ABSTRACT
The effect of the absence of melatonin signal, induced by pinealectomy as well as by continuous light to the oxidative metabolism of nervous structures of the male rat was studied. The selected nervous tissues structures involved in sexual processes of the male rat were amygdala, ventral hypothalamus, septal area pituitary and posterior cortex (latero-occipital); the anterior cortex (latero-frontal) was studied as the control brain area of the rat's sexual activity, while the testes were also studied. Oxidative metabolism was determined by its O2 uptake (QO2) in these tissues. Four groups of rats were studied viz., controls killed during daytime (7 h after lights on), controls killed at night time (5 h after lights off), pinealectomized rats killed during daytime, and male rats kept under constant lighting from birth. The results did not show statistically significant differences of the QO2 (microliters O2/mg wet tissue/h) in the nervous structures involved in sexual processes or in the testes of the rat subjected to pinealectomy or continuous light. Only the QO2 of the anterior cortex showed significant difference (P < 0.05) between day time and night time values of the control group. The pineal gland weight showed a suppressive effect produced by continuous light from birth compared to control group values during the day (P < 0.05) and at night (P < 0.01). The results of this study indicate that the inhibitory effect of the pineal gland on the neuroendocrine reproductive axis of the rat is due to a longer increased nocturnal peak of melatonin, and that the lack of the pineal gland has no effect on the functional activity of nervous structures involved in sexual processes of the rat.