The effect of clonidine on centrally and peripherally evoked submaxillary salivation.

In anaesthetised cats, clonidine (10 microgram/kg, i.v.) produced a 60% reduction in submaxillary salivation induced by brain stem stimulation at 10 and 15 Hz and reductions of 35 and 15% in salivation evoked by chorda tympani nerve stimulation at 5 and 15 Hz respectively. Pretreatment with clonidine (20 microgram/kg/day, orally) for 28 days reduced peripherally evoked salivation by 45%. These results suggest that both central and peripheral mechanisms are involved in the diminished salivation produced by clonidine, and the reduction on peripheral stimulation may reflect the presence of presynaptic alpha-adrenoceptors inhibiting cholinergic transmission.