Components of after-hyperpolarization in magnocellular neurones of the rat supraoptic nucleus in vitro
Article first published online: 22 SEP 2004
The Journal of Physiology
Volume 513, Issue 2, pages 493–506, December 1998
How to Cite
Greffrath, W., Martin, E., Reuss, S. and Boehmer, G. (1998), Components of after-hyperpolarization in magnocellular neurones of the rat supraoptic nucleus in vitro. The Journal of Physiology, 513: 493–506. doi: 10.1111/j.1469-7793.1998.493bb.x
- Issue published online: 22 SEP 2004
- Article first published online: 22 SEP 2004
- (Received 3 April 1998; accepted after revision 13 August 1998)
- 1The pharmacological sensitivity of hyperpolarizing components of spike train after-potentials was examined in sixty-one magnocellular neurones of the rat supraoptic nucleus using intracellular recording techniques in a brain slice preparation.
- 2In 26 % of all neurones a slow after-hyperpolarization (AHP) was observed in addition to a fast AHP. In 31 % of all neurones a depolarizing after-potential (DAP) was observed.
- 3The fast AHP was blocked by apamin whereas the slow AHP was blocked by charybdotoxin (ChTX). The DAP was enhanced by ChTX or a DAP was unmasked if not present during the control period.
- 4Low concentrations of TEA (0.15–1.5 mm) induced effects on the slow AHP and the DAP essentially resembling those of ChTX. The same was true for the effects of CoCl2 (1 mm).
- 5Spike train after-potentials were not affected by either iberiotoxin (IbTX), a selective high-conductance potassium (BK) channel antagonist, or margatoxin (MgTX), a Kv1.3 α-subunit antagonist.
- 6Kv1.3 α-subunit immunohistochemistry revealed that these units are not expressed in the somato-dendritic region of supraoptic neurones.
- 7The effects of ChTX, IbTX, MgTX, TEA, CoCl2 and CdCl2 on spike train after-potentials are interpreted in terms of an induction of the slow AHP by the activation of calcium-dependent potassium channels of intermediate single channel conductance (IK channels).
- 8The results suggest that at least the majority of supraoptic magnocellular neurones share the capability of generating both a slow AHP and a DAP. The slow AHP may act to control the expression of the DAP, thus regulating the excitability of magnocellular neurones. The interaction of the slow AHP and the DAP may be important for the control of phasic discharge.