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Postnatal development of GABA B receptor‐mediated modulation of voltage‐activated Ca 2+ currents in mouse brain‐stem neurons
Author(s) -
Zhang W.,
Elsen F.,
Barnbrock A.,
Richter D. W.
Publication year - 1999
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1046/j.1460-9568.1999.00655.x
Subject(s) - agonist , baclofen , medicine , endocrinology , receptor , chemistry , antagonist , neuroscience , biology
GABA B receptors modulate respiratory rhythm generation in adult mammals. However, little is currently known of their functional significance during postnatal development. In the present investigation, the effects of GABA B receptor activation on voltage‐activated Ca 2+ currents were examined in rhythmically active neurons of the pre‐Bötzinger complex (PBC). Both low‐ (LVA) and high‐voltage‐activated (HVA) Ca 2+ currents were present from the first postnatal day (P1). The density of LVA Ca 2+ currents increased during the first week, whilst the density of HVA Ca 2+ currents increased after the first week. In the second postnatal week, the HVA Ca 2+ currents were composed of L‐ (47 ± 10%) and N‐type (21 ± 8%) currents plus a ‘residual’ current, whilst there were no N‐type currents detectable in the first few days. The GABA B receptor agonist baclofen (30 μ m ) increased LVA Ca 2+ currents (30 ± 11%) at P1–P3, but it decreased the currents (35 ± 11%) at P7–P15 without changing its time course. At all ages, baclofen (30 μ m ) decreased the HVA Ca 2+ currents by ≈ 54%. Threshold of baclofen effects on both LVA and HVA Ca 2+ currents was 5 μ m at P1–P3 and lower than 1 μ m at P7–P15. The effect of baclofen was abolished in the presence of the GABA B receptor antagonist CGP 55845A (50 n m ). We conclude that both LVA and HVA Ca 2+ currents increased postnatally. The GABA B receptor‐mediated modulation of these currents undergo marked developmental changes during the first two postnatal weeks, which may contribute essentially to modulation of respiratory rhythm generation.