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Orexin depolarizes rat hypothalamic paraventricular nucleus neurons
T Shirasaka1, S Miyahara, T Kunitake
1Department of Anesthesiology, Miyazaki Medical College, 5200 Kihara, Kiyotake, Miyazaki, 889 - 1692, Japan.
Summary
Orexin-B excites hypothalamic paraventricular nucleus (PVN) neurons by depolarizing their membrane potential. This study reveals orexin-B
Area of Science:
- Neuroscience
- Neuroendocrinology
- Molecular Biology
Background:
- Orexins (hypocretins) are hypothalamic peptides involved in physiological functions.
- Orexin receptors, particularly orexin receptor 2, are prevalent in the hypothalamic paraventricular nucleus (PVN).
- The specific influence of orexins on PVN neurons remains largely uncharacterized.
Purpose of the Study:
- To investigate the effects of orexin-B on PVN neurons.
- To elucidate the mechanism underlying orexin-B's action on PVN neurons.
Main Methods:
- Whole-cell patch-clamp recordings were performed on rat brain slices.
- Orexin-B was applied in varying concentrations (0.01-1.0 microM).
- Experiments were conducted in the presence of tetrodotoxin (TTX) and cadmium ions (Cd2+) to differentiate synaptic and postsynaptic mechanisms.
Main Results:
- Orexin-B induced concentration-dependent depolarization in 80.8% of type 1 and 79.2% of type 2 PVN neurons.
- The depolarizing effects persisted after TTX application, indicating postsynaptic mechanisms.
- Cadmium ions significantly attenuated the orexin-B-induced depolarization in type 2 neurons, suggesting calcium channel involvement.
Conclusions:
- Orexin-B exerts excitatory effects on PVN neurons.
- These excitatory effects are mediated through postsynaptic membrane depolarization.
- The findings highlight a novel role for orexins in regulating PVN neuronal activity.