Important Concepts of Receptor Theory

Characterization of arginine vasopressin actions in human uterine artery: lack of role of the vascular endothelium

“…However, it should be mentioned that the pKB values (9.29-9.32) for [d(CH2)5Tyr(Me)]AVP obtained in quiescent preparations using the method of Kenakin (1987) were similar to those values (9.61-9.66) obtained using the method according to Arunlakshana & Schild (1959). This similarity implies that the pKA values obtained in our study are correct, according to the established criteria (Kenakin, 1987;Yanigasawa et al, 1989 (Ruffolo, 1982;Kenakin, 1987). The KA/EC5o ratios for AVP are significantly higher than unity, and a considerable receptor reserve exists in these tissues for the half-maximal and maximal responses for AVP.…”

“…However, recently, a vasocontractile effect of AVP, mediated by vasopressin V2 receptors, has also been reported (Chiba & Tsukada, 1992). The pA2 value for an antagonist in blocking the response to an agonist should be an accurate indication of its affinity for binding to the receptor site if certain criteria are fulfilled (Furchgott, 1972;Ruffolo, 1982;Kenakin, 1987 (Manning et al, 1983;1987). The slopes of the Schild plots for both [d(CH2)5Tyr (Me)]AVP and [d(CH2)5,D-Ile2,Ile4]AVP were not significantly different from unity, indicating that the antagonism is competitive and therefore that the obtained pA2 value constrained to unity can be taken to be the -log KB value (Arunlakshana & Schild, 1959).…”

Central α2‐autoreceptors: agonist dissociation constants and recovery after irreversible inactivation

“…The analysis yielded rectangular hyperbolae for all three agonists indicating receptor reserve (Ruffolo, 1982). For instance, 90% of the agonist-mediated inhibition of 3H-overflow occurred at fractions of active receptors of approximately 12%, 25%, and 45% for NA, bromoxidine, and clonidine, respectively.…”

μ Opiate Receptor Gene Dose Effects on Different Morphine Actions Evidence for Differential in vivo μ Receptor Reserve

“…If, after inactivating some receptors, concentrationresponse curves display full efficacy with no depression of the maximal responses, receptor reserve is present (Chavkin and Goldstein 1984;Adams et al 1990;Zernig et al 1995). This phenomenon is also cited as evidence for "spare receptors" (Furchgott 1967;Ruffolo 1982;Kenakin 1984).…”