These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Orexin peptides enhance median preoptic nucleus neuronal excitability via postsynaptic membrane depolarization and enhancement of glutamatergic afferents.
    Author: Kolaj M, Coderre E, Renaud LP.
    Journal: Neuroscience; 2008 Sep 09; 155(4):1212-20. PubMed ID: 18674591.
    Abstract:
    Subpopulations of neurons in the median preoptic nucleus (MnPO) located within the lamina terminalis contribute to thermoregulatory, cardiovascular and hydromineral homeostasis, and sleep-promotion. MnPO is innervated by lateral hypothalamic neurons that synthesize and secrete the arousal-promoting and excitatory orexin (hypocretin) neuropeptides. To evaluate the hypothesis that orexins modulate the excitability of MnPO neurons, we used patch-clamp recording techniques applied in rat brain slice preparations to assess the effects of exogenously applied orexin A and orexin B peptides on their intrinsic and synaptic properties. Whole cell recordings under current-clamp mode revealed that 11/15 tested MnPO neurons responded similarly to either orexin A or B (500-1000 nM) with a slowly rising, prolonged (10-15 min) and reversible membrane depolarization. Under voltage-clamp mode, orexin applications induced a tetrodotoxin-resistant inward current of -7.2+/-1.6 pA, indicating a direct (postsynaptic) activation, with a time course similar to the observed membrane depolarization. The orexin-induced responses in 4/7 neurons were associated with a significant decrease in membrane conductance and the net orexin-induced current that reversed at -99+/-5 mV, suggesting closure of potassium channels. Orexins did not attenuate the properties of excitatory (n=4) or inhibitory (n=7) postsynaptic currents evoked by subfornical organ stimulation. By contrast, orexins applications induce a significant increase in both frequency and amplitude of spontaneous glutamatergic postsynaptic currents (5/7 cells) but had no influence on spontaneous GABAergic currents (6/6 cells). Thus, in addition to a direct postsynaptic receptor-mediated excitation, orexins can also increase the excitability of MnPO neurons via increasing their excitatory inputs, presumably through an orexin receptor-mediated excitation of local glutamatergic neurons whose axons project to MnPO neurons.
    [Abstract] [Full Text] [Related] [New Search]