Damage of the medial preoptic area impairs peripheral pilocarpine-induced salivary secretion.
The existence of neural connections between the medial preoptic area (MPOA) and the salivary glands and the increase in salivation by thermal or electrical stimulation of the MPOA have suggested an important role of MPOA in the control of salivary gland function. Although direct cholinergic activation of the salivary glands induces salivation, recent studies have suggested that salivation produced by i.p. pilocarpine may also depend on the activation of central mechanisms. Therefore, in the present study, we investigated the effects of bilateral electrolytic lesions of the MPOA on the salivation induced by i.p. pilocarpine. Adult male Holtzman rats (n = 11-12/group) with bilateral sham or electrolytic lesions of the MPOA were used. One, five, and fifteen days after the brain surgery, under ketamine anesthesia, the salivation was induced by i.p. pilocarpine (1 mg/kg of body weight), and saliva was collected using pre-weighed small cotton balls inserted into the animal's mouth. Pilocarpine-induced salivation was reduced 1 and 5 days after MPOA lesion (341 +/- 41 and 310 +/- 35 mg/7 min, respectively, vs. sham lesions: 428 +/- 32 and 495 +/- 36 mg/7 min, respectively), but it was fully recovered at the 15th day post-lesion (561 +/- 49 vs. sham lesion: 618 +/- 27 mg/7 min). Lesions of the MPOA did not affect baseline non-stimulated salivary secretion. The results confirm the importance of MPOA in the control of salivation and suggest that its integrity is necessary for the full sialogogue effect of pilocarpine. However, alternative mechanisms probably involving other central nuclei can replace MPOA function in chronically lesioned rats allowing the complete recovery of the effects of pilocarpine.
Department of Physiology and Pathology, School of Dentistry, Paulista State University, UNESP, Rua Humaitá 1680, 14801-903 Araraquara, SP, Brazil.
Roberto
R
Lopes de Almeida
Laurival Antonio
LA
De Luca
Débora Simões
DS
de Almeida Colombari
José Vanderlei
JV
Menani
Antonio
A
Renzi
D000818:Animals; D004556:Electric Injuries / Q000503:physiopathology; D008297:Male; D018721:Muscarinic Agonists / Q000494:pharmacology*; D010862:Pilocarpine / Q000494:pharmacology*; D011301:Preoptic Area / Q000293:injuries / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012472:Salivation / Q000187:drug effects*; D013997:Time Factors
D018721:Muscarinic Agonists; D010862:Pilocarpine