A possible role of neuropeptide Y in the control of the onset of puberty in female rhesus monkeys.

Abstract

The onset of puberty is heralded by an increase in pulsatile LHRH release. Since neuropeptide Y (NPY) has been implicated as a major regulator in the control of pulsatile LHRH release in mature monkeys, we have hypothesized that maturational changes in the NPY neuronal system play an important role in puberty. To test this hypothesis, three experiments were conducted in female rhesus monkeys using a push-pull perfusion method. In the first experiment, changes in NPY release in the stalk-median eminence (S-ME) during puberty were determined in 9 prepubertal, 7 early pubertal and 8 midpubertal monkeys. NPY and LHRH levels were measured in aliquots of the same perfusate samples obtained from the S-ME. NPY release was pulsatile in all three groups. Mean NPY release and pulse frequency increased significantly from the prepubertal through the midpubertal stage. These developmental changes in NPY release were parallel to those observed for LHRH release in the same monkeys. In order to examine whether NPY infusion into the S-ME influences LHRH release during puberty, in the second experiment, NPY (10(-6) or 10(-8) M) or vehicle was infused into the S-ME for 10 min at 90-min intervals in 5 prepubertal and 9 midpubertal monkeys. In the midpubertal stage, infusion of NPY at doses of 10(-8) and 10(-6) M resulted in significant (p < 0.01) increases in LHRH release, while vehicle administration had no effect. In contrast, in prepubertal monkeys, neither NPY nor vehicle infusion altered LHRH release. In order to test whether endogenous NPY plays a role in the maintenance of pulsatile LHRH release, in the third experiment, a specific antiserum to NPY (aNPY) was infused into the S-ME of 6 prepubertal and 8 midpubertal monkeys. Infusion of aNPY (1:100, 1:1,000 dilution) significantly suppressed LHRH release in midpubertal but not prepubertal monkeys. The results are summarized as follows. (1) In prepubertal monkeys, NPY release is low, and the presence of NPY in the S-ME does not influence LHRH release. (2) At the onset of puberty, NPY release begins to increase, and NPY probably starts to stimulate LHRH release. (3) In the midpubertal period, NPY release increases further, and NPY in the S-ME is highly stimulatory to LHRH release.(ABSTRACT TRUNCATED AT 400 WORDS)