[External validity of a relevant model for Irritable Bowel Syndrome (IBS) using chronic stress by water avoidance in Wistar rats]. / Validez externa de un modelo experimental para síndrome de intestino irritable (SII) mediante estrés crónico por evitación al agua en ratas Wistar.

BACKGROUND: Development of animal models has been one of the most remarkable achievements for Irritable Bowel Syndrome (IBS) research. These models need to exhibit face validity, construct and predictive validity, as well as internal (replicability) and external validity (generalizability). Among these models, chronic stress induced by water avoidance exposure (WA) has been validated in rats through increasing visceral hypersensitivity, motility impairment, anxiety and, colonic immune activity, all related to IBS. OBJECTIVE: To assess the external validity of WA indirectly on colonic motility in Wistar rats. METHOD: Ten male-Wistar rats were exposed to WA and compared with ten Wistar rats not exposed (controls). At the end of each exposure, the quantity of fecal pellets were determined and considered as a sign of autonomic regulation of colonic motility. Data was analyzed with a general linear model for repeated measures. RESULTS: Rats exposed to WA had higher number or pellets than controls: 7.46 ± 0.45 (95%CI: 6.51, 8.41) vs. 2.88 ± 0.45 (1.93, 3.83), p < 0.001. The higher number of pellets was related to WA exposure as there were no other significant interactions. In both groups, the number of pellets was higher during the first day and then decreased progressively. CONCLUSIONS: Chronic stress induced through WA in Wistar rats, exhibits external validity as an experimental model for IBS research and our findings of increased number of fecal pellets coincide with the appearance hypermotility related to IBS. The model is optimum for research studies on this disorder.

[Communication based on the P300 component of event-related potentials: a proposal for a matrix with images]. / Comunicación basada en el componente P300 de los potenciales relacionados con eventos: propuesta de una matriz con imágenes.

INTRODUCTION: For more than two decades, several research groups have tried to build a device called "brain computer interface" (BCI) to make it available for people having several disabilities such as the locked in syndrome through the use of the recording of electroencephalography activity while the patients are being visually stimulated. AIM. To obtain a P300 component elicited by intensifications of images arranged in a matrix in an oddball paradigm in two selection modes: assigned and free. SUBJECTS AND METHODS: A 5 x 5 matrix for communication purposes was used to visually stimulate 12 volunteers while their event related potentials were recorded in three leads (Fz, Cz and Pz). Off-line analyses were performed to obtain the P300 component which was elicited by targets images intensified randomly by rows or columns. RESULTS: In both modalities assigned and free, all volunteers generated a reliable P300 component. Confirmation of the selected images was made through a comparison of the P300 when each target, row and column matched. In the free selection mode, higher amplitude and a broader activation including frontal leads was observed. No significant differences in the P300 latency were found. CONCLUSION: In all volunteers the elicited P300 allows the identification of the selected images in the 5 x 5 matrix. In the present study the use of drawings representing ideas instead of letters might increase the communication rate in a P300-based BCI.