Intrathecal galanin potentiates the spinal analgesic effect of morphine: electrophysiological and behavioural studies.

The interaction between intrathecally (i.t.) applied galanin (GAL) and morphine was examined in electrophysiological and behavioural experiments. The physiological experiments were performed on decerebrate, spinalized, unanesthetized rats where the effects of i.t. GAL and morphine on the hamstring flexor reflex were studied. In the behavioural experiments sensitivity to noxious thermal stimulation was assessed on the hot plate test in rats injected with GAL and morphine via chronically implanted i.t. catheters. GAL at 100 ng in 10 microliters, which by itself has no depressive effect, potentiated the depressive effect of morphine on the flexor reflex. In the behavioral study the same dose of GAL potentiated the antinociceptive effect of morphine on the hot plate test without having an analgesic effect by itself. It is suggested that GAL may enhance the analgesic effect of opiates in the spinal cord.