Intrathecal anaesthesia alters intracellular Ca²⁺/Mg²⁺ homeostasis in the spinal cord neurones of experimental rats

Abstract

Background and objective The effect of anaesthesia induced by intrathecal injection of 6.3% MgS0₄ or 4% lidocaine on intracellular electrolyte homeostasis in spinal cord neurones of a rat model was investigated. Methods Intracellular Ca²⁺, Mg²⁺, Na⁺ and K⁺ concentrations were determined at different times after intrathecal administration of NaCI (saline, a control group), MgS0₄ or lidocaine.

Results In both thoracic and lumbar spinal cord segments, Ca²⁺ concentrations rose significantly 30min and 2 h after 6.3% MgSO₄ injection, and after 24 h were still significantly increased compared with the values obtained from the control group which were subjected to sham ‘anaesthesia’ by saline injection (172,121 and 108ngmg⁻¹ protein vs. control 23ngmg⁻¹ protein, respectively, in the thoracic segment and 222, 229 and 176ngmg⁻¹ protein vs. control 43ngmg⁻¹ protein, respectively, in the lumbar segment). Lidocaine injection also produced a significant increase in intracellular Ca²⁺ in the thoracic and lumbar spinal cord segments (69, 64 and 53ngmg⁻¹ protein vs. control 33.4 ngmg⁻¹ protein and 26, 94 and 46ngmg⁻¹ protein vs. 23ngmg⁻¹ protein respectively). Only a modest rise in intracellular Mg²⁺ was observed after intrathecal MgS0₄ or lidocaine injection (27ngmg⁻¹ protein vs. 23ngmg⁻¹ protein). Na⁺ and K⁺ concentrations decreased 24 h after MgS0_4and 1h after lidocaine injection.

Conclusion Intrathecal anaesthesia by MgS0₄ or lidocaine alters intracellular electrolyte homeostasis in spinal cord neurones of experimental rats. A possible common mechanism of action via Ca²⁺ ion channels is discussed.