Involvement of excitatory amino acid pathways in the expression of precipitated opioid withdrawal in the rostral ventrolateral medulla: an in vivo voltammetric study

Involvement of excitatory amino acid pathways in the expression of precipitated opioid withdrawal... Previous studies have shown that catecholaminergic neurons in the rostral ventrolateral medulla (RVLM) become hyperactive during opioid withdrawal. In the present study, the role of excitatory amino acid pathways in the expression of opioid withdrawal in the RVLM was examined by using differential normal pulse voltammetry (DNPV) to measure changes in the catecholamine oxidation current (CA · OC) following naloxone challenge in rats treated with acute or chronic morphine. Acute morphine (10 μg i.c.v.) significantly reduced the CA · OC signal in the RVLM and the mean arterial pressure to 37.1 ± 6.6% and 21.1 ± 3.5% below baseline, respectively. Naloxone (1 mg kg −1 i.v.) reversed the morphine effect of produced a significant increase in the CA · OC signal to 25.6 ± 15.2% above baseline. In animals treated with chronic morphine (10 μg h −1 i.c.v., 5 days), naloxone (1 mg kg −1 i.v.) produced a significant increase in the CA · OC signal to 54.2 ± 16.5% above baseline. Both the nonselective excitatory amino acid antagonist, γ- d -glutamylglycine (DGG, 200 μg i.c.v.) and the selective NMDA antagonist, d (−)-amino-7-phosphohepatonic acid (D-APH, 25 μg i.c.v.) attenuated the naloxone-induced increase in the CA · OC by 50.7% and 46.0% respectively. In morphine naive animals, DGG and D-APH depressed the CA · OC by 42.8 ± 8.7% and 17.7 ± 9.8%, respectively. To the extent that the CA · OC is an index of neuronal activity, these results suggest that RVLM hyperactivity during morphine withdrawal is dependent, in part, upon activation of NMDA receptors. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Brain Research Elsevier

Involvement of excitatory amino acid pathways in the expression of precipitated opioid withdrawal in the rostral ventrolateral medulla: an in vivo voltammetric study

Brain Research, Volume 697 (1) – Oct 30, 1995

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Publisher
Elsevier
Copyright
Copyright © 1995 Elsevier Science B.V. All rights reserved
ISSN
0006-8993
DOI
10.1016/0006-8993(95)00803-X
Publisher site
See Article on Publisher Site

Abstract

Previous studies have shown that catecholaminergic neurons in the rostral ventrolateral medulla (RVLM) become hyperactive during opioid withdrawal. In the present study, the role of excitatory amino acid pathways in the expression of opioid withdrawal in the RVLM was examined by using differential normal pulse voltammetry (DNPV) to measure changes in the catecholamine oxidation current (CA · OC) following naloxone challenge in rats treated with acute or chronic morphine. Acute morphine (10 μg i.c.v.) significantly reduced the CA · OC signal in the RVLM and the mean arterial pressure to 37.1 ± 6.6% and 21.1 ± 3.5% below baseline, respectively. Naloxone (1 mg kg −1 i.v.) reversed the morphine effect of produced a significant increase in the CA · OC signal to 25.6 ± 15.2% above baseline. In animals treated with chronic morphine (10 μg h −1 i.c.v., 5 days), naloxone (1 mg kg −1 i.v.) produced a significant increase in the CA · OC signal to 54.2 ± 16.5% above baseline. Both the nonselective excitatory amino acid antagonist, γ- d -glutamylglycine (DGG, 200 μg i.c.v.) and the selective NMDA antagonist, d (−)-amino-7-phosphohepatonic acid (D-APH, 25 μg i.c.v.) attenuated the naloxone-induced increase in the CA · OC by 50.7% and 46.0% respectively. In morphine naive animals, DGG and D-APH depressed the CA · OC by 42.8 ± 8.7% and 17.7 ± 9.8%, respectively. To the extent that the CA · OC is an index of neuronal activity, these results suggest that RVLM hyperactivity during morphine withdrawal is dependent, in part, upon activation of NMDA receptors.

Journal

Brain ResearchElsevier

Published: Oct 30, 1995

References

  • In vivo monitoring of catecholaminergic metabolism in the C1 region of rat medulla oblongata: a comparative study by voltammetry and intracerebral microdialysis
    Lambás-Sen˜as, L.; Gillon, J.-Y.; Bouilloux, J.-P.; Seccia, M.; Buda, M.; Renaud, B.
  • Excitatory amino acids and morphine withdrawal: differential effects of central and peripheral kynurenic acid administration
    Rasmussen, K.; Krystal, J.H.; Aghajanian, G.K.
  • Metabotropic glutamate receptors in the ventrolateral medulla of rats
    Tsuchihashi, T.; Averill, D.B.

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