Dual effect of dynorphin A on single-unit spike potentials in rat trigeminal nucleus
The Korean Journal of Physiology and Pharmacology
;
: 213-221, 2001.
Article
in English
| WPRIM
| ID: wpr-728215
ABSTRACT
The amygdala is known as a site for inducing analgesia, but its action on the trigeminal nucleus has not been known well. Little information is available on the effect of dynorphin on NMDA receptor-mediated electrophysiological events in the trigeminal nucleus. The purpose of this study was to investigate the changes in the single neuron spikes at the trigeminal nucleus caused by the amygdala and the action of dynorphin on the trigeminal nucleus. In the present study, extracellular single unit recordings were made in the dorsal horn of the medulla (trigeminal nucleus caudalis) and the effects of microiontophoretically applied compounds were examined. When (D-Ala2, N-Me-Phe4, Glys5-ol)enkephalin (DAMGO, 10-25 mM), a mu-opioid receptor agonist, was infused into the amygdala, the number of NMDA-evoked spikes at the trigeminal nucleus decreased. However, the application of naloxone into the trigeminal nucleus while DAMGO being infused into the amygdala increased the number of spikes. Low dose (1 mM) of dynorphin in the trigeminal nucleus produced a significant decrease in NMDA-evoked spikes of the trigeminal nucleus but the NMDA-evoked responses were facilitated by a high dose (5 mM) of dynorphin. After the kappa receptors were blocked with naloxone, dynorphin induced hyperalgesia. After the NMDA receptors were blocked with AP5, dynorphin induced analgesia. In conclusion, dynorphin A exerted dose-dependent dual effects (increased & decreased spike activity) on NMDA-evoked spikes in the trigeminal nucleus. The inhibitory effect of the dynorphin at a low concentration was due to the activation of kappa receptors and the excitatory effect at a high concentration was due to activation of NMDA receptors in the trigeminal neurons.
Full text:
Available
Index:
WPRIM (Western Pacific)
Main subject:
Trigeminal Nuclei
/
Action Potentials
/
Dynorphins
/
N-Methylaspartate
/
Receptors, N-Methyl-D-Aspartate
/
Receptors, Opioid, kappa
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Enkephalin, Ala(2)-MePhe(4)-Gly(5)-
/
Horns
/
Amygdala
/
Hyperalgesia
Limits:
Animals
Language:
English
Journal:
The Korean Journal of Physiology and Pharmacology
Year:
2001
Type:
Article
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