Psychopharmacologia (Berl.) 44, 303- 305 (1975) - 9 by Springer-Verlag 1975
Methaqualone" Tolerance and Physical Dependence in Mice HERBERT P. ALPERN 1, CHARLES A. GREER 1, JEFFREY S. STRIPLING 1, A. C. COLLINS 2, and RICHARD K. OLSON 3 1 Department of Psychology and Institute for Behavioral Genetics, 2 School of Pharmacy and Institute for Behavioral Genetics, and 3Department of Psychology, University of Colorado Boulder, Colorado Received March 5, 1975; Final Version July 15, 1975
Abstract. Tolerance and physical dependence was produced in C57B1/6 male mice that had been exposed, for 36 days, to methaqualone in food pellets via an automated system, Tolerance was revealed in the reduction of sleep-times folKey words: Methaqualone - Tolerance - Physical dependence
Evidence supports contemporary folklore that methaqualone (Quaalude, Sopor) is highly sought after in the illicit drug market (Rock and Silsby, 1974; Bridge and Ellinwood, 1973; Gerald and Schwirian, 1973; I n a b a et al., 1973; and Pascarelli, 1973). Although clinical reports, characterized by a lack of adequate control populations and objective analysis, suggest development of tolerance and dependence to this compound, conclusive empirical confirmation has yet to be presented (Madden, 1966; Ewart and Priest, 1967). Other investigators have reported tolerance effects and some marginal dependence in rats with methaqualone; however, the behaviors used to ascertain tolerance were not exclusively under central nervous system (CNS) control (Kohli, Singh and Kulshrestha, 1974). Moreover, the manner in which methaqualone was administered did not guarantee that the animals were always under the influence of the drug, which could have notably diminished the magnitude and extent of the observable dependence (Kohli et al., 1974; Kalant et al., 1971; Seevers and Deneau, 1963). Consequently, we devised a drugexposure schedule to assess tolerance and dependence after long-term administration which insured that our subjects would be continually under the influence of methaqualone. We also selected behavioral indices which would provide a clear indication of methaqualone-induced alterations in CNS function: sleeptime as a measure of tolerance; and latencies to onset of fturothyl-induced myoclonic jerks, clonic convulsions, and tonic convulsions as a measure of physical dependence.
lowing intraperitoneal injection of methaqualone. Physical dependence was manifested as an alteration in neural sensitivitytoflurothyl-inducedconvulsions. - Addiction - Flurothyl - Mice.
Methods Forty-five adult male C57B1/6 mice (75- 90 days of age) were individually housed for the duration of the investigation. Water was continuously available; however, food (sixty 45-mg food pellets) was automatically administered daily to each animal. Within a 24-hr period there were 4 one-hour feeding sessions each separated by 5 hrs. We had previously determined that it required 3 _+ 0.2 g of food to maintain a single C57 mouse in a free-feed environment. However, with the automated food system, the total available food was slightly reduced so that the subjects were maintained at 90 _+ 5 ~o of normal body weight. This procedure ensured total consumption of all available food. During each feeding session, one pellet was delivered to each animal every 4 rain. The animals were alerted to the initiation of a feeding session by the click of the solenoid-operated feeders. It was rare for all pellets not to be consumed during the 1-hr session. To habituate the animals to this novel feeding procedure, all animals received standard pellets as outlined above on Days 1-5. On Day 3, 30 animals were injected intraperitoneally with 50 mg/kg (1 gl/g of body weight) of methaqualone dissolved in propylene glycol and 15 mice were similarly injected with propylene glycol. Following this anesthetic dose, sleep-times, from loss of righting-reflex to recovery of righting-reflex, were then measured in a V-shaped trough whose walls were separated by 90~. The trough configuration ensured when the animals righted themselves it was a purposeful movement (Kakihana, 1965). On Day 6 the 30 methaqualone-treated animals were randomly divided into 2 equal groups (Methaqualone Group and Control Group I). The other 15 subjects comprised Control Group II. Early in the experiment one subject assigned to the Methaqualone Group and one to Control Group II died and were discarded from all data analyses. The control groups received standard pellets for the duration of the experiment. The Methaqualone Group received standard pellets prepared with 8 different dosages of methaqualone per pellet: 0.04, 0.10, 0.17, 0.23, 0.29, 0.35, 0.42, and 0.48 mg. Beginning with the smallest, a particular dosage
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Psychopharmacologia (Berl.), Vol. 44, Fasc. 3 (1975)
