Facilitation of respiratory rhythm by a mu-opioid agonist in newborn rat pons-medulla-spinal cord preparations.

Abstract

We investigated the effect of a mu-opioid agonist, DAGO, on the respiratory frequency of pons-medulla-spinal cord preparations from newborn rats. Bath application of a low concentration of DAGO (0.2 microM) facilitated respiratory rhythm in pons-medulla-spinal cord preparations, whereas it induced respiratory depression in medulla-spinal cord preparations (without pons). At a higher concentration (1.0 microM), at which the inspiratory burst generation in the medulla was strongly depressed, the respiratory rhythm in half of the pons-medulla-spinal cord preparations increased and then decreased, thus showing a biphasic response. In the other half of these preparations, only the facilitatory effect was observed. The burst rate of pre-inspiratory neurons in the rostral ventrolateral medulla was also facilitated by DAGO application. Such facilitation of the respiratory rhythm is probably due to disinhibition of a pontine inhibitory system. Our findings also suggest the existence of a pontine excitatory system, which is depressed by the pontine inhibitory system under control conditions.

• Authors: Ayaka Tanabe, Tomoko Fujii, Hiroshi Onimaru
• Journal: Neuroscience letters (Neurosci Lett) Vol. 375 Issue 1 Pg. 19-22 (Feb 25 2005) ISSN: 0304-3940 [Print] Ireland
• PMID: 15664115 (Publication Type: Comparative Study, Journal Article)

Chemical References

• Oprm1 protein, rat
• Receptors, Opioid, mu
• Enkephalin, Ala(2)-MePhe(4)-Gly(5)-
• Naloxone

Topics

• Action Potentials (drug effects)
• Animals
• Animals, Newborn
• Dose-Response Relationship, Drug
• Enkephalin, Ala(2)-MePhe(4)-Gly(5)- (pharmacology)
• In Vitro Techniques
• Medulla Oblongata (drug effects)
• Naloxone (pharmacology)
• Neural Networks, Computer
• Pons (drug effects)
• Rats
• Rats, Wistar
• Receptors, Opioid, mu (antagonists & inhibitors)
• Respiration (drug effects)
• Spinal Cord (drug effects)