Enhanced effects of amphetamine but reduced effects of the hallucinogen, 5-MeO-DMT, on locomotor activity in 5-HT1A receptor knockout mice: Implications for schizophrenia

Serotonin-1A (5-HT1A) receptors may play a role in schizophrenia and the effects of certain antipsychotic drugs. However, the mechanism of interaction of 5-HT1A receptors with brain systems involved in schizophrenia, remains unclear. Here we show that 5-HT1A receptor knockout mice display enhanced locomotor hyperactivity to acute treatment with amphetamine, a widely used animal model of hyperdopaminergic mechanisms in psychosis. In contrast, the effect of MK-801 on locomotor activity, modeling NMDA receptor hypoactivity, was unchanged in the knockouts. The effect of the hallucinogen 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT) was markedly reduced in 5-HT1A receptor knockout mice. There were no changes in apomorphine-induced disruption of PPI, a model of sensory gating deficits seen in schizophrenia. Similarly, there were no major changes in density of dopamine transporters (DAT) or dopamine D1 or D2 receptors which could explain the behavioural changes observed in 5-HT1A receptor knockout mice. These results extend our insight into the possible role of these receptors in aspects of schizophrenia. As also suggested by previous studies using agonist and antagonist drugs, 5-HT1A receptors may play an important role in hallucinations and to modulate dopaminergic activity in the brain.

► Enhanced amphetamine locomotor hyperactivity in 5-HT1A receptor knockout (KO) mice.
► Markedly reduced effect of the hallucinogen 5-MeO-DMT in 5-HT1A receptor KO mice.
► No KO effect on MK-801 locomotor hyperactivity or apomorphine PPI disruption.
► No major changes in the density of dopamine transporters, D1 or D2 receptors.
► Important role of 5-HT1A receptors in hallucinations and dopaminergic activity.