Effect of Intracerebroventricular injection of thyrotropin-releasing hormone on the nociceptive discharges in mesencephalic reticular formation in the rat

Abstract

Extracelluar recording method was used to examine the effect of thyrotropin-releasing hormone (TRH) on 71 unit discharges of pain-excited neurons (PEN) in mesencephalic reticular formation (MRF) in 58 rats. Intracerebroventricular (icv) injection of TRH (10 Hg/10 μ) produced significant decrease of pain discharge rate of PEN. TRH potentiated the inhibitory effect of el elctroacupuncture (EA) on nociceptive discharges when application of EA at bilateral “Zusanli” was coupled with icv injection of TRH. Both of these inhibiting effects of TRH were completely offset or strikingly decreased by icv preinject ion of the cholinergic M-receptor blocker atropine. The results mentioned above and the mechanism of the inhibitory effect of TRH on pain discharges were discussed in this paper.

Keywords

thyrotropin-releasing hormone / mesencephalic reticular formation / pain discharge / electroacupuncture / atropine