Effect of leflunomide on sciatic nerve of adult albino rats: a histological and immunohistochemical study

Leflunomide is a commonly used disease-modifying antirheumatic drug. Potential clinical neurotoxic symptoms in patients treated with leflunomide in daily practice have been reported recently. It is unclear whether leflunomide is directly related to the occurrence of such nerve toxicity or whether other factors may be involved. This study was carried out to demonstrate the effect of leflunomide on sciatic nerve experimentally. For this purpose, 17 adult albino rats were used and were divided into three groups: a control group [five rats], the second group [seven rats], which received 2 mg/kg body weight of leflunomide orally once daily for 8 weeks, and the third group [five rats], which received 2 mg/kg body weight of leflunomide orally once daily for 8 weeks and left for 4 weeks withdrawal. Sciatic nerve specimens were processed for histological study by light microscopy, electron microscopy, and immunohistochemistry. The light microscopy data were morphometrically analyzed in the sciatic nerves of the groups. We observed splitting of myelin lamellae, presence of marked intramyelinic edematous clefts between the split myelin lamellae, infolded myelin loops, and myelin degeneration. Changes in the axons included formation of myelin rings and figures in some of the larger axons, degeneration, compression, irregularity, and shrinkage. Therefore, it is recommended that patients under leflunomide treatment should be regularly examined for neurophysiological effects of leflunomide on peripheral nerves

Histological characteristics of botulinum neurotoxin-A on rat skeletal muscles

Botulinum neurotoxins-A [BT-A] are bacterial enzymes that block neurotransmitter release. BT-A is widely used to treat spasticity and dystonias, and also in pharmacocosmetic and in the management of various types of pain. It is therefore important to clarify the histological characteristics involved in muscular tissue postinjection and to reconcile its injection for cosmoses under scope. Fifteen adult albino rats were used in this study and divided into three groups [five rats each]. Group I served as negative control; groups II and III were injected into the right gastrocnemius muscle with BT-A in addition to saline into the left side to serve as positive control. Muscle harvest was examined by LM, EM, and morphometry at 28th day for group II with two rats of group I and at 56th day for group III with three rats of group I. Histological examination revealed neurogenic atrophy, target fiber change, hypertrophied fibers, and dilated aggregates of the sarcotubular system. Neurogenic muscle atrophy following a single BT-A injection should be taken into consideration when repeated BT-A injections into the same muscle are needed