Behavioural brain research
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Alzheimer's disease (AD) is a progressive neurodegenerative disease clinically characterized by learning and memory function deterioration. While it is well established that exercise can improve cognitive performance in AD, there have been few basic cellular and molecular mechanisms research performed to test the interaction between exercise and AD. In this study, we aimed at investigating whether treadmill exercise improves learning and memory function in APP/PS1 transgenic mouse model of Alzheimer's disease by enhancing long-term potentiation (LTP) and up-regulation of brain-derived neurotrophic factor (BDNF) mRNA expression. ⋯ Treadmill exercise enhanced learning and memory function not only in wild type mice but also in APP/PS1 mice paralleled by LTP. However, BDNF has emerged as a crucial regulator of synaptic plasticity mechanisms underlying learning and memory in wild-type mice, but not in APP/PS1 mice. Hence, this investigation demonstrates that treadmill exercise is an effective therapeutic that alleviate learning and memory decline in APP/PS1 mouse model, and enhanced LTP maybe a cellular mechanism involved in neuropathological course of AD and cognitive improvement induced by exercise.
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Depressive disorders represent a major public health problem worldwide. The limitations of current antidepressant drugs have warranted on-going research to identify pharmacological agents and strategies that offer a greater therapeutic efficacy. The NMDA/L-arginine nitric oxide (NO)-cyclic guanosine monophosphate (cGMP) cascade is an important signaling pathway that is also implicated in the regulation of depression. ⋯ The effect of antidepressants on brain NO metabolism paralleled their behavioral action in case of IMI and VENL which decreased the nitrite+nitrate concentration in the brain. BUPR and FLX did not have any effect on brain nitrite+nitrate concentration. These results support the idea that some antidepressants are able to inhibit nitric oxide synthesis in the brain, an effect which could be mechanistically related to the ability of L-arginine to counteract their antidepressant-like effects.
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Mechanical pain sensitivity is characteristic of many orofacial pain conditions; however, few models exist to quantify this pain. Here we evaluated a novel adaptation of our existing operant system to characterize orofacial pain following mechanical and thermal stimuli. We demonstrate that the operant system is able to detect painful and analgesic responses to mechanical stimuli. These findings allow comparison of both mechanical and thermal stimuli using the same outcome measures.
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Comparative Study
Effects of intracerebral ventricular administration of gastrin-releasing peptide and its receptor antagonist RC-3095 on learned fear responses in the rat.
Several lines of evidence have implicated bombesin and its mammalian analogue, gastrin-releasing peptide (GRP), in the mediation and/or modulation of the stress response. However, the physiological role of GRP in mediating conditioned fear responses remains to be elucidated. The objective of the present study was to characterize the role(s) of GRP and its receptor antagonist (D-Tpi6, Leu13 psi[CH2NH]-Leu14) BB((6-14)) (RC-3095) in fear-related responses using two animal models of conditioned fear. ⋯ Further, in the FPS paradigm, i.c.v. administration of GRP significantly attenuated the fear-potentiated startle response at medium and high doses without affecting basal startle amplitude. In contrast, pretreatment with RC-3095 at the highest dose (9.0 nmol) significantly increased the basal startle amplitude without affecting fear-potentiation, suggesting elevated fear at the onset of testing. These data provide further evidence that GRP is involved in conditioned fear responses.
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Flavor is a result of the complex combination of olfactory, gustatory and trigeminal sensations perceived during oral processing of foods, including thermal, painful, tactile and/or kinesthetic effects. Aim of this study was to better understand interactions between synchronous tactile (texture) and olfactory (odor) sensations, using a psychophysical and an electrophysiological approach. Texture stimuli were aliquots of lean milk and thickened lean milk. A butter aroma was presented either orthonasally or retronasally after oral processing and before swallowing the oral stimulus or in the absence of an oral stimulus. Eighteen subjects (11 women, 7 men, mean age 24 years), naïve to the expected effects, rated both odor and texture intensity of each stimulus. Event-related potentials (ERP) were obtained from five recording positions. For the psychophysical data, the presence of an oral stimulus increased odor intensity, irrespective of odor presentation route. For the electrophysiological data, both early and late chemosensory ERPs were affected by odor conditions, texture conditions, and their respective interaction. ⋯ (1) perceptual interactions occurred between food texture and odor, with cross-modal interactions being found for both orthonasal and retronasal odor administration, and (2) these interactions between texture and odor occur at both primary-sensory and cognitive evaluative levels of stimulus processing. The temporal dimension plays then a critical role in the investigation of odor-texture interactions.