Spinal pharmacology of antinociception produced by microinjection of mu or delta opioid receptor agonists in the ventromedial medulla of the rat

R W Hurley; P Banfor; D L Hammond

doi:10.1016/S0306-4522(03)00041-1

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Spinal pharmacology of antinociception produced by microinjection of mu or delta opioid receptor agonists in the ventromedial medulla of the rat

Journal article

Peer reviewed

Spinal pharmacology of antinociception produced by microinjection of mu or delta opioid receptor agonists in the ventromedial medulla of the rat

R W Hurley, P Banfor and D L Hammond

Neuroscience, Vol.118(3), pp.789-796

2003

DOI: 10.1016/S0306-4522(03)00041-1

PMID: 12710986

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Abstract

This study examined the role of spinal GABAergic, serotoninergic and alpha(2) adrenergic receptors in the antinociception produced by the microinjection of equi-antinociceptive doses of selective opioid receptor agonists in the nucleus raphe magnus (NRM) or the nucleus reticularis gigantocellularis pars alpha (NGCpalpha) of the rat. Rats were pretreated with intrathecal administration of either the GABA(A) receptor antagonist bicuculline, the GABA(B) receptor antagonist CGP35348, the serotonin(1/2) receptor antagonist methysergide, the alpha(2) adrenergic receptor antagonist yohimbine or saline. Ten minutes later, either the delta(1) opioid receptor agonist [D-Pen(2,5)]enkephalin (DPDPE), delta(2) opioid receptor agonist [D-Ala(2),Glu(4)]deltorphin (DELT) or mu opioid receptor agonist [D-Ala(2),NMePhe(4),Gly-ol(5)]enkephalin (DAMGO) was microinjected into the NRM, NGCpalpha or sites in the medulla outside these two regions. The increase in tail-flick latency produced by microinjection of DPDPE into the NRM or NGCpalpha was antagonized by intrathecal pretreatment with either methysergide or yohimbine. Intrathecal pretreatment with CGP35348 antagonized the antinociception produced by microinjection of DPDPE in the NRM, whereas bicuculline antagonized the antinociception produced by microinjection of DPDPE in the NGCpalpha. The increase in tail-flick latency produced by microinjection of DELT into the NGCpalpha, but not the NRM was antagonized by intrathecal pretreatment with yohimbine or CGP35348. Intrathecal pretreatment with methysergide or bicuculline did not antagonize the antinociception produced by microinjection of DELT into either the NRM or the NGCpalpha. The increase in tail-flick latency produced by microinjection of DAMGO in the NRM was antagonized by intrathecal pretreatment with methysergide or CGP35348, but not by bicuculline or yohimbine. Taken together, these results support the hypothesis that the antinociception produced by activation of delta(1), delta(2) or mu opioid receptors in the rostral ventromedial medulla is mediated by different neural substrates.

Receptors, Opioid, delta - metabolism

Receptors, Opioid - agonists

Spinal Cord - drug effects

Spinal Cord - metabolism

Receptors, Serotonin - drug effects

Male

Adrenergic alpha-Antagonists - pharmacology

Receptors, Opioid, mu - agonists

Pain - metabolism

Efferent Pathways - drug effects

Medulla Oblongata - cytology

Reaction Time - drug effects

Neurons - metabolism

Spinal Cord - cytology

Neurons - drug effects

Receptors, GABA - drug effects

Receptors, Opioid - metabolism

Medulla Oblongata - drug effects

Receptors, Opioid, mu - metabolism

Medulla Oblongata - metabolism

Rats

Reaction Time - physiology

Serotonin Antagonists - pharmacology

Efferent Pathways - cytology

Rats, Sprague-Dawley

Receptors, Serotonin - metabolism

Efferent Pathways - metabolism

GABA Antagonists - pharmacology

Animals

Pain - physiopathology

Drug Interactions - physiology

Receptors, GABA - metabolism

Nociceptors - metabolism

Narcotics - pharmacology

Nociceptors - drug effects

Receptors, Opioid, delta - agonists

Details

Title: Subtitle: Spinal pharmacology of antinociception produced by microinjection of mu or delta opioid receptor agonists in the ventromedial medulla of the rat
Creators: R W Hurley - Department of Anesthesia and Critical Care, University of Chicago, Chicago, IL 60637, USA
P Banfor
D L Hammond
Resource Type: Journal article
Publication Details: Neuroscience, Vol.118(3), pp.789-796
Publisher: United States
DOI: 10.1016/S0306-4522(03)00041-1
PMID: 12710986
ISSN: 0306-4522
eISSN: 1873-7544
Grant note: DA 05784 / NIDA NIH HHS F30 DA005784 / NIDA NIH HHS DA 06736 / NIDA NIH HHS
Language: English
Date published: 2003
Academic Unit: Iowa Neuroscience Institute; Nursing; Anesthesia; Neuroscience and Pharmacology
Record Identifier: 9984006340402771

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