PHARMACOLOGY Lecture : Drugs Acting on Autonomic Nervous System-Cholinergic Drugs
17 Oct 2022
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These are drugs which produce actions similar to that of ach, either by directly interacting with cholinergic receptors (cholinergic agonists) or by increasing availability of ach at these sites (anticholinesterases). Depending on the type of receptor through which it is mediated the peripheral actions of ach may be classified as muscarinic or nicotinic. The central actions are not so classifiable and are described separately: muscarinic actions, heart ach hyperpolarizes the sa nodal cells and decreases their rate of diastolic depolarization. The force of atrial contraction is markedly reduced and rp of atrial fibres is abbreviated. Due to nonuniform vagal innervation, the intensity of effect on rp and conductivity of different atrial fibres varies considerably, inducing inhomogeneity and predisposing to atrial fibrillation or flutter. Ventricular contractility is also decreased but the effect is not marked: blood vessels all blood vessels are dilated, though only few (skin of face, neck) receive cholinergic innervation.
