W. T. O'Connor

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Skilled forelimb use was studied in rats with unilateral lesions of the sensorimotor cortex, the caudate-putamen, or the dopaminergic nigrostriatal bundle, in a task involving reaching for food. Limb preference and efficiency were evaluated, as well as the relationship between limb use, spontaneous, and methamphetamine-induced rotation bias, both(More)
In vivo microdialysis was used to study the effect of intracerebral administration of dopamine agonists on dynorphin B release in the striatum and substantia nigra of rats. The release of dopamine and GABA was also investigated. Administration of the dopamine D1 agonist SKF 38393 (10-100 microM) into the striatum increased extracellular dynorphin B and GABA(More)
Recent pharmacological data suggest that a receptor-receptor interaction between adenosine A2 and dopamine D2 receptors in the brain underlies the behavioral effects of adenosine agonists and adenosine antagonists, such as caffeine and theophylline. According to this interaction, stimulation of A2 receptors inhibits and their blockade potentiates the(More)
We describe a Bayesian inference scheme for quantifying the active physiology of neuronal ensembles using local field recordings of synaptic potentials. This entails the inversion of a generative neural mass model of steady-state spectral activity. The inversion uses Expectation Maximization (EM) to furnish the posterior probability of key synaptic(More)
Cognitive functions regulated by the prefrontal cortex are sensitive to changes in dopaminergic and serotoninergic transmission. The non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist ketamine influences dopaminergic transmission and induces psychotic symptoms in normal and schizophrenic individuals. This study examined the effect of single and(More)
Recent studies have shown the existence of a specific antagonistic interaction between adenosine A2a receptors and dopamine D2 receptors in the brain. This A2a-D2 interaction seems to be essential for the behavioural effects of adenosine agonists and antagonists, like caffeine. In the present study quantitative receptor autoradiography and brain(More)
Using in vivo microdialysis, changes in extracellular dorsolateral striatum and nucleus accumbens dopamine, GABA and acetylcholine following acute and chronic haloperidol (0.25 mg/kg, s.c.) were evaluated in rats concurrent with the measurement of catalepsy. When administered to drug-naive and chronically treated rats, haloperidol was associated with a(More)
Caffeine is a commonly used drug that increases arousal, a condition associated with increased cholinergic activity in the mammalian cerebral cortex including the hippocampus. We have used the technique of microdialysis in association with microbore high-performance liquid chromatography to investigate the effects of caffeine on the extracellular levels of(More)
The effects of the cannabinoid receptor agonist WIN 55,212-2 (0.1-5 mg/kg i.p.) on endogenous extracellular gamma-aminobutyric acid (GABA) levels in the cerebral cortex of the awake rat was investigated by using microdialysis. WIN 55,212-2 (1 and 5 mg/kg i.p.) was associated with a concentration-dependent decrease in dialysate GABA levels (-16% +/- 4% and(More)