The innervation of the adrenal gland. I. The source of pre- and postganglionic nerve fibres to the rat adrenal gland.

The sympathetic innervation of the rat adrenal medulla was studied using the fluorescent tracer Fast Blue. Labelled preganglionic cell bodies were located in the intermediolateral horn of the spinal cord at segments T1 and L1; the greatest number was found in T9. The ILp nucleus contained 95%, the ILf nucleus 4%, and the IC nucleus 1% of the total number of labelled preganglionic cells. Labelled postganglionic cell bodies were found in the sympathetic ganglia at levels T4 and T12; the maximum number were located in ganglia at T9 and T10. In addition, labelled cells were found in the suprarenal ganglion. No labelled cells were found in the ganglia of the coeliac plexus. The number of labelled preganglionic cells in the spinal cord accounted for 88.6%, the labelled cells in the sympathetic chain for 8.7% and those in the suprarenal ganglia for 2.7% of the total number of labelled cells found. The detailed distribution within the gland of postganglionic axons has yet to be determined, but it is thought that some are destined for the adrenal cortex.