Modulation and selection of neurotransmitter responses during synapse formation between identified leech neurons.
1. Serotonin (5-HT) modulates two different responses in the pressure sensitive neurons (P) of the leech: an inhibitory, Cl- dependent synaptic response and a depolarizing extrasynaptic response. 2. Serotonergic Retzius cells (R) in vivo and in culture elicit inhibitory Cl- dependent responses in P neurons. Moreover, at discrete sites of contact between R and P cells, the excitatory response to 5-HT is gradually lost prior to synapse formation. This phenomenon is specifically mediated by R cells. 3. The extrasynaptic response is mediated by cation channels sensitive to protein kinase C (PKC). Cation channels are present at the sites of contact but they become insensitive to PKC. Moreover, cation channels from single P cells are no longer modulated by PKC if they are inserted (by cramming the patch pipette) into the cytoplasm of a P cell in contact with an R cell. 4. Blockers of tyrosine kinases prevent the uncoupling of cation channel modulation and inhibit synapse formation between the R and the P neurons. 5. We suggest that cell contact induces an intracellular, tyrosine kinase-dependent signal as part of the mechanism of neuronal recognition leading to synapse formation.
Catarsi
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Centre for Research in Neuroscience, McGill University, Montreal, Quebec, Canada.
Drapeau
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D000818:Animals; D002478:Cells, Cultured; D018118:Chloride Channels / Q000187:drug effects / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019833:Genistein; D015640:Ion Channel Gating / Q000187:drug effects; D007529:Isoflavones / Q000494:pharmacology; D007865:Leeches / Q000502:physiology*; D008465:Mechanoreceptors / Q000187:drug effects / Q000502:physiology*; D009419:Nerve Tissue Proteins / Q000037:antagonists & inhibitors / Q000502:physiology; D009475:Neurons, Afferent / Q000145:classification / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D010636:Phenols / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000502:physiology; D012701:Serotonin / Q000494:pharmacology / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects; D013569:Synapses / Q000187:drug effects / Q000502:physiology*
D018118:Chloride Channels; D004791:Enzyme Inhibitors; D007529:Isoflavones; D009419:Nerve Tissue Proteins; D010636:Phenols; D012701:Serotonin; C062898:lavendustin A; D019833:Genistein; D011505:Protein-Tyrosine Kinases