EFFECT OF DIFFERENT CHRONIC INTERMITTENT STRESSORS AND ACETYL-L-CARNITINE ON HYPOTHALAMIC BETA-ENDORPHIN AND GNRH AND ON PLASMA TESTOSTERONE LEVELS IN MALE-RATS

Chronic stress affects the reproductive function by modifying the neur oendocrine homeostasis. The aim of the present study was to clarify th e neuroendocrine and the gonadal changes following chronic intermitten t stress in male rats and the action of a neuroactive drug, acetyl-l-c arnitine (ALC). The effect of two different stressors, cold water swim ming or ether, on central beta-endorphin (beta-EP) and GnRH contents, and on plasma testosterone levels was investigated. In addition, the r esponse to an acute stress in chronically stressed rats, treated or un treated with ALC (10 mg/day/rat p.o.), was evaluated. The stressors we re applied twice a day for 10 days, and rats were killed before, durin g and after the last stress session. Mediobasal hypothalamus (MBH) bet a-EP and GnRH contents, and plasma testosterone levels were evaluated by radioimmunoassay. The following results were obtained: (1) both chr onic swimming and ether stress caused a decrease in hypothalamic beta- EP contents; (2) MBH GnRH contents increased after chronic swimming st ress but not after ether stress; (3) chronic swimming stress induced a twofold decrease in plasma testosterone levels, while no changes were observed after ether stress; (4) the treatment with ALC prevented the decrease in plasma testosterone levels after chronic swimming stress, and (5) acute stress in chronically stressed animals caused an increa se in MBH beta-EP. The present data showed that chronic swimming stres s reduces the reproductive capacity and impairs the capacity to respon d to the acute stress and that ALC modulates the hormonal changes to p hysical stress and prevents the antireproductive effect of chronic col d swimming.