Effects of single and simultaneous combined nanoinjections of Met-enkephalin into rat midbrain and medulla on activity of differentially nociresponsive ventral medullary neurons.
Neuronal activity classified by receptive field, adequate stimulus, and raphe-spinal (R-S) projection in 48 lightly anaesthetized rats was recorded from raphe magnus (RM) area. Effects of nanoinjections of Met-enkephalin in periaqueductal gray (PAG; 2 or 10 micrograms), nucleus reticularis paragigantocellularis (PGC; 1 or 5 micrograms), and both sites (conjointly) were studied. Most of the 78 neurons studied responded to noxious stimulation, some with increased responses ('on-cells') and some with decreased responses ('off-cells').


RESULTS
(1) Met-enkephalin in PAG and PGC depressed the response of on-cells and enhanced the response of off-cells; (2) for a given RM or R-S cell, PAG and PGC effects were typically identical; and (3) conjoint injections tended to produce greater effects than single effects, whether enhancing or depressing.
Rosenfeld
J P
JP
Northwestern University, Evanston, IL 60208.
Huang
K H
KH
Xia
L Y
LY
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D004744:Enkephalin, Methionine / Q000494:pharmacology*; D006358:Hot Temperature; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects / Q000502:physiology*; D009619:Nociceptors / Q000187:drug effects / Q000502:physiology*; D010487:Periaqueductal Gray / Q000187:drug effects / Q000502:physiology*; D011903:Raphe Nuclei / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains
D004744:Enkephalin, Methionine