Central neurotransmitter receptors in hypertensive rats

Abstract

Muscarinic cholinergic ([ 3H]QNB), α 1 − ([ 3H]WB-4101), and α 2 − ([ 3H]clonidine) adrenergic ligand binding was measured in various regions of the brains of adult normotensive, spontaneously hypertensive, and DOCA-salt hypertensive rats. There was a 66% increase in the number of α 1-adrenergic receptors in hypothalamus of the spontaneously hypertensive rats as compared to normotensive controls, with no change in the K d value. There were no other differences in the spontaneously hypertensive rats and none in the DOCA-salt model. α 1-Adrenergic binding was elevated in hypothalamus of spontaneously hypertensive rats 4–20 weeks of age even though blood pressure in the 4-week old animals was not at hypertensive levels (i.e., <150 mmHg). Treatment of adult spontaneously hypertensive rats with clonidine HCl significantly reduced blood pressure but failed to alter the binding of [ 3H]WB-4101 in hypothalamus. Thus, it appears that the enhanced number of α 1-adrenergic receptors in hypothalamus of spontaneously hypertensive rats is neither a consequence of the increased blood pressure, nor a phenomenon common to all models of hypertension.