Resumo

RIASCOS BERNAL, DARÍO FERNANDO et al. IN VITRO EFFECT OF LITHIUM ON THE EXCITABILITY OF A RAT PHRENIC NERVE-DIAPHRAGM MODEL AND ITS RELATION WITH TREMOR. rev.fac.med [online]. 2007, vol.15, n.1, pp.15-25. ISSN 0121-5256.

One of the most common adverse effects detected with the use of lithium in clinical practice is tremor. Currently the explanation for this phenomenon is incomplete; therefore, its treatment is difficult. This study evaluated the lithium's effect on neuromuscular junction excitability using an in vitro preparation. In order to investigate a peripheral mechanism that could explain lithium induced tremor. The in vitro rat phrenic nerve-diaphragm preparation was exposed to increasing concentrations of Lithium (0,25 - 8 mmol/l). The preparation excitability was assessed under direct and indirect stimulation by measuring both the minimal stimulating frequency necessary to achieve a completely fused tetanus and the minimal stimulating voltage necessary to achieve a regular contractile response. We also looked for spontaneous contractile activity. Finally, nonparametric tests were used to detect differences between control and lithium groups. An increase on the minimal frequency necessary to achieve a completely fused tetanus compared with control was detected under direct stimulation (p=0,000) and under indirect stimulation (p=0,014). We did not detect a significant change on the minimal voltage necessary to achieve a regular contractile response nor a spontaneous activity in the preparation. In our experimental model Lithium does not increase the excitability of the neuromuscular phrenic nerve-diaphragm preparation; therefore, it does not predispose to tremor development. In view of our finding, our study suggests that lithium tremor is not caused by a peripheral mechanism of action of the drug.

Palavras-chave : lithium; adverse effects; tremor; neuromuscular junction; skeletal muscle; nerve muscle preparation.

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