Gating and braking of short- and long-term modulatory effects by interactions between colocalized neuromodulators.
Spinal locomotor networks in the lamprey are modulated by tachykinin neuropeptides. A single 10 min application of the tachykinin substance P evokes a short-term ( approximately 1 hr) presynaptic facilitation of glutamate release and the postsynaptic potentiation of NMDA responses. The latter effect induces a long-term (>24 hr) protein synthesis-dependent increase in the frequency of network activity. Tachykinins are contained in a ventromedial spinal plexus into which the medial dendrites of network neurons project. Neurons in this plexus also contain colocalized dopamine and 5-HT. Here, dynamic plasticity evoked by modulator interactions has been examined by investigating the effects of 5-HT and dopamine on specific cellular, synaptic, and network effects of substance P. Preapplied 5-HT blocked the substance P-mediated increase in the network burst frequency and the potentiation of NMDA-evoked cellular responses that underlies its induction. 5-HT also blocked the presynaptic facilitation of glutamatergic synaptic transmission by substance P. The presynaptic, but not postsynaptic, effect of 5-HT was reduced by the protein phosphatase 2B inhibitor cypermethrin. Dopamine did not directly modulate the effects of substance P. However, it reduced the presynaptic interactive effect of 5-HT and thus gated the presynaptic potentiation of glutamatergic inputs by substance P. However, the substance P-mediated potentiation of NMDA responses was not gated by dopamine, and thus the long-term network modulation was not induced. Neuromodulator effects and their interactions can thus be modulated. By selecting components from the modulatory repertoire of substance P, these interactions evoke dynamic changes in short- and long-term synaptic and network plasticity.
Svensson
E
E
Nobel Institute for Neurophysiology, Department of Neuroscience, Karolinska Institute, S-17177, Stockholm, Sweden.
Grillner
S
S
Parker
D
D
D000818:Animals; D001683:Biological Clocks / Q000187:drug effects / Q000502:physiology; D065095:Calcineurin Inhibitors; D004298:Dopamine / Q000494:pharmacology; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism; D007798:Lampreys; D008124:Locomotion / Q000187:drug effects / Q000502:physiology; D008297:Male; D016202:N-Methylaspartate / Q000494:pharmacology; D009415:Nerve Net / Q000187:drug effects / Q000378:metabolism*; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D018377:Neurotransmitter Agents / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology; D012701:Serotonin / Q000494:pharmacology; D013116:Spinal Cord / Q000187:drug effects / Q000378:metabolism*; D013373:Substance P / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology
D065095:Calcineurin Inhibitors; D004791:Enzyme Inhibitors; D018690:Excitatory Amino Acid Agonists; D018377:Neurotransmitter Agents; D012701:Serotonin; D013373:Substance P; D018698:Glutamic Acid; D016202:N-Methylaspartate; D004298:Dopamine