Effect of quinine and atabrine on gastric secretion; a preliminary communication

Histamine H2 receptors, which are intricately located on the basolateral membrane of parietal cells, play a crucial role in modulating gastric acid secretion. When released from enterochromaffin-like cells, histamine engages H2 receptors, initiating the cyclic AMP (cAMP) pathway. In this pathway, adenylyl cyclase converts ATP into cAMP, elevating intracellular cAMP levels. The activation of protein kinase A follows, stimulating the proton pump. This stimulation prompts the secretion of hydrogen...

Serotonin, a crucial neurotransmitter synthesized by enterochromaffin cells, plays a cardinal role in regulating gastrointestinal (GI) motility. With over 90% of the body's total serotonin in the GI tract, its influence on digestive processes is profound. Serotonin is swiftly released upon various stimuli, such as food boluses or certain drugs, triggering intrinsic sensory neurons in the myenteric plexus and extrinsic vagal and spinal sensory neurons. This leads to the activation of the...

In the complex environment of the gastric lumen, excessive acid secretion can lead to the formation or worsening of ulcers within the delicate mucosal layer. Antacids, such as sodium bicarbonate and calcium carbonate, provide relief by neutralizing this acid, transforming it into harmless salt and water. This neutralization process raises the gastric pH from a highly acidic level of 1 to a more basic 3-4, reducing the acidity within the stomach.
However, this neutralization reaction between...

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...

Cholinergic antagonists—such as antimuscarinics—are available in oral, topical, ocular, parenteral, and inhalational formulations. Most antimuscarinics are oral formulations,  while scopolamine is available as a topical patch, and ipratropium and tiotropium are available as inhalation aerosols or powders. Atropine, tropicamide, and cyclopentolate are topically instilled in the eye. Most antimuscarinics are lipid-soluble and readily absorbed from the gastrointestinal tract and the conjunctiva.

Indirect-acting cholinergic agonists, also known as anticholinesterases, exert their pharmacological effects by enhancing cholinergic transmission in various body parts, including the neuromuscular junction, autonomic cholinergic synapses, and the brain.
At the neuromuscular junction, these agents work by inhibiting the breakdown of acetylcholine, allowing it to remain bound to the receptor and bind to nearby receptors. This process leads to repetitive firing of the endplate, causing muscle...