Efferent connections of the septal area in the rat: An analysis utilizing retrograde and anterograde transport methods

Meibach, Richard C.; Siegel, Allan

doi:10.1016/0006-8993(77)90088-9

Cited by 436 publications

(121 citation statements)

References 43 publications

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“…Best known of the entorhinal connections is the perforant pathway, a massive association projection via the medial septum/diagonal band to the molecular layer of the dentate gyrus and Ammon's horn. The findings of reciprocal connections between the septum and the entorhinal area extend previous investigations showing prominent connections between the septum and the hippocampal formation (Meibach and Siegel 1977;Swanson and Cowan 1977). It has been proposed that septal modulation of hippocampal activity can occur at different levels within the hippocampal region, including the entorhinal area (Alonso and Kohler 1984;Ylinen et al 1995).…”

Section: Discussionsupporting

confidence: 85%

Changes in electrocortical power and coherence in response to the selective cholinergic immunotoxin 192 IgG-saporin

Holschneider

Waite

Leuchter

et al. 1999

Experimental Brain Research

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Changes in brain electrical activity in response to cholinergic agonists, antagonists, or excitotoxic lesions of the basal forebrain may not be reflective entirely of changes in cholinergic tone, in so far as these interventions also involve noncholinergic neurons. We examined electrocortical activity in rats following bilateral intracerebroventricular administration of 192 IgG-saporin (1.8 μg/ventricle), a selective cholinergic immunotoxin directed to the low-affinity nerve growth factor receptor p75. The immunotoxin resulted in extensive loss of choline acetyl transferase (ChAT) activity in neocortex (80%-84%) and hippocampus (93%), with relative sparing of entorhinalpiriform cortex (42%) and amygdala (28%). Electrocortical activity demonstrated modest increases in 1-to 4-Hz power, decreases in 20-to 44-Hz power, and decreases in 4-to 8-Hz intraand interhemispheric coherence. Rhythmic slow activity (RSA) occurred robustly in toxin-treated animals during voluntary movement and in response to physostigmine, with no significant differences seen in power and peak frequency in comparison with controls. Physostigmine significantly increased intrahemispheric coherence in lesioned and intact animals, with minor increases seen in interhemispheric coherence. Our study suggests that: (1) electrocortical changes in response to selective cholinergic deafferentation are more modest than those previously reported following excitotoxic lesions; (2) changes in cholinergic tone affect primarily brain electrical transmission within, in contrast to between hemispheres; and (3) a substantial

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Section: Discussionsupporting

confidence: 85%

Changes in electrocortical power and coherence in response to the selective cholinergic immunotoxin 192 IgG-saporin

Holschneider

Waite

Leuchter

et al. 1999

Experimental Brain Research

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“…Third, the septum shows strong connections to areas implicated in stress responses, such as the paraventricular nucleus of the hypothalamus, the dorsal raphe nucleus, and the locus coeruleus (Swanson and Cowan, 1979;Silverman et al, 1981;Sawchenko and Swanson, 1983;Moga et al, 1991;Staiger and Nürnberger, 1991). The medial septum has a direct projection to the amygdala, whereas the lateral septum has both a direct projection and a more extensive indirect projection to the amygdala (Meibach and Siegel, 1977;Russchen, 1982;Dudley et al, 1990;Volz et al, 1990;Staiger and Nürnberger, 1991).…”

mentioning

confidence: 99%

Role of the Septum in the Excitatory Effect of Corticotropin-Releasing Hormone on the Acoustic Startle Reflex

