Stress response in rat brain after different durations of noise exposure.

The alteration in the levels of plasma corticosterone, brain norepinephrine (NE), and expression of brain heat shock proteins (Hsp70) after different durations of noise exposure (acute, 1 day; sub-acute, 15 days; chronic, 30 days) has been studied to analyze their role in combating time-dependent stress effects of noise. Broadband white noise (100dB) exposure to male Wistar albino rats significantly increased the levels of plasma corticosterone and NE in all three durations of noise exposure. The sustained increase observed in their levels in the chronic group suggests that animals are not getting adapted to noise even after 30 days of exposure. The important role of Hsp70 in combating noise induced stress is evident from the significant increase in its expression after chronic exposure, while there was a reciprocal decrease in the NE and corticosterone when compared with their levels after acute and sub-acute noise exposure. This clearly indicates that the time-dependent stress response to noise exposure is a complex mechanism involving highly interconnected systems such as hypothalamo-pituitary-adrenal (HPA) axis, heat shock proteins and may have serious implications in vital organs, particularly in the brain when there is a prolonged noise exposure.

Oxidative stress induced by methotrexate alone and in the presence of methanol in discrete regions of the rodent brain, retina and optic nerve.

The vulnerability of the nervous system due to methanol (MeOH) intoxication is a well known fact and reports on the production of free radicals due to MeOH exposure and their involvement in excitotoxicity and neuronal apoptosis are being increasingly reported. We report on MeOH induced free radical changes and oxidative damages to proteins in the discrete regions of rat brain, retina and optic nerve. The present study used rats administered with methotrexate (MTX) to induce folate deficiency. Three groups of animals, namely saline control, MTX control, MTX-MeOH group were tested. The rats were injected intraperitoneally with MeOH (3 g/kg). After 24 h of MeOH administration, the levels of free radical scavengers, superoxide dismutase, catalase, glutathione peroxidase and reduced glutathione levels were estimated in the six discrete regions of brain (cerebral cortex, cerebellum, midbrain, pons medulla, hippocampus and hypothalamus), retina and optic nerve specimens. The levels of protein thiol, protein carbonyl and lipid peroxidation were also estimated and the expression of HSP70 in the hippocampus was analyzed by Western blot. Marked reduction in the levels of glutathione in the MTX-MeOH group in relation to MTX control was observed and found to be increased in MTX control in relation to saline control. Increased protein carbonyls and decreased protein thiols were documented in all the specimens tested. In addition, marked expression of HSP70 was observed in the hippocampus. The present investigation suggest that MeOH exposure results in increased generation of free radicals and significant protein oxidative damage and attempts to study the underlying mechanisms involved might reveal more insights to our existing knowledge on MeOH intoxication and related areas.

Noise-stress-induced brain neurotransmitter changes and the effect of Ocimum sanctum (Linn) treatment in albino rats.

In this modern world, stress and pollution are unavoidable phenomena affecting the body system at various levels. A large number of people are exposed to potentially hazardous noise levels in daily modern life, such as noise from work environments, urban traffic, and household appliances. A variety of studies have suggested an association between noise exposure and the occurrence of disorders involving extra-auditory organs such as disorders of the nervous, endocrine, and cardiovascular systems. In this study, Wistar strain albino rats were subjected to 100 dB broadband white noise, 4 h daily for 15 days. The high-pressure liquid chromatographic estimation of norepinephrine, epinephrine, dopamine, and serotonin in discrete regions of the rat brain indicates that noise stress can alter the brain biogenic amines after 15 days of stress exposure. Ocimum sanctum (OS), a medicinal herb that is widely claimed to posses antistressor activity and used extensively in the Indian system of medicine for a variety of disorders, was chosen for this study. Administration of the 70% ethanolic extract of OS had a normalizing action on discrete regions of brain and controlled the alteration in neurotransmitter levels due to noise stress, emphasizing the antistressor potential of this plant.