Udk 619:615.211 the Influence of Lidocaine and Beta-blockers on L-name-induced Potentiation of the Isolated Rat Hemidiaphragm Contractility

L-NAME (1 10 mM, 30 min of incubation) potentiates the tension developed (Td) in the isolated rat hemidiaphragm stimulated by direct subtetanic electrical stimulation (DSES) (F = 14 Hz). The aim of our study was to investigate the possible modulatory effect of local anaesthetic (lidocaine) and beta adrenergic blockers, propranolol and atenolol, on the L-NAMEinduced potentiation of isometric contractility (IC). Lidocaine (0.1 mM, 5 min incubation) did not change Td by itself. Also, in the presence of lidocaine (0.1 mM, 5 min incubation), the stimulatory effect of L-NAME (3 mM, 30 min incubation) was preserved. In contrast, lidocaine itself (0.1 mM, 30 min incubation) produced an increase of Td up to 50%. The incubation of the muscle with both lidocaine (0.1 mM, 30 min incubation) and L-NAME (3 mM, 30 min incubation) produced an almost additive stimulatory effects, up to 90%, on Td. Propranolol itself (1 M, 5 min incubation) did not change Td. In the presence of propranolol, L-NAME maintained the stimulatory effect on Td. Propranolol (1 M, 30 min incubation) did not change Td itself, but abolished the stimulatory effect of L-NAME. Atenolol (1 M, 30 min incubation) neither significantly changed Td nor L-NAME-induced potentiation of Td.