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      Noradrenergic and Dopaminergic Activity in the Hypothalamic Paraventricular Nucleus after Naloxone-Induced Morphine Withdrawal

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          Previous research has shown an increase in hypothalamo-pituitary-adrenal axis activity following naloxone administration to morphine-dependent rats. In the present study, we investigated the adaptive changes in the noradrenaline (NA) and dopamine (DA) systems in the hypothalamic paraventricular nucleus (PVN) during morphine dependence and withdrawal. Additionally, we examined the possible change in 3′,5′-cyclic adenosine monophosphate (cAMP) levels in that nucleus under the same conditions. Rats were made dependent on morphine by morphine or placebo (naïve) pellet implantation for 7 days. On day 8, rat groups received an acute injection of saline or naloxone (1 mg/kg subcutaneously) and were decapitated 30 min later. NA and DA content as well as their metabolite production in the PVN were estimated by HPLC/ED. Both plasma corticosterone levels and cAMP concentration in the PVN were measured by RIA. Naloxone administration to morphine-dependent rats (withdrawal) induced a pronounced increase in the production of both the NA metabolite MHPG and the DA metabolite DOPAC and an enhanced NA and DA turnover. Furthermore, an increase in corticosterone secretion was observed in parallel to the changes in catecholamine turnover. However, no alterations in cAMP levels were seen during morphine withdrawal. These results raise the possibility that catecholaminergic afferents to the PVN could play a significant role in the alterations of PVN functions and consequently in the pituitary-adrenal response during morphine abstinence syndrome. These data provide further support for the idea of adaptive changes in catecholaminergic neurons projecting to the PVN during chronic morphine exposure.

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          Most cited references 12

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          Drugs of abuse: anatomy, pharmacology and function of reward pathways.

           George F Koob (1992)
          Drugs of abuse are very powerful reinforcers, and even in conditions of limited access (where the organism is not dependent) these drugs will motivate high rates of operant responding. This presumed hedonic property and the drugs' neuropharmacological specificity provide a means of studying the neuropharmacology and neuroanatomy of brain reward. Three major brain systems appear to be involved in drug reward--dopamine, opioid and GABA. Evidence suggests a midbrain-forebrain-extrapyramidal circuit with its focus in the nucleus accumbens. Data implicating dopamine and opioid systems in indirect sympathomimetic and opiate reward include critical elements in both the nucleus accumbens and ventral tegmental areas. Ethanol reward appears to depend on an interaction with the GABAA receptor complex but may also involve common elements such as dopamine and opioid peptides in this midbrain-forebrain-extrapyramidal circuit. These results suggest that brain reward systems have a multidetermined neuropharmacological basis that may involve some common neuroanatomical elements.
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            3-Methoxy-4-hydroxyphenylethyleneglycol concentrations in discrete hypothalamic nuclei reflect the activity of noradrenergic neurons

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              Chronic exposure to morphine and naltrexone induces changes in catecholaminergic neurotransmission in rat brain without altering μ-opioid receptor sensitivity


                Author and article information

                S. Karger AG
                January 2000
                14 January 2000
                : 71
                : 1
                : 60-67
                Unit of Pharmacology, Department of Physiology and Pharmacology, University School of Medicine, Murcia, Spain
                54521 Neuroendocrinology 2000;71:60–67
                © 2000 S. Karger AG, Basel

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                Page count
                Figures: 5, References: 41, Pages: 8
                Hypothalamic Neurotransmitter Interactions


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