Bacterial Melanin Favors Regeneration after Motor Tract and Peripheral Nerve Damage

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 Ca2+-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.