Abstract

Rosenblueth and Luco demonstrated in 1939 that, during prolonged stimulation of a motor nerve, neuromuscular fatigue is followed by a rise of tension that has been called the Rosenblueth Phenomenon. The purpose of this work was to investigate the Rosenblueth Phenomenon in a cat neuromuscular preparation in which the nerves were severed at different levels and stimulated at 60 Hz for several hours. It was demonstrated that in the longer nerve preparation the Rosenblueth Phenomenon starts earlier and its maximal tension is higher. Acetylcholine sensitivity was studied in the superior cervical ganglion preparation and no change was observed when tested before stimulation, during fatigue, and during the Rosenblueth Phenomenon. It is concluded that the onset and amplitude of the Rosenblueth Phenomenon depend on the length of the peripheral nerve stump: the longer the stump, the earlier and higher the response. It is suggested that the Rosenblueth Phenomenon is produced by an increase in the transmitter release which would be due to axonal progression of molecules along the nerve.