RAT STRAIN MINIMALLY INFLUENCES ANESTHETIC AND CONVULSANT REQUIREMENTS OF INHALED COMPOUNDS IN RATS

We assessed the effect of rat strain on susceptibility to anesthesia a nd convulsions produced by inhaled compounds. We determined the minimu m alveolar anesthetic concentration (MAC) of desflurane and nitrous ox ide, and the convulsive 50% effective dose (ED50) of 1,2-dichlorohexaf luorocyclobutane, flurothyl, and difluoromethyl-1-chlorotetrafluoroeth yl ether in five strains (three inbred [Long Evans, Sprague-Dawley, an d Wistar] and two outbred [Fischer and Brown Norway]). Strain had slig ht effects on anesthetic potency, the strains with the highest MAC val ues (Long Evans and Brown Norway) having values less than or equal to 28% greater than the strains with the lowest values (Sprague Dawley an d Wistar). MAC for nitrous oxide correlated directly with MAC for desf lurane as a function of strain. MAC for either desflurane or nitrous o xide correlated inversely with the convulsive ED50 of 1,2-dichlorohexa fluorocyclobutane, but correlated poorly land directly) with the convu lsive ED50 of the remaining compounds. Convulsivity varied little as a function of strain (greatest difference 21%) and did not vary consist ently as a function of strain. No consistent difference was seen betwe en inbred versus outbred strains. Implications: Rat strain has a minim al effect on the potency of inhaled anesthetics or the convulsant acti vity of inhaled compounds. It seems that the sites acted on by inhaled compounds to produce anesthesia and convulsions are conserved across common rat strains.