Agmatine modulates neuroadaptations of glutamate transmission in the nucleus accumbens of repeated morphine-treated rats.
Summary of "Agmatine modulates neuroadaptations of glutamate transmission in the nucleus accumbens of repeated morphine-treated rats."
It has been proved that agmatine inhibits opioid dependence, yet the neural mechanism remains unclear. In the present study, the effect of agmatine on the neuroadaptation of glutamate neurotransmission induced by morphine dependence, including changes of the extracellular glutamate level and glutamate receptors in the nucleus accumbens was investigated. We found that agmatine (2.5-20mg/kg, s.c.) inhibited development of morphine dependence, which was consistent with our previous report. In rats repeatedly treated with morphine, the glutamate level in the nucleus accumbens dialysate was markedly increased after naloxone-precipitated withdrawal. When agmatine (20mg/kg, s.c.) was co-pretreated with morphine or was applied before naloxone-precipitated withdrawal, this elevation of the extracellular glutamate level was inhibited. In the synaptosome model, repeated morphine treatment and naloxone precipitation induced an increase in glutamate release, while agmatine (20mg/kg, s.c.) co-pretreated with morphine reversed the increase of glutamate release. However, neither morphine or agmatine treatment alone nor morphine and agmatine co-administration had any influence on [3H]-glutamate uptake. It indicated that the elevation of the glutamate level in the nucleus accumbens might be caused by the increase of glutamate release of synaptosome in the withdrawal conditions of morphine-dependent rat. Furthermore, agmatine concomitant treatment with morphine entirely abolished the up-regulation of the NR1 subunit of N-methyl-d-aspartate (NMDA) receptors in the nucleus accumbens in repeated morphine-treated rats. Taken together, the present study demonstrated that agmatine could modulate the neuroadaptations of glutamate transmission in the nucleus accumbens in the case of morphine dependence, including modulating extracellular glutamate concentration and NMDA receptor expression.
Affiliation
Beijing Institute of Pharmacology and Toxicology, 27th Taiping Road, Beijing 100850, China.
Journal Details
This article was published in the following journal.
Name: European journal of pharmacology
ISSN: 1879-0712
Pages: 200-5
Links
- PubMed Source: http://www.ncbi.nlm.nih.gov/pubmed/20950603
- DOI: http://dx.doi.org/10.1016/j.ejphar.2010.09.071
Medical and Biotech [MESH] Definitions
Receptors, Glutamate
Cell-surface proteins that bind glutamate and trigger changes which influence the behavior of cells. Glutamate receptors include ionotropic receptors (AMPA, kainate, and N-methyl-D-aspartate receptors), which directly control ion channels, and metabotropic receptors which act through second messenger systems. Glutamate receptors are the most common mediators of fast excitatory synaptic transmission in the central nervous system. They have also been implicated in the mechanisms of memory and of many diseases.
Ventral Tegmental Area
A region in the mesencephalon which is dorsomedial to the substantia nigra and ventral to the red nucleus. The mesocortical and mesolimbic dopaminergic systems originate here, including an important projection to the nucleus accumbens. Overactivity of the cells in this area has been suspected to contribute to the positive symptoms of schizophrenia.
Nucleus Accumbens
Collection of pleomorphic cells in the caudal part of the anterior horn of the lateral ventricle, in the region of the olfactory tubercle, lying between the head of the caudate nucleus and the anterior perforated substance. It is part of the so-called ventral striatum, a composite structure considered part of the basal ganglia.
Receptor, Serotonin, 5-ht1d
A serotonin receptor subtype that is localized to the CAUDATE NUCLEUS; PUTAMEN; the NUCLEUS ACCUMBENS; the HIPPOCAMPUS, and the RAPHE NUCLEI. It plays a role as a terminal autoreceptor that regulates the rate of SEROTONIN release from nerve endings. This serotonin receptor subtype is closely related to and has similar drug binding properties as the 5-HT1B RECEPTOR, but is expressed at low levels. It is particularly sensitive to the agonist SUMATRIPTAN and may be involved in mediating the drug's antimigrane effect.
Phenobarbital
A barbituric acid derivative that acts as a nonselective central nervous system depressant. It promotes binding to inhibitory GAMMA-AMINOBUTYRIC ACID subtype receptors, and modulates chloride currents through receptor channels. It also inhibits glutamate induced depolarizations.
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