Studies On Pain Control System (Rept. 106): Vagal Dysfunction Caused Nociceptive Neuroplasticity

Gustatory responses were investigated in sham vagotomized (SVgX) and selective gastric vagotomized (VgX) male rats by 1-h single-bottle tests using 3% sucrose, 13% glucose, 0.2% saccharin, 0.9% sodium chloride, 0.16% citric acid, 0.001% quinine sulphate and tap water as test solutions. The intakes of sucrose, glucose, saccharin and sodium chloride were significantly less in VgX rats, compared to SVgX ones. When all these rats were exposed to graded concentrations of sucrose (0.1%, 0.5%, 1% and 5%), a maximum preference was shown to 5% and the least to 0.1% sucrose by both SVgX and VgX rats, even though the VgX rats consumed less than SVgX ones. Vagotomy produced a maximum suppression of 5% sucrose intake, a moderate suppression of 1% and 0.5% sucrose intake and no significant change in the intake of 0.1% sucrose. The results also indicated a probable reduction in the ability of VgX rats to discriminate taste intensities within a close range. Pharmacological blocking of vagal efferents with atropine methyl nitrate (5 mg/kg) did not produce any significant change in the intakes. The possibility of an excitatory input through the gastric vasal afferents selectively influencing the intake of sapid substances is suggested.