Somatostatin selectively enhances acetylcholine-induced excitations in rat hippocampus and cortex.

Mancillas, Jorge R.; Siggins, George R.; Bloom, Floyd E.

doi:10.1073/pnas.83.19.7518

Cited by 84 publications

(42 citation statements)

References 29 publications

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“…Two previous in vivo studies also reported that SST decreases neuronal activity in the rabbit lateral vestibular nucleus (ChanPalay et al, 1982) and in the rat cortex and hippocampus (Mancillas et al, 1986). Noteworthy, these two latter regions express high levels of sst 2A receptors (Dournaud et al, 1996;Schindler et al, 1997).…”

Section: Discussionmentioning

confidence: 95%

“…In agreement with this hypothesis, we observed that the reduction of firing level was sometimes accompanied by an increase in action potential size evocative of hyperpolarization. As observed in hippocampus, cortex (Mancillas et al, 1986), and hypothalamus (Peineau et al, 2003), the activation of sst 2A receptors might also lower the discharge rate of MS-DB GABAergic neurons by reducing the postsynaptic excitatory effects of glutamate. This effect might have important functional consequences, because NMDA receptors in the MS-DB are likely to modulate the amplitude of hippocampal theta (Leung and Shen, 2004).…”

Section: Discussionmentioning

confidence: 99%

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Medial Septal GABAergic Neurons Express the Somatostatin sst_2AReceptor: Functional Consequences on Unit Firing and Hippocampal Theta

Bassant¹,

Simon²,

Poindessous‐Jazat³

et al. 2005

J. Neurosci.

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GABAergic septohippocampal neurons play a major role in the generation of hippocampal theta rhythm, but modulatory factors intervening in this function are poorly documented. The neuropeptide somatostatin (SST) may be one of these factors, because nearly all hippocampal GABAergic neurons projecting to the medial septum/diagonal band of Broca (MS-DB) express SST. In this study, we took advantage of the high and selective expression of the SST receptor sst 2A in MS-DB to examine its possible role on theta-related activity. Immunohistochemical experiments demonstrated that sst 2A receptors were selectively targeted to the somatodendritic domain of neurons expressing the GABAergic marker GAD67 but were not expressed by cholinergic neurons. In addition, a subpopulation of GABAergic septohippocampal projecting neurons expressing parvalbumin (PV) also displayed sst 2A receptors. Using in vivo juxtacellular recording and labeling with neurobiotin, we showed that a number of bursting and nonbursting neurons exhibiting high discharge rates and brief spikes were immunoreactive for PV or GAD67 and expressed the sst 2A receptor. Microiontophoresis applications of SST and the sst 2A agonist octreotide (OCT) showed that sst 2A receptor activation decreased the discharge rate of both nonbursting and bursting MS-DB neurons and lessened the rhythmic activity of the latter. Finally, intraseptal injections of OCT and SST in freely moving rats reduced the power of hippocampal EEG in the theta band. Together, these in vivo experiments suggest that SST action on MS-DB GABAergic neurons, through sst 2A receptors, represents an important modulatory mechanism in the control of theta activity.

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Section: Discussionmentioning

confidence: 95%

Section: Discussionmentioning

confidence: 99%

Medial Septal GABAergic Neurons Express the Somatostatin sst_2AReceptor: Functional Consequences on Unit Firing and Hippocampal Theta

Bassant¹,

Simon²,

Poindessous‐Jazat³

et al. 2005

J. Neurosci.

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“…Immunocytochemical and in situ hybridization analysis of this region has shown that the majority of somatostatin-containing neurons are present in the outer part of stratum oriens and in the polymorphic region of the hilus of the dentate gyrus (Johansson et al, 1984;Kiyama and Emson, 1990). Electrophysiological studies have shown a direct inhibitory action of somatostatin on the spontaneous activity of CA 1-CA3 pyramidal neurons (Olpe et al, 1980;Pittman and Siggins, 198 1 ) and a facilitation of the excitatory responses induced by acetylcholine on the same cells (Mancillas et al, 1986).…”

mentioning

confidence: 99%

Extracellular Somatostatin Measured by Microdialysis in the Hippocampus of Freely Moving Rats: Evidence for Neuronal Release

Vezzani

Ruiz

Monno

et al. 1993

Journal of Neurochemistry

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Abstract:Intracerebral microdialysis combined with a sensitive and specific radioimmunoassay was used to monitor the neuronal release of somatostatin (somatostatin-like immunoreactivity, SLI) in the dorsal hippocampus of freely moving rats. The sensitivity of the radioimmunoassay was optimized to detect < 1 fmol/ml. The basal concentration of SLI in 20-min dialysate fractions (5 pl/min) collected 24 h after probe implantation was stable over at least 200 min. The spontaneous efflux dropped by 54 k 6.4% ( p < 0.05) when Ca2+ was omitted and I mM EGTA added to the Krebs-Ringer solution and by 65.

