Electrophysiologic alterations in the excitability of the sciatic and vagus nerves during early stages of sepsis

Lúcio Ricardo Leite Diniz,1 Viviane Gomes Portella,2 Kerly Shamira da Silva Alves,2 Pâmella Cristina da Costa Araújo,2 Ricardo Luiz Cavalcanti de Albuquerque Júnior,3 Aline Alice Cavalcante de Albuquerque,2 Andrelina Noronha Coelho-de-Souza,2 José Henrique Leal-Cardoso2 1Department of Physiology, Federal University of Sergipe, São Cristóvão, Brazil; 2Department of Physiology, Superior Institute of Biomedical Sciences, State University of Ceará, Fortaleza, Brazil; 3Laboratory of Morphology and Structural Biology, Science and Technology Institute – ITP, Aracaju, Brazil Background: Nonspecific and delayed diagnosis of neurologic damage contributes to the development of neuropathies in patients with severe sepsis. The present study assessed the electrophysiologic parameters related to the excitability and conductibility of sciatic and vagus nerves during early stages of sepsis.Materials and methods: Twenty-four hours after sepsis induced by cecal ligation and puncture (CLP) model, sciatic and vagus nerves of septic (CLP group) and control (sham group) rats were removed, and selected electric stimulations were applied to measure the parameters of the first and second components of the compound action potential. The first component originated from fibers with motor and sensory functions (Types Aα and Aβ fibers) with a large conduction velocity (70–120 m/s), and the second component originated from fibers (Type Aγ) with sensorial function. To evaluate the presence of sensorial alterations, the sensitivity to non-noxious mechanical stimuli was measured by using the von Frey test. Hematoxylin and eosin staining of the nerves was performed. Results: We observed an increase of rheobase followed by a decrease in the first component amplitude and a higher paw withdrawal threshold in response to the application of von Frey filaments in sciatic nerves from the CLP group compared to the sham group. Differently, a decrease in rheobase and an increase in the first component amplitude of vagal C fibers from CLP group were registered. No significant morphologic alteration was observed. Conclusion: Our data showed that the electrophysiologic alterations in peripheral nerves vary with the fiber type and might be identified in the first 24 h of sepsis, before clinical signs of neuromuscular disorders. Keywords: sepsis, sciatic nerve, vagus nerve, neuronal excitability, neuropathy, peripheral nerves