UNSPECIFIED. (2005) Angiotensin II induces calcium-dependent rhythmic activity in a Subpopulation of rat hypothalamic median preoptic nucleus neurons. JOURNAL OF NEUROPHYSIOLOGY, 93 (4). pp. 1970-1976. ISSN 0022-3077

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Abstract

Whole cell patch-clamp recordings revealed a subpopulation (16%, n = 18/112) of rat median preoptic nucleus (MnPO) neurons responded to bath-applied angiotensin II (Ang II; 100 nNl to 5 mu M; 30-90 s) with a prolonged TTX-resistant membrane depolarization and rhythmic bursting activity. At rest, cells characteristically displayed relatively low input resistance and negative resting potentials. Ang-II-induced responses featured increased input resistance, a reversal potential of -95 2 mV, an increase in action potential duration from 2.9 +/- 0.5 to 4.3 +/- 0.8 ms, and the appearance of a rebound excitation at the offset of membrane responses to hyperpolarizing current injection. The latter was sensitive to Ni2+ (0.5-1 mM; n = 5), insensitive to extracellular Cs+ (1 mM, n = 7), and intracellular QX-314 (4 mM, n = 5), consistent with activation of a T-type Ca2+ conductance. Coincident with the Ang-II-induced depolarization was the appearance of rhythmic depolarizing shifts at a frequency of 0.14 +/- 0.09 Hz with superimposed bursts of 4-22 action potentials interspersed with silent periods persisting for >1 h after washout. These TTX-resistant depolarizing shifts increased in amplitude and decreased in frequency with membrane hyperpolarization with activity ceasing beyond approximately -80mV, and were abolished in low-Ca2+/high-Mg2+ bathing medium (n = 6), Co2+ (1 mM; n = 6), or Ni2+ (0.5-1 mM; n = 8). Thus in a subpopulation of MnPO neurons, Ang II induces "pacemaker-like" activity by reducing a K+-dependent leak conductance that contributes to resting membrane potential and promoting of Ca2+-dependent regenerative auto-excitation mediated, in part, by a T-type Ca2+ conductance.

Item Type:	Journal Article
Subjects:	R Medicine > RC Internal medicine > RC0321 Neuroscience. Biological psychiatry. Neuropsychiatry Q Science > QP Physiology
Journal or Publication Title:	JOURNAL OF NEUROPHYSIOLOGY
Publisher:	AMER PHYSIOLOGICAL SOC
ISSN:	0022-3077
Official Date:	April 2005
Volume:	93
Number:	4
Number of Pages:	7
Page Range:	pp. 1970-1976
Identification Number:	10.1152/jn.00769.2004
Publication Status:	Published
URI:	http://wrap.warwick.ac.uk/id/eprint/7256

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