Opioid involvement in TRH-induced antinociception in the rat following intracerebral administration

Abstract

Thyrotropin-releasing hormone (TRH) has an antinociceptive action in the rat. Antinociception was observed using a thermal stimulus (tail-flick test) after TRH administration into lateral ventricle, nucleus raphe magnus, nucleus reticularis paragigantocellularis and amygdaloid nuclei. This effect was short-lived since it was completely abolished 60 min after intracerebroventricular administration. TRH may interact with the opioid systems as its antinociceptive effect was blocked by pretreatment with naloxone.