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An intact dopaminergic system is required for context-conditioned release of 5-HT in the nucleus accumbens of postweaning isolation-reared rats.

Abstract

We investigated the effect of the tyrosine hydroxylase inhibitor, alpha-methyl-para-tyrosine (AMPT) on extracellular dopamine and 5-HT levels in the nucleus accumbens of group- and isolation-reared rats. Microdialysis with high-performance liquid chromatography-electrochemical detection was used to quantify dopamine and 5-HT efflux in the nucleus accumbens following foot shock and in association with a conditioned emotional response (CER). Isolation- and group-reared rats received i.p. injections of either saline (0.9%) or AMPT (200 mg/kg) 15 h and 2 h prior to sampling. There was no significant difference between saline-treated isolation- or group-reared rats for basal efflux of dopamine or 5-HT, however as expected, AMPT-treatment significantly reduced dopamine efflux in both groups to an equivalent level (50-55% saline-treated controls). Exposure to mild foot shock stimulated basal dopamine efflux in saline-treated groups only, although the effect was significantly greater in isolation-reared rats. In AMPT-treated rats, foot shock did not affect basal dopamine efflux in either rearing group. Foot shock evoked a prolonged increase in 5-HT efflux in both isolation- and group-reared saline-treated rats but had no effect on 5-HT efflux in AMPT-treated rats. In response to CER, isolation-rearing was associated with significantly greater efflux of both dopamine and 5-HT in saline-treated rats, compared to saline-treated, group-reared controls. However in AMPT-treated rats, efflux of dopamine or 5-HT did not change in response to CER. These data suggest that unconditioned or conditioned stress-induced changes in 5-HT release of the nucleus accumbens are dependent upon intact catecholaminergic neurotransmission. Furthermore, as the contribution of noradrenaline to catecholamine efflux in the nucleus accumbens is relatively minor compared to dopamine, our findings suggest that dopamine efflux in the nucleus accumbens is important for the local regulation of 5-HT release in this region. Finally, these findings implicate the isolation-enhanced presynaptic dopamine function in the accumbens with the augmented ventral striatal 5-HT neurotransmission characterized by isolation-reared rats.

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  • Authors+Show Affiliations

    ,

    Department of Anatomy, University of Bristol, Southwell Street, Bristol BS2 8EJ, UK. A.J.Fulford@bris.ac.uk

    Source

    Neuroscience 149:2 2007 Oct 26 pg 392-400

    MeSH

    Animals
    Chromatography, High Pressure Liquid
    Conditioning (Psychology)
    Dopamine
    Dopamine Antagonists
    Electroshock
    Enzyme Inhibitors
    Extracellular Space
    Fear
    Male
    Microdialysis
    Motor Activity
    Nucleus Accumbens
    Rats
    Receptors, Presynaptic
    Serotonin
    Social Environment
    Social Isolation
    Synaptic Transmission
    Tyrosine 3-Monooxygenase
    alpha-Methyltyrosine

    Pub Type(s)

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

    Language

    eng

    PubMed ID

    17869434

    Citation

    Fulford, A J., and C A. Marsden. "An Intact Dopaminergic System Is Required for Context-conditioned Release of 5-HT in the Nucleus Accumbens of Postweaning Isolation-reared Rats." Neuroscience, vol. 149, no. 2, 2007, pp. 392-400.
    Fulford AJ, Marsden CA. An intact dopaminergic system is required for context-conditioned release of 5-HT in the nucleus accumbens of postweaning isolation-reared rats. Neuroscience. 2007;149(2):392-400.
    Fulford, A. J., & Marsden, C. A. (2007). An intact dopaminergic system is required for context-conditioned release of 5-HT in the nucleus accumbens of postweaning isolation-reared rats. Neuroscience, 149(2), pp. 392-400.
    Fulford AJ, Marsden CA. An Intact Dopaminergic System Is Required for Context-conditioned Release of 5-HT in the Nucleus Accumbens of Postweaning Isolation-reared Rats. Neuroscience. 2007 Oct 26;149(2):392-400. PubMed PMID: 17869434.
    * Article titles in AMA citation format should be in sentence-case
    TY - JOUR T1 - An intact dopaminergic system is required for context-conditioned release of 5-HT in the nucleus accumbens of postweaning isolation-reared rats. AU - Fulford,A J, AU - Marsden,C A, Y1 - 2007/08/08/ PY - 2007/05/23/received PY - 2007/07/27/revised PY - 2007/08/02/accepted PY - 2007/9/18/pubmed PY - 2008/1/17/medline PY - 2007/9/18/entrez SP - 392 EP - 400 JF - Neuroscience JO - Neuroscience VL - 149 IS - 2 N2 - We investigated the effect of the tyrosine hydroxylase inhibitor, alpha-methyl-para-tyrosine (AMPT) on extracellular dopamine and 5-HT levels in the nucleus accumbens of group- and isolation-reared rats. Microdialysis with high-performance liquid chromatography-electrochemical detection was used to quantify dopamine and 5-HT efflux in the nucleus accumbens following foot shock and in association with a conditioned emotional response (CER). Isolation- and group-reared rats received i.p. injections of either saline (0.9%) or AMPT (200 mg/kg) 15 h and 2 h prior to sampling. There was no significant difference between saline-treated isolation- or group-reared rats for basal efflux of dopamine or 5-HT, however as expected, AMPT-treatment significantly reduced dopamine efflux in both groups to an equivalent level (50-55% saline-treated controls). Exposure to mild foot shock stimulated basal dopamine efflux in saline-treated groups only, although the effect was significantly greater in isolation-reared rats. In AMPT-treated rats, foot shock did not affect basal dopamine efflux in either rearing group. Foot shock evoked a prolonged increase in 5-HT efflux in both isolation- and group-reared saline-treated rats but had no effect on 5-HT efflux in AMPT-treated rats. In response to CER, isolation-rearing was associated with significantly greater efflux of both dopamine and 5-HT in saline-treated rats, compared to saline-treated, group-reared controls. However in AMPT-treated rats, efflux of dopamine or 5-HT did not change in response to CER. These data suggest that unconditioned or conditioned stress-induced changes in 5-HT release of the nucleus accumbens are dependent upon intact catecholaminergic neurotransmission. Furthermore, as the contribution of noradrenaline to catecholamine efflux in the nucleus accumbens is relatively minor compared to dopamine, our findings suggest that dopamine efflux in the nucleus accumbens is important for the local regulation of 5-HT release in this region. Finally, these findings implicate the isolation-enhanced presynaptic dopamine function in the accumbens with the augmented ventral striatal 5-HT neurotransmission characterized by isolation-reared rats. SN - 0306-4522 UR - https://www.unboundmedicine.com/medline/citation/17869434/An_intact_dopaminergic_system_is_required_for_context_conditioned_release_of_5_HT_in_the_nucleus_accumbens_of_postweaning_isolation_reared_rats_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0306-4522(07)01004-4 DB - PRIME DP - Unbound Medicine ER -