Lack of effect of baclofen on substance P and somatostatin release from the spinal cord in vitro.

High concentrations of K+ increase the release of substance P (SP) and somatostatin (SRIF) from superfused slices of rat spinal cord. This increase is Ca-dependent. Baclofen (100-500 microM) does not significantly alter the K+-evoked release of SP or SRIF. Stereoisomers of baclofen and GABA, similarly, are without effect. The spinal analgesic action of baclofen does not appear to be due to alterations in the release of SP or SRIF.