The effect of chronic stress in pregnant mothers on the responsiveness to morphine in mice: a behavioral sensitization study

The mechanisms which are plots for individual's willing to use Morphine are not yet recognized. Carried out researches indicated that tendency to narcotics is increased during stress or after it. In this research we studied the desire change of the second generation to morphine using induced restraint stress which is a kind of behavioral sensitization.

This research was a kind of experimental interferer. At first mice were crossed after insuring about their pregnancy, Sub stress was put on them using special instruments. Some of the embryos head was cut to be studied histologically. After maturing their embryos in order to clarify their left and right handedness to be studied using T-Maze and they were compared with the control group. In order to find the effectiveness of the administrated acute morphine, five groups of stressed and non-stressed were chosen Both groups were divided into five: a control (without being injected), saline, Morphine 1 mg/kg, morphine 10 mg/kg and morphine 50 mg/kg. They were studied. Movement measuring done after being injected by open filled. Mentioned groups in the previous experiment, In order to determine their previous induced sensitization, were reexamined 48 hours after being injected 1 mg/kg morphine.

Findings showed that the tissue thickness on the frontal cortex in stressed group was less than the control group (p<0.01) And also the number of stressed right handedness in males was less, but the number of left handedness in female ones was higher. Injection low dose morphine in experimental group had no effect, but in high dose caused induced motion activations. But this motion activity was much less than the control group. The low dose morphine injection (1 mg/Kg) in stressed groups caused induced motion activities which this action in dose 50mg/kg was significant statistically (** P<0/01).

Results showed that inducing a psychological relatively slight stress (a short-term restrain) could cause major changes, firstly in embryos brain and secondly in right handedness and left handedness and thirdly a response to morphine.