The muscarinic cholinergic receptors in the posterior hypothalamus of hypertensive and normotensive rats

Abstract

The density of [ 3H]quinuclidin-3-yl benzilate ([ 3H]QNB) binding sites in the posterior hypothalamus was determined in spontaneously hypertensive (SHR) and Wistar Kyoto (WKY) rats at the ages of 1, 3, 11 and 50 weeks. In SHR, even at the early age of 1 week which is prehypertensive, the values obtained were 1.5 times greater than those of age-matched WKY rats. The values of the equilibrium dissociation constant (K D) did not differ between SHR and WKY rats of the same age. In the pons medulla, however, the density of [ 3H]QNB binding sites was not different between the two strains of rats of matching age. Isolation-induced hypertension in adult Wistar rats and an increase in the density of [ 3H]QNB binding sites in the posterior hypothalamus were observed to arise concomitantly. A hypothesis is offered whereby a relative increase in ACh receptor sites in the posterior hypothalamus is a primary cause of hypertension in the models considered.