The Effects of Glycerol Detubulation, of Manganese Ions, of Dantrolene and of Nitrate Ions on the Responses of Isolated Chronically Denervated Soleus Muscles of the Mouse to Acetylcholine

Abstract

In the isolated chronically denervated soleus muscle of the mouse acetylcholine produced a biphasic contraction. In muscles detubulated by glycerol treatment, the first phase of the acetylcholine contraction was almost abolished, but the second was only slightly reduced or was unaffected. Manganese ions (10 mM) reduced the first phase of the acetylcholine response, but enhanced the second. Dantrolene sodium (5.94 times 10−5 M) reduced the first phase of the acetylcholine response, but not the second. Nitrate ions (118 mM) augmented the first phase but not the second. It was concluded that the first phase requires the excitation‐contraction‐coupling sequence: membrane depolarization‐T‐tubules‐Ca2+ release from sarcoplasmic reticulum. In contrast, the second phase appears to occur independently of these processes.