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“…It should be kept in mind that there is a close neuronal interaction between the somatostatinergic and cholinergic systems in the mammalian hippocampus and cortex, as indicated by a number of electrophysiological (Mancillas et al, 1986;Matsuoka et al, 1991), neurochemical (Araujo et al, 1990;Barrios et al, 1990;Gaykema et al, 1991;Zee et al, 1991;Álvaro and Arilla, 1992) and behavioral studies (Haroutunian et al, 1989;Ohno et al, 1993). In the rat hippocampus, cholinergic terminals make synaptic contacts on SS-immunoreactive cells (Leranth and Frotscher, 1987).…”

Section: Discussionmentioning

confidence: 99%

A vitamin A-free diet results in impairment of the rat hippocampal somatostatinergic system

2006

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Abstract-Previous studies have revealed the presence of retinoid specific receptors in the hippocampus and have demonstrated that vitamin A deficiency produces a severe deficit in spatial learning and memory which are linked to a proper hippocampal functioning. It is also well known that the tetradecapeptide somatostatin binds to specific receptors in the hippocampus and, when injected into this brain area, facilitates the acquisition of spatial tasks. In addition, depletion of somatostatin by cysteamine impairs acquisition of these tasks. Taken together, these studies support the idea that the hippocampal somatostatinergic system might be regulated by vitamin A. Hence, we evaluated the effects of vitamin A deprivation and subsequent administration of vitamin A on the rat hippocampal somatostatinergic system. Rats fed a vitamin A-free diet exhibited a significant reduction of somatostatin-like immunoreactivity content in the hippocampus whereas the somatostatin mRNA levels were unaltered. Vitamin A deficiency increased the somatostatin receptor density and its dissociation constant. Functional Gi activity as well as the capacity of somatostatin to inhibit basal and forskolin-stimulated adenylyl cyclase activity was decreased in vitamin A deficiency rats as compared with the control animals. All these parameters were fully restored when vitamin A was replaced in the diet. Furthermore, we found that the Gi␣ 1 , Gi␣ 2 and Gi␣ 3 protein levels were unaltered in hippocampal membranes from rats fed a vitamin A-free diet whereas subsequent vitamin A administration to these rats caused a significant increase in the levels of Gi␣1 and Gi␣2. Altogether, the present findings suggest that dietary vitamin A levels modulate the somatostatinergic system in the rat hippocampus.

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Somatostatin selectively enhances acetylcholine-induced excitations in rat hippocampus and cortex.

Abstract: The neuronal effects of somatostatin-14

Cited by 84 publications

References 29 publications

Medial Septal GABAergic Neurons Express the Somatostatin sst_2AReceptor: Functional Consequences on Unit Firing and Hippocampal Theta

Medial Septal GABAergic Neurons Express the Somatostatin sst_2AReceptor: Functional Consequences on Unit Firing and Hippocampal Theta

Extracellular Somatostatin Measured by Microdialysis in the Hippocampus of Freely Moving Rats: Evidence for Neuronal Release

A vitamin A-free diet results in impairment of the rat hippocampal somatostatinergic system

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Somatostatin selectively enhances acetylcholine-induced excitations in rat hippocampus and cortex.

Abstract: The neuronal effects of somatostatin-14

Cited by 84 publications

References 29 publications

Medial Septal GABAergic Neurons Express the Somatostatin sst2AReceptor: Functional Consequences on Unit Firing and Hippocampal Theta

Medial Septal GABAergic Neurons Express the Somatostatin sst2AReceptor: Functional Consequences on Unit Firing and Hippocampal Theta

Extracellular Somatostatin Measured by Microdialysis in the Hippocampus of Freely Moving Rats: Evidence for Neuronal Release

A vitamin A-free diet results in impairment of the rat hippocampal somatostatinergic system

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Medial Septal GABAergic Neurons Express the Somatostatin sst_2AReceptor: Functional Consequences on Unit Firing and Hippocampal Theta

Medial Septal GABAergic Neurons Express the Somatostatin sst_2AReceptor: Functional Consequences on Unit Firing and Hippocampal Theta