Endocrinology, Vol 99, 875-880, Copyright © 1976 by Endocrine Society

ARTICLES

Anesthetics and thyrotropin secretion in the rat

PT Mannisto, A Saarinen and T Ranta

The effects of seven anesthetics (thiopentone, 50 mg/kg ip; pentobarbitone, 50 mg/kg ip; chloral hydrate, 300 mg/kg ip; urethane, 1,5 g/kg, 1/2ip, 1/2sc; ether; methoxyflurane, 1,5%; halothane, 2%) on basal serum TSH concentrations and on the cold-induced as well as the TRH-induced TSH responses were studied in Sprague-Dawley rats. The basal TSH level in female rats were decreased by ether and halothane at 30 min and somewhat increased by pentobarbitone and chloral hydrate. The cold-induced (4C, 30-60 min) TSH response of the warm-adapted male rats (30 C, 7 days) was decreased by all of the anesthetics studied, but the effect of pentobarbitone was not significant. The TRH-induced (50 ng iv) TSH response in female rats was totally abolished only by deep ether anesthesia but augmented by bariturates and chloral hydrate. It is concluded that all of the anesthetics studied can modify the secretion of TSH by their central effects. Ether in high concentration seems to be effective also at the pituitary level. The use of anesthetics may be a source of error when studying the neurotransmitter control of TSH-TRH secretion in the rat.