Objective To investigate the influence of clenbuterol on the expression of nerve growth factor (NGF) in denervated red and white muscles and the neurotrophism of the denervated muscles.Methods Sixty-four Wister rats, weighed 200-250 g, were divided into 8 groups(8 rats per group), including 4 experimental groups and 4 control groups. The denervated model was made in rats by dissection of sciatic nerves. Clenbuterol was given at a dose of 200 μg/kg per day in the experimental group, saline in the control group. The expression of NGF was measured with immunohistochemistry after 1, 3, 7 and 14 days of injury. The culture methods of dorsal root ganglions of the chick embryos were used to measure the neurotrophism of extracts of the muscles. Results Compared with the control groups, the NGF content of gastrocnemious(GAS) increased on the 1st day (Plt;0.05) and the NGF content of soleus(SOL) increased greatly on the 1st, 3rd and 7th dayafter injury in the experimental groups (Plt;0.01). In the experimental groups, the NGF amount of GAS reached the highest value on the 1st day after injury(Plt;0.01) and then decreased gradually. And the NGF amount of SOL had slight difference between different time. The NGF content of the SOL was higher than that of GASon the 7th day (Plt;0.05). The sensory neurotrophism of the extracts was similar between SOL and GAS.Conclusion Clenbuterol can change the expression of NGF in denervated muscles, but the change was different in SOL and GAS. The sensory neurotrophism of the denervated muscles were determined by all of the neurotrophic factors in them.
In order to explore the effects of clenbuterol on intramuscular collagen metabolism in denervated skeletal muscles, a randomized, double-masked and placebo-controlled group were studied. Seventy-one patients with complete function loss in muscularcutaneous nerve resulted from brachial plexus injury were administered clenbuterol or placebo 60 micrograms Bid for more than 3 months. Biopsies of the biceps brachia muscle were performed at the beginning and end of this study. The biopsied muscles were processed with anti-collagen I and IV immunohistochemical stains and image analysis as well. The result showed that the collagen proliferation of both type I and IV was much reducible in the clenbuterol-treated group than that of the placebo-treated group (P lt; 0.05). It was concluded that clenbuterol could inhibit partially the proliferation of intramuscular collagens in denervated skeletal muscle.