SUSTAINED EFFECTS OF A SINGLE INJECTION OF ETHANOL ON THE HYPOTHALAMIC-PITUITARY-GONADAL AXIS IN THE MALE-RAT

The hormones responsible for regulating the hypothalamic-pituitary-gon adal axis are essential for proper reproductive function, Ethanol (EtO H) has been shown to exert its effects at all three levels of this axi s. The present study defines striking differences in the time course o f recovery of luteinizing hormone (LH) in gonadally intact, compared w ith, castrated male rats after acute EtOH administration, Serum levels of LH and testosterone were measured at various time points up to 2 w eeks (1.5, 3, 24, 48, 72, 96, 168, and 336 hr) after a single intraper itoneal injection of either saline or 3 g/kg of EtOH in intact adult m ale rats, One EtOH injection significantly suppressed testosterone lev els to as low as 20% (p < 0.01) of saline-injected intact rats, This o ccurred as early as 1.5 hr after EtOH administration (the first measur ed time point), and statistically significant suppression was sustaine d for 96 hr, Similarly, LH levels showed a significant decrease, Howev er, this significant fall in LH did not begin until 3 hr (p < 0.05) an d continued up to 96 hr (p < 0.01), with a gradual return to control l evels at 168 and 336 hr after treatment, Despite the significant and p rolonged fail in testosterone levels in the EtOH-treated intact rats, beta-LH mRNA levels were inappropriately not elevated, as would be exp ected in the context of low circulating testosterone. However, at 168 and 336 hr, steady-state levels of beta-LH mRNA were significantly hig her than seen in saline-injected controls (p < 0.05 and p < 0.01, resp ectively), temporally correlating with the return of serum LH to contr ol. LH levels in the castrated animals were significantly suppressed a t 1.5 hr (p < 0.05) and 3 hr (p < 0.01) after EtOH treatment, compared with controls, yet they returned much more quickly by 24 hr after tre atment, beta-LH mRNA levels of castrated animals also showed a signifi cant depression at 1.5 and 3 hr, and returned to control levels by 24 hr. In these rats, the hypothalamic LH-releasing hormone mRNA levels w ere not altered by a single EtOH injection at anytime point, However, in the intact animals, there was a transient increase in LH-releasing hormone mRNA at 72 and 96 hr (p < 0.01 and p < 0.05, respectively) tha t may lead to the upregulation of beta-LH mRNA expression, These studi es indicate that EtOH causes prolonged decreases in important serum ho rmones that are essential to the reproductive axis of the adult male r at.