The spinal neurons of the @entity1238 embryo that participate in the swimming motor pattern possess two kinetically distinct sets of @entity972 currents: the fast IKf and @entity1372 -dependent IKNa, which together constitute approximately 80% of the outward current; and the slow IKs, which constitutes the remainder. To study their respective roles in cell excitability and the swimming pattern, we have characterized their pharmacological properties. @entity6153 selectively blocked the fast @entity972 currents (IC50, approximately 10 microM). The block was voltage-dependent, with partial unblocking occurring at positive voltages. alpha-Dendrotoxin and @entity70148 selectively blocked the slow @entity972 current. @entity6153 and the dendrotoxins had different effects on membrane excitability: @entity6153 caused spike broadening but had little effect on repetitive firing, whereas both dendrotoxins markedly @entity101 without affecting spike width. By applying these agents to the whole embryo, we tested the role of the fast and slow currents in motor pattern generation. @entity6153 had little effect on fictive swimming, suggesting that the fast K+ currents are not critical to circuit operation. However, dendrotoxin disrupted swimming early in the episode and increased the duration of ventral root bursts. The slow K+ current, which is a minor component of the total outward current, thus appears to play an important role in motor pattern generation.

The pharmacology and roles of two K+ channels in motor pattern generation in the XXXX embryo.

@entity1238 :: ('8355', 'Species') :: ['Xenopus'] @entity101 :: ('MESH:D006973', 'Disease') :: ['increased repetitive firing'] @entity1372 :: ('MESH:D012964', 'Chemical') :: ['sodium'] @entity70148 :: ('MESH:C108582', 'Chemical') :: ['dendrotoxin-I'] @entity972 :: ('MESH:D011188', 'Chemical') :: ['potassium'] @entity6153 :: ('MESH:C034221', 'Chemical') :: ['catechol', 'Catechol']
@entity1238 :: (8355,Species) :: ['Xenopus']
