Cover illustration

Cover image: Cover photograph: The white matter of the central nervous system is often considered a simple conduit through which axonal bundles pass like wires in a cable, connecting the synaptic mass of gray matter. The light micrograph on the cover illustrates a newly discovered network of neuronal cell bodies and neuropil in the dorsal column white matter of the rat spinal cord. This midline sagittal section shows cell bodies and long dendrites of the neurons labeled by fluorescence immunocytochemistry for neurokinin-1 receptor, the target of the peptide substance P. The neurons extend from lamina X, seen at the bottom of the picture as a mass of brightly labeled neuronal processes, to the dorsal surface of the spinal cord. These planar neurons, described by Abbadie et al. on pages 260 – 265 in this issue, receive a rich synaptic input, are under tonic γ-aminobutyric acid-ergic control, and are found in several species.