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Indirect modulation by alpha7 nicotinic acetylcholine receptors of noradrenaline release in rat hippocampal slices: interaction with glutamate and GABA systems and effect of nicotine withdrawal.
Mol Pharmacol. 2006 Feb; 69(2):618-28.MP

Abstract

Nicotinic acetylcholine receptors (nAChRs) can modulate transmitter release. Striatal [(3)H]dopamine ([(3)H]DA) release is regulated by presynaptic nAChR on dopaminergic terminals and alpha7 nAChR on neighboring glutamatergic afferents. Here, we explored the role of alpha7 nAChR in the modulation of [(3)H]noradrenaline ([(3)H]NA) release from rat hippocampal slices. The nicotinic agonist anatoxin-a (AnTx) evoked monophasic [(3)H]NA release (EC(50) = 1.2 microM) that was unaffected by alpha-conotoxin-MII or dihydro-beta-erythroidine, antagonists of alpha3/alpha6beta2* and beta2* nAChR, respectively. In contrast AnTx-evoked striatal [(3)H]DA release was biphasic (EC(50) = 138.9 nM; 7.1 microM) and blocked by these antagonists. At a high AnTx concentration (25 microM), alpha7 nAChR antagonists (methyllycaconitine, alpha-conotoxin-ImI) and glutamate receptor (GluR) antagonists [kynurenic acid, 6,7-dinitroquinoxaline-2,3-dione (DNQX)] partially inhibited [(3)H]NA release. The alpha7 nAChR-selective agonist choline evoked [(3)H]NA release (E(max) = 33% of that of AnTx) that was blocked by GluR antagonists, supporting a model in which alpha7 nAChRs trigger glutamate release that subsequently stimulates [(3)H]NA release. A GABAergic component was also revealed: choline-evoked [(3)H]NA release was partially blocked by the GABA(A) receptor antagonist bicuculline, and coapplication of bicuculline and DNQX fully abolished this response. These findings support alpha7 nAChR on GABAergic neurons that can promote GABA release which, in turn, leads to [(3)H]NA release, probably by disinhibition. To investigate the impact of long-term nicotine exposure on this model, rats were exposed for 14 days to nicotine (4 mg/kg/day) with or without 3 or 7 days of withdrawal. alpha7 nAChR responses were selectively and transiently up-regulated after 3 days of withdrawal. This functional up-regulation could contribute to the withdrawal effects of nicotine.

Authors+Show Affiliations

Department of Biology and Biochemistry, University of Bath, UK.No affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

16269536

Citation

Barik, Jacques, and Susan Wonnacott. "Indirect Modulation By Alpha7 Nicotinic Acetylcholine Receptors of Noradrenaline Release in Rat Hippocampal Slices: Interaction With Glutamate and GABA Systems and Effect of Nicotine Withdrawal." Molecular Pharmacology, vol. 69, no. 2, 2006, pp. 618-28.
Barik J, Wonnacott S. Indirect modulation by alpha7 nicotinic acetylcholine receptors of noradrenaline release in rat hippocampal slices: interaction with glutamate and GABA systems and effect of nicotine withdrawal. Mol Pharmacol. 2006;69(2):618-28.
Barik, J., & Wonnacott, S. (2006). Indirect modulation by alpha7 nicotinic acetylcholine receptors of noradrenaline release in rat hippocampal slices: interaction with glutamate and GABA systems and effect of nicotine withdrawal. Molecular Pharmacology, 69(2), 618-28.
Barik J, Wonnacott S. Indirect Modulation By Alpha7 Nicotinic Acetylcholine Receptors of Noradrenaline Release in Rat Hippocampal Slices: Interaction With Glutamate and GABA Systems and Effect of Nicotine Withdrawal. Mol Pharmacol. 2006;69(2):618-28. PubMed PMID: 16269536.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Indirect modulation by alpha7 nicotinic acetylcholine receptors of noradrenaline release in rat hippocampal slices: interaction with glutamate and GABA systems and effect of nicotine withdrawal. AU - Barik,Jacques, AU - Wonnacott,Susan, Y1 - 2005/11/03/ PY - 2005/11/5/pubmed PY - 2006/3/11/medline PY - 2005/11/5/entrez SP - 618 EP - 28 JF - Molecular pharmacology JO - Mol. Pharmacol. VL - 69 IS - 2 N2 - Nicotinic acetylcholine receptors (nAChRs) can modulate transmitter release. Striatal [(3)H]dopamine ([(3)H]DA) release is regulated by presynaptic nAChR on dopaminergic terminals and alpha7 nAChR on neighboring glutamatergic afferents. Here, we explored the role of alpha7 nAChR in the modulation of [(3)H]noradrenaline ([(3)H]NA) release from rat hippocampal slices. The nicotinic agonist anatoxin-a (AnTx) evoked monophasic [(3)H]NA release (EC(50) = 1.2 microM) that was unaffected by alpha-conotoxin-MII or dihydro-beta-erythroidine, antagonists of alpha3/alpha6beta2* and beta2* nAChR, respectively. In contrast AnTx-evoked striatal [(3)H]DA release was biphasic (EC(50) = 138.9 nM; 7.1 microM) and blocked by these antagonists. At a high AnTx concentration (25 microM), alpha7 nAChR antagonists (methyllycaconitine, alpha-conotoxin-ImI) and glutamate receptor (GluR) antagonists [kynurenic acid, 6,7-dinitroquinoxaline-2,3-dione (DNQX)] partially inhibited [(3)H]NA release. The alpha7 nAChR-selective agonist choline evoked [(3)H]NA release (E(max) = 33% of that of AnTx) that was blocked by GluR antagonists, supporting a model in which alpha7 nAChRs trigger glutamate release that subsequently stimulates [(3)H]NA release. A GABAergic component was also revealed: choline-evoked [(3)H]NA release was partially blocked by the GABA(A) receptor antagonist bicuculline, and coapplication of bicuculline and DNQX fully abolished this response. These findings support alpha7 nAChR on GABAergic neurons that can promote GABA release which, in turn, leads to [(3)H]NA release, probably by disinhibition. To investigate the impact of long-term nicotine exposure on this model, rats were exposed for 14 days to nicotine (4 mg/kg/day) with or without 3 or 7 days of withdrawal. alpha7 nAChR responses were selectively and transiently up-regulated after 3 days of withdrawal. This functional up-regulation could contribute to the withdrawal effects of nicotine. SN - 0026-895X UR - https://www.unboundmedicine.com/medline/citation/16269536/Indirect_modulation_by_alpha7_nicotinic_acetylcholine_receptors_of_noradrenaline_release_in_rat_hippocampal_slices:_interaction_with_glutamate_and_GABA_systems_and_effect_of_nicotine_withdrawal_ L2 - http://molpharm.aspetjournals.org/cgi/pmidlookup?view=long&pmid=16269536 DB - PRIME DP - Unbound Medicine ER -