Angiotensin II influences the hyperpolarization-activated current Ih in neurones of the rat paraventricular nucleus.
The hypothalamic paraventricular nucleus (PVN) consists of mainly two types of neurones (type I and type II), according to their characteristic electrophysiological properties. An excitatory influence of angiotensin II (Ang II) on PVN neurones has been shown to be mediated by the AT(1) receptor. We investigated the underlying mechanism of the Ang II effect on PVN neurones with patch-clamp experiments. Using current-clamp mode, we identified a sag in 59% of only type II neurones due to a hyperpolarization-activated current I(h). Voltage-clamp measurements revealed that Ang II (1 microM) provokes a shift of the I(h) activation curve to more depolarized values by 8.1 mV, an effect reduced by the additional application of the AT(1) receptor antagonist Losartan (10 microM). These findings suggest that the excitatory effect of Ang II in type II neurones is at least partially due to an increased population of active I(h) channels.
Egli
Marcel
M
Division of Neurobiology, University of Berne, Baltzerstrasse 6, CH 3012 Berne, Switzerland.
Berger
Thomas
T
Imboden
Hans
H
D000804:Angiotensin II / Q000502:physiology*; D057911:Angiotensin Receptor Antagonists; D000818:Animals; D054815:Cyclic Nucleotide-Gated Cation Channels; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D007473:Ion Channels / Q000502:physiology*; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D010286:Paraventricular Hypothalamic Nucleus / Q000166:cytology / Q000502:physiology*; D015221:Potassium Channels; D051381:Rats; D017208:Rats, Wistar; D044140:Receptor, Angiotensin, Type 1; D011945:Receptors, Angiotensin / Q000502:physiology
D057911:Angiotensin Receptor Antagonists; D054815:Cyclic Nucleotide-Gated Cation Channels; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D007473:Ion Channels; D015221:Potassium Channels; D044140:Receptor, Angiotensin, Type 1; D011945:Receptors, Angiotensin; D000804:Angiotensin II