Studies of postmortem electrical excitability changes of skeletal muscle in adult male rats

Abstract EN

The estimation of prolonged postmortem intervals is of great importance in forensic medicine.

In this experimental study the varieties of excitability of gastrocnemius muscle via sciatic nerve as per different death models (blunt head trauma and drowning) at room temperature and after cooling was investigated on adult male rats.

The sciatic nerve was stimulated with micro-electrode connected to the electronic stimulator (SEN-3201).

Set the stimulator frequency at 25 sec, the duration to 2 msec and the strength of 5 volts at the moment of death (control).

The similar measurement procedure was performed every two hours after deaths up to 12 hours and then at 24 hours intervals until the muscle stopped to contract in response to electrical stimulation. The study revealed that the force of contraction of skeletal muscle after head traumatic death and after drowning death at room temperature and after cooling resulted in curves with a rising portion and a descending slope.

After head traumatic death at room temperature and after cooling, the force of contraction started to increase at 4 hours PM, reached the maximum at 6 hours and at 8 hours respectively.

Then followed by gradual decrease with increasing PMI untill unelicitable at 72 hour and at 120 hours PM successively.

On the other hand the rate of contraction maximally decreased at 48 hours and at 96 hours respectively untill unelicitable at 72 hours and at 120 hours PM at room temperature and after cooling respectively.

The force of contraction after drowning start to increase earlier at 2 hours PM at room temperature and after cooling, then reached maximum at 6 hours and at 8 hours PM.

respectively.

Then followed by gradual decrease with increasing PMI untill unelicitable at 48 hours and 120 hours PM respectively.

The rate of contraction decrease at 24 hours and at 96 hours PM successively untill unelicitable at 48 hours and at 120 hours respectively Cooling delayed the PM decay in muscular response when subjected to electrical stimulation.

Analysis of the results shows a correlation between the rate of decay of muscular response with the PMI and that this decay depend, on the reason of death. These findings may be used for determination time passed since death and evaluate the effect of different modes of death at different environments.