Septo-hippocampal and other medial septum-diagonal band neurons: electrophysiological and pharmacological properties

doi:10.1016/0006-8993(84)90588-2

Brain Research

Volume 309, Issue 2, 10 September 1984, Pages 217-226

https://doi.org/10.1016/0006-8993(84)90588-2 Get rights and content

Abstract

Neurons located in the medial septum-nucleus of the diagonal band (vertical limb) area and antidromically activated by electrical stimulation of the fimbria were recorded in urethane anesthetized rats. Forty-five percent of these septo-hippocampal neurons (SHNs) discharged rhythmically in short bursts (mean burst frequency, 4 Hz). They were antidromically driven at short latencies from the fimbria. SHNs driven at long latencies (above 5 ms) were never bursting neurons. Fimbria stimulation also had a powerful inhibitory effect on the spontaneous activity of SHNs.

The vast majority of the septo-hippocampal neurons were excited by the iontophoretic application of acetylcholine or cholinergic agonists, carbachol being the most effective. The acetylcholine-induced excitations were readily abolished by atropine. In contrast hexamethonium and mecamylamine were less effective. The rhythmic bursting activity could not be consistently altered by the iontophoretic application of cholonergic agonists or antagonists or of divalent cations. SHNs were also sensitive to various othe putative neurotransmitters (substance P, GABA) known to play a role in the medial septal area. Bursting neurons and ACh-sensitive neurons were less frequent among unidentified medial septal neurons. The regulation of the septo-hippocampal cholinergic pathway is therefore not likely to be due to a direct feedback inhibition by locally released acetylcholine. However a strong inhibitory feedback could be exerted by the hippocampo-septal pathway impinging directly or indirectly on septo-hippocampal neurons.

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Moreover, cholinergic activity of the MS was proposed to be a critical factor for working memory, which may be blocked by scopolamine [57]. ACh could excite MS neurons [58,59], and that infusion of scopolamine into the MS area dose-dependently decreased ACh release in the hippocampus support this hypothesis [60]. Furthermore, intra-MS infusion of NMDA by itself increased memory acquisition.
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Septo-hippocampal and other medial septum-diagonal band neurons: electrophysiological and pharmacological properties

Abstract

Life Sci.

Brain Research

Neuroscience

Neuroscience

Neuroscience

Neuropharmacology

Brain Research

Brain Research

Brain Research

Neurosci. Lett.

Brain Res. Rev.

Electroenceph. clin. Neurophysiol.

Europ. J. Pharmacol.

Exp. Neurol.

Brain Research

Brain Res. Bull.

Exp. Neurol.

Neuroscience

Brain Research

Brain Research

Neuroscience

Brain Research

Electroenceph. clin. Neurophysiol.

Brain Research