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Introduction-Cannabinoids produce a spectrum of effects in humans including euphoria, cognitive impairments, psychotomimetic effects, and perceptual alterations. The extent to which dopaminergic systems contribute to the effects of Δ-9-tetrahydrocannabinol (Δ-9-THC) remains unclear. This study evaluated whether pretreatment with a dopamine receptor antagonist altered the effects of Δ-9-THC in humans.

Sarcoidosis is a chronic inflammatory disease of unknown cause, characterized by granuloma formation similar to tuberculosis, but without clear evidence of a microbial infection. Because sarcoidosis is linked with clinical anergy and other evidence of diminished cellular immunity, we hypothesized that decreased skin delayed-type hypersensitivity (DTH) responses to recall Ags in affected individuals would be associated with decreased function of their blood dendritic cells (DCs). Our study involved ex vivo isolation, phenotyping, and functional testing of myeloid DCs (mDCs), plasmacytoid DCs, and T lymphocytes from blood of normal healthy volunteers and sarcoidosis subjects with active, untreated pulmonary disease. We found mDC function in the allogeneic MLR directly corresponded to the magnitude of skin DTH reactions to recall Ags in both sarcoidosis subjects and normal volunteers. However, both of these outcomes were significantly decreased in the sarcoidosis group. Diminished mDC function occurred despite up-regulated costimulatory and maturation markers. Clinical relevance is suggested by the inverse relationship between both mDC allogeneic responses and skin DTH responses with clinical disease severity as measured by chest radiograms. Because granulomas form when cellular immunity fails to clear antigenic stimuli, attenuated mDC function in sarcoidosis may contribute to susceptibility and persistence of the chronic inflammation characteristic of this disease.

Background Auditory mismatch negativity (MMN) and P300 event related potentials (ERP) are reduced in schizophrenia patients, and healthy volunteers administered the N-methyl-D-aspartate (NMDA) glutamate receptor antagonist, ketamine. In rodents, N-acetylcysteine (NAC), a stimulator of the cystine-glutamate exchanger, attenuates the cognitive and behavioral effects of NMDA receptor antagonists. Based on these findings, we tested whether NAC would reduce ketamine effects on behavior, MMN, and P300 in healthy humans. Methods This randomized, double-blind, placebo-controlled study consisted of two test days during which subjects (N=16) were administered oral NAC (3000 mg in divided doses) or matching placebo 165 minutes prior to the infusion of saline and then ketamine (as a bolus of 0.23 mg/kg over one minute followed by 0.58 mg/kg for 30 min, and then 0.29 mg/kg for 40 min) in a fixed order. Behavioral and ERP data including auditory MMN and P300 were collected during each test day. Results Ketamine produced psychotic-like positive symptoms, reductions in working memory and sustained attention performance, and amplitude reductions for the frequency- and intensity-deviant MMNs and P300. NAC pretreatment did not reduce the behavioral or ERP effects of ketamine. In addition, NAC reduced frequency-deviant MMN amplitude and increased target and novelty P3 amplitudes. The decrements in frequency-deviant MMN amplitude produced by ketamine and NAC were not additive. Conclusions In contrast to previous studies in animals, NAC did not attenuate the effects of ketamine in humans. NAC merits further investigation as a cognitive enhancing agent due to its ability to increase the P300 amplitude.