Journal of Neuroscience, Vol 9, 3596-3605, Copyright © 1989 by Society for Neuroscience
A comparison of neuronal growth cone and cell body membrane: electrophysiological and ultrastructural properties
PB Guthrie, RE Lee and SB Kater
Program in Neuronal Growth and Development, Colorado State University, Ft. Collins 80523.
This study investigated a broad set of general electrophysiological and
ultrastructural features of growth cone and cell body membrane of
individual neurons where membrane from different regions of the same neuron
can be directly compared. Growth cones were surgically isolated from
identified adult Helisoma neurons in culture and compared with the cell
body using whole-cell patch-clamp recording techniques. All isolated growth
cones generated overshooting regenerative action potentials. Five neurons
(buccal neurons B4, B5, and B19; pedal neurons P1 and P5) were selected
that displayed distinctive action potential waveforms. In all cases, the
growth cone action potential was indistinguishable from the cell body
action potential and different from growth cones from other identified
neurons. Two of these neurons (B5 and B19) were studied further using
voltage-clamp procedures; growth cones and cell bodies again revealed major
similarities within one neuron type and differences between neuron types.
The only suggested difference between the growth cone and cell body was an
apparent reduction in the magnitude of the A-current in the growth cone.
Peak inward and outward current densities, as with other
electrophysiological features, were different between neuron types, but
were, again, similar between the growth cone and the cell body of the same
neuron. Freeze-fracture analysis of intramembraneous particles (IMPs) was
also performed on identified regions of the same neuron in culture. Both
the density and the size distribution of IMPs were the same in growth cone,
cell body, and neurite membranes. In these general electrophysiological and
ultrastructural characteristics, therefore, growth cone membranes appear to
retain the identity of the parent neuron cell body membrane.