Serotonin-norepinephrine interactions in the tremorolytic actions of phenoxybenzamine and trazodone.

Phenoxybenzamine (5 mg/kg IP) and trazodone (5 mg/kg IP) reduced tremors produced in mice by administration of oxotremorine (10 mg/kg), harmaline (80 mg/kg), catechol (60 mg/kg), kepone (200 mg/kg) and clonidine (100 mg/kg). Azapetine (10 mg/kg IP) in combination with L-5-hydroxytryptophan (50 mg/kg IP) reduced the tremor induced by oxotremorine, catechol, kepone and clonidine. In mice with lower thoracic spinal cord transection, phenoxybenzamine and trazodone reduced catechol-induced tremor above and below the site of transection. These findings suggest that an alpha noradrenergic-serotonergic neuronal balance in the spinal cord may modulate tremors of different etiologies.