Endogenous opioid peptide-mediated neurotransmission in central and pericentral nuclei of the inferior colliculus recruits μ1-opioid receptor to modulate post-ictal antinociception.

Abstract

BACKGROUND:

The aim of the present work was to investigate the involvement of the μ1-endogenous opioid peptide receptor-mediated system in post-ictal antinociception.

METHODS:

Antinociceptive responses were determined by the tail-flick test after pre-treatment with the selective μ1-opioid receptor antagonist naloxonazine, peripherally or centrally administered at different doses.

RESULTS:

Peripheral subchronic (24 h) pre-treatment with naloxonazine antagonised the antinociception elicited by tonic-clonic seizures. Acute (10 min) pre-treatment, however, did not have the same effect. In addition, microinjections of naloxonazine into the central, dorsal cortical and external cortical nuclei of the inferior colliculus antagonised tonic-clonic seizure-induced antinociception. Neither acute (10-min) peripheral pre-treatment with naloxonazine nor subchronic intramesencephalic blockade of μ1-opioid receptors resulted in consistent statistically significant differences in the severity of tonic-clonic seizures shown by Racine's index (1972), although the intracollicular specific antagonism of μ1-opioid receptor decreased the duration of seizures.

CONCLUSION:

μ1-Opioid receptors and the inferior colliculus have been implicated in several endogenous opioid peptide-mediated responses such as antinociception and convulsion. The present findings suggest the involvement of μ1-opiate receptors of central and pericentral nuclei of the inferior colliculus in the modulation of tonic-clonic seizures and in the organisation of post-ictal antinociception.

• Authors: Tatiana Tocchini Felippotti, Renato Leonardo de Freitas, Norberto Cysne Coimbra
• Journal: Neuropeptides (Neuropeptides) Vol. 46 Issue 1 Pg. 39-47 (Feb 2012) ISSN: 1532-2785 [Electronic] Netherlands
• PMID: 22104092 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2011 Elsevier Ltd. All rights reserved.

Chemical References

• Opioid Peptides
• Oprm1 protein, rat
• Receptors, Opioid, mu
• Naloxone
• naloxonazine
• Pentylenetetrazole

Topics

• Animals
• Inferior Colliculi (drug effects, metabolism)
• Male
• Naloxone (administration & dosage, analogs & derivatives, pharmacology)
• Opioid Peptides (metabolism)
• Pentylenetetrazole (administration & dosage, pharmacology)
• Rats
• Rats, Wistar
• Receptors, Opioid, mu (antagonists & inhibitors, metabolism)
• Seizures (chemically induced)
• Synaptic Transmission (drug effects, physiology)