DIFFERENCES IN RESPONSES TO PROPOFOL IN ELDERLY AND YOUNG-ADULT WISW RATS

How elderly and young adults differ in their susceptibility to propofo l, a GABA-mimetic drug, was studied in WISW rats. The incidence of nar cosis (4 - 20 mg/kg) or in the potency of propofol to inhibit withdraw al reflexes(ED50: 1.2 mg/kg) did not differ, but narcosis lasted longe r (20 mg/kg: 25 min v. 17 min), and both the onset (t(1/2) : 0.7 min v . 0.3 min) and decay (t(1/2) : 16 min v. 7 min) of reflex inhibition w ere slower in elderly than in young adults. Moreover, propofol-induced behavior differed: tail flicks, head and body shakes and walking diff iculties occurred less frequently, whereas vacuous chewing occurred mo re often in elderly than in young adult rats. In all, age-dependent di fference in the potency of propofol show in susceptibility for certain side-effects and these may relate to rapidity of effect and GABA func tionality in the brain. (C) 1997 John Wiley & Sons, Ltd.