THE TIME-DEPENDENT STIMULUS EFFECTS OF R(-)-2,5-DIMETHOXY-4-METHAMPHETAMINE (DOM) - IMPLICATIONS FOR DRUG-INDUCED STIMULUS-CONTROL AS A METHOD FOR THE STUDY OF HALLUCINOGENIC AGENTS

The pharmacodynamic characteristics of the stimulus effects of the hal lucinogens d-LSD and (-)DOM were investigated in the rat. The stimulus control induced by (-)DOM (0.56 mg/kg) was significantly less stable at the 15-min pretreatment time than at the 75-min pretreatment time. In addition, (-)DOM (0.8 mg/kg) produced a time-dependent substitution for the LSD stimulus in LSD trained subjects (0.1 mg/kg, 15-min pretr eatment time). As pretreatment times were increased, the substitution of (-)DOM (0.8 mg/kg) for the LSD stimulus increased, culminating in a maximal level of 99.5% LSD-appropriate responding at the 75-min pre-t reatment time. A dose-response relationship for the substitution of (- )DOM (75-min pretreatment time) for the LSD stimulus, indicated that 0 .2 mg/kg (-)DOM was the minimum-dose which elicited greater than 90% L SD-appropriate responding. LSD (0.32 mg/kg, 15-min pretreatment time) fully substituted for (-)DOM in the (-)DOM trained subjects (0.56 mg/k g, 75-min pretreatment time). These findings suggest that the pharmaco dynamic parameters of d-LSD and (-)DOM-induced stimulus control differ . The time of onset for the stimulus effects of (-)DOM is markedly lon ger than that of LSD in the rat.