Fig. 1.

Effects of DOM, ketanserin, MDL100907, and ritanserin in rats discriminating between saline and either 0.56 mg/kg DOM (left), 1.0 mg/kg ketanserin (center), or 0.1 mg/kg MDL100907 (right). Ordinates: upper, percentage of responses on the drug-associated lever; lower, rate of responding in responses per second. Abscissae: dose in mg/kg body weight; points above “V” represent data obtained after the administration of saline vehicle. Each entry is the mean ± S.E.M. for eight rats. Lower, dashed lines represent the 95% confidence limits of the mean rate of responding over the preceding 10 vehicle-training sessions in which the test criteria were satisfied.