Exogenous GM1 ganglioside and thyrotropin-releasing hormone do not affect survival rate of spinal motorneurons and number of ventral root myelinated fibers following early postnatal sciatic nerve transection

Abstract

Treatment with gangliosides or thyrotropin-releasing hormone has been shown to stimulate structural and functional recovery that follows mechanical or chemical lesions in the nervous system. We studied the possible effects of the ganglioside GM1 and thyrotropin-releasing hormone on the survival rate of spinal motorneurons after sciatic nerve transection at the age of 1 week in the rat. GM1 (30 mg/kg body weight, i.p.) was administered 24 and 1 h before and once daily for 2 weeks after transection. TRH (2 mg/kg body weight, i.p.) was administered 1 h before, at 2, 16, and 24 h, and thereafter once daily for 7 days after transection. Nine weeks postlesion, the number of motorneuron profiles labeled by retrograde transport from the proximal stump of the sciatic nerve was counted and measured using a computerized image analysis system, and the number of myelinated axons in ventral roots L4 and L5 was estimated. Compared with controls, no significant effects of GM1 or hormone treatment were observed with regard to the number, diameter, and area of motorneuron profiles and the number of ventral root myelinated axons ipsilateral to sciatic nerve injury. The results may indicate principal differences between various lesions and/or metabolic reactions following a lesion of developing and adult neurons. The present lesion model with an intense axon reaction and extensive nerve cell death does not seem to respond to administration of exogenous GM1 or thyrotropin-releasing hormone.