Hypothalamic, Pituitary, Testicular, and Secondary Organ Functions and Interactions During the Sexual Maturation of the Male Rat

Abstract

Puberty in the male rat is a complex process that involves maturational changes in the hypothalamus, pituitary, testes, and secondary sexual organs and in their interrelationships. During the course of sexual maturation the negative feedback control systems for the gonadotropins become less responsive to testosterone while the testes become more responsive to LH. In the immature rat testosterone can potentiate the effect of LH-RH on pituitary LH release; this response is lost with sexual maturation. LH-RH sensitizes the mature male pituitary glands for subsequent LH-RH administration; this self-priming effect is not present in the immature rat. The responsiveness of the secondary organs to testosterone is also altered with age, as is the relative proportion of testosterone and androstendione secreted by the testes. Experiments designed to prevent or mimic the transition in testicular steroid secretion suggest that it may be a critical component of sexual maturation in the male rat. An elevation in androstendione appears to be capable of delaying the maturation of the LH negative feedback system, the prostate gland, and the LH-RH self-priming effect.

Key Words:

• Hypothalamus
• Pituitary
• Testes
• FSH
• LH
• Testosterone