Galanin-5-hydroxytryptamine interactions : Electrophysiological, immunohistochemical and in situ hybridization studies on rat dorsal raphe neurons with a note on galanin R1 and R2 receptors

摘要: Abstract Galaninergic mechanisms related to 5-hydroxytryptamine neurons in the dorsal raphe nucleus of rat were analysed using electrophysiology, immunohistochemistry and situ hybridization. Galanin caused a dose-dependent hyperpolarization accompanied by decrease membrane resistance most 5-hydroxytryptamine-sensitive neurons. The galanin-induced outward current reversed at about −105 mV shifted more positive potential with increasing extracellular potassium concentrations. 5-hydroxytryptamine-induced was enhanced prolonged preincubation low concentration galanin (1–10 nM). immunohistochemical analysis showed (i) generally levels cell bodies, (ii) moderate numbers galanin-positive nerve endings around (iii) presence galanin-like immunoreactivity 5-hydroxytryptamine-positive dendrites (iv) galanin-positive, 5-hydroxytryptamine-negative boutons making synaptic contact dendrites. hybridization results suggest that receptor present galanin/5-hydroxytryptamine is not recently cloned galanin-R1 type. Taken together these indicate exerts an inhibitory effect via increase K+ conductance acting on postsynaptic receptor. In addition, low, possibly physiological concentrations enhances soma level. We propose primarily released from adjacent galaninboutons lacking also may thus be involved manifold functions hitherto ascribed ascending neurons, for example mood regulation.