TCAs act by blocking presynaptic reuptake of norepinephrine or serotonin; they theoretically increase the effects of direct- or indirect-acting agonists at these synapses. TCAs may also block alpha-adrenergic receptors
, which causes hypotension resulting from reduction of myocardial contractility and systemic vascular resistance., TCAs inhibit Na/K-ATPase and act like quinidine-like antiarrhythmics by stabilizing excitable membranes and delaying His bundle conduction.
TABLE 1: Alpha-adrenergic receptor
gene expression in the kidney cortex of Zucker lean (ZL), untreated Zucker diabetic fatty (ZD), and fenofibrate-treated diabetic fatty (F-ZD) rats.
It showed that blocking the beta-receptor alone promotes cardiac remodelling via growth of cardiac fibroblasts induced by alpha-adrenergic receptor
Nevertheless the measurement of alpha-adrenergic receptor
subtypes via PCR is a well-established method to investigate the adrenergic receptor system in hypertensive patients.
(5) At that time, it was shown that aerobic exercisers had greater alpha-adrenergic receptor
density and significantly lower beta-adrenergic receptor density than weight trainers.