RESUMO
BACKGROUND: In Ayurveda; an Indian system of traditional medicine, Ocimum sanctum is said to have remedial effect on hriddaurbalya (problems affecting the mind), aakshepayukta vikara (nervous disorders) and shiroroga (diseases of head). Hence, in Ayurvedic practice, it is profoundly used as an antistress medicine. Stress is known to affect neurons of functionally significant brain regions like substantia nigra. However, experimental evidence showing its effect on morphology of substantia nigral neurons is lacking. In addition, whether the O. sanctum treatment attenuates stress induced substantia nigral neuronal structural changes is not known. OBJECTIVES: To know the effect of stress on morphology of substantia nigral neurons and the effect of O. sanctum fresh leaf extract (OSE) on substantia nigral neurons of stressed rats. MATERIAL AND METHODS: Present study included three experiments. Experiment I: To study the effect of 3 and 6 weeks of foot shock stress in rats; Experiment II- To study the effect of 3 weeks of OSE treatment on 3 week-stress undergoing rats and on 3 week-stressed rats; Experiment III- To study the effect of 6 weeks of OSE treatment in 6 week-stress undergoing rats and in 6 week-stressed rats. RESULTS: In experiment I, stress had significant deleterious effect on dendritic arborization of substantia nigral neurons. Experiments II and III showed prevention and attenuation of the stress induced dendritic atrophy of substantia nigral neurons in both 2 ml and 4 ml OSE treatment groups. Protective effect of OSE was more pronounced in rats which are treated for a longer duration. CONCLUSIONS: Foot shock stress induces neuronal damage in the substantia nigra of rats. Treatment with fresh leaf extract of O. sanctum could prevent and attenuate the foot shock stress induced behavioral deficit and substantia nigral neuronal damage.
RESUMO
Altered sensitivity to the chronotropic effect of catecholamines and a reduction in the ß1/ß2-adrenoceptor ratio have previously been reported in right atria of stressed rats, human failing heart, and aging. In this report, we investigated whether left atrial inotropism was affected by foot-shock stress. Male rats were submitted to 3 foot-shock sessions and the left atrial inotropic response, adenylyl cyclase activity, and ß-adrenoceptor expression were investigated. Left atria of stressed rats were supersensitive to isoprenaline when compared with control rats and this effect was abolished by ICI118,551, a selective ß2-receptor antagonist. Schild plot slopes for the antagonism between CGP20712A (a selective ß1-receptor antagonist) and isoprenaline differed from unity in atria of stressed but not control rats. Atrial sensitivity to norepinephrine, as well as basal and forskolin- or isoprenaline-stimulated adenylyl cyclase activities were not altered by stress. The effect of isoprenaline on adenylyl cyclase stimulation was partially blocked by ICI118,551 in atrial membranes of stressed rats. These findings indicate that foot-shock stress equally affects inotropism and chronotropism and that ß2-adrenoceptor upregulation contributes to the enhanced inotropic response to isoprenaline.