Plasma vasopressin is not involved in footshock-induced analgesia in rats.

Abstract

Summary Whether plasma vasopressin (VP) mediates footshockinduced analgesia was examined in conscious rats. Footshocks significantly increased threshold temperature of tail flick and plasma VP as reported previously. Intravenous VP increased the threshold only in doses that are considered to elevate plasma VP to a level more than 500 times higher than that after footshocks. In addition, posterior pituitary stimulation increased plasma VP to a level ten times higher than that after footshocks but did not significantly change the threshold. It is therefore highly likely that plasma VP is not involved in footshock-induced analgesia.