early pregnancy in the bonnet monkey (Macaca radiata).

Serum testosterone concentrations have been determined during the menstrual cycle and early pregnancy in the bonnet monkey, Macace rediata. During the cycle, there is an increase around the time of ovulation and a secondary peak in the late luteal phase. In pregnancy, there is a distinct peak around 23-25 days, a period which corresponds to the peak of chorionic gonadotropin reported by Atkinson et al. (1975) in Rhesus monkeys. Administration of exogenous hCG causes a significant rise in the serum testosterone level in cycling monkeys.