[Effects of kindling epilepsy and low frequency of epileptic focus on spontaneous neuropathic pain in rats].

OBJECTIVE

To investigate the effects of epileptogenesis and low frequency stimulation at epileptic focus on spontaneous neuropathic pain in rats.

METHODS

Bipolar stimulating electrodes were implanted in the amygdala and current with constant intensity was applied to evoke kindling-induced seizures. In partial and generalized stages of seizure acquisition, neuroma model of spontaneous neuropathic pain was prepared by completely transection of the left sciatic and saphenous nerves of rats. Autotomy behavior was scored daily until d 63 postoperatively. Rats were divided into 5 groups: Control (n=7), rats with partial seizures (1-3 stages, n=5), rats with generalized seizures (4-5 stages, n=7), rats with partial seizures and low frequency stimulation(n=4), rats with generalized seizures and low frequency stimulation(n=4). Low frequency stimulation was applied to the amygdala, the epileptic focus for 21 d from the d 2 after nerve transection.

RESULTS

Autotomy level in rats with partial seizures was significantly lower than that in controls. The autotomy scores during postoperative d 40 ≊63 were significantly lower than those of controls, the area under the progression curve of autotomy behavior was decreased from 308.2 ±51.57 to 45.80 ±24.64, the onset day of autotomy was postponed by 32 d and none of the animals with partial seizures showed high autotomy, while 71.4 % of controls showed that on d 63 postoperatively. Rats with generalized seizures showed autotomy similar to controls, except that the onset day was postponed by 16 d. Autotomy behavior in rats receiving low frequency stimulation of the amygdala was not different from that in controls.

CONCLUSIONS

Focal seizures can lower sensitivity to spontaneous neuropathic pain in rats, while low frequency stimulation applied to the focus can abolish such effect.