Abstract
Endomorphin-1 is a novel endogenous μ-opioid ligand. We investigated the antinociceptive interaction between endomorphin-1 and nifedipine, an L-type calcium channel blocker, microinjected into the midbrain ventrolateral periaqueductal gray (vPAG), using the spinally-organized tail-flick test and the supraspinally-organized tail-pressure test in rats. Sprague-Dawley rats were stereotaxically implanted with a guide cannula lowered into the vPAG. Microinjection of endomorphin-1 into the vPAG led to dose-related increases in antinociceptive responses in the tail-flick test and tail-pressure test. Pretreatment with the μ-opioid receptor-selective antagonist β-funaltrexamine blocked the antinociceptive effect of endomorphin-1. Pretreatment with β-funaltrexamine alone had no effect on the tail-flick latency and tail-pressure threshold. Microinjection of nifedipine alone into the vPAG did not produce an antinociceptive response in the tail-flick test and tail-pressure test. However, injection of nifedipine into the vPAG potentiated the antinociceptive effect of endomorphin-1, producing a significant leftward shift in the dose-response curve of endomorphin-1 in both the tail-flick and tail-pressure tests. This result shows that the potent antinociceptive effect of endomorphin-1 microinjected into the vPAG is mediated through the μ-opioid receptor and is potentiated by concomitant administration of nifedipine.
| Original language | English |
|---|---|
| Pages (from-to) | 1065-1071 |
| Number of pages | 7 |
| Journal | Anesthesia and Analgesia |
| Volume | 96 |
| Issue number | 4 |
| State | Published - Apr 1 2003 |
| Externally published | Yes |
Fingerprint
ASJC Scopus subject areas
- Anesthesiology and Pain Medicine
Cite this
Nifedipine potentiates the antinociceptive effect of endomorphin-1 microinjected into the periaqueductal gray in rats. / Hao, Shuanglin; Mamiya, Keiko; Takahata, Osamu; Iwasaki, Hiroshi; Mata, Marina; Fink, David J.
In: Anesthesia and Analgesia, Vol. 96, No. 4, 01.04.2003, p. 1065-1071.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Nifedipine potentiates the antinociceptive effect of endomorphin-1 microinjected into the periaqueductal gray in rats
AU - Hao, Shuanglin
AU - Mamiya, Keiko
AU - Takahata, Osamu
AU - Iwasaki, Hiroshi
AU - Mata, Marina
AU - Fink, David J.
PY - 2003/4/1
Y1 - 2003/4/1
N2 - Endomorphin-1 is a novel endogenous μ-opioid ligand. We investigated the antinociceptive interaction between endomorphin-1 and nifedipine, an L-type calcium channel blocker, microinjected into the midbrain ventrolateral periaqueductal gray (vPAG), using the spinally-organized tail-flick test and the supraspinally-organized tail-pressure test in rats. Sprague-Dawley rats were stereotaxically implanted with a guide cannula lowered into the vPAG. Microinjection of endomorphin-1 into the vPAG led to dose-related increases in antinociceptive responses in the tail-flick test and tail-pressure test. Pretreatment with the μ-opioid receptor-selective antagonist β-funaltrexamine blocked the antinociceptive effect of endomorphin-1. Pretreatment with β-funaltrexamine alone had no effect on the tail-flick latency and tail-pressure threshold. Microinjection of nifedipine alone into the vPAG did not produce an antinociceptive response in the tail-flick test and tail-pressure test. However, injection of nifedipine into the vPAG potentiated the antinociceptive effect of endomorphin-1, producing a significant leftward shift in the dose-response curve of endomorphin-1 in both the tail-flick and tail-pressure tests. This result shows that the potent antinociceptive effect of endomorphin-1 microinjected into the vPAG is mediated through the μ-opioid receptor and is potentiated by concomitant administration of nifedipine.
AB - Endomorphin-1 is a novel endogenous μ-opioid ligand. We investigated the antinociceptive interaction between endomorphin-1 and nifedipine, an L-type calcium channel blocker, microinjected into the midbrain ventrolateral periaqueductal gray (vPAG), using the spinally-organized tail-flick test and the supraspinally-organized tail-pressure test in rats. Sprague-Dawley rats were stereotaxically implanted with a guide cannula lowered into the vPAG. Microinjection of endomorphin-1 into the vPAG led to dose-related increases in antinociceptive responses in the tail-flick test and tail-pressure test. Pretreatment with the μ-opioid receptor-selective antagonist β-funaltrexamine blocked the antinociceptive effect of endomorphin-1. Pretreatment with β-funaltrexamine alone had no effect on the tail-flick latency and tail-pressure threshold. Microinjection of nifedipine alone into the vPAG did not produce an antinociceptive response in the tail-flick test and tail-pressure test. However, injection of nifedipine into the vPAG potentiated the antinociceptive effect of endomorphin-1, producing a significant leftward shift in the dose-response curve of endomorphin-1 in both the tail-flick and tail-pressure tests. This result shows that the potent antinociceptive effect of endomorphin-1 microinjected into the vPAG is mediated through the μ-opioid receptor and is potentiated by concomitant administration of nifedipine.
UR - http://www.scopus.com/inward/record.url?scp=0037378618&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0037378618&partnerID=8YFLogxK
M3 - Article
C2 - 12651662
AN - SCOPUS:0037378618
VL - 96
SP - 1065
EP - 1071
JO - Anesthesia and Analgesia
JF - Anesthesia and Analgesia
SN - 0003-2999
IS - 4
ER -