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| Andrea Viggiano |
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Dept. Experimental Medicine, via Costantinopoli 16, 80138 Napoli
e-mail: andrea.viggiano@unina2.it |
Poster Presentation: |
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| OREXIN A INCREASES EXTRACELLULAR GABA INTO THE VENTROMEDIAL HYPOTHALAMUS. |
| A. Viggiano, A. Pirozzi, B. De Luca and M. Monda | |
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Dept. Experimental Medicine, via Costantinopoli 16, 80138 Napoli |
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| Orexin A is an hypothalamic neuropeptide that induces an increase in food intake when administered into the cerebral lateral ventricle. Since it is well known that the ventromedial hypothalamus (VMH) is involved in the feeding behavior also through GABAergic circuits, the aim of this experiment was to investigate the effect of an Orexin A injection on the extracellular levels of GABA in the VMH. GABA levels in the VMH was evaluated in 6 rats by microdialysis and HPLC-electrochemical detection 30 min before and every 30 min for an over all period of 6 hours after an intracerebroventricular injection of orexin A. The same procedure was used in another group of 6 rats but saline was injected into the lateral ventricle as control. The results showed that extracellular GABA increased in the VMH after injection of orexin A at 60 min and at 3 hour after the injection. This finding suggests a possible mechanism by which orexin A should induce hyperphagia in the first hour after injection. Since it is already known that the inhibition of the VMH by injection of GABA cause an increase of food intake, it is possible that orexin A causes an in crease of food intake by increasing GABA release in the VMH. The lack of increase in GABA level after the 4th hour is consistent with the lack of increase in food intake at this time, as we observed in previous experiments. The finding of a biphasic increase in GABA level, at 60 min and at 3 hour, was unexpected and should be further investigated.
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