[Influence of lithium on the neuromuscular blockade produced by atracurium and cisatracurium: study on rat phrenic nerve-diaphragm preparations.].
OBJECTIVE
Lithium is widely used for the treatment of bipolar disorders and can interact with neuromuscular blockers. There is a controversy about the mechanisms by which it affects neuromuscular transmission and its interaction with neuromuscular blockers. The objective of this study was to evaluate, on the rat diaphragm, the effects of lithium on the muscular response and indirect stimulation, and the possible interaction with neuromuscular blockers.


METHODS
Rats weighing between 250 and 300 g were sacrificed under urethane anesthesia. The phrenic nerve-diaphragm preparation was assembled according to the Bulbring technique. The diaphragm was kept under tension, connected to an isometric transducer, and submitted to indirect stimulation with a frequency of 0.1 Hz. The contractions of the diaphragm were registered on a physiograph. The analysis of the amplitude of the muscular responses evaluated: the effects of the isolated drugs: lithium (1.5 mg.mL-1); atracurium (20 microg.mL-1), and cisatracurium (3 microg.mL-1); the lithium-neuromuscular blockers association; and the effects of lithium on the neuromuscular blockade produced by atracurium (35 microg.mL-1) and cisatracurium (5 microg.mL-1). The effects were evaluated before and 45 minutes after the addition of the drugs. The effects of lithium on membrane potentials (MP) and miniature end-plate potentials (MEPP) were also evaluated.


RESULTS
Lithium by itself did not change the amplitude of the muscular responses, but it decreased significantly the neuromuscular blockade produced by atracurium and cisatracurium. It did not change MP and caused an initial increase in MEPP.


CONCLUSIONS
Lithium by itself did not compromise neuromuscular transmission and increased the resistance to the effects of atracurium and cisatracurium. It did not show any action on the muscle fiber, and the changes in miniature end-plate potentials indicated pre-synaptic action.
Fernandes
Samanta Cristina Antoniassi
SC
Departamento de Farmacologia, FCM, UNICAMP.
Braga
Angélica de Fátima de Assunção
Ade F
Braga
Franklin Sarmento da Silva
FS
Loyola
Yolanda Christina S
YC
Souza
Silmara Rodrigues de
SR
Barcelos
Caroline Coutinho de
CC