Electrophysiological properties of substantia gelatinosa neurones in a novel adult spinal slice preparation.

A novel longitudinal spinal cord slice prepared from adult rats aged 3-6 weeks is described. This preparation differs from conventional slices in that it retains multiple dorsal roots, each more than 10 mm in length, and presents a sagittal section through the laminae of the dorsal and ventral horns. The substantia gelatinosa can be visually distinguished from the other laminae of the dorsal horn, thus making the preparation particularly suited for the study of neurones located in this region. Extracellular recordings were made from 142 substantia gelatinosa cells, most of which responded to electrical stimulation of a dorsal root. Using measurements of latency it was possible to estimate conduction velocities for afferent input fibres. The effects of iontophoretically applied excitatory amino acids and of tachykinin peptides on spontaneous and afferent-evoked firing are briefly described. The preparation has applications in the investigation of mechanisms of primary afferent transmission within the dorsal horn and of transmission of afferent input between successive spinal segments.