Eddie Castañeda

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Squads of rats were assayed at three intervals following MA-induced neurotoxicity to investigate the persistence of monoamine deficits, the potential for monoamine recovery, and spatial task abilities. At 48, 139, and 237 days postinjection, MA animals showed significant monoamine depletions compared with controls. Investigating percent depletions(More)
Both cocaine and cocaine-associated stimuli can reinstate extinguished self-administration behavior in animals. It has been suggested that reinstatement of drug-seeking behavior may be mediated by enhanced dopamine (DA) neurotransmission. To examine this hypothesis, DA overflow was measured in the nucleus accumbens (NAc) of rats during both extinction and(More)
Exposure to amphetamine (AMPH) in vivo produces an enduring enhancement ('sensitization') in AMPH-stimulated striatal DA release in vitro. Experiments were conducted to determine whether striatal DA release evoked by neuronal depolarization is altered by AMPH pretreatment in a similar manner. It was found that AMPH pretreatment produced a long-lasting (at(More)
Intracerebral microdialysis was used to measure the extracellular concentration of striatal dopamine (DA) and its metabolites in freely moving rats depleted of DA by the bilateral infusion of 6-hydroxydopamine into the substantia nigra approximately 1 month earlier. It was found that the basal extracellular concentration of DA remained within the same range(More)
Rats depleted of dopamine (DA) by intraventricular 6-hydroxydopamine (6-OHDA) in infancy show behavioral impairments as adults, but their basic sensory-motor functions and feeding abilities are intact; at least relative to the pronounced deficits seen in rats given similar treatment in adulthood. Here we investigate whether presynaptic changes culminating(More)
Mathematical principles of reinforcement (MPR; Killeen, 1994) is a quantitative model of operant behavior that contains three parameters representing motor capacity (delta), motivation (a), and short term memory (lambda). The present study applied MPR to characterize the effects of bilateral infusions of 6-OHDA into the substantia nigra pars compacta in the(More)
The repeated intermittent administration of amphetamine (AMP) produces an enduring enhancement in the response of dopamine (DA) systems in the brain to a subsequent "challenge" with amphetamine. However, former amphetamine addicts are not only hypersensitive to amphetamine, but also to "physical or psychological stress". This suggests that sensitization to(More)
It is reported that in rats the repeated intermittent administration of amphetamine produces a long-lasting enhancement in medial frontal cortex dopamine utilization. This change in mesocortical dopamine activity may be involved in the behavioral sensitization produced by psychomotor stimulant drugs, and some of the cognitive abnormalities (e.g. amphetamine(More)
To compare the effectiveness of 2 phytase enzymes (Phyzyme and Natuphos), growth performance, fibula ash, and Ca and P digestibilities were evaluated in 4 studies. The first 3 studies used 832 pigs (i.e., 288 in the nursery phase, initial BW 8.1 kg; 288 in the grower phase, initial BW 24.2 kg; and 256 in the finisher phase, initial BW 57.8 kg) and were(More)
An easily constructed, inexpensive and simple system is described for the superfusion of neural tissue. To characterize the system, the dynamics of endogenous dopamine and dihydroxyphenylacetic acid release from striatal tissue were studied before and after exposure to potassium, amphetamine or cocaine.