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A parasympathomimetic drug, sometimes called a cholinomimetic drug [1] or cholinergic receptor stimulating agent, [2] is a substance that stimulates the parasympathetic nervous system (PSNS). [ 3 ] [ 2 ] These chemicals are also called cholinergic drugs because acetylcholine (ACh) is the neurotransmitter used by the PSNS.
The mechanisms of sympathomimetic drugs can be direct-acting (direct interaction between drug and receptor), such as α-adrenergic agonists, β-adrenergic agonists, and dopaminergic agonists; or indirect-acting (interaction not between drug and receptor), such as MAOIs, COMT inhibitors, release stimulants, and reuptake inhibitors that increase the levels of endogenous catecholamines.
An adrenergic agonist is a drug that stimulates a response from the adrenergic receptors.The five main categories of adrenergic receptors are: α 1, α 2, β 1, β 2, and β 3, although there are more subtypes, and agonists vary in specificity between these receptors, and may be classified respectively.
The action of drugs on the human body (or any other organism's body) is called pharmacodynamics, and the body's response to drugs is called pharmacokinetics. The drugs that enter an individual tend to stimulate certain receptors, ion channels, act on enzymes or transport proteins. As a result, they cause the human body to react in a specific way.
Agonist vs. antagonist. In pharmacology the term agonist-antagonist or mixed agonist/antagonist is used to refer to a drug which under some conditions behaves as an agonist (a substance that fully activates the receptor that it binds to) while under other conditions, behaves as an antagonist (a substance that binds to a receptor but does not activate and can block the activity of other agonists).
Activation of β 2 receptors induces smooth muscle relaxation in the lungs, gastrointestinal tract, uterus, and various blood vessels. Increased heart rate and heart muscle contraction are associated with the β1 receptors; however, β 2 cause vasodilation in the myocardium. [citation needed] β3 receptors are mainly located in adipose tissue. [5]
The drug has a relatively intermediate duration of action when compared to other non-depolarizing agents. [2] The drug has an onset of 2 to 3 minutes in adults and an expected peak effect at 3 to 5 minutes. [2] Recovery is expected to begin within 20 to 35 minutes of the initial dose, but it may take up to 70 minutes to achieve 95% recovery. [2]
The most common of these binding sites, benzodiazepine, allows for both agonist and antagonist effects on the receptor. A common drug, diazepam, acts as an allosteric enhancer at this binding site. [5] Another receptor for GABA, known as GABA B, can be enhanced by a molecule called baclofen. This molecule acts as an agonist, therefore ...