Nitric oxide release from substantia gelatinosa of the rat spinal cord in vitro.

To study characteristics of nitric oxide (NO) release from substantia gelatinosa (SG) in the spinal cord, we measured NO concentration in transverse spinal cord slices of rats using electrochemical NO probes. Electrical stimulation of the dorsomedial white matter adjacent to SG elicited transient current changes in NO probes placed on SG and the amplitude corresponded to a NO concentration of 200-300 pM. This NO release was not affected by the application of antagonists of glutamate or substance P receptors. The NO release in the rats, which were neonatally treated with capsaicin for denervating C-fibers, was significantly smaller than that in control rats. These data suggest that NO is mainly derived from the unmyelinated afferent nerves in the SG of the spinal cord.