Johnson M A, Hill R G, Hughes J
Parke-Davis Research Unit, Addenbrookes Hospital site, Cambridge, UK.
NIDA Res Monogr. 1986;75:69-72.
The effect of calcium on responses to selective mu (fentanyl and DAGO) and selective kappa agonists was investigated on guinea pig ileum. The dose-response curves were shifted to the right in a non-parallel fashion with increasing calcium concentration (0.9-3.6 mM). However U50488 was shifted more than either fentanyl or DAGO. Both fentanyl and U50488 could not produce 100% inhibition of twitch in 3.6 mM calcium. It is concluded that the efficacy of the agonists changes with calcium concentration and that the kappa agonist U50488 is affected more than the mu agonists because kappa receptor activation directly inhibits calcium entry whereas mu receptors inhibit calcium by increasing potassium conductance.
在豚鼠回肠上研究了钙对选择性μ（芬太尼和DAGO）和选择性κ激动剂反应的影响。随着钙浓度（0.9 - 3.6 mM）增加，剂量 - 反应曲线以非平行方式向右移动。然而，U50488的移动幅度比芬太尼或DAGO更大。在3.6 mM钙中，芬太尼和U50488均不能产生100%的抽搐抑制。结论是激动剂的效力随钙浓度变化，并且κ激动剂U50488比μ激动剂受影响更大，因为κ受体激活直接抑制钙内流，而μ受体通过增加钾电导来抑制钙。
