Differential control of spontaneous and evoked GABA release by presynaptic L-type Ca2+ channels in the rat medial preoptic nucleus
(English)Manuscript (preprint) (Other academic)
To clarify the role of presynaptic L-type Ca2+ channels in GABA-mediated transmission in the medial preoptic nucleus (MPN), spontaneous as well as impulse-evoked inhibitory postsynaptic currents (sIPSCs and eIPSCs, respectively) were recorded from MPN neurons in a slice preparation from rat brain. The effects of different stimulus protocols and pharmacological tools to detect contributions of L-type Ca2+ channels and of Ca2+-activated K+ (KCa) channels were analysed. Block of L-type channels did not affect the sIPSCs properties (frequency, amplitude, decay time course) in the absence of external stimulation, but unexpectedly potentiated the eIPSCs evoked at low stimulus frequency (0.1 – 2.0 Hz). This effect was similar to and overlapping with the effect of KCa-channel blockers. High-frequency stimulation (50 Hz for 10 s) induced a substantial post-tetanic potentiation (PTP) of the eIPSC amplitude as well as of the sIPSC frequency. Block of L-type channels still potentiated the eIPSC during PTP, but in contrast reduced the sIPSC frequency during PTP. It was concluded that L-type channels provide a means for differential control of spontaneous and impulse-evoked GABA release and that this differential control is prominent during short-term synaptic plasticity. Functional coupling of the presynaptic L-type channels to KCa channels explains the observed effects on eIPSCs.
L-type Ca2+ channel, GABA release, synaptic plasticity, post-tetanic potentiation, medial preoptic nucleus
Research subject Physiology
IdentifiersURN: urn:nbn:se:umu:diva-25870OAI: oai:DiVA.org:umu-25870DiVA: diva2:234471