EFFECTS OF ELECTROLYTIC LESIONS OR CHOLINERGIC BLOCKADE OF THE MEDIAL SEPTAL AREA ON THE SALIVARY SECRETION AND WATER INTAKE INDUCED BY PERIPHERAL PILOCARPINE

Abstract

Cholinergic receptors are present in the medial septal area (MSA) and the MSA connects with forebrain areas involved in the control of salivary secretion and water intake. In the present study we investigated the effects of electrolytic lesions or the cholinergic blockade of the MSA on the salivary secretion and water intake induced by ip pilocarpine (PILO, 1 mg/kg b. wt.). Male Holtzman rats (280–320 g, n = 7–13/group) with stainless steel cannulas implanted into the MSA or submitted to sham or electrolytic (1 mA × 10 s) MSA lesions (1 or 15 days) were used. Saliva was collected in anesthetized rats using pre-weighed cotton balls inserted into the animal's mouth. Atropine methyl or saline were injected into the MSA 15 min before ip PILO. MSA lesion (1 day) reduced the salivary secretion (334 ± 45 vs. sham: 495 ± 27 mg/7 min) and water intake (2.6±0.4 vs sham: 4.0±0.4 ml/1 h) induced by ip PILO. In 15 day MSA-lesioned rats, ip PILO-induced water intake was still reduced (2.6±0.4 vs. sham: 4.0±0.4 ml/1 h) while the salivary secretion was not different from sham rats. Atropine methyl (4 nmol/0.5 μl) injected into the MSA also reduced PILO-induced salivary secretion (233±49 vs. saline: 489±68 mg/7min) and water intake (1.6±0.4 vs. saline 3.1±0.4 ml/1 h). The results suggest that cholinergic receptors of the MSA are part of the forebrain circuitry involved in salivary secretion and water intake induced by ip pilocarpine. Supported by FAPESP