Naloxone and vitamin E block stress-induced reduction of locomotor activity and elevation of plasma corticosterone

Abstract

Normal rats, on being repetitively stressed by being restrained in a tight container for two hours, had higher levels of plasma corticosterone compared to pre stress values. These rats also reacted to the stress by a behavioral response in which there was marked decrease in locomotor activity assessed by the open field test (pre stress: 71.3 +/- 2.6 squares crossed versus post stress: 14.3 +/- 2.5 squares crossed) by counting the number of squares entered by the rat over 5 minutes. By the 6th to 7th exposures to the repetitive stress, the rats adapted to the stress and had normal plasma corticosterone levels and locomotor activity scores comparable to the pre stress values. These responses to stress were completely blocked by the administration of 0.32 microg/100 g BW of naloxone i.p at 10 minutes prior to the stress. In rats fed with rat chow supplemented with 90 mg/kg rat chow or 150 mg/kg rat chow of vitamin E, there was significant reduction of the plasma corticosterone levels and improvement in the locomotor activity. Stress thus caused opioid mediated increase in plasma corticosterone and reduction in locomotor activity which could be blocked by naloxone. These stress responses probably also involved generation of oxygen free radicals which were scavenged by the vitamin E, thus reducing the effects of repetitive stress on locomotor activity and serum corticosterone levels.

α-Tocopherol Protects Against Oxidative Stress in the Fragile X Knockout Mouse: an Experimental Therapeutic Approach for the Fmr1 Deficiency

“…We have observed a normalization of corticosterone levels by 100 mg/kg a-tocopherol treatment. In agreement with our results, it has been published that plasma corticosterone was significantly reduced to the control values in stressed rats by 150 mg/kg a-tocopherol treatment (Ainsah et al, 1999).…”

Dietary Vitamin E Deficiency Increases Anxiety-Like Behavior in Juvenile and Adult Rats

“…Vitamin E deficiency significantly increased corticosterone concentrations under the stress of the EPM test, and tended to increase under basal conditions (two-way ANOVA, p=0.087 for the effect of diet). It has been reported that corticosterone levels under restraint stress were elevated by vitamin-E deficiency and were reduced by treatment with vitamin E. 25,26) In addition, the association between anxiety and HPA axis reactivity suggests the importance of the HPA axis in anxiety behavior on the EPM test. 13,14) The result that vitamin-E deficiency did not increase anxiety behavior in adrenalectomized rats indicates that corticosterone is important for the anxiogenic effect of vitamin-E deficiency (Terada et al, manuscript in preparation).…”

The effects of palm vitamin E on stress hormone levels and gastric lesions in stress-induced rats

“…Rats have been widely used in stress studies. There is an established model for producing gastric lesions by various methods of stress, such as restraint [1, 2], water-immersion restraint [3] and cold-restraint stress [4]. …”

“…It includes factors which disrupt gastric mucosal integrity, such as changes in gastric acid, mucus and bicarbonate secretions, inhibition of gastric mucosal prostaglandin synthesis, reduction of gastric mucosal blood flow [5, 6] as well as changes in stress hormones [1, 3, 7, 8] and gastric motility [9, 10]. …”