Apparent pA2 value of naltrexone is not changed in rats following continuous exposure to morphine or naloxone.
Apparent pA2 value of naltrexone is not changed in rats following continuous exposure to morphine or naloxone.
复制标题
连续暴露于吗啡或纳洛酮的大鼠中，纳曲酮的表观 pA2 值没有变化。
DOI：
10.1016/0024-3205(92)90259-r
复制
发表时间：
1992
期刊：
影响因子：
6.1
通讯作者：
Holtzman,SG
中科院分区：
文献类型：
--
作者：
Paronis,CA;Holtzman,SG
Chronic opioid antagonist administration increases opioid binding sites and potentiates behavioral responses to morphine. Conversely, chronic opioid agonist administration attenuates behavioral responses to morphine, though this is not necessarily accompanied by a parallel loss of binding sites. We examined the possibility that thein vivoaffinity of the μ receptors might be altered as a consequence of the continuous administration of either naloxone or morphine. Rats were implanted sc with naloxone- or morphine-filled osmotic pumps; control animals were implanted with sham pumps. One week later, 24 hr after removing the osmotic pumps, cumulative dose-response curves for fentanyl analgesia were generated in the presence of 0.0, 0.03, 0.1, or 0.3 mg/kg naltrexone, using a tail-flick procedure. The analgesic ED50(with 95% C.L.) of fentanyl in sham implanted animals, following saline pretreatment was 0.027 mg/kg (0.019, 0.039). The potency of fentanyl was decreased in rats infused with morphine, ED50= 0.051 mg/kg (0.028, 0.093), and increased in rats that received naloxone, ED50= 0.018 mg/kg (0.015, 0.022). The mean apparent pA2value for naltrexone (with 95% C.L.) in the control group was 7.7 (7.5, 7.9). No differences were detected in animals that had received either naloxone or morphine for 7 days, pA2=7.8 (7.5, 8.1) and (7.3, 7.6), respectively. Our results indicate that there is no change in the apparent affinity of the μ-receptor following continuous exposure to either an opioid agonist or antagonist, at a time when the analgesic potency of the agonist is decreased or increased, respectively.
