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Related Concept Videos

Cholinergic Receptors: Muscarinic01:25

Cholinergic Receptors: Muscarinic

The pharmacological actions of acetylcholine are elicited via its binding to two families of cholinergic receptors or cholinoceptors, namely, muscarinic and nicotinic receptors. Muscarinic receptors are G protein-coupled receptors and have five subtypes, M1–M5. All mAChR subtypes are activated by acetylcholine and blocked by the antagonist, atropine. 
The subtypes M1, M3, and M5 couple with the Gq subunit and activate the phospholipase C (PLC) activity, mobilizing intracellular Ca2+. Activation...
Cholinergic Antagonists: Pharmacological Actions01:28

Cholinergic Antagonists: Pharmacological Actions

Antimuscarinic drugs block muscarinic receptors in multiple systems, including the gut, eye, smooth muscles, respiratory tract, cardiovascular, and central nervous systems. They produce similar effects with varying selectivity depending on the specific agent and tissue. Here are the key pharmacological actions of antimuscarinics:
Gastrointestinal Effects: Antimuscarinics reduce gut contractions, increase gastric emptying, and slow intestinal transit. They partly inhibit gastric acid secretion...
Pharmacokinetics in Geriatric Patients: Effect of Age on Drug Distribution01:00

Pharmacokinetics in Geriatric Patients: Effect of Age on Drug Distribution

Drug distribution in the human body is influenced by several factors, including plasma protein concentration, body composition, blood flow, tissue-protein concentration, and tissue fluid pH. Among these, changes in plasma protein concentration and body composition due to aging significantly affect how drugs are distributed within the body. Specifically, aging is associated with a decrease in albumin levels by about 10% and an increase in α1-acid glycoprotein levels. These alterations are not...
Pharmacokinetics in Geriatric Patients: Effect of Age on Drug Metabolism01:18

Pharmacokinetics in Geriatric Patients: Effect of Age on Drug Metabolism

Geriatric patients show significant variation in how their bodies process medications, which can change how effective and safe treatments are. The liver is the primary organ where drug metabolism occurs, involving two main types of chemical reactions: phase I and II. Phase I metabolism is driven by the cytochrome P450 enzyme system, which includes key types such as CYP3A, CYP2D6, and CYP2C9. Research indicates that while aging doesn't notably alter the levels or activity of these enzymes, it...
Pharmacokinetics in Geriatric Patients: Effect of Age on Drug Excretion01:18

Pharmacokinetics in Geriatric Patients: Effect of Age on Drug Excretion

In geriatric patients, renal physiology undergoes significant changes, including diminished renal blood flow and a lower glomerular filtration rate (GFR), leading to alterations in medication clearance. Drugs such as aminoglycoside antibiotics, lithium, and digoxin, which rely on glomerular filtration for removal from the body, particularly impact pharmacokinetics. These drugs tend to have slower clearance rates in older adults, necessitating careful dosage considerations.Evaluation of renal...
Pharmacodynamics in Geriatric Patients: Effects of Age01:27

Pharmacodynamics in Geriatric Patients: Effects of Age

Age-related pharmacokinetic changes are extensively documented, but understanding age-related pharmacodynamic alterations is relatively limited. This knowledge gap can be partly attributed to the complexity of developing appropriate measures of drug responses compared to bioanalytical methods for determining drug concentrations.Most information regarding age-related differences in human pharmacodynamics originates from cross-sectional studies. However, these studies assume that observed mean...

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Related Experiment Video

Updated: Jul 7, 2026

Ex Vivo Assessment of Contractility, Fatigability and Alternans in Isolated Skeletal Muscles
14:02

Ex Vivo Assessment of Contractility, Fatigability and Alternans in Isolated Skeletal Muscles

Published on: November 1, 2012

Cardiac muscarinic receptors decrease with age. In vitro and in vivo studies

O E Brodde1, U Konschak, K Becker

  • 1Institute of Pharmacology and Toxicology, Martin Luther University Halle-Wittenberg, D-06097 Halle/Saale, Germany.

The Journal of Clinical Investigation
|February 7, 1998
PubMed
Summary
This summary is machine-generated.

Pirenzepine lowers heart rate by affecting M1 receptors, but this effect diminishes with age. This age-related decline is linked to reduced M2 receptor density and function in the heart.

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Area of Science:

  • Cardiovascular Physiology
  • Pharmacology
  • Aging Research

Background:

  • Low doses of pirenzepine, an M1 muscarinic receptor antagonist, reduce resting heart rate.
  • This effect is known to decrease with advancing age.

Purpose of the Study:

  • To investigate the mechanisms behind pirenzepine's age-dependent effect on heart rate.
  • To examine the role of M1 and M2 muscarinic receptors in this phenomenon.

Main Methods:

  • Assessed pirenzepine's effect on isoprenaline-induced heart rate changes in young and older volunteers.
  • Evaluated pirenzepine's impact on resting heart rate in native and transplanted sinus nodes of heart transplant recipients.
  • Measured M2 muscarinic receptor density and adenylyl cyclase activity in atrial tissue from patients of various ages.

Main Results:

  • Pirenzepine caused a greater heart rate reduction in young volunteers compared to older ones.
  • Pirenzepine decreased resting heart rate in native sinus nodes but not in transplanted ones.
  • M2 receptor density and acetylcholine's inhibitory effect on adenylyl cyclase decreased with patient age.

Conclusions:

  • Pirenzepine reduces heart rate by inhibiting presynaptic M1 autoreceptors, leading to acetylcholine release.
  • The diminished heart rate-lowering effect of acetylcholine in older individuals is due to decreased M2 receptor density and function in the right atrium.