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

Abstract

TERPSTRA, G. K. AND J. L. SLANGEN. Central blockade of(methyl-) atropine on carbachol drinking: a dose-response study. PHYSIOL. BEHAV. 8 (4) 715--719, 1972. 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 ~tg) 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 ~tg) 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 p~g) was discussed. Water intakeCarbachol stimulation Dose-response relationship Tractus diagonalisAtropine Methylatropine LOCAL stimulation of different parts of the limbic system of the rat with cholinergic substances, like carbachol and acetylcholine, elicits water drinking in water satiated rats [4,7,8].A dose response curve for the water intake elicited by injection of carbachol in the feeding-drinking area of the hypothalamus has been established. A maximal intake of water occurred after administration of 2.4 × 10-°M of carbachol (= 0.4 ~g)[16]. Levitt et aL [15] found for a number of different structures a maximal effect with a dose of 1 ~g of carbachol. Detailed observations have been made concerning the role of the preoptic and septal area in the elicitation of drinking behavior after local administration of carbachol [3,5,14].Carbachol-elicited drinking was inhibited by atropine when administered systemically [9,18]. On the other hand atropine not only blocked the effect of carbachol when administered in the same brain region as carbachol [9,14,19], but also when administered in another brain region in the limbic system [14].On the assumption that drinking elicited by carbachol is the result of activation of a cholinergic system, atropine, administered peripherally as well as centrally, has been used by several authors in order to block the effects of carbachol administered in the septal area. These results have been obtained by using about equal dosages of carbachol and atropine (tzg). It is not known however whether these doses of atropine axe likely to block only the stimulated parts of the cholinergic drinking system or other cholinergic systems affecting behavior as well. To answer that question information about the dose response relationship of carbachol elicited drinking and atropine is needed. To investigate this relationship in all areas of the limbic system that are supposed to play a role in the regulation of water intake is simply prohibiting. In our experiments we therefore concentrated on the anterior part of the preoptic area which is believed to be a part of the limbic drinking circuit [5].The purpose of the following ...

The role of the tractus diagonalis in drinking behaviour induced by central chemical stimulation, water deprivation and salt injection

“…As expected from earlier experiments (TERPSTRA and SLANGEN, 1972) the inhibition of carbachol-induced drinking by central administration of atropine and methylatropine in the tractus diagonalis was nearly complete. No difference in effect was found between atropine and methylatropine.…”

“…In experiments concerning the nature of the transmission system involved it appeared that administration of atropine and methylatropine in the limbic system inhibited drinking induced by carbachol stimulation (GROSSMAN, 1962b(GROSSMAN, , 1964STEIN and SEIFTER, 1962;LEVITT and FISHER, 1966). It was further demonstrated that the effects ofatropine and methylatropine on carbachol-induced drinking were not significantly different when both substances were administered in the tractus diagonalis (TERPSTRA and SLANGEN, 1972).…”