Neurobiology 8. (2000)

3. szám - Preliminary notes

348 Seventh Annual Meeting of HNS anterograde tracer injections into the CN labelled terminals with round vesicles, making multiple asymmetrical synapses on the soma and principal dendrites oriented towards the side of injection were observed in the ipsilateral LSO and in the MSO of both sides. In the NLL the labelled terminals were in contact with dendrites without any preference to their direction. In the CNIC the labelled fiber bundles were making synaptic contact with both soma and proximal dendrites. Injections into the MSO and LSO revealed fine labelled fibers establishing asymmetrical synaptic contact with the peripheral dendrites in the NLL and CNIC. In combined experiments the labelled ascending terminals were in synaptic engagement with both the labelled relay and unlabelled interneurons with similar distribution. The descending fibers from the CNIC had preference for the soma and proximal dendrites of neurons in the lower auditory relay nuclei. MODULATION OF ION CHANNELS BY MOLLUSCAN NEUROPEPTIDES Kiss, T. Balaton Limnological Research Institute of the Hungarian Academy of Sciences, Tihany, Hungary Cell membrane ion channels are integral parts of signaling pathways in almost all cells. A number of extracellular ligands including neuropeptides, membrane potential, phosphorylation, ions themselves and second messengers are well established regulators of the channel activity. A wide variety of kinetically and pharmacologically distinct К channels, including several voltage-dependent and -independent ion channels can be modulated by neuropeptides. Here, we summarize some of the experimental data, with emphasis on the MIP (Mytilus inhibitory peptide), concerning the types of К currents, the role of G proteins involved in coupling the neuropeptide receptors to the ion channels and the mechanism whereby the G-proteins exert their control. К channel types controlled by neuropeptides carry inwardly rectifying (Ik(ir)), Ca-dependent (1к(Са>) and serotonin sensitive (Ikcs)) K- currents. Recently, two additional К-conductances were described following application of the neuropeptides. One is similar to Ik<s> but voltage dependent (Kits et al. 1997), and the second is a Na-activated К-current (Kiss et al. 2000). Activation of К channels by neuropeptides involves either the direct interaction of G proteins with the channels, or the intervention of enzyme systems and second messengers. This work was supported by a Hungarian Scientific Research Fund (OTKA) grant, No.29559. References Kits, K. S. (1997) J. Gen. Physiol. 110, 611-628. Kiss, T. (2000) Acta Biol. Hung. 51 (in press)

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