 |
||||
|
||||
|
||||
|
||||
Previous Article | Next Article
The Journal of Neuroscience, May 15, 1998, 18(10):3529-3536
Morphine Administered in the Substantia Gelatinosa of the Spinal Trigeminal Nucleus Caudalis Inhibits Nociceptive Activities in the Spinal Trigeminal Nucleus Oralis
Radhouane Dallel, Christian Dualé, and Jean-Louis Molat Laboratoire de Physiologie Oro-Faciale, Faculté de Chirurgie Dentaire, 63000 Clermont-Ferrand, France
The present study investigates the effects of morphine microinjection into the spinal trigeminal nucleus caudalis (Sp5C) or the spinal trigeminal nucleus oralis (Sp5O) on C-fiber-evoked activities of Sp5O convergent neurons, after supramaximal percutaneous electrical stimulation in halothane-anesthetized rats.
When it was microinjected into the Sp5O, morphine (2.5 µg in 0.25 µl) never depressed the C-fiber-evoked responses of Sp5O convergent neurons (n = 13), whereas these neurons were responsive to the inhibitory effects of systemic morphine (6 mg/kg, i.v.) in a naloxone-reversible manner. On the contrary, morphine microinjected into the Sp5C produced a naloxone-reversible inhibition of the C-fiber-evoked responses of Sp5O neurons (n = 14). The magnitude and the time course of this effect varied according to the location of the injection sites. After microinjection into the superficial laminae (n = 7), a strong depressive effect of morphine (7 ± 5% of control) on the C-fiber-evoked responses was apparent as soon as 5 min after the injection and could always be reversed by naloxone, administered either intravenously (0.4 mg/kg) or locally (2.5 µg in 0.6 µl) at the same site as morphine. After microinjection into deeper laminae (V-VI), a significant depressive effect (34 ± 5% of control) of morphine could be detected only 20 min after the injection and was reversed only by intravenous administration of naloxone.
These results suggest that morphine exerts its antinociceptive action on Sp5O convergent neurons by blocking the C-fiber inputs that relay in the Sp5C substantia gelatinosa. The mechanisms that underlie the activation of Sp5O convergent neurons by C-fibers and the inhibition of C-fiber-evoked responses of Sp5O convergent neurons by morphine microinjected into the Sp5C are discussed.
Key words: nociception; trigeminal; substantia gelatinosa; convergent neuron; C-fiber; rat
Copyright © 1998 Society for Neuroscience 0270-6474/98/18103529-08$05.00/0
This article has been cited by other articles:
R. Benoliel, J. Epstein, E. Eliav, R. Jurevic, and S. Elad
Orofacial Pain in Cancer: Part I--Mechanisms
J. Dent. Res., June 1, 2007; 86(6): 491 - 505.
[Abstract] [Full Text] [PDF]
J. E. Belforte and J. H. Pazo
Striatal Inhibition of Nociceptive Responses Evoked in Trigeminal Sensory Neurons by Tooth Pulp Stimulation
J Neurophysiol, March 1, 2005; 93(3): 1730 - 1741.
[Abstract] [Full Text] [PDF]
H. Hirata, K. Okamoto, and D. A. Bereiter
GABAA Receptor Activation Modulates Corneal Unit Activity in Rostral and Caudal Portions of Trigeminal Subnucleus Caudalis
J Neurophysiol, November 1, 2003; 90(5): 2837 - 2849.
[Abstract] [Full Text] [PDF]
A. Woda
Pain in the Trigeminal System: from Orofacial Nociception to Neural Network Modeling
J. Dent. Res., October 1, 2003; 82(10): 764 - 768.
[Full Text] [PDF]
B. Hu, C. Y. Chiang, J. W. Hu, J. O. Dostrovsky, and B. J. Sessle
P2X Receptors in Trigeminal Subnucleus Caudalis Modulate Central Sensitization in Trigeminal Subnucleus Oralis
J Neurophysiol, October 1, 2002; 88(4): 1614 - 1624.
[Abstract] [Full Text] [PDF]
A. F. M. DaSilva, L. Becerra, N. Makris, A. M. Strassman, R. G. Gonzalez, N. Geatrakis, and D. Borsook
Somatotopic Activation in the Human Trigeminal Pain Pathway
J. Neurosci., September 15, 2002; 22(18): 8183 - 8192.
[Abstract] [Full Text] [PDF]
C. Y. Chiang, B. Hu, J. W. Hu, J. O. Dostrovsky, and B. J. Sessle
Central Sensitization of Nociceptive Neurons in Trigeminal Subnucleus Oralis Depends on Integrity of Subnucleus Caudalis
J Neurophysiol, July 1, 2002; 88(1): 256 - 264.
[Abstract] [Full Text] [PDF]
S. J. Park, C. Y. Chiang, J. W. Hu, and B. J. Sessle
Neuroplasticity Induced by Tooth Pulp Stimulation in Trigeminal Subnucleus Oralis Involves NMDA Receptor Mechanisms
J Neurophysiol, May 1, 2001; 85(5): 1836 - 1846.
[Abstract] [Full Text] [PDF]
H. Hirata, S. Takeshita, J. W. Hu, and D. A. Bereiter
Cornea-Responsive Medullary Dorsal Horn Neurons: Modulation by Local Opioids and Projections to Thalamus and Brain Stem
J Neurophysiol, August 1, 2000; 84(2): 1050 - 1061.
[Abstract] [Full Text] [PDF]
L. Monconduit, L. Bourgeais, J.-F. Bernard, D. Le Bars, and L. Villanueva
Ventromedial Thalamic Neurons Convey Nociceptive Signals from the Whole Body Surface to the Dorsolateral Neocortex
J. Neurosci., October 15, 1999; 19(20): 9063 - 9072.
[Abstract] [Full Text] [PDF]
|
|
|
|
 |
|