| First Author | Deardorff AS | Year | 2013 |
| Journal | J Physiol | Volume | 591 |
| Issue | 4 | Pages | 875-97 |
| PubMed ID | 23129791 | Mgi Jnum | J:205979 |
| Mgi Id | MGI:5547491 | Doi | 10.1113/jphysiol.2012.240879 |
| Citation | Deardorff AS, et al. (2013) Expression of postsynaptic Ca2+-activated K+ (SK) channels at C-bouton synapses in mammalian lumbar -motoneurons. J Physiol 591(Pt 4):875-97 |
| abstractText | Small-conductance calcium-activated potassium (SK) channels mediate medium after-hyperpolarization (AHP) conductances in neurons throughout the central nervous system. However, the expression profile and subcellular localization of different SK channel isoforms in lumbar spinal alpha-motoneurons (alpha-MNs) is unknown. Using immunohistochemical labelling of rat, mouse and cat spinal cord, we reveal a differential and overlapping expression of SK2 and SK3 isoforms across specific types of alpha-MNs. In rodents, SK2 is expressed in all alpha-MNs, whereas SK3 is expressed preferentially in small-diameter alpha-MNs; in cats, SK3 is expressed in all alpha-MNs. Function-specific expression of SK3 was explored using post hoc immunostaining of electrophysiologically characterized rat alpha-MNs in vivo. These studies revealed strong relationships between SK3 expression and medium AHP properties. Motoneurons with SK3-immunoreactivity exhibit significantly longer AHP half-decay times (24.67 vs. 11.02 ms) and greater AHP amplitudes (3.27 vs. 1.56 mV) than MNs lacking SK3-immunoreactivity. We conclude that the differential expression of SK isoforms in rat and mouse spinal cord may contribute to the range of medium AHP durations across specific MN functional types and may be a molecular factor distinguishing between slow- and fast-type alpha-MNs in rodents. Furthermore, our results show that SK2- and SK3-immunoreactivity is enriched in distinct postsynaptic domains that contain Kv2.1 channel clusters associated with cholinergic C-boutons on the soma and proximal dendrites of alpha-MNs. We suggest that this remarkably specific subcellular membrane localization of SK channels is likely to represent the basis for a cholinergic mechanism for effective regulation of channel function and cell excitability. |
