Fig. 5. Dose–response relation of isoflurane on phorbol-12,13-dibutyrate (PDBu)–induced force. Mean ± SD (n = 3). Force after administration of isoflurane is expressed as percent of control force (steady state PDBu-induced force before administration of isoflurane). Peak contraction = isoflurane-increased force; late relaxation = force at 60 min after administration of isoflurane. *P < 0.05 compared with that of time control at 0% isoflurane. Isoflurane dose-dependently increased (A ) and then decreased (B ) the PDBu-induced force. However, there was no significant difference between 3% and 5% isoflurane.