Behavioural brain research
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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.