Salivary secretion induced by L-DOPA in haloperidol-treated rats.
The effect of chronic haloperidol treatment on salivary secretion induced by L-dopa, was studied in male Sprague-Dawley rats. Dose-response relationships for L-dopa, obtained 24 h after haloperidol treatment, showed that salivary secretion was greater in rats that had been injected with haloperidol (2 mg/kg/day, i.p.) for 7 days than in controls. The threshold doses requirements were significantly reduced in that group. Pretreatment with carbidopa suppressed the salivary secretion produced by L-dopa in haloperidol-treated and control rats whose glands had been denervated. The secretory response in innervated glands was higher in haloperidol-treated animals than in controls. Haloperidol treatment also increased salivation induced by L-noradrenaline as determined by dose-response relationships. This was associated with a decrease in the threshold doses requirement. In controls and in rats chronically treated with haloperidol, the salivary responses to L-noradrenaline were temporarily depressed by 80-90% by a prior acute injection of haloperidol (2 mg/kg, i.v.) presumably acting as an alpha blocker. A similar reduction was observed after acute treatment with phentolamine (3 mg/kg, i.v.). The data obtained in this study, i.e. that chronic administration of haloperidol increases the salivary response to L-dopa and L-noradrenaline, suggests that such an affect could be due to the development of supersensitivity of striatal dopamine receptors as well as of peripheral alpha-adrenergic receptors.
D000818:Animals; D002230:Carbidopa / Q000494:pharmacology; D003714:Denervation; D006220:Haloperidol / Q000494:pharmacology*; D007980:Levodopa / Q000494:pharmacology*; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D010646:Phentolamine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012463:Saliva / Q000378:metabolism*; D013363:Submandibular Gland / Q000187:drug effects / Q000378:metabolism
D007980:Levodopa; D006220:Haloperidol; D002230:Carbidopa; D009638:Norepinephrine; D010646:Phentolamine