TY - JOUR T1 - THE EFFECT OF VARIOUS NEUROHUMORAL MODULATORS ON THE ACTIVITY OF MORPHINE AND THE NARCOTIC ANTAGONISTS IN THE TAIL-FLICK AND PHENYLQUINONE TESTS JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 435 LP - 442 VL - 175 IS - 2 AU - WILLIAM L. DEWEY AU - LOUIS S. HARRIS AU - JOHN F. HOWES AU - JO ANN NUITE Y1 - 1970/11/01 UR - http://jpet.aspetjournals.org/content/175/2/435.abstract N2 - We have investigated the effect of a number of agents which alter central neurohumeral tone on the activity of morphine and the narcotic antagonists in the tail-flick and the phenylquinone tests. In general, an increase in central adrenergic tone caused an increase in the activity of morphine in the tail-flick test. However, some exceptions were observed which suggest mechanisms other than changes in neuromodulator tone might be responsible for the alterations of the potency of morphine. A number of these have been investigated and were found not to be contributing factors. Drugs which decrease adrenergic tone decreased the activity of morphine in this procedure. Alterations in adrenergic tone did not affect the analgesic activity of the antagonists. 5-Hydroxytryptophan caused an increase in the potency of morphine in the tail-flick procedure, thus indicating a possible involvement of central serotonergic mechanisms. A correlation between adrenergic or cholinergic tone and activity in the p-phenylquinone test was not evident. The significance of these results and the resultant validity of these procedures screens for analgesics is discussed. © 1970 by The Williams & Wilkins Co. ER -