GnRH but not warm temperature induces recrudescence of quiescent testes in the tropical lizard Calotes versicolor (Daud.) during postbreeding phase.

The effects of temperature and various doses of GnRH on testicular recrudescence were studied in Calotes versicolor during the postbreeding (December-January) resting phase. Adult lizards (n = 51) were segregated into seven groups. Group I served as the initial control. Groups II, III, and IV were maintained at room temperature (23 +/- 1 degrees, range 17.5-25.5 degrees ) and natural photoperiod (12.25 h light:11.35 h dark). Groups V, VI, and VII were maintained at 30 +/- 1 degrees in an environmental chamber with 12 h light:12 h dark. Groups II and V received 0.2 ml saline, groups III and VI received 0.1 microgram GnRH/0.2 ml saline, and groups IV and VII received 0.5 microgram GnRH/0.2 ml saline on alternate days for 30 days. In the two groups that received 0.5 microgram GnRH, there was a significant increase in the diameter of the seminiferous tubules and Leydig cell nuclei, 3beta-HSDH activity in Leydig cells, and plasma testosterone level compared to those in other groups. There was no evidence of testicular recrudescence in lizards exposed to room/high temperatures treated with saline or 0.1 microgram GnRH. This study of C. versicolor shows that during the resting phase, high temperature per se does not stimulate testicular recrudescence, whereas 0.5 microgram GnRH does so. Also, the findings suggest that either higher brain centers regulating hypothalamus or hypothalamus itself become dormant, causing testicular inactivity (inactivation of hypophysial-testicular axis) during the postbreeding resting phase. Copyright 2000 Academic Press.