Galanin enhances noradrenaline-induced outward current on locus coeruleus noradrenergic neurons

Interactions between galanin and noradrenaline (NA) were studied in a locus coeruleus (LC) slice preparation using intracellular recording technique. Both galanin (10-100 nM) and NA induced an outward current. Idazoxan, an alpha2-adrenoceptor antagonist, blocked the NA- but not the galanin-induced outward current, indicating that different receptors mediate these responses. Moreover, the outward current induced by NA was enhanced and prolonged by preincubation with a low concentration of galanin (0.05-0.1 nM), which had no detectable effect on the membrane current by itself. This sensitizing effect may be of physiological importance and could be caused by galanin released from dendrites and soma of galanin/NA neurons and/or from galanin afferents. Thus, besides a direct action of galanin on locus coeruleus neurons, our results also indicate an indirect, modulating effect.