Release of immunoreactive somatostatin in the spinal dorsal horn of the cat.

Antibody microprobes were used to investigate the possible release of immunoreactive somatostatin (irSS) within the lumbar spinal cord of anaesthetized cats. A basal release of irSS was detected in the region of the substantia gelatinosa of the dorsal horn. By comparison with in vitro standards the concentration of SS detected in this region was estimated at 10(-7) M. This release of irSS was not significantly altered by electrical stimulation of large myelinated primary afferent fibres but was increased when unmyelinated afferents were additionally stimulated. Release of irSS was also detected at the spinal cord surface. The results support a role for somatostatin in nociceptive transmission in the spinal cord.