Chronic ethanol or glucose consumption alter TRH content and pyroglutamyl aminopeptidase II activity in rat limbic regions

Thyrotropin-releasing hormone (TRH), its receptors and inactivating enzyme (PPII) are present in limbic regions. Nutritional changes or acute ethanol administration in male rats differentially modulate TRH or PPII expression. Chronic ethanol effect was studied in male (3, 6 and 8 weeks) and female rats (6 weeks) including naïve and pair-fed (glucose) groups. Daily solid food and liquid intake, serum TSH and corticosterone, TRH content and PPII activity in limbic regions, were quantified. Gender differences were found in ethanol and total caloric intake and body weight gain, TSH and corticosterone levels. Ethanol consumption decreased TRH content and PPII activity in frontal cortex of male rats after 3-6 weeks. In contrast, glucose ingestion altered, by the third week, TRH content in amygdala, hippocampus, hypothalamus and nucleus accumbens, PPII activity in hippocampus and frontal cortex; by the sixth week, TRH content in amygdala and n. accumbens of male and females. Withdrawal at 24 h after 3-week ethanol ingestion decreased TRH content in amygdala and PPII activity in n. accumbens, while withdrawal from glucose reverted some of the effects produced by chronic glucose ingestion. Variations in TRH content or PPII activity support a region specific involvement of TRH neurons that depend on the treatment.