Autonomic Pharmacology PDF

Autonomic pharmacology 30 November 2024 19:56 ### **Drugs which target the entire autonomic nervous system** Both the sympathetic and parasympathetic nervous systems use nicotinic ACh receptors at synapses between preganglionic and postganglionic neurones. These receptors are also present on sk...

Autonomic pharmacology 30 November 2024 19:56 ### **Drugs which target the entire autonomic nervous system** Both the sympathetic and parasympathetic nervous systems use nicotinic ACh receptors at synapses between preganglionic and postganglionic neurones. These receptors are also present on skeletal muscles, however the structure is different/ Generally a nicotinic AChR is pentameric transmembrane ion channel with 5 subunits. In skeletal muscle, the AChR uses **α~1~ subunits**, whereas the nicotinic AChRs of the ANS use **α~2-7~ subunits**. This allows drugs to be used that specifically target the subunits of ANS receptors. One drug is **hexamethonium**. This is a non-competitive antagonist of ANS NAChRs (nicotinic ACh receptors). It blocks all the effects of autonomic stimulation, both sympathetic and parasympathetic, while not affecting skeletal muscle. It has **anti-hypertensive** effects. It is no longer used due to the large number of side effects, as it blocks all aspects of sympathetic and parasympathetic transmission. **Drugs which target the parasympathetic nervous system** --------------------------------------------------------- Postganglionic neurones of the PaNS exert their effects on effectors via **muscarinic ACh receptors**. Drugs that specifically target the PaNS will target these rceptors. Muscarinic ACh receptors are G-protein coupled receptors, consisting of 7 transmembrane domains. There are 5 types of muscarinic receptors, most importantly - - - ### **Muscarinic agonists/parasympathomimetic drugs** These are drugs that activate muscarinic ACh receptors, achieving same effects as parasympathetic stimulation, such as: - - - - - - Muscarine poisoning can occur due to over-consumption of muscarine containing mushrooms. In this case, extreme parasympathetic effects occur, such as bradycardia, hypotension, increased gut motility and pain, bronchoconstriction and miosis of pupils (abnormal constriction) This poisoning can be reversed by atropine, which is a competitive antagonist for muscarine. An example of a muscarinic agonist is pilocarpine, which is used to treat glaucoma of the eyes by topical administration directly into the eye via eyedrops. This way, only the M~3~ receptors of ciliary muscles are targeted, preventing side effects caused by parasympathetic effects across the entire body. ### **Muscarinic antagonists** Used to treat: - - - - - - Muscarinic agonists can also be used to counter the effects of **ACh esterase inhibitors.** - - - **Drugs which target the sympathetic nervous system** ----------------------------------------------------- Sympathetic postganglionic neurones use noradrenaline (NA) as neurotransmitter, allowing them to be specifically targeted. **Adrenoceptors** are G-protein coupled receptors, there are 5 types: - - - - - Drugs which target adrenoceptors can either be **adrenergic agonists** or **adrenergic antagonists**. They can be further categorised based on what type of adrenoreceptor they act on. ### **α-adrenoceptor agonist** Uses: - - - - ### **α-adrenoceptor antagonists (alpha-blockers)** Uses: - - ### **β-adrenoceptor agonists** - - - ### **β-adrenoceptor antagonists (beta-blockers)** - - - - Another example is metoprolol, which targets β~1~ receptors. **Drugs which target the SyNS via catecholamine regulation** ------------------------------------------------------------ ### **Regular noradrenaline regulation** 1. 2. 3. 4. Drugs that target SyNS via catecholamine regulation will interfere with this process, there are 3 main types ### **NAT inhibitors** - - - - A diagram of a nerve cell Description automatically generated ### **MAO inhibitors** - - - - - ### **Sympathetic amines** - - - - -