Response of succinate dehydrogenase activity in fibres of rabbit tibialis anterior muscle to chronic nerve stimulation.

Succinate dehydrogenase activity (SDH) was estimated kinetically in individual muscle fibres from the rabbit tibialis anterior, in cryostat sections using computer-linked microphotometry to record initial reaction velocities. These were correlated with fibre type based on myofibrillar actomyosin ATPase staining. Analysis of type IIA and IIB fibre populations in control muscles demonstrated wide variations in SDH activity between fibres of identical myosin ATPase type, with a considerable overlap in oxidative activities of the IIA and IIB populations. Muscles chronically stimulated via the peroneal nerve, using two different frequency patterns, showed increases in SDH activity which were primarily located in the type IIB fibres. This increase was observed both in muscles stimulated continuously at 10 Hz, and when similar numbers of stimuli were applied in brief trains at higher frequency. An earlier onset and more rapid rate of increase of SDH activity was seen with 10 Hz stimulation than with higher frequency, though the levels after 14 days of either pattern of stimulation were not significantly different.