was administered for 4 consecutive days (Days 6 - 9 ) ; the remaining dosages were administered similarly in an ascending fashion (Days 10-37). Based upon average weights of the mice for each 4-day dosage-period, the Methaqualone Group received successively 102, 282, 451,642, 716, 851, 1045, and 1288 mg/kg/day of drug. On Day 37 all animals were injected intraperitoneally with 50 mg/kg of methaqualone and their ensuing sleep-times recorded. This assessment was performed during a feeding period, and it should be noted that for the Methaqualone Group, standard pellets without drug were substituted during the preceding feeding session. Thus, the Methaqualone Group was injected 11 hrs after it last received methaqualone in its food. Any methaqualone still present at this time would have augmented the effect of the injection and consequently, would have counteracted the manifestation of tolerance. No further measures were taken on Control Group II. Following the test for tolerance the mice in the Methaqualone Group were maintained on the highest-dose pellets for 78 hrs, after which the mice were withdrawn from methaquatone and standard pellets substituted. Control Group I continued to receive standard food pellets for this 78-hr period. Eighteen hours into withdrawal the animals from the Methaqtlalone Group and Control Group I were tested for alterations in CNS sensitivity. Animals were individually placed into a 431.6 cc glass jar which was sealed with a cap. The cap contained a rubber septum and 15 mm below the septum a pledget of filter paper was suspended in a Plexiglas tube. The cap also contained 2 channels, one going to a clamped rubber tubing and the other to a vacuum inlet. Five microliters of flurothyl were then injected through the septum and latencies recorded to onset of the: (a) first myoclonic jerk of the neck and head musculature; (b) clonic convulsion with loss of posture; and (c) tonic convulsion with full leg extension (see Adler et al., 1967). Flurothyl, although not extensively used in this type of research, has proven to be a highly sensitive agent for detecting modifications of CNS excitability (Adler et al., 1974). Since it is an inhalant, its use avoids problems associated with administering drugs to mice intravenously, and problems with rates of absorption across animals using other modes of administration.
Results There were no differences in sleep-time between the Methaqualone G r o u p and Control G r o u p I after the initial injection of methaqualone (t = 0.17, df = 27). However, there was a highly significant difference in sleep-time (Table 1), when the Methaquatone G r o u p was compared with both controls after the second injection o f methaqualone (t = 6.8, df = 27, P
Methaqualone" Tolerance and Physical Dependence in Mice HERBERT P. ALPERN 1, CHARLES A. GREER 1, JEFFREY S. STRIPLING 1, A. C. COLLINS 2, and RICHARD K. OLSON 3 1 Department of Psychology and Institute for Behavioral Genetics, 2 School of Pharmacy and Institute for Behavioral Genetics, and 3Department of Psychology, University of Colorado Boulder, Colorado Received March 5, 1975; Final Version July 15, 1975
Abstract. Tolerance and physical dependence was produced in C57B1/6 male mice that had been exposed, for 36 days, to methaqualone in food pellets via an automated system, Tolerance was revealed in the reduction of sleep-times folKey words: Methaqualone - Tolerance - Physical dependence
Evidence supports contemporary folklore that methaqualone (Quaalude, Sopor) is highly sought after in the illicit drug market (Rock and Silsby, 1974; Bridge and Ellinwood, 1973; Gerald and Schwirian, 1973; I n a b a et al., 1973; and Pascarelli, 1973). Although clinical reports, characterized by a lack of adequate control populations and objective analysis, suggest development of tolerance and dependence to this compound, conclusive empirical confirmation has yet to be presented (Madden, 1966; Ewart and Priest, 1967). Other investigators have reported tolerance effects and some marginal dependence in rats with methaqualone; however, the behaviors used to ascertain tolerance were not exclusively under central nervous system (CNS) control (Kohli, Singh and Kulshrestha, 1974). Moreover, the manner in which methaqualone was administered did not guarantee that the animals were always under the influence of the drug, which could have notably diminished the magnitude and extent of the observable dependence (Kohli et al., 1974; Kalant et al., 1971; Seevers and Deneau, 1963). Consequently, we devised a drugexposure schedule to assess tolerance and dependence after long-term administration which insured that our subjects would be continually under the influence of methaqualone. We also selected behavioral indices which would provide a clear indication of methaqualone-induced alterations in CNS function: sleeptime as a measure of tolerance; and latencies to onset of fturothyl-induced myoclonic jerks, clonic convulsions, and tonic convulsions as a measure of physical dependence.
lowing intraperitoneal injection of methaqualone. Physical dependence was manifested as an alteration in neural sensitivitytoflurothyl-inducedconvulsions. - Addiction - Flurothyl - Mice.
