INVOLVEMENT OF THE CENTRAL-NERVOUS-SYSTEM IN THE SALIVARY SECRETION INDUCED BY PILOCARPINE IN RATS

The effect in rats of an anteroventral third ventricle (AV3V) electrol ytic lesion on salivary secretion induced by intraperitoneal (i.p.) or intracerebroventricular (i.c.v.) injection of a cholinergic agonist ( pilocarpine) was investigated. Sham- or AV3V-lesioned rats anesthetize d with urethane and with a stainless steel cannula implanted into the lateral ventricle (LV) were used. The amount of salivary secretion was studied over a seven-minute period after i.c.v. or i.p. injection of pilocarpine. In sham-operated rats, i.p. injection of pilocarpine (1 m g/kg b.w.) (after 6 h, 2, 7, and 15 days) produced salivary secretion (486 +/- 21, 778 +/- 85, 630 +/- 50, and 560 +/- 55 mg/7 min, respecti vely). This effect was reduced 6 h, 2, and 7 days after an AV3V lesion (142 +/- 22, 113 +/- 32, and 290 +/- 62 mg/7 min, respectively), but not 15 days after an AV3V lesion (516 +/- 19 mg/7 min). I.c.v. injecti on of pilocarpine (120 mug in 1 muL), in sham-operated rats after 6 h, 2, 7, and 15 days also produced salivary secretion (443 +/- 20, 417 /- 81, 496 +/- 14, and 427 +/- 47 mg/7 min, respectively). The effects of i.c.v. pilocarpine were also reduced 6 h, 2, and 7 days after an A V3V lesion (143 +/- 19, 273 +/- 14, and 322 +/- 17 mg/7 min, respectiv ely), but not after 15 days (450 +/- 28 mg/7 min). The results demonst rate that the central nervous system, and particularly the AV3V region , is important for the effect of pilocarpine on salivary secretion in rats. Moreover, they suggest that activation of central pathways may p lay an important part in the salivary secretion to peripheral pilocarp ine in rats.