TY - JOUR AU - HOU Tian-De AU - DU Ji-Zeng PY - 2016 TI - Beta-endorphin suppresses release of thyrotropin-releasing hormone in rat hypothalamus during acute hypoxia exposure. JF - Acta Pharmacologica Sinica; Vol 23, No 10 (October 2002): Acta Pharmacologica Sinica Y2 - 2016 KW - N2 - AIM: To study the influences of beta-endorphin (beta-EP) on the responses of thyrotropin-releasing hormone (TRH) in median eminence (ME) and paraventricular nucleus (PVN) of hypothalamus to acute hypoxia in conscious rats. METHODS: Brain TRH, serum T3 and T4 were measured by radioimmunoassay. The male Wistar rats were exposed in a simulated hypobaric chamber at 7000 m altitude (8.2 % O2) for 2 h. beta-EP was given by intraventricular injection (icv) before hypoxia. RESULTS: beta-EP (0.1 or 1 micromol/L, icv) elevated TRH levels of ME by 12 % (P <0.05) and 15 % (P < 0.05) in treated groups comparing with saline control group (4.8+/-0.3) microg/g protein, and enhanced TRH of PVN by 24 % (P <0.05) and 44 % (P < 0.01) in treated groups comparing with control group (180+/-21) ng/g protein during hypoxia. Meanwhile, serum T3 and T4 were significantly decreased (P < 0.05 or P < 0.01). Naloxone 10 micromol/L abolished the effects of beta-EP (0.1 micromol/L) on TRH in ME (P <0.01) and PVN (P < 0.01) as well as T3 and T4. Naloxone (10 micromol/L, icv) alone reduced contents of TRH in ME and PVN (P <0.05 or P <0.01), but increased the levels of serum T3 and T4 (P <0.01). CONCLUSION: beta-Endorphin was involved in the modulation of hypothalamic TRH release of rats during hypoxia, through an inhibitory mechanism of TRH release in ME and PVN of hypothalamus. UR - http://www.chinaphar.com/article/view/7174