Bacterial Melanin Favors Regeneration after Motor Tract and Peripheral Nerve Damage

T R Petrosyan

doi:10.11131/2013/101014

Abstract

Experiments were performed on 48 albino rats. All experimental animals were initially trained to a balancing instrumental conditioned reflex (ICR). Unilateral bulbar pyramidotomy performed in 24 rats caused contralateral hemiparesis. On the next day following the operation 12 rats (first group) were injected intramuscularly with bacterial melanin (BM) solution. Recovery periods of ICR and paralyzed hindlimb movements were registered for melanin injected rats ( n = 12) and for operated rats, not treated with melanin ( n = 12, second group). In rats injected with bacterial melanin the posttraumatic recovery is shorter than in animals not treated with melanin. Morphohistochemical examination was carried out to confirm the results of behavioral and electrophysiological experiments. Medulla slices were prepared to trace the regeneration of nerve fibers. Examination of transection area revealed that bacterial melanin increases vascularization, dilates the capillaries in nervous tissue and stimulates the process of sprouting. Ischiadic nerve transection was performed in third and fourth groups of rats (12 rats in each group). Third group animals were injected with BM on the next day of surgery. ICR was used to assess the recovery of movements after nerve damage. Method for Ca 2+ -dependent acidic phosphatase activity measurement was used to examine sections of nerve fibers and to trace the recovery of the nerve and limb movements after its injury. Acceleration of the instrumental conditioned reflex recovery and data from morphohistochemical study showed that bacterial melanin has neuroprotective action and facilitates recovery of limb movements after peripheral nerve or motor tract lesions.

Highlights

In the experiments on laboratory animals with brain surgical trauma it was revealed that bacterial melanin (BM) facilitated the recovery of instrumental conditioned reflexes after unilateral ablation of sensorimotor cortex that had caused paresis of limbs
Balancing movements of paralyzed hindlimb recovered in 15,5-17 days in transected rats without treatment and in melanin injected animals after the transection hindlimb movements recovered in 2-4 days
Morphohistochemical data of the present study indicate that the influence of bacterial melanin induces regenerative efforts in damaged peripheral nerve

Summary

Introduction

In the experiments on laboratory animals (white rats) with brain surgical trauma it was revealed that BM facilitated the recovery of instrumental conditioned reflexes after unilateral ablation of sensorimotor cortex that had caused paresis of limbs. The investigations of the past two decades have radically changed specialists’ notion on inability of neurons of the central nervous system (CNS) to regenerate [2]. Key researchers in the field of neurobiology in their literary reviews consider in detail mechanisms of axon regeneration in mammalians’ CNS [3], regeneration in the spinal cord [4], formation of glial cicatrix [5], neuroglia activation in the damaged brain [6], strategy of axon regeneration maintenance or assistance [6], regeneration of peripheral nerve subjected to damage [7].

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