PREJUNCTIONAL REGULATORY ACTIONS OF ANDROGENS ON A HORMONE-SENSITIVE MUSCLE

The influence of androgens and time course of effects induced by hormo ne deprivation were examined on the spontaneous transmitter release in the levator ani (LA) muscle of 30-180-day-old male rats. The resting membrane potential (RMP) and miniature endplate potentials (mepps) wer e recorded intracellularly from LA muscle fibers of intact animals or gonadectomized at different ages. In intact animals, the frequency of mepps increased proportionately to the muscle fiber growth up to 60 da ys, stabilizing thereafter. Gonadectomy at any age did not affect the RMP, but increased the frequency of mepps by 65% to 140%. The effect w as detected after 15 days and was unrelated to the degree of muscle at rophy. Independently of the age of gonadectomy control values of mepp frequency were restored after 90 days, while the accompanying postjunc tional changes persisted. These results indicate that androgens exert a prejunctional inhibitory influence on the spontaneous transmitter re lease in the rat LA muscle. The transient nature of the prejunctional effect induced by hormone deprivation indicates an adjustment of nerve terminals to persistent postjunctional alterations. (C) 1994 John Wil ey & Sons, Inc.