Browsing by Author "Antonio Fuentealba, Jose"

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    Repeated Treatment With the κ-Opioid Agonist U-69593 Increases K+-Stimulated Dopamine Release in the Rat Medial Prefrontal Cortex
    (2010) Antonio Fuentealba, Jose; Gysling, Katia; Estela Andres, Maria
    Acute activation of K-opioid receptors (KOR) decreases dopamine (DA) extracellular levels in both the medial prefrontal cortex (mPFC) and the nucleus accumbens (NAc). Also, the acute activation of KOR prevents alterations in behavior and neurochemistry occurring after repeated use of psychostimulants. Opposing to the acute effects, repeated administration of the KOR agonist, U-6593, potentiates both high-potassium and amphetamine induced DA release in the NAc, suggesting that repeated activation of KOR sensitizes mesolimbic dopaminergic neurotransmission. This study investigated the effect of repeated treatment with U-69593 on basal and stimulated DA and serotonin (5HT) extracellular levels in the rat mPFC. Rats were injected once daily with U-69593 (0.16-0.32 mg/kg) or vehicle for 4 days. One day after the last injection, microdialysis experiments assessing DA and 5HT extracellular levels in mPFC were conduced. The repeated treatment with U-69593 significantly augmented potassium-stimulated DA extracellular levels, without affecting potassium-stimulated 5HT extracellular levels, suggesting an increase in DA releasability. Synapse 64:898 904, 2010. (C)2010 Wiley-Liss, Inc.
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    Susceptibility to express amphetamine locomotor sensitization correlates with dorsolateral striatum bursting activity and GABAergic synapses in the globus pallidus
    (2022) Ignacio Gatica, Rafael; Aguilar-Rivera, Marcelo; Henny, Pablo; Antonio Fuentealba, Jose
    Repeated psychostimulant administration results in behavioral sensitization, a process that is relevant in the early phases of drug addiction. Critically, behavioral sensitization is not observed in all subjects. Evidence shows that differential neuronal activity in the dorsolateral striatum (DLS) accompanies the expression of amphetamine (AMPH) locomotor sensitization. However, whether individual differences in DLS activity previous to AMPH administration can predict the expression of locomotor sensitization has not been assessed. Here, we examined DLS neuronal activity before and after repeated AMPH administration and related it to the susceptibility of rats to sensitize. For that, single-unit recordings on DLS medium spiny neurons (MSNs) were carried out in freely moving male Sprague Dawley rats during repeated AMPH administration. We also examined differences in neurostructure that could accompany sensitization. We quantified the density of the inhibitory postsynaptic marker gephyrin (Geph) in the entopeduncular nucleus (EP) and globus pallidus (GP). A higher burst firing and a lower percentage of correlation between MSNs post-Saline firing rate vs. locomotion predicted the expression of locomotor sensitization. Moreover, during the AMPH challenge, we observed that burst firing decreased in sensitized rats, in contrast to non-sensitized rats in which burst firing was maintained. Finally, a higher Geph density on GP but not EP was observed in non-sensitized rats after AMPH challenge. These results indicate that initial differences in DLS burst firing might underlie the susceptibility to express locomotor sensitization and suggest that the potentiation of dorsal striatum indirect pathway could be considered a protective mechanism to locomotor sensitization.