Pathways

Nicotinic acetylcholine receptors, or nAChRs, are receptor polypeptides that respond to the neurotransmitter acetylcholine. Nicotinic receptors also respond to drugs such as the agonist nicotine. They are found in the central and peripheral nervous system, muscle, and many other tissues of many organisms. At the neuromuscular junction they are the primary receptor in muscle for motor nerve-muscle communication that controls muscle contraction. In the peripheral nervous system: (1) they transmit outgoing signals from the presynaptic to the postsynaptic cells within the sympathetic and parasympathetic nervous system, and (2) they are the receptors found on skeletal muscle that receive acetylcholine released to signal for muscular contraction. In the immune system, nAChRs regulate inflammatory processes and signal through distinct intracellular pathways. The nicotinic receptors are considered cholinergic receptors, since they respond to acetylcholine. Nicotinic receptors get their name from nicotine which does not stimulate the muscarinic acetylcholine receptors but selectively binds to the nicotinic receptors instead. As ionotropic receptors, nAChRs are directly linked to ion channels. New evidence suggests that these receptors can also use second messengers (as metabotropic receptors do) in some cases. Nicotinic acetylcholine receptors are the best-studied of the ionotropic receptors. Opening of the channel allows positively charged ions to move across it; in particular, sodium enters the cell and potassium exits. The net flow of positively charged ions is inward. The nAChR is a non-selective cation channel, meaning that several different positively charged ions can cross through. The activation of receptors by nicotine modifies the state of neurons through two main mechanisms. On one hand, the movement of cations causes a depolarization of the plasma membrane (which results in an excitatory postsynaptic potential in neurons) leading to the activation of voltage-gated ion channels. On the other hand, the entry of calcium acts, either directly or indirectly, on different intracellular cascades. This leads, for example, to the regulation of activity of some genes or the release of neurotransmitters.

Nifedipine, or BAY a 1040, is a first generation dihydropyridine L-type calcium channel blocker, similar to nicardipine. Nifedipine was developed by Bayer and first described in the literature, along with other dihydropyridines, in 1972. Since nifedipine's development, second and third generation dihydropyridines have been developed with slower onsets and longer durations of action. The most popular of the third generation dihydropyridines is amlodipine. Nifedipine was granted FDA approval on 31 December 1981. (DrugBank) Nifedipine blocks voltage gated L-type calcium channels in vascular smooth muscle and myocardial cells. This blockage prevents the entry of calcium ions into cells during depolarization, reducing peripheral arterial vascular resistance and dilating coronary arteries. These actions reduce blood pressure and increase the supply of oxygen to the heart, alleviating angina. (DrugBank)

Nifedipine (also known as Adalat or Procardia) is a dihydropyridine calcium channel blocker that may be used for treatment of hypertension and exertion-related angina in the absence of vasospasm. Nifedipine binds the major channel in muscle cells: L-type calcium channels. Binding of Nifedipine on L-type calcium channels can change channels' confirmation to its inactive form, so that the channel couldn't faciltate the influx of calcium ions, which leads to decreased arterial smooth muscle contractility and subsequent vasoconstriction. Activated mysoin light chain kinase (MLCK) is required for muscle contraction since it can catalyze the phosphorylation of the regulatory light chain subunit of myosin. Without calcium ions in muscle cell, calmodulin couldn't form the calcium-bound calmodulin, which is required for binding and activating MLCK. Lack of initial influx of calcium can also reduce the level of contractile activity of muscle cells and results in vasodilation, which ultimately lead to overall decresing in blood pressure.

Nifedipine is a dihydropyridine calcium channel blocker indicated for the management of several subtypes of angina pectoris, and hypertension. It can be found under the brand names Adalat, Afeditab CR, Nifediac, Nifedical, and Procardia. Nifedipine, or BAY a 1040, is a first generation dihydropyridine L-type calcium channel blocker, similar to nicardipine. Nifedipine was developed by Bayer and first described in the literature, along with other dihydropyridines, in 1972. Since nifedipine's development, second and third generation dihydropyridines have been developed with slower onsets and longer durations of action. Nifedipine blocks voltage gated L-type calcium channels in vascular smooth muscle and myocardial cells. This blockage prevents the entry of calcium ions into cells during depolarization, reducing peripheral arterial vascular resistance and dilating coronary arteries. The alpha-1C, alpha-1D, and beta-2 subunits are targeted. Nifedipine can be administered via oral capsules or tablets. These actions reduce blood pressure and increase the supply of oxygen to the heart, alleviating angina. Some side effects of using nifedipine may include headaches, dizziness, flushing, and palpitations.

Nifedipine is predominantly metabolized by CYP3A4. Nifedipine is predominantly metabolized to 2,6-dimethyl-4-(2-nitrophenyl)-5-methoxycarbonyl-pyridine-3-carboxylic acid, and then further metabolized to 2-hydroxymethyl-pyridine carboxylic acid. Nifedipine is also minorly metabolized to dehydronifedipine. (DrugBank)

Nifurtimox is a drug that is not metabolized by the human body as determined by current research and biotransformer analysis. Nifurtimox passes through the liver and is then excreted from the body mainly through the kidney.