Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale
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Comparative Study
Painful and non-painful pressure sensations from human skeletal muscle.
Painful and non-painful pressure sensations from muscle are generally accepted to exist but the peripheral neural correlate has not been clarified. The aim of the present human study was to assess the non-painful and painful pressure sensitivity with (1) anaesthetised skin, and (2) anaesthetised skin combined with a block of large diameter muscle afferents. The skin was anaesthetised by a topically applied anaesthetic cream and later lidocaine was administrated subcutaneously. ⋯ In a third experiment, the tactile sensations elicited by electrical stimulation of the tibialis anterior muscle and skin at the lower leg were significantly decreased after 20 min of ischaemia, validating the blocking effects of group I and II nerve fibres. The present data show a marginal contribution of cutaneous afferents to the pressure pain sensation that, however, is relatively more dependent on contributions from deep tissue group III and IV afferents. Moreover, a pressure sensation can be elicited from deep tissue probably mediated by group III and IV afferents involving low-threshold mechanoreceptors.
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Experimental model based on the C5 ventral root avulsion was used to evaluate the efficacy of brain-derived neurotrophic factor (BDNF) and Cerebrolysin treatment on motor neuron maintenance and survival resulted in the functional reinnervation of the nerve stump. In contrast to vehicle, BDNF treatment reduced the loss and atrophy of motor neurons and enhanced the regrowth axon sprouts into the distal stump of musculocutaneous nerve. However, the axon diameter of the myelinated fibers was smaller than those of control rats. ⋯ The mean score of grooming test suggested better results of the functional motor reinnervation than after BDNF administration. The majority of rescued motor neurons regenerating their axons through nerve graft in both BDNF- and Cerebrolysin-treated rats expressed choline acetyltransferase immunostaining. The results demonstrate that BDNF has more modest effects in preventing the death of motor neurons and functional recovery of injured motor nerve after root avulsion than Cerebrolysin.