Methods Forty-five adult male C57B1/6 mice (75- 90 days of age) were individually housed for the duration of the investigation. Water was continuously available; however, food (sixty 45-mg food pellets) was automatically administered daily to each animal. Within a 24-hr period there were 4 one-hour feeding sessions each separated by 5 hrs. We had previously determined that it required 3 _+ 0.2 g of food to maintain a single C57 mouse in a free-feed environment. However, with the automated food system, the total available food was slightly reduced so that the subjects were maintained at 90 _+ 5 ~o of normal body weight. This procedure ensured total consumption of all available food. During each feeding session, one pellet was delivered to each animal every 4 rain. The animals were alerted to the initiation of a feeding session by the click of the solenoid-operated feeders. It was rare for all pellets not to be consumed during the 1-hr session. To habituate the animals to this novel feeding procedure, all animals received standard pellets as outlined above on Days 1-5. On Day 3, 30 animals were injected intraperitoneally with 50 mg/kg (1 gl/g of body weight) of methaqualone dissolved in propylene glycol and 15 mice were similarly injected with propylene glycol. Following this anesthetic dose, sleep-times, from loss of righting-reflex to recovery of righting-reflex, were then measured in a V-shaped trough whose walls were separated by 90~. The trough configuration ensured when the animals righted themselves it was a purposeful movement (Kakihana, 1965). On Day 6 the 30 methaqualone-treated animals were randomly divided into 2 equal groups (Methaqualone Group and Control Group I). The other 15 subjects comprised Control Group II. Early in the experiment one subject assigned to the Methaqualone Group and one to Control Group II died and were discarded from all data analyses. The control groups received standard pellets for the duration of the experiment. The Methaqualone Group received standard pellets prepared with 8 different dosages of methaqualone per pellet: 0.04, 0.10, 0.17, 0.23, 0.29, 0.35, 0.42, and 0.48 mg. Beginning with the smallest, a particular dosage
304
Psychopharmacologia (Berl.), Vol. 44, Fasc. 3 (1975)
was administered for 4 consecutive days (Days 6 - 9 ) ; the remaining dosages were administered similarly in an ascending fashion (Days 10-37). Based upon average weights of the mice for each 4-day dosage-period, the Methaqualone Group received successively 102, 282, 451,642, 716, 851, 1045, and 1288 mg/kg/day of drug. On Day 37 all animals were injected intraperitoneally with 50 mg/kg of methaqualone and their ensuing sleep-times recorded. This assessment was performed during a feeding period, and it should be noted that for the Methaqualone Group, standard pellets without drug were substituted during the preceding feeding session. Thus, the Methaqualone Group was injected 11 hrs after it last received methaqualone in its food. Any methaqualone still present at this time would have augmented the effect of the injection and consequently, would have counteracted the manifestation of tolerance. No further measures were taken on Control Group II. Following the test for tolerance the mice in the Methaqualone Group were maintained on the highest-dose pellets for 78 hrs, after which the mice were withdrawn from methaquatone and standard pellets substituted. Control Group I continued to receive standard food pellets for this 78-hr period. Eighteen hours into withdrawal the animals from the Methaqtlalone Group and Control Group I were tested for alterations in CNS sensitivity. Animals were individually placed into a 431.6 cc glass jar which was sealed with a cap. The cap contained a rubber septum and 15 mm below the septum a pledget of filter paper was suspended in a Plexiglas tube. The cap also contained 2 channels, one going to a clamped rubber tubing and the other to a vacuum inlet. Five microliters of flurothyl were then injected through the septum and latencies recorded to onset of the: (a) first myoclonic jerk of the neck and head musculature; (b) clonic convulsion with loss of posture; and (c) tonic convulsion with full leg extension (see Adler et al., 1967). Flurothyl, although not extensively used in this type of research, has proven to be a highly sensitive agent for detecting modifications of CNS excitability (Adler et al., 1974). Since it is an inhalant, its use avoids problems associated with administering drugs to mice intravenously, and problems with rates of absorption across animals using other modes of administration.
Results There were no differences in sleep-time between the Methaqualone G r o u p and Control G r o u p I after the initial injection of methaqualone (t = 0.17, df = 27). However, there was a highly significant difference in sleep-time (Table 1), when the Methaquatone G r o u p was compared with both controls after the second injection o f methaqualone (t = 6.8, df = 27, P