Lee

Davis

1997

J. Neurosci.

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Intracerebroventricular administration of corticotropin-releasing hormone (CRH) elicits a constellation of behavioral, autonomic, and endocrinological changes typically observed in stress. One of the behavioral changes after intracerebroventricular CRH is a profound increase of startle amplitude (CRH-enhanced startle). The present study examined the role of the septum in CRHenhanced startle. The septum has direct and indirect connections to the amygdala and inhibits the amygdala. Electrophysiological data show that CRH in the septum is inhibitory. Therefore, it has been hypothesized that intracerebroventricular CRH inhibits the septum, which in turn disinhibits the amygdala, resulting in a constellation of changes via activation of amygdala efferent targets. In testing this hypothesis, it was found that electrolytic lesions of the medial septum, but not the lateral septum, blocked CRH-enhanced startle. However, fibersparing chemical lesions of the medial septum did not block CRH-enhanced startle, suggesting that the blockade seen with the electrolytic lesions was caused by damage to fibers of passage. A major fiber bundle passing through the medial septum is the fornix, the primary efferent pathway for the hippocampus. Fimbria transection blocked CRH-enhanced startle almost completely, whereas the large electrolytic lesions of the dorsal hippocampus did not block CRH-enhanced startle. Taken together, these data suggest that perhaps the ventral hippocampus and its efferent target areas, which communicate via the fimbria, may be critically involved in CRH-enhanced startle.

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“…MSA has a major projection to all of the cell fields of the hippocampus (HPC) via fibers running in the fimbria and fornix (Raisman, 1966;Meibach and Siegel, 1977;Swanson and Cowan, 1977). Disrupting this projection, whether by making lesions in the medial septal area or in the fornix and fimbria, can abolish hippocampal 0 activity; 8 in the septal pole of the hippocampus appears 292 The Journal of Neuroscience Septoentorhinal Interactions to depend upon fibers running in the dorsomedial portion of the fornix, while 6 in the temporal poles depends on fibers running in the fimbria .…”

mentioning

confidence: 99%

“…The MSA also projects to all of the entorhinal cortex (EC) diffusely across all cortical layers (Meibach and Siegel, 1977;Segal, 1977;Siegel and Tassoni, 1971;Swanson and Cowan, 1977). The route taken by the fibers of this pathway has been identified for only the most ventral portion of EC (Meibach and Siegel, 1977).…”

mentioning

confidence: 99%

Medial septal area lesions disrupt theta rhythm and cholinergic staining in medial entorhinal cortex and produce impaired radial arm maze behavior in rats

Mitchell¹,

Rawlins²,

Steward³

et al. 1982

J. Neurosci.

355

165

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This study was designed to determine (1) which brain area paces the 8 rhythm in the medial entorhinal cortex (MEC) of rats and (2) the extent to which the behavioral effects of lesions in the medial septal area (MSA), which disrupt the cholinesterase-related pathway to the hippocampal formation, resemble the effects previously reported to result from fimbria-fornix lesions.MSA lesions abolished or decreased B rhythm in dorsal hippocampus (DHPC) and MEC; acetylcholinesterase (AChE) staining was depleted or diminished in all of the hippocampus and entorhinal cortex. Rats with MSA lesions were impaired on acquisition of a radial arm maze task.Unilateral fimbria lesions left 8 rhythm and AChE staining essentially unaltered in ipsilateral DHPC and MEC but depleted AChE in ipsilateral ventral hippocampus (VHPC) and ventral lateral entorhinal cortex (LEC). A lesion of the dorsal fornix at the level of the hippocampal flexure left ipsilateral DHPC 8 rhythm and AChE stain unaltered while causing a substantial reduction in 0 rhythm and depletion of AChE in ipsilateral MEC. AChE staining was complete in VHPC and LEC.These results suggest that MSA paces MEC 8 rhythm and that the presumed cholinergic projection which mediates this function travels in the dorsal fornix. The fimbria carries a presumed cholinergic projection to ventral LEC. Rats with MSA lesions can learn a radial arm maze task, unlike rats with fimbria-fornix lesions, but they learn significantly slower than normal rats.

show abstract

Efferent connections of the septal area in the rat: An analysis utilizing retrograde and anterograde transport methods

Cited by 436 publications

References 43 publications

Changes in electrocortical power and coherence in response to the selective cholinergic immunotoxin 192 IgG-saporin

Changes in electrocortical power and coherence in response to the selective cholinergic immunotoxin 192 IgG-saporin

Role of the Septum in the Excitatory Effect of Corticotropin-Releasing Hormone on the Acoustic Startle Reflex

Medial septal area lesions disrupt theta rhythm and cholinergic staining in medial entorhinal cortex and produce impaired radial arm maze behavior in rats

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