Effects of enkephalin analogue and naloxone on cat spinal cord dorsal root potentials.
A systemically active enkephalin analogue, FK33824, given intravenously depressed dorsal root potentials in cat spinal cord. The negative DR V and positive DR VI, measured by computer, were both decreased; this effect was reversed by small doses of intravenous naloxone. Naloxone, given alone, with no previous analogue produced no changes in dorsal root potentials suggesting the absence of a basal enkephalin tone. A second injection of FK33824 was much less effective that the first dose. The results were discussed in relation to presynaptic mechanisms for analgesia: we proposed that FK33824 causes presynaptic inhibition by modulation rather than by depolarization of primary afferent fibers.
D000818:Animals; D002415:Cats; D004723:Endorphins / Q000494:pharmacology*; D004745:Enkephalins / Q000494:pharmacology*; D005260:Female; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009270:Naloxone / Q000494:pharmacology*; D013126:Spinal Nerve Roots / Q000187:drug effects*; D013997:Time Factors
D004723:Endorphins; D004745:Enkephalins; D009270:Naloxone