PT - JOURNAL ARTICLE AU - Edson Xavier Albuquerque AU - Cedric M. Smith TI - STIMULATION OF MUSCLE SPINDLE AFFERENTS BY DMPP DP - 1965 Sep 01 TA - Journal of Pharmacology and Experimental Therapeutics PG - 320--328 VI - 149 IP - 3 4099 - http://jpet.aspetjournals.org/content/149/3/320.short 4100 - http://jpet.aspetjournals.org/content/149/3/320.full SO - J Pharmacol Exp Ther1965 Sep 01; 149 AB - The relationships between dose and effects of intraarterially injected 1, 1-dimethyl-4-phenylpiperazinium iodide (DMPP) on 36 afferent nerves and endings of acutely de-efferented triceps surae muscle spindles of the cat were studied. DMPP produced excitation of all 36 muscle spindle afferent units. The degree of excitation produced by DMPP was related to the conduction velocity of the afferent fiber: the more rapidly conducting fibers exhibited a greater degree of increase in discharge frequency. DMPP was less potent than SCh in activating primary afferent endings, but was equal to or more potent than SCh in activating secondary afferent endings. DMPP was half as potent as SCh and 20 times more potent than nicotine in producing a block of extrafusal neuromuscular transmission. It is suggested that DMPP acts at the same sites and/or by the same mechanisms as does succinylcholine. The possibility that the mechanism of action of DMPP and succinylcholine is the induction of contracture of certain intrafusal muscle fibers is discussed. The Williams & Wilkins Comapny