Controladores del tiempo y el envejecimiento: núcleo supraquiasmático y glándula pineal / Aging process entrainment: suprachiasmatic nucleus and pineal gland

El núcleo supraquiasmático (NSQ) es el principal reloj biológico de los mamíferos y sincroniza la actividad de la glándula pineal al ciclo luz-oscuridad a través de una vía polisináptica. El efecto de asa de retroalimentación neuroendocrina se lleva a cabo por la melatonina. El presente trabajo pretende demostrar que la glándula pineal modula la sensibilidad a la luz en el NSQ. Se utilizaron ratas Wistar, y se asignaron a 3 grupos: grupo A (falsa pinealectomía -sham-, sin luz), grupo B (falsa pinealectomía -sham- + luz) y grupo C al cual se le realizó la pinealectomía + luz, después de la manipulación se sacrifican para realizar inmunohistoquímica para c-Fos y al final conteo celular por técnica de estereología. Se obtuvo una reducción del 46,8% del promedio de células inmunorreactivas a c-Fos en el grupo C en comparación del grupo B. Este trabajo muestra que la sensibilidad a la luz está modulada por la actividad de la glándula pineal.

The suprachiasmatic nucleus (SCN) is the main and major biological clock in mammals and is responsible for the synchronization of the pineal gland to the light/darkness cycle through a polysynaptic pathway. The neuroendocrine feedback loop effect is carried out by melatonin. This study was carried out to demonstrate that the pineal gland adjusts the sensibility to light in the suprachiasmatic nucleus. Wistar rats were allocated in 3 groups: Group A (sham pinalectomy, without light), group B (sham pinealectomy + light) and group C which underwent real pinalectomy + light. After the intervention the animals were slain to perform immunohistochemistry for c-Fos and cell counting by stereology technique. A 46.8% average reduction in c-Fos immunoreactive cells was achieved in-group C as compared with group B. The present work shows that sensibility to the light is modulate by the activity of the pineal gland.

Changes in orexin-A and neuropeptide Y expression in the hypothalamus of the fasted and high-fat diet fed rats

This study was aimed to investigate the changes of orexin-A (OXA) and neuropeptide Y (NPY) expression in the hypothalamus of the fasted and high-fat diet fed rats. For the experiments, the male Sprague-Dawley (SD) rats were used as the model of high-fat diet-induced obesity. The mean loss of body weight (MLBW) did not show the linear pattern during the fasting; from 24 h to 84 h of fastings, the MLBW was not significantly changed. The numbers of OXA-immunoreactive (IR) neurons were decreased at 84 h of fasting compared with those in other five fasting subgroups. The NPY immunoreactivities in the arcuate nucleus (ARC) and the suprachiasmatic nucleus (SCN) observed at 84 h of fasting were higher than that observed at 24 h of fasting. The number of OXA-IR neurons of the LHA (lateral hypothalamic area) in the high-fat (HF) diet fed group was more increased than that of the same area in the normal-fat (NF) diet fed group. The NPY immunoreactivities of the ARC and the SCN were higher in HF group than those observed in the same areas of NF group. Based on these results, it is noteworthy that the decrease of the body weight during the fast was not proportionate to the time-course, implicating a possible adaptation of the body for survival against starvation. The HF diet might activate the OXA and the NPY in the LHA to enhance food intake.