Central nervous system receptors

Clinical signs and symptoms of toxicity are related to the overstimulation of muscarinic, nicotinic, and central nervous system receptors in the nervous system. Muscarinic receptors are those activated by the alkaloid drug muscarine. These receptors are under the control of the parasympathetic nervous system, and their hyperactivity results in respiratory and gastrointestinal dysfunction, incontinence, salivation, bradycardia, miosis, and sweating. Nicotinic receptors are those activated by nicotine. Hyperactivity of these receptors results in muscle fasciculations even greater stimulation results in blockade and muscle paralysis (Lefkowitz et al. 1996 Tafliri and Roberts 1987). Hyperactivity of central nervous system receptors results in the frank neurological signs of confusion, ataxia, dizziness, incoordination, and slurred speech, which are manifestations of acute intoxication. Muscarine and nicotine are not... 

Antipsychotic drugs have profound effects on multiple central nervous system receptors, and these effects are compounded when... 

In aged animal models, chronic administration of ginkgo for 3-4 weeks led to modifications in central nervous system receptors and neurotransmitters. Receptor densities increased for muscarinic, e2, and 5-HTla receptors and decreased for... 

In aged animal models, chronic administration of ginkgo for 3-4 weeks led to modifications in central nervous system receptors and neurotransmitters. Receptor densities increased for muscarinic, 2, and 5-HTla receptors and decreased for B-adrenoceptors. Increased serum levels of acetylcholine and norepinephrine and enhanced synaptosomal reuptake of serotonin have also been reported. Additional mechanisms that may be involved include reversible inhibition of MAO-A and MAO-B, reduced corticosterone synthesis, inhibition of amyloid-beta fibril formation, and enhanced GABA levels. 

Although not necessarily involving photoactive complexes, a variety of approaches have been used to design radiopharmaceuticals for imaging central nervous system receptors. Ultimately, such studies are an important extension of photochemical applications of Re complexes since the design of radiopharmaceuticals that luminescence (for detection) and are therapeutic (by radiation) is a topic of current interest [19]. Re complexes are usually studied prior to the preparation of Tc derivatives since their chemistries are so similar, although the use of Re isotopes for therapy is also possible. 

Ahn HS, Barnett A. Selective displacement of [ H] mepyr-amine from peripheral vs. central nervous system receptors by loratadine, a non-sedating antihistamine. Eur J Pharmacol 1986 127(l-2) 153-5. 

Chapter 5. Adaptive Changes in Central Nervous System Receptor Systems... 

Jiang, J.G., X.J. Huang, and J. Chen. 2007. Separation and purification of saponins from Semen Ziziphus jujuba and their sedative and hypnotic effects. /. Pharm. Pharmacol. 59(8) 1175-1180. Koetter, U., M. Barrett, S. Lacher, A. Abdelrahman, and D. Dokiick. 2009. Interactions of Magnolia and Ziziphus extracts with selected central nervous system receptors. J. Ethnopharmacol. 124(3) 421-425. 

Taste-active chemicals react with receptors on the surface of sensory cells in the papillae causing electrical depolarization, ie, drop in the voltage across the sensory cell membrane. The collection of biochemical events that are involved in this process is called transduction (15,16). Not all the chemical steps involved in transduction are known however, it is clear that different transduction mechanisms are involved in different taste quaUties different transduction mechanisms exist for the same chemical in different species (15). Thus the specificity of chemosensory processes, ie, taste and smell, to different chemicals is caused by differences in the sensory cell membrane, the transduction mechanisms, and the central nervous system (14). 

P-Endorphin. A peptide corresponding to the 31 C-terminal amino acids of P-LPH was first discovered in camel pituitary tissue (10). This substance is P-endorphin, which exerts a potent analgesic effect by binding to cell surface receptors in the central nervous system. The sequence of P-endorphin is well conserved across species for the first 25 N-terminal amino acids. Opiates derived from plant sources, eg, heroin, morphine, opium, etc, exert their actions by interacting with the P-endorphin receptor. On a molar basis, this peptide has approximately five times the potency of morphine. Both P-endorphin and ACTH ate cosecreted from the pituitary gland. Whereas the physiologic importance of P-endorphin release into the systemic circulation is not certain, this molecule clearly has been shown to be an important neurotransmitter within the central nervous system. Endorphin has been invaluable as a research tool, but has not been clinically useful due to the avadabihty of plant-derived opiates. 

Mode of Motion. Nicotine, anabasine, and imidocloprid affect the ganglia of the insect central nervous system, faciUtating transsynaptic conduction at low concentrations and blocking conduction at higher levels. The extent of ionisation of the nicotinoids plays an important role in both their penetration through the ionic barrier of the nerve sheath to the site of action and in their interaction with the site of action, which is befleved to be the acetylcholine receptor protein. There is a marked similarity in dimensions between acetylcholine and the nicotinium ion. 

Dmg receptors represent another type of receptor family. The central nervous system (CNS) effects of the anxiolytic, diazepam, and the psychotropic actions of the caimabiaoids and phencycUdine have resulted ia the identification of specific receptors for these molecules. This has resulted ia the search for an endogenous ligand for these receptors. Thus, ia these situations, the pharmacological action has preceded the discovery of the receptor which, ia turn, has provided clues ia several iastances to the endogenous ligand. 

Beta receptors of the beta-1 subtype mediate an increase in heart rate and increased force of contraction they are also found in the central nervous system. E and NE are equaHy potent agonists and selective antagonists are atenolol [29122-68-7] and betaxolol [63659-18-7]. Beta-2 receptors are weH known for their involvement in relaxing bronchioles. E is a more potent agonist than NE procaterol [72332-33-3] is a selective agonist ICl 118551 and a-methylpropranolol are selective antagonists. A particular amine may act on both alpha and beta receptors or predominandy on one type. NE acts mainly on alpha-1, E on both alpha and beta, and isoprotemol [7683-59-2] almost exclusively on beta receptors. Numerous antagonists also differentiate between... 

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