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The Journal of Neurophysiology Vol. 82 No. 3 September 1999, pp. 1560-1568
Copyright ©1999 by the American Physiological Society
Department of Physiology, College of Medicine, and University of Florida Brain Institute, University of Florida, Gainesville, Florida 32610
Zhu, Mingyan,
Craig H. Gelband,
Philip Posner, and
Colin Sumners.
Angiotensin II Decreases Neuronal Delayed Rectifier Potassium
Current: Role of Calcium/Calmodulin-Dependent Protein Kinase II. J. Neurophysiol. 82: 1560-1568, 1999. Angiotensin II (Ang II) acts at specific receptors located on neurons
in the hypothalamus and brain stem to elicit alterations in blood
pressure, fluid intake, and hormone secretion. These actions of Ang II
are mediated via Ang II type 1 (AT1) receptors and involve
modulation of membrane ionic currents and neuronal activity. In
previous studies we utilized neurons cultured from the hypothalamus and
brain stem of newborn rats to investigate the AT1
receptor-mediated effects of Ang II on neuronal K+
currents. Our data indicate that Ang II decreases neuronal delayed rectifier (Kv) current, and that this effect is partially due to
activation of protein kinase C (PKC), specifically PKC
. However, the
data also indicated that another Ca2+-dependent mechanism
was also involved in addition to PKC. Because Ca2+/calmodulin-dependent protein kinase II (CaM KII) is a
known modulator of K+ currents in neurons, we investigated
the role of this enzyme in the AT1 receptor-mediated
reduction of neuronal Kv current by Ang II. The reduction of neuronal
Kv current by Ang II was attenuated by selective inhibition of either
calmodulin or CaM KII and was mimicked by intracellular application of
activated (autothiophosphorylated) CaM KII
. Concurrent inhibition of
CaM KII and PKC completely abolished the reduction of neuronal Kv by
Ang II. Consistent with these findings is the demonstration that Ang II
increases CaM KII activity in neuronal cultures, as evidenced by
increased levels of autophosphorylated CaM KII
subunit. Last,
single-cell reverse transcriptase (RT)-PCR analysis revealed the
presence of AT1 receptor-, CaM KII
-, and PKC
subunit
mRNAs in neurons that responded to Ang II with a decrease in Kv
current. The present data indicate that the AT1
receptor-mediated reduction of neuronal Kv current by Ang II involves
a Ca2+/calmodulin/CaM KII pathway, in addition to the
previously documented involvement of PKC.
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