Serotonin 5-HT1A receptor

Class

Selective, high-affinity 5-HT1A receptor agonist (small molecule)

Pathway

Serotonergic 5-HT1A agonism to reduce L-DOPA-induced dyskinesia in Parkinson's disease

The serotonin 5-HT1A receptor is a G protein-coupled receptor found throughout the central nervous system, including on the serotonin-producing neurons of the raphe nuclei and on neurons in the cortex, hippocampus, and striatum. Its activation dampens neuronal excitability and reduces neurotransmitter release, making it a longstanding target for anxiety and mood disorders. A distinct application arises in Parkinson's disease. Long-term treatment with L-DOPA, the precursor used to replace lost dopamine, can trigger involuntary movements known as L-DOPA-induced dyskinesia. This occurs partly because surviving serotonergic neurons take up L-DOPA and convert it to dopamine, then release it without the normal regulatory feedback that dopamine neurons provide, producing erratic dopamine signaling in the striatum. Selective 5-HT1A agonists engage the same receptors that ordinarily restrain serotonergic neuron firing, reducing this aberrant, unregulated dopamine release while sparing the therapeutic dopamine replacement supplied directly by L-DOPA. High selectivity for 5-HT1A over other serotonin receptor subtypes is intended to achieve this dampening effect without introducing the perceptual or cardiovascular effects associated with activating other serotonin receptors. This mechanism broadly matters wherever motor complications of dopaminergic therapy limit long-term treatment tolerability.