PROPOFOL POTENTIATES THE DEPRESSANT EFFECT OF ALFENTANIL IN ISOLATED NEONATAL RAT SPINAL-CORD AND BLOCKS NALOXONE-PRECIPITATED HYPERRESPONSIVENESS

Our previous studies have shown that a benzodiazepine potentiates opio id actions on spinal cord by blocking a hyperresponsiveness that may b e related to the development of opioid tolerance and withdrawal. The p resent study was designed to test whether propofol, which like benzodi azepines acts on GABA(A) receptors, displays similar interactions with opioids. Spinal cords isolated from 1-7 day old rats were arranged to record the slow ventral root potential (sVRP) elicited by stimulating a lumbar dorsal root. A concentration of propofol which by itself did not depress sVRP significantly enhanced the apparent potency of alfen tanil and blocked the increase in sVRP observed when alfentanil is fol lowed by naloxone. The results suggest that enhancement of GABA inhibi tion may increase opioid potency by inhibiting the development of acut e tolerance. (C) 1997 Elsevier Science Ireland Ltd.