Inhibition of cerebral type 1 cannabinoid receptors is associated with impaired auditory mismatch negativity generation in the ketamine model of schizophrenia

Preclinical and clinical research suggests that the endogenous cannabinoid system is involved in cognitive impairments related to schizophrenia. In particular, deficient generation of mismatch negativity (MMN) indicating auditory sensory memory is a characteristic finding in schizophrenic patients. Experimental studies implicate deficient N-methyl-D-aspartate (NMDA) receptor functioning in such abnormalities. The primary aim of this study was to investigate the effects of the cannabinoid CB1 receptor antagonist rimonabant on MMN deficits in the NMDA receptor antagonist model of schizophrenia by using ketamine. Twenty healthy male subjects participated in a randomized, double-blind, placebo-controlled cross-over study with subanesthetic doses of intravenous ketamine. The MMNs to frequency and duration deviants were elicited within an auditory oddball paradigm and recorded by 32 channel EEG. Ketamine infusion had no significant effect on MMN amplitudes in both deviance conditions. In contrast to placebo, co-administration of rimonabant produced significant deficits in MMN amplitudes to duration deviants at electrode position Fz. The results point to the involvement of the endogenous cannabinoid system in auditory sensory memory as a cognitive key feature in schizophrenia. They particularly suggest that CB1 receptor antagonism may impair cognitive performance by disturbed interaction between endocannabinergic activity and glutamatergic neurotransmission implied in schizophrenia.