Potentiation of DOM-induced stimulus control by non-competitive NMDA antagonists: a link between the glutamatergic and serotonergic hypotheses of schizophrenia

The present investigation examined the interaction between 2,5-dimethoxy-4-methylamphetamine DOM] and non-competitive NMDA antagonists in rats trained with DOM 0.6 mg/kg; 75 min pretreatment time] as a discriminative stimulus. Pretreatment with phencyclidine PCP] at a dose of 3 mg/kg shifted the DOM dose-response relationship to the left. When a fixed dose of DOM 0.1 mg/kg] which by itself yielded 32% DOM-appropriate responding was combined with a range of doses of PCP, dizocilpine, and ketamine, DOM-appropriate percentages increased to maxima of 73%, 84%, and 79%, respectively. When given alone, PCP, dizocilpine, and ketamine were followed by maxima of 36%, 15%, and 13%, respectively. It is concluded that the effects of DOM as a discriminative stimulus are potentiated by pretreatment with non-competitive antagonists of glutamate receptors of the NMDA subtype. These data suggest that the application of the technique of drug-induced stimulus control may prove useful in the reconciliation and integration of current hypotheses as to the etiology of psychotic disorders.