Neuroscience
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Comparative Study
Individual responses to novelty predict qualitative differences in d-amphetamine-induced open field but not reward-related behaviors in rats.
Differences in the locomotor response of rats to a novel environment (high responders [HR] versus low responders [LR]) have been associated with differences in vulnerability to psychostimulants. In the present study we profiled extensively the behavioral repertoire of HR and LR rats (differentiated on the basis of vertical activity) during exposure to a novel environment and in response to d-amphetamine (d-amp; 1.5 mg/kg, i.p.). Moreover, we ascertained whether HR and LR rats differ in the rewarding effects of medial forebrain bundle electrical self-stimulation and in the ability of d-amp to increase the reinforcing efficacy of self-stimulation. ⋯ Additionally, brain stimulation reward thresholds for the two groups were not differentially affected by d-amp. The above results suggest that HR and LR can be further differentiated upon exposure to a novel environment and in response to d-amp. This differentiation is primarily based on qualitative cohorts of their behavioral structure, but not on deviations in the reward processes as assessed by intracranial self-stimulation.
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In seven freely moving squirrel monkeys (Saimiri sciureus), the neuronal activity in the periaqueductal gray (PAG) and bordering structures was registered during vocal communication, using a telemetric single-unit recording technique. In 9.3% of the PAG neurons, a vocalization-correlated activity was found. Four reaction types could be distinguished: a) neurons, showing an activity burst immediately before vocalization onset; b) neurons, firing during vocalization, and starting shortly before vocalization onset; c) neurons, firing exclusively during vocalization; d) neurons, firing in the interval between perceived vocalizations (i.e. vocalizations produced by group mates) and self-produced vocal response. ⋯ None of the neurons reflected simple acoustic parameters, such as fundamental frequency or amplitude, in its discharge rate. None of the neurons reacted to vocalizations of other animals not responded to by the experimental animal. All four reaction types found in the PAG were also found in the reticular formation bordering the PAG, though in lower density.
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Neurokinins such as substance P and neurokinin A have long been thought to act as neurotransmitters or modulators in the nucleus tractus solitarius. However, the role and location of the receptors for these peptides have remained unclear. We examined the consequences of activation of the neurokinin-1 (NK1) receptor subtype in the rat nucleus tractus solitarius using whole-cell patch clamp recordings in brain slices. ⋯ The increase in GABA release was also shown to be protein kinase C-dependent. The data presented here show NK1 receptors in the rat nucleus tractus solitarius are present both excitatory and inhibitory neurons. Activation of these receptors can result in increases in release of both GABA and glutamate, suggesting a crucial modulatory role for NK1 receptors in the rat nucleus tractus solitarius.
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Low glutathione levels have been observed in the prefrontal cortex and the cerebrospinal fluid of schizophrenic patients, possibly enhancing the cerebral susceptibility to oxidative stress. We used osteogenic disorder Shionogi mutant rats, which constitute an adequate model of the human redox regulation because both are unable to synthesize ascorbic acid. To study the long-term consequences of a glutathione deficit, we treated developing rats with L-buthionine-(S,R)-sulfoximine (BSO), an inhibitor of glutathione synthesis, and later investigated their behavior until adulthood. ⋯ Inhibition of brain glutathione synthesis and dopamine uptake in developing rats induce long-term cognitive deficits occurring in adulthood. Males are affected earlier and more intensively than females, at least concerning object recognition. The present study suggests that the low glutathione levels observed in schizophrenic patients may participate in the development of some of their cognitive deficits.
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Comparative Study
Accumulation of Ym1/2 protein in the mouse olfactory epithelium during regeneration and aging.
A unique feature of the olfactory system is its efficiency to produce new neurons in the adult. Thus, destruction of the olfactory receptor neurons (ORNs) using chemical (intranasal perfusion with ZnSO4) or surgical (axotomy or bulbectomy) methods, leads to an enhanced rate of proliferation of their progenitors and to complete ORNs regeneration. The aim of our study was to identify new factors implied in this regenerative process. ⋯ In the olfactory mucosa of control mice, Ym1/2 was hardly detectable in young animals and became more and more abundant with increasing age. In injured and aged mice, Ym1/2 mainly accumulates in the cytoplasm of supporting cells as well as in other cells located throughout the olfactory epithelium. Our results suggest that Ym1/2 is involved in olfactory epithelium remodeling following several kinds of lesions of the adult olfactory mucosa and support the view of a critical role of inflammatory cues in neurodegeneration and aging.