LOCALIZATION OF PROTEIN KINASE-C-ALPHA, KINASE-C-BETA AND KINASE-C-GAMMA SUBSPECIES IN SENSORY AXON TERMINALS OF THE RAT MUSCLE-SPINDLE

The localization of protein kinase C (PKC) alpha, beta and gamma subsp ecies in sensory axon terminals of muscle spindles in the plantar lumb rical muscles of rat was investigated by light and electron microscopi c immunocytochemistry using monoclonal and polyclonal antibodies. Immu noreactivity for these subspecies was detected specifically in sensory axon terminals which wound spirally around the intrafusal muscle fibr es of the muscle spindle. Immunostaining was found to be stronger with polyclonal than with monoclonal antibodies. By electron microscopy, i mmunoreactivity for alpha, beta and gamma subspecies was almost diffus ely distributed in the cytoplasm of the axon terminal, and the overall pattern of distribution of immunoreactivity was similar for all three subspecies. In the cases of alpha and beta subspecies, some intensely immunostained regions were found in the cytoplasm, but no definite su bcellular structures corresponding to such regions could be identified . Considering that PKC plays a crucial role in the regulation of ion c hannels, it is suggested that PKC might be involved in the control of mechanoelectric transduction in sensory axon terminals.