| Abstract No.: | 200 |
| Country: | Canada |
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| Title: | Thalamic Paraventricular Nucleus Neurons: Unique Properties, Uniquely Connected |
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| Authors/Affiliations: | Leo P Renaud*, Milos Kolaj, Li Zhang, Petro Doroshenko, Trevor Richter.
Neurosciences Program, Ottawa Health Research Institute and University of Ottawa, ON, Canada
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| Content: | The thalamic paraventricular nucleus (PVT) is an elongated rostrocaudal cell group in the dorsal thalamic midline with interesting connectivity. PVT is innervated by neurons in the suprachiasmatic nucleus (SCN), a critical site for regulating circadian rhythms in mammals. PVT also receives a prominent innervation from lateral hypothalamic / perifornical neurons that uniquely synthesize the ‘arousal and appetite-stimulating’ orexin(hypocretin) neuropeptides. While functional studies using c-Fos suggest that PVT neurons have a role in stress, psychostimulant and reward-motivated behaviours, little is known about cellular properties of PVT neurons. Our initial observations using patch clamp techniques in rat brain slice preparations reveal that most PVT neurons display state-dependent tonic or burst firing, inward rectification and low threshold spikes due to T type currents. Low voltage-activated calcium currents may trigger unique long duration slow afterhyperpolarizations and calcium-induced calcium release, properties that both appear to be uniquely expressed among midline thalamic neurons. During the subjective day, most PVT neurons have a hyperpolarized membrane potential and are silent. During the night (active period), PVT neurons are relatively depolarized and exhibit burst or tonic firing, possibly due to orexin-induced reduction in a TASK-like ‘leak’ potassium conductance. Activation of SCN monosynaptically evokes rapid amino acid-mediated responses in PVT neurons, and SCN is a likely source for additional peptide neurotransmitter to PVT. These observations imply that PVT and other midline thalamic neurons possess properties that are unique to this area of thalamus. Supported by CIHR and HSFO. |
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