Effect of pineal indoles on testicular histology of mice.

The effect of late afternoon injections of melatonin, 5-methoxytryptamine, 5-methoxytryptophol, and 5-methoxyindole-3-acetic acid on testicular histology in mice were examined. Melatonin and 5-methoxytryptophol injections caused a reduction in the diameters of seminiferous tubules. The tests of melatonin-treated animals underwent some detectable regressive changes in the seminiferous tubules, whereas administration of 5-methoxytryptamine or 5-methoxytryptophol appeared to cause atrophy in some tubules. The percentage of aspermic tubules in melatonin-treated and methoxytryptamine-treated mice was significantly higher than that of the control. In involuted testes, some seminiferous tubules contained only Sertoli cells together with spermatogonia and spermatocytes, but no discernible spermatids and spermatozoa. Regressing spermatids and cell debris were frequently observed in the tubules. The tested of mice that received daily injections of 5-hydroxytryptophol and 5-methoxyindole-3-acetic acid were indistinguishable from those of the controls.