Milled Stress Reduces Morphine-Induced Locomotion in F2 NMRI Mice

Document Type: Research article

Authors

1 Neuroscience Research Center, Baqyiatallah (A.S.) University of Medical Sciences, Tehran, Iran.

2 Department of Pharmacology, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran.

3 Department of Psychology, School of Medicine, Baqyiatallah (A.S.) University of Medical Sciences, Tehran, Iran.

4 Molecular Biology Research Center, Baqyiatallah (A.S.) University of Medical Sciences, Tehran, Iran.

Abstract

In the present study, the effects of pregnant NMRI mice restraint stress on the responsibility of their children to the behavioral properties of morphine, sulpiride and dextromethorphan were investigated in the F2 generation.
Twenty four pregnant NMRI female mice (W: 25 g) were divided into the experimental and control groups (n = 12/group). Animals in the experimental group were kept in the restraint cylinder (ID = 6 cm, L = 20 cm) for 60 min/day for 15 consecutive days, while the control group did not receive stress. On the 8th day, blood samples were taken from the retro-orbital of both groups for corticosterone measurement (ELYSA method). After the F2 weight gained 20-25 g, their tendency for right-handedness or Left-handedness and response to the new environment was determined by T-maze and open field method, respectively. In addition, the effects of morphine, sulpiride and dextromethorphan on the animals’ motor activity were studied.
Results showed that plasma corticosterone level in the experimental group was elevated significantly with respect to the controls. In the off-springs, left-handedness was more frequent in both the male and female animals whose mothers experienced restrained stress. In the open field paradigm, however, the females of experimental group showed more activity compared to the others. While the females of the control group showed more response to morphine (50 mg/Kg), interestingly, both male and female animals in the experimental group showed hypo activity to morphine (0.5, 5, and 50 mg/Kg). Similarly, sulpiride (25 and 50 mg/Kg) reduced the animals’ activity in both groups, while dextromethorphan did not cause any difference. In conclusion, it can be summarized that stress during the gestation period may change the response to the morphine-induced motor activity, in a sex-dependent manner.

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