Effects of methaqualone on punished and nonpunished behavior.

Effects of methaqualone were studied on the key pecking of pigeons maintained under various schedules of food presentation. One group of pigeons responded under a multiple fixed-ratio, fixed-interval schedule. Methaqualone (3.0--10.0 mg/kg) decreased the relatively low rates of responding under the fixed-interval schedule but left unchanged the higher rates under the fixed-ratio schedule. Higher doses of methaqualone decreased responding under both schedules. Another group of pigeons responded under a fixed-interval schedule in which responding was suppressed (punished) by electric shock presented according to a fixed-ratio schedule. Suitable doses of methaqualone increased punished responding. A 2-fold change in shock intensity produced little change in rates and patterns of responding, yet methaqualone produced much greater increases in responding punished by the lower intensity shock. Regardless of whether or not responding was punished, the effects of methaqualone on fixed-interval performance depended on the rate of responding in the absence of drug; low rates of responding in the early periods of the fixed-interval were increased by doses that increased less or decreased the higher response rates in the later periods. These rate-dependent effects of methaqualone were modulated by the shock intensity; the rate-increasing effects obtained at the lower intensity shock were uniformly greater than those obtained at the higher intensity. The behavioral effects of methaqualone were generally qualitatively similar to effects reported for many sedative hypnotics.