Receptor spare

Spare receptors, another term for receptor reserve (see Receptor reserve). 

Signal-to-noise ratio, 71, 154 Simpson s paradox, 231 Slope covariance, 2491 Spare receptors, 21 Specific binding, 60 Spiropiperidines, 155f Spongo thymidine, 148 Spongouridine, 148 SSq, 239 SSqc, 241... 

Figure 1.26 shows log concentration-response curves drawn according to this expression. In A, the response has been assumed to be directly proportional to pactive there are no spare receptors. In B, spare receptors have been assumed to be present, and accordingly the presence of a relatively low concentration of the antagonist causes an almost parallel shift before the maximum is reduced. 

A corollary is that a demonstration of the Schild equation holding over a small range of concentrations should not be taken as proof that the action of an antagonist is competitive. Clearly, as wide as practicable a range of antagonist concentrations should be tested, especially if there is evidence for the presence of spare receptors. 

Note, too, the convergence at low agonist concentrations of the curves plotted in Figure 1.27. The antagonist becomes less active when the response is small, because there are fewer receptors in the AR form available to combine with C. Again, in contrast to the other kinds of antagonism that have been described, there is no initial parallel displacement of the curves (even if many spare receptors are present), and the Schild equation is never obeyed. 

Meller, E., Hizami, R., and Kreuter, L. Hypothermia in mice D2 dopamine receptor mediation and absence of spare receptors. Pharmacol. Biochem. Behav. 32 141, 1989. 

Sanders No, the smooth muscle cells have the receptors. It s the old concept of spare receptors. Whether or not they are coupled to the same mechanisms, I think David Hirst s point is that neurally released transmitters may do something quite different to bath-applied transmitters. 

This, at one time, was described as spare receptors but this is a misinterpretation of the role of the relationship. The response of the effector system is most sensitive to the change in hormone concentration when it is below the value of the dissociation complex. This principle is the same as that for the binding of a regulatory molecule to an enzyme (Chapter 3). 

In mice carrying the mutated a2A-D79N receptor gene, presynaptic function in the vas deferens did not differ from wild-type control mice (Altman et al. 1999). This finding indicates (1) that channel coupling is not required for presynaptic function of a2A-receptors in sympathetic nerves and (2) that there is a high number of spare receptors at the presynaptic site, as expression of the a2A-D79N receptor was found to be reduced to 20% of the wUd-type level (MacMillan et al. 1996). Thus, Ca channels in presynaptic nerve terminals are essential for neurotransmitter release, and current... 

How can we account for the phenomenon of spare receptors In the example of the 13 adrenoceptor, receptor activation... 

The concept of spare receptors is very useful clinically because it allows one to think precisely about the effects of drug dosage without needing to consider biochemical details of the signaling response. The of the agonist-receptor interaction... 

How do cellular mechanisms for amplifying external chemical signals explain the phenomenon of spare receptors ... 

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