当前位置： SCI文献检索 > BRAIN RESEARCH期刊下所有文献 > Extracellular cholecystokinin levels in the rat spinal cord following chronic morphine exposure: an in vivo microdialysis study.

Extracellular cholecystokinin levels in the rat spinal cord following chronic morphine exposure: an in vivo microdialysis study.

Abstract：

:Conflicting results concerning the issue of whether or not chronic morphine exposure induces an increase in CCK biosynthesis have been found in many CNS sites, including the spinal cord, where CCK activity may contribute to the facilitation of the development of opiate tolerance. The present study was undertaken in order to monitor the extracellular level of CCK under spontaneous and stimulus-evoked release in the spinal cord dorsal horn of drug naive and morphine tolerant rats. Tolerance was induced by implantation of two morphine pellets (2x75 mg) which induced a stable morphine plasma concentration after 48 h post-implantation. The tail-flick test and naloxone precipitated withdrawal were used as indexes of tolerance and dependence to morphine. The effect of morphine-pellet implantation on basal and K+-induced release of CCK-like immunoreactivity (CCK-LI) in the rat dorsal horn were monitored with in vivo microdialysis 96 h after implantation of morphine or placebo pellets, when rats showed tolerance and dependence. Basal CCK levels were below the detection limit of the assay (0.6 pM) in both tolerant and normal animals. K+ (100 mM) in the perfusion medium induced a more than 3-fold increase of the extracellular level of CCK-LI in control animals, and a more than 4-fold increase on CCK-LI in morphine-pellet implanted animals. However, this difference was not significant. In addition, naloxone (2 mg/kg; i.v.), did not induce any change in the extracellular level of CCK in either group. The present study suggests that the modulatory interaction between CCK and opioids in the development of tolerance in the spinal cord may occur without necessarily increasing the extracellular level of CCK. Another possible explanation of the finding is that the microdialysis technique is not sensitive enough to detect differences in unstimulated CCK levels in normal and tolerant animals.

journal_name

Brain Res

journal_title

Brain research

authors

Lucas GA,Hoffmann O,Alster P,Wiesenfeld-Hallin Z

doi

10.1016/s0006-8993(99)01068-9

subject

Has Abstract

pub_date

1999-03-06 00:00:00

pages

79-86

issue

eissn

0006-8993

issn

1872-6240

pii

S0006899399010689

journal_volume

821

pub_type

杂志文章

在线工具

Extracellular cholecystokinin levels in the rat spinal cord following chronic morphine exposure: an in vivo microdialysis study.