We have used a combination of retrograde axonal tracing and intracellular dye injections to determine the soma size of sympathetic vasoconstrictor neurons projecting from the superior cervical ganglion to the cutaneous vascular bed of the eartips, or to the vascular beds of the masseter muscle, of guinea-pigs. Neurons projecting to vasculature of the masseter muscle had a cross-sectional area of 956 ± 295 μm2 (mean ± SD; n = 45 cells) and were significantly larger than neurons projecting to the vasculature of the eartip skin (mean cross-sectional area ± SD, 604 ± 251 μm2; n = 39 cells). These results are consistent with physiological observations showing that muscle vasoconstrictor neurons have faster conduction velocities than cutaneous vasoconstrictor neurons. Furthermore, they suggest that muscle vasoconstrictor neurons may innervate a larger volume of vasculature compared with cutaneous vasoconstrictor neurons.
- Cutaneous vasculature
- Muscle vasculature