PART III: Cellular Mechanism of Atropine
The acetylcholine (Ach) is the primary neurotransmitter for the nerves in the heart. The nerves are called the vagus nerves. When there is excessive vagal action, contractility reduces and thus the heart rate goes down (Klabunde, 1). Atropine is used to inhibit this action and therefore the primary function is to increase the heart rate. Atropine is therefore used as a nerve agent to treat poisoning and other instances that result in slow heart rate.
The Ach binds to the muscarinic receptors. Atropine also binds to the muscarinic cholinergic receptor to prevent the action of Ach (Coyne, 12). Araki et al. (739) found that phasic elements of stimulated contractions were inhibited upon pre-treatment. Atropine therefore mainly acts in situations where cholinergic axons are present. Ehrenpreis found that only low concentrations of atropine were necessary for abolishment of electrically induced contractions. (68).
PART IV: Cellular Mechanism of Morphine
Of the three opioid receptors, morphine binds to the mu (m) receptor. When morphine binds to these receptors, analgesics are effected in the body. Morphine helps prevent the production of certain neurotransmitters. One of which is Substance P. This is involved with pain sensations. These messages of inhibition are transmitted through the G proteins (Goodsell, 717).
Action of morphine on field stimulated contractions is different because of the mechanism through which it relives pain relief. While atropine affects cholinergic axons, morphine prevents release of pain related neurotransmitters. Therefore, morphine would react to field stimulated contractions by preventing neurotransmitters from communicating by exercising its anticholinergic aspect and then spreading relieving messages through the G proteins. Morphine acts by mimicking the body’s own pain management actions.
Works Cited
Araki H, Cheng J. T, Ogino K, Taniyama K, Matsumoto H. “Irreversible inhibitory effect of atropine on contractile responses to drugs in isolated rabbit ileum.” Japanese Journal of Pharmacology, 16.6(1976), 737-42
Coyne, Cody. Comparative Diagnostic Pharmacology: Clinical and Research Applications in Living-System Models. IOWA: John Wiley & Sons (2008)
Klabunde, Richard. “General Pharmacology.” Cardiovascular Pharmacology Concepts. (2007) Available at: https://www.cvpharmacology.com/antiarrhy/atropine
Ehrenpreis, Seymour. Actions of Opiates and Their Antagonists on Cholinergic Transmission in the Guinea Pig Ileum. In: Advances in General and Cellular Pharmacology. Boston, MA:Springer (1976)
Goodsell, David. “The Molecular Perspective: Morphine.” The Oncologist 9.6 (2004), 717-718