Selective receptors

Phenylephrine (90) is a selective receptor agonist (+)-niguldipine (91) is a selective antagonist for the receptor. Pra2osin (92) and 5-methylurapidil (93) are nonselective a -receptor antagonists. CEC can differentiate receptors from the other receptors. Pra2osin has low and high affinity for and receptors, respectively. 

The opioid peptides vary in their binding affinities for the multiple opioid receptor types. Leu- and Met-enkephalin have a higher affinity for 5-receptors than for the other opioid receptor types (68), whereas the dynorphin peptides have a higher affinity for K-sites (69). P-Endorphin binds with equal affinity to both p- and 5-receptors, but binds with lower affinity to K-sites (70). The existence of a P-endorphin-selective receptor, the S-receptor, has been postulated whether this site is actually a separate P-endorphin-selective receptor or is a subtype of a classical opioid receptor is a matter of controversy (71,72). The existence of opioid receptor subtypes in general is quite controversial although there is some evidence for subtypes of p- (73), 5-(74), and K-receptors (72,75), confirmation of which may be obtained by future molecular cloning studies. 

The most probable mechanism for inverse agonism is the same one operable for positive agonism namely, selective receptor state affinity. However, unlike agonists that have a selectively higher affinity for the receptor active state (to induce G-protein activation and subsequent physiological response) inverse agonists have a selectively higher affinity for the inactive receptor state and thus uncouple already spontaneously coupled [RaG] species in the system. 

Although trace amine-selective receptors had been hypothesized for several decades and trace amine binding sites had been reported earlier, it was only... 

Based on these observations a selective receptor for lithium 117 has been synthesized from a smaller diazadioxa macrocycle [160]. Ligands 110 and 117 may be regarded also as binucleating ligands capable of binding two cations at a time. 

Funk OF, Kettmann V, Drimal J, Langer T. Chemical function based pharmacophore generation of endothelin-A selective receptor antagonists. J Med Ghent 2004 47 2750-60. 

Raso, V., and Basala, M. (1984) A highly cytotoxic human transferrin - Ricin A chain conjugate used to select receptor-modified cells./. Biol. Chem. 259, 1143. 

The natural product westiellamide (158) and other unnatural cyclopeptide alkaloids were synthesised by cyclooligomerisation reactions <00T9143>. The benzene-based tripodal tris(oxazolines) 159 were developed as new selective receptors toward alkylammonium ions <00CEJ3399>. 

Smith CL, O Malley BW (2004) Co-regulator function a key to understanding tissue specificity of selective receptor modulators. Endocr Rev 25 45-71... 

Another problem in validating targets for behavioral disorders related to neurotransmitter abnormalities is the interplay between several neurotransmitter systems in specific brain regions. For example, in the hippocampus, limbic, and nigral-striatal areas, functions connected by serotonin, norepinephrine, and dopamine are interconnected so that blocking selected receptor subtypes or changing synaptic levels of certain neurotransmitters may... 

In fields such as biosensing, analyte binding often relies on very specific molecular recognition interactions that nature has supplied, such as antibody-antigen interactions or strands of complimentary DNA forming double hefices. Unfortunately, because versatile and highly selective receptors for TNT or other explosive molecules are not available, chemists are left to rely on less specific interactions. 

With this in mind, the coordination chemistry of 52 with different diazine structural isomers was investigated. There were no detectable changes in the H NMR spectrum of 52 in a THF-Jg solution when either pyrazine or pyrimidine were added in 1 1 or 1 2 molar ratios, which suggested that only weak interactions might occur between 52 and these bases. In contrast, incremental addition of pyridazine or phthalazine to a THF-Jg solution of 52 at 25 °C resulted in an upheld shift of the aromatic NMR resonances of the diindacycle 52 thus reflecting the formation of complexes between 52 and the 1,2-diazines. Analysis of the tritration data clearly indicated the formation of 1 1 Lewis acid-diazine complexes 52-pyridazine-(THF)2 and 52-phthalazine-(THF)2 whose stability constants are equal to 80 ( 10) and 1000 ( 150) M respectively (Scheme 29). These data, as a whole, indicate that 52 is a selective receptor for 1,2-diazines. 

Fig. 2. Selected receptor-based radiopharmaceuticals using the bifunctional approach...

Pharmacology Prostanoid selective receptor agonists are believed to reduce lOP by increasing the outflow of aqueous humor. 

Deslerotadine (Clarinex) [Antihislamine/Selective Receptor Antagonist] Uses Seasonal p ennial aU gic rhinitis chronic idiopathic urticaria Action Active metabohte of Claritin, Hpantihistamine, blocks inflammatory mediators Dose Adul Peds >12 y. 5 mg PO daily 5 mg PO qod... 

Mechanism of Action An ophthalmic agent that is a prostanoid selective receptor agonist. Therapeutic Effect Reduces intraocular pressure (lOP) by reducing aqueous humor production. 

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