U. Kim et Da. Mccormick, FUNCTIONAL AND IONIC PROPERTIES OF A SLOW AFTERHYPERPOLARIZATION IN FERRET PERIGENICULATE NEURONS IN-VITRO, Journal of neurophysiology, 80(3), 1998, pp. 1222-1235
Intracellular recordings from spontaneously spindling GABAergic neuron
s of the ferret perigeniculate nucleus in vitro revealed a fast afterh
yperpolarization after each action potential, a medium-duration afterh
yperpolarization after each low-threshold Ca2+ spike, and a slow after
hyperpolarization after the cessation of spindle waves. The slow after
hyperpolarization was associated with an increase in membrane conducta
nce, and the reversal potential was sensitive to extracellular [K+](o)
, indicating that it is mediated at least in part by the activation of
a K+ conductance. However, the block of Ca2+ channels did not block t
he slow afterhyperpolarization, whereas the block of Na+ channels did
block this event, even after the generation of repetitive Ca2+ spikes,
indicating that it is mediated by a Na+-activated K+ current. Applica
tion of apamin reduced the afterhyperpolarization and enhanced a plate
au potential after each low-threshold Ca2+ spike. This plateau potenti
al could result in a prolonged depolarization of perigeniculate neuron
s, even before the application of apamin, resulting in the generation
of tonic discharge. The plateau potential was blocked by the local app
lication of tetrodotoxin, indicating that it is mediated by a persiste
nt Na+ current. The activation and interaction of these slowly develop
ing and persistent currents contributes significantly to low-frequency
components of spindle wave generation. In particular, we suggest that
the activation of the slow afterhyperpolarization may contribute to t
he generation of the spindle wave refractory period in vitro.