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In the presence of a stimulus above the center lever, monkeys and rats were required to complete one of two fixed-ratios (FRs) on the center lever (FR20 or FR40, monkeys; FR8 or FR16, rats). Completion of the ratio turned off the center-lever stimulus and produced a stimulus above each of the two side levers. If the completed ratio was high (e.g., FR40), a(More)
MK-801, a high-affinity phencyclidine (PCP) analogue, is a noncompetitive antagonist of the N-methyl-D-aspartate (NMDA) subclass of glutamate receptor that elicits hyperactivity, stereotypic behaviors, and "popping," an explosive episodic jumping behavior, in mice. The schizophreniform psychosis precipitated by PCP in humans has stimulated interest in(More)
Naturally occurring 3-alpha-hydroxy ring A-reduced metabolites of progesterone and deoxycorticosterone and their synthetic analogues bind to specific sites within the hydrophobic channel domain of the GABAA receptor complex. Acting at these sites, these ligands function as positive allosteric effectors of the complex; they potentiate GABA-stimulated(More)
Diminished facial expressivity is a common feature of schizophrenia that interferes with effective interpersonal communication. This study was designed to determine if real-time visual feedback improved the ability of patients with schizophrenia to imitate and produce modeled facial expressions. Twenty patients with schizophrenia and 10 controls viewed(More)
Naive rats injected with LiCl at various times following consumption of a novel saccharin solution subsequently avoided the ingestion of saccharin with the degree of the aversion related to the interval between ingestion and LiCl administration. Although a similar relationship was also evident in animals which had received a single intragastric(More)
We examined possible genetic contributions to MK-801-elicited "popping" behavior in mice. MK-801-elicited "popping" behavior may represent a preclinical screening paradigm for identifying novel antipsychotic medications. Specifically, we studied the sensitivity of four inbred strains of mice (BALB/c, C57BL/6, AKR, and DBA/2) to MK-801-elicited "popping"(More)
Cold water swim stress has been shown to decrease the ability of flurazepam, a prototypic GABA-positive benzodiazepine, to antagonize the electrical precipitation of seizures in mice. This stress-induced reduction in the antiseizure efficacy of flurazepam is not due to a reduction in the threshold voltage for seizure production. In this study, we examined(More)
In persons with Down syndrome, soluble Abeta peptides, which result from the processing of the amyloid precursor protein, appear in the brain decades before the extracellular deposition of neuritic plaques. These soluble amyloidogenic peptides accumulate intraneuronally and can be secreted extracellularly. Their appearance has been reported in the brains of(More)
GABA, the major inhibitory neurotransmitter in the brain, is synthesized from L-glutamate and packaged within a family of highly differentiated inhibitory interneurons. Individual GABA inhibitory interneurons in the frontal cortex can make terminal synaptic connections with more than 200 distinct pyramidal neurons, the principal output neuron. Moreover, the(More)