These include affecting cholinergic system agonists/antagonists (arecoline 15 mg/kg), dopaminergic neurotransmission (apomorphine 0.1 mg/kg and amphetamine 5 mg/kg), the adrenergic system (evaluation of smooth muscle contractile activity), and (or) 5-HT3 serotonin receptors (model of serotonin-induced muscle spasm). The gene discussed is HTR3A; the disease is muscle cramp.