Central blockade of (methyl-)atropine on carbachol drinking: A dose-response study

Abstract

Administration of carbachol in the tractus diagonalis in rats elicited drinking and no eating. Norepinephrine administered in the same place did not induce drinking or eating. The specific drinking response induced by stimulation with 7.2 nmol (= 1.3 μg) of carbachol was gradually inhibited by preceding injections of graded doses of atropine and methylatropine at the same site. A 90% inhibiting action of atropine and methylatropine was possible with a 3–10 times lower dose (0.18 μg) than used in earlier studies. Significant differences between the inhibition by atropine and methylatropine could not be demonstrated. A possible difference in inhibition at the lowest dose of atropine and methylatropine used (= 0.04 μg) was discussed.