Alterations in β adrenergic and muscarinic receptors in aged rat heart. Effects of chronic administration of propranolol and atropine

摘要: The cardiac responses to sympathetic and vagal stimulations are attenuated with ageing. To understand these findings, the densities of β adrenergic (βR) muscarinic (MR) receptors in left ventricles have been quantitated parallel male Wistar rats (4- 24-month-old) using [125I]iodocyanopindolol [3H]quinuclidinyl benzilate as specific radioligands. homologous regulation receptor was also explored after a 7-day continuous infusion propranolol or atropine. As compared young rats, βR MR aged animals were decreased (from 31 ± 23 2 fmol/mg protein, P < 0.05 for βR; from 104 7 54 3 0.001 MR) but diminution more pronounced (−48%) than that (−26%), resulting drop β/MR ratio. Continuous atropine up-regulated (respectively +50%, 0.01 +33%, 0.05) not adult rats. We therefore conclude: (i) response during ageing may be partly explained by decrease corresponding density; (ii) changes reversible density two groups can return control values chronic administration appropriate antagonist.