A single subanesthetic dose of intranasal esketamine rapidly increases the volume of specific right thalamic structures in healthy young adults. In a placebo-controlled crossover study with 26 participants, magnetic resonance imaging revealed significant enlargement of the right thalamus, the pulvinar anterior nucleus, and the right mediodorsal lateral parvocellular nucleus after esketamine administration. These structural changes occurred in thalamic regions that relay visual information to the cortex, suggesting that ketamine's effects on visual perception may arise from rapid adaptations in these brain areas. The findings highlight the thalamus as a key target for modeling schizophrenia symptoms and understanding ketamine's mechanism of action.
Ketamine reduces sexual arousal in a sex-specific manner, which may explain why it is used recreationally in chemsex settings despite dampening sexual experience. In two placebo-controlled crossover studies with 67 healthy volunteers, subacute S-ketamine lowered arousal to heterosexual stimuli in women and to lesbian stimuli in men, while decreasing sexual aversion to gay stimuli in both sexes. Late racemic ketamine reduced arousal to heterosexual stimuli in men but increased aversion to gay stimuli in women. Ketamine also modulated calcarine gyrus activity differently in men and women. These sex-dependent effects on brain activity and sexual response may relate to ketamine's known sex-specific influences on stress resilience and psychosis-like symptoms.