14/04/06 23:53:59.07 ob5R6JgR.net
>>87
>Vagus nerve stimulation (VNS) is an approved treatment for
>epilepsy and depression, and cognition-enhancing effect in
>patients with Alzheimer`s disease has been reported as well.
>The hippocampus is widely recognized to be related with epilepsy,
>depression and Alzheirmer`s disease. One possible mechanism of
>VNS involves the effect on the hippocampus. VNS has been
>demonstrated to increase release of norepinephrine (NE)
>in the hippocampus. However, the effect of VNS on
>synaptic transmission in the hippocampus remains unanswered.
>Therefore, in this study, to determine whether VNS can
>modulate hippocampus, we investigated the effect of VNS on
>perforant path (PP)-CA3 synaptic transmission using
>electrophysiologial experiments. The vagus nerve was stimulated for
>10 min (20 Hz frequency, 500 μs pulse width, 1 mA output) in
>anesthetized rats. Induced fEPSP at CA3 through the stimulation of
>perforant path produced a persistent enhancement. Arc, an immediate
>early gene was used to detect the `active` brain regions
>after the treatment of VNS to demonstrate the mechanism
>of the enhancement. The locus coeruleus (LC) containing
>the perikarya of noradrenergic projections showed more Arc positive cells,
>as measured by in-situ hybridization, after 10 min treatment of VNS
>. In addition, electrical lesion of LC neurons or the intraventricular
>administration of the β adrenergic receptor antagonist timolol
>prevented the enhancing action of VNS on PP-CA3 responses.
>In conclusion, the persistent enhancement of PP-CA3synaptic
>transmission induced by VNS involves the activation of LC and β
>adrenergic receptors.