2. Muscarinic agonists (m-cholinomimetics)

List of drugs

Pilocarpine hydrochloride

Mechanism of action

Direct stimulation of M-cholinoreceptors. Don’t stimulate N-cholinoreceptors!

Pharmacological effects

Type of receptors	Organ	Effect
Stimulation of M-cholinoreceptors	Eye	Constriction of pupil (miosis)
	Salivary glands	Increasing of saliva secretion
	Heart	Decreasing of heart rate, heart contractility, heart conductance and heart excitability
	Bronchi	Constriction (due to contraction of smooth muscles of bronchi)
	Gastro-intestinal tract (GIT) organs: stomach, small intestine, gall bladder etc.	Increasing of motility (due to contraction of smooth muscles of GIT organs)
	Urinary bladder	Constriction (due to contraction of smooth muscles of urinary bladder)

Indications

1. Glaucoma (increasing of intraocular pressure)

Pilocarpine → constriction of pupil → decreasing of intraocular pressure → treating of glaucoma.

This effect depends on M-cholinoreceptors.

3. Nicotinic agonists (n-cholinomimetics)

List of drugs

Lobeline hydrochloride

Mechanism of action

Direct stimulation of N-cholinoreceptors. Don’t stimulate M-cholinoreceptors!

Pharmacological effects

The most important effect is the stimulation of N-cholinoreceptors of carotid sinus (angle of bifurcation of the common carotid artery). As consequence, there will be the reflex stimulation of respiratory center → increasing of respiratory rate and respiratory depth.

Indications

1. Reflex inhibition of breathing (e.g., asphyxia caused by drowning).

Lobeline → stimulation of N-cholinoreceptors of carotid sinus → stimulation of respiratory center → restoration of breathing.

Simplicified version

2. (Cholinonegative drugs)

1. Muscarinic antagonists (m-cholinoblockers)

List of drugs

Nonselective M-cholinoblockers: Atropine sulfate, Belladonna extract (contains atropine!),

Metocinii iodidum, Scopolamine

Selective M-cholinoblockers: Pirenzepine, Ipratropium bromide, Platyphyllini hydrotartras

Mechanism of action

Competitive blockage of M-cholinoreceptors.

Pharmacological effects

Previous time you studied the pharmacological effects of Muscarinic agonists (M-cholinomimetics (see my previous material). For today topic «Muscarinic antagonists (M-cholinoblockers)» pharmacological effects will be strongly opposite (see table):

Type of receptors	Organ	Effect
Blockage of M-cholinoreceptors	Eye	Dilation of pupil (mydriasis)
	Salivary glands	Decreasing of saliva secretion
	Heart	Increasing of heart rate, heart contractility, heart conductance and heart excitability
	Bronchi	Dilation (due to relaxation of smooth muscles of bronchi)
	Gastro-intestinal tract (GIT) organs: stomach, small intestine, gall bladder etc.	Decreasing of motility (due to relaxation of smooth muscles of GIT organs)
	Urinary bladder	Relaxation (due to relaxation of smooth muscles of urinary bladder)

Indications

1. Dilation of pupil to treat iritis (inflammation of iris): atropine

Dilation of pupil for diagnostic purpose (looking for eye diseases): metocinium

2. Preventing of some complications of general anaesthesia during surgery (premedication) – preventing of excessive secretion of salivary glands and bronchi, preventing of bronchospasm, cardiac arrest etc.: atropine, metocinium.

3. In cases of decreasing of heart conductance (e.g. atrioventricular heart block (AV block)):

Atropine.→ increasing of heart conductance → relieving of atrioventricular heart block

4. Relieving and prophylaxy of bronchospasm

Platyphyllinum, Ipratropium → dilation of bronchi → relieving and prophylaxy of bronchospasm.

5. Treatment of gastric hyperacidity, gastric ulcer, duodenal ulcer:

Atropine, Belladonna extract, Pirenzepine → decreasing of secretion of gastric juice → treating of gastric hyperacidity, gastric ulcer and duodenal ulcer.

6. Relieving of renal colic, hepatic colic, intestinal colic.

Atropine, Belladonna extract, Platyphyllinum → relaxation of smooth muscles of kidneys, liver and intestine → relieving of renal colic, hepatic colic, intestinal colic.

7. Motion sickness (during travelling in aeroplane or ship):

Scopolamine → decreasing of nausea and vomiting during travelling in aeroplane or ship.

NB! You should study all drugs, but the most important drugs (first choice drugs) underlined.