Pharmacology DOR 101 Abdelkader Ashour, Ph.D. 3 rd Lecture, contd.

Parasympathetic Nervous System

Drugs Acting on the Parasympathetic Nervous System, Responses to parasympathetic activation

Parasympathetic Nervous System, Receptors for acetylcholine (Cholinergic Receptors) I.Nicotinic receptors, nAChRs (the nicotinic actions of ACh are those that can be reproduced by the injection of nicotine) Location: nAChRs are located … 1.At neuromuscular junctions of skeletal muscle 2.On postganglionic neurons in the autonomic ganglia 3.On some central nervous system neurons 4.On adrenal medulla  ACh stimulates secretion of adrenaline from adrenal medulla

Parasympathetic Nervous System, Receptors for acetylcholine II.Muscarinic receptors, mAChRs (the muscarinic actions of ACh are those that can be reproduced by the injection of muscarine) ---- Location: mAChRs are located …  in tissues innervated by postganglionic parasympathetic neurons such as  On smooth muscle  On cardiac muscle  On gland cells  in postganglionic sympathetic neurons to sweat glands  In the central nervous system

Muscarinic Autonomic Effects of Acetylcholine  Eye (iris sphincter muscle) Contraction (miosis)  Eye (ciliary muscle) Contraction (for near vision)  SA node Bradycardia (slow heart rate)  Atrium Reduced contractility  Arteriole Dilatation  Bronchial muscle Muscle Contraction  Bronchial secretion Increase  GIT (motility) Increase  GIT (secretion) Increase  GIT (sphincters) Relaxation  Urinary bladder (wall) Contraction  Urinary bladder (sphincter) Relaxation  Penis Erection (but not ejaculation)  Sweat glands Secretion (sympathetic cholinergic!)  Salivary glands Secretion  Lacrimal glands Secretion