Intracerebroventricular administration of β-endorphin releases immunoreactive met-enkephalin from the spinal cord in cats, guinea pigs and mice

It has previously been reported that β-endorphin, given intraventricularly, releases methionine-enkephalin from the spinal cord in rats. The present studies sought to determine whether β-endorphin, given supraspinally, also released immunoreactive met-enkephalin from the spinal cord in cats, guinea pigs and mice. Intracerebroventricular injection of β-endorphin caused a dose-dependent increase of the release of immunoreactive met-enkephalin from the spinal cord in these animals. The results support the hypothesis that the pharmacological actions produced by β-endorphin are mediated by the release of met-enkephalin.