MITOCHONDRIAL DISTRIBUTION WITHIN THE TERMINAL NEURITE OF THE PACINIAN CORPUSCLE

Electron-microscopic analyses of the mitochondrial organization within the neurite innervating the Pacinian corpuscle (PC) were performed to test the hypothesis that the sites of mechanotransduction are the fil opodia projecting from the neurite's surface. Since high concentration s of mitochondria imply the need for metabolic energy, and since trans duction mechanisms are heavily dependent on such energy, it was reason ed that the greatest concentration of mitochondria should occur near t he filopodia if they are involved in mechanotransduction. The analysis showed that the mitochondria lie close to the terminal neurite's memb rane, on average within 0.4 mu m, and thus are ideally located for sup plying energy for membrane mechanisms. Although they can be found in a ring-like array, as seen in cross-sections of the terminal neurite, t heir greatest concentration occurs where the filopodia project from th e terminal neurite. A linear algebraic analysis of the data set confir med a high probability of the joint occurrence of a filopodial base an d an increased frequency (number) of mitochondria. Thus the results pr ovide further circumstantial support for the hypothesis that transduct ion within the PC mechanoreceptors takes place at or near the filopodi a.