 |
 Previous Article | Next Article 
Journal of Neuroscience, Vol 6, 1803-1813, Copyright © 1986 by Society for Neuroscience
Stimulation-produced spinal inhibition from the midbrain in the rat is mediated by an excitatory amino acid neurotransmitter in the medial medulla
LD Aimone and GF Gebhart
It has been previously established that a bulbar relay plays an important
role in descending inhibition of spinal dorsal horn nociceptive neurons and
nociceptive reflexes produced by stimulation in the midbrain periaqueductal
gray (PAG). In the present study, selected receptor antagonists were
microinjected into the medial medullary nucleus raphe magnus (NRM) to
determine whether descending inhibition of the tail flick (TF) reflex in
the rat produced by focal electrical stimulation in the midbrain PAG was
mediated by serotonin, opioid, or glutamate receptors on bulbospinal
neurons in the NRM. It was determined in initial experiments that the
serotonin receptor antagonist methysergide, the opioid receptor antagonist
naloxone, the local anesthetic lidocaine, and the glutamate receptor
antagonists gamma-D-glutamylglycine (DGG) and
DL-2-amino-5-phosphonovalerate (APV) microinjected into the medulla all
significantly increased the threshold of focal electrical stimulation in
the medulla required to inhibit the TF reflex. The antinociceptive efficacy
of agonists at opioid, serotonin, and glutamate receptors was also tested
in other experiments. The microinjection of morphine (2.5-10 micrograms)
into the NRM increased significantly TF latencies in a dose-dependent
manner in rats in the awake or lightly anesthetized state; morphine was
more potent in awake rats. Inhibition of the TF reflex produced by the
microinjection of morphine was reversed by a subsequent microinjection of
naloxone into the same site in the medulla. The microinjection of serotonin
(5 and 10 micrograms), however, did not affect the latency of the TF reflex
in either awake or lightly anesthetized rats. Glutamate (100 microM, 0.5
microliter) microinjected into the rostral ventral medulla produced an
inhibition of the TF reflex of short duration that could be blocked or
attenuated significantly by the glutamate receptor antagonists DGG or APV
microinjected into the same site. In subsequent experiments, a nonspecific
functional block was introduced adjacent to the NRM bilaterally in the
medullary reticular formations (MRFs) by the microinjection of the local
anesthetic lidocaine; receptor antagonists were then microinjected into the
NRM and their effect on the threshold of focal electrical stimulation in
the PAG to inhibit the TF reflex determined. No increase was seen in
stimulation thresholds in the PAG following the microinjection of either
methysergide or naloxone into the NRM. Following the microinjection of
lidocaine, DGG or APV into the NRM, the stimulation threshold in the PAG
for inhibition of the TF reflex was increased significantly.(ABSTRACT
TRUNCATED AT 400 WORDS)
This article has been cited by other articles:
|
|
|
|
 
J. Fichna, A. Janecka, J. Costentin, and J.-C. Do Rego
The Endomorphin System and Its Evolving Neurophysiological Role
Pharmacol. Rev.,
March 1, 2007;
59(1):
88 - 123.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
C. W. Winkler, S. M. Hermes, C. I. Chavkin, C. T. Drake, S. F. Morrison, and S. A. Aicher
Kappa Opioid Receptor (KOR) and GAD67 Immunoreactivity Are Found in OFF and NEUTRAL Cells in the Rostral Ventromedial Medulla
J Neurophysiol,
December 1, 2006;
96(6):
3465 - 3473.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
S. Maione, T. Bisogno, V. de Novellis, E. Palazzo, L. Cristino, M. Valenti, S. Petrosino, V. Guglielmotti, F. Rossi, and V. D. Marzo
Elevation of Endocannabinoid Levels in the Ventrolateral Periaqueductal Grey through Inhibition of Fatty Acid Amide Hydrolase Affects Descending Nociceptive Pathways via Both Cannabinoid Receptor Type 1 and Transient Receptor Potential Vanilloid Type-1 Receptors
J. Pharmacol. Exp. Ther.,
March 1, 2006;
316(3):
969 - 982.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
I. D. Meng, J. P. Johansen, I. Harasawa, and H. L. Fields
Kappa Opioids Inhibit Physiologically Identified Medullary Pain Modulating Neurons and Reduce Morphine Antinociception
J Neurophysiol,
March 1, 2005;
93(3):
1138 - 1144.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
M. A. Baez, T. S. Brink, and P. Mason
Roles for Pain Modulatory Cells during Micturition and Continence
J. Neurosci.,
January 12, 2005;
25(2):
384 - 394.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
M. W. Nason Jr. and P. Mason
Modulation of Sympathetic and Somatomotor Function by the Ventromedial Medulla
J Neurophysiol,
July 1, 2004;
92(1):
510 - 522.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
B. Bie and Z. Z. Pan
Presynaptic Mechanism for Anti-Analgesic and Anti-Hyperalgesic Actions of {kappa}-Opioid Receptors
J. Neurosci.,
August 13, 2003;
23(19):
7262 - 7268.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
V. Tortorici and M. M. Morgan
Comparison of Morphine and Kainic Acid Microinjections Into Identical PAG Sites on the Activity of RVM Neurons
J Neurophysiol,
October 1, 2002;
88(4):
1707 - 1715.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
A. Kalra, M. O. Urban, and K. A. Sluka
Blockade of Opioid Receptors in Rostral Ventral Medulla Prevents Antihyperalgesia Produced by Transcutaneous Electrical Nerve Stimulation (TENS)
J. Pharmacol. Exp. Ther.,
July 1, 2001;
298(1):
257 - 263.
[Abstract]
[Full Text]
|
|
|
|
|
|
|
H. Bester, C. De Felipe, and S. P. Hunt
The NK1 Receptor Is Essential for the Full Expression of Noxious Inhibitory Controls in the Mouse
J. Neurosci.,
February 1, 2001;
21(3):
1039 - 1046.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
D. Budai and H. L. Fields
Endogenous Opioid Peptides Acting at µ-Opioid Receptors in the Dorsal Horn Contribute to Midbrain Modulation of Spinal Nociceptive Neurons
J Neurophysiol,
February 1, 1998;
79(2):
677 - 687.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
K. Gao, Y.-H. H. Kim, and P. Mason
SEROTONERGIC Pontomedullary Neurons Are Not Activated by Antinociceptive Stimulation in the Periaqueductal Gray
J. Neurosci.,
May 1, 1997;
17(9):
3285 - 3292.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
