title: Medial septal GABAergic neurons express the somatostatin sst2A receptor: functional consequences on unit firing and hippocampal theta.
abstract: 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 sst2A in MS-DB to examine its possible role on theta-related activity. Immunohistochemical experiments demonstrated that sst2A 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 sst2A 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 sst2A receptor. Microiontophoresis applications of SST and the sst2A agonist octreotide (OCT) showed that sst2A 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 sst2A receptors, represents an important modulatory mechanism in the control of theta activity.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale, U549, Centre Paul Broca, F-75014 Paris, France.
authors.forename: Marie-Hélène
authors.initials: MH
authors.lastname: Bassant
authors.forename: Axelle
authors.initials: A
authors.lastname: Simon
authors.forename: Frédérique
authors.initials: F
authors.lastname: Poindessous-Jazat
authors.forename: Zsolt
authors.initials: Z
authors.lastname: Csaba
authors.forename: Jacques
authors.initials: J
authors.lastname: Epelbaum
authors.forename: Pascal
authors.initials: P
authors.lastname: Dournaud
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D004569:Electroencephalography / Q000187:drug effects; D006624:Hippocampus / Q000187:drug effects* / Q000502:physiology; D007267:Injections; D007478:Iontophoresis; D008297:Male; D009434:Neural Pathways / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D015282:Octreotide / Q000008:administration & dosage / Q000494:pharmacology; D010320:Parvalbumins / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D017481:Receptors, Somatostatin / Q000819:agonists / Q000187:drug effects / Q000502:physiology*; D012688:Septum Pellucidum / Q000166:cytology; D013004:Somatostatin / Q000008:administration & dosage / Q000494:pharmacology*; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
chemical_list: D010320:Parvalbumins; D017481:Receptors, Somatostatin; C106140:somatostatin receptor sst2A; D013004:Somatostatin; D005680:gamma-Aminobutyric Acid; D015282:Octreotide
references.citation: Neuroscience. 1999 Mar;89(3):909-26
references.pmid: 10199624
references.citation: Neuroscience. 1999 Mar;90(3):859-74
references.pmid: 10218786
references.citation: Neuroscience. 1999;92(2):589-600
references.pmid: 10408608
references.citation: J Comp Neurol. 1999 Sep 13;412(1):69-82
references.pmid: 10440710
references.citation: Exp Brain Res. 1999 Aug;127(3):244-58
references.pmid: 10452212
references.citation: Invest Ophthalmol Vis Sci. 1999 Sep;40(10):2376-82
references.pmid: 10476805
references.citation: Neuroscience. 1999;94(3):775-83
references.pmid: 10579568
references.citation: J Neurosci. 2000 Feb 1;20(3):1179-89
references.pmid: 10648722
references.citation: J Neurosci. 2000 May 15;20(10):3785-97
references.pmid: 10804219
references.citation: Neuroscience. 2000;98(4):661-8
references.pmid: 10891609
references.citation: J Neurophysiol. 2001 Apr;85(4):1709-18
references.pmid: 11287493
references.citation: Mol Cell Neurosci. 2001 Apr;17(4):646-61
references.pmid: 11312601
references.citation: Neuron. 2002 Jan 31;33(3):325-40
references.pmid: 11832222
references.citation: J Neurosci. 2002 Jul 1;22(13):5374-86
references.pmid: 12097489
references.citation: J Comp Neurol. 2002 Dec 9;454(2):192-9
references.pmid: 12412143
references.citation: J Physiol. 2003 Jan 1;546(Pt 1):101-17
references.pmid: 12509482
references.citation: Endocrinology. 2003 Apr;144(4):1564-73
references.pmid: 12639941
references.citation: Eur J Neurosci. 2003 May;17(9):1861-72
references.pmid: 12752786
references.citation: J Physiol. 2003 Sep 15;551(Pt 3):927-43
references.pmid: 12865506
references.citation: Brain Res. 2004 Apr 23;1006(1):74-86
references.pmid: 15047026
references.citation: J Neurosci. 2004 Apr 7;24(14):3527-36
references.pmid: 15071100
references.citation: Eur J Neurosci. 2004 Apr;19(8):2299-309
references.pmid: 15090056
references.citation: Eur J Neurosci. 2004 May;19(10):2753-68
references.pmid: 15147309
references.citation: Hippocampus. 2004;14(4):510-25
references.pmid: 15224986
references.citation: Eur J Neurosci. 2004 Oct;20(8):2149-58
references.pmid: 15450094
references.citation: J Neurosci. 2004 Sep 29;24(39):8470-9
references.pmid: 15456820
references.citation: Neuroscience. 1992;48(2):353-62
references.pmid: 1603324
references.citation: Neuroscience. 1991;42(2):451-62
references.pmid: 1680227
references.citation: Brain Res. 1989 Sep 18;497(2):315-24
references.pmid: 2573406
references.citation: Proc Natl Acad Sci U S A. 1986 Oct;83(19):7518-21
references.pmid: 2876428
references.citation: Brain Res. 1989 Jan 30;478(2):375-81
references.pmid: 2924136
references.citation: Nature. 1988 Nov 10;336(6195):170-3
references.pmid: 3185735
references.citation: J Comp Neurol. 1985 Sep 8;239(2):237-46
references.pmid: 4044938
references.citation: Biophys J. 1967 Jul;7(4):391-418
references.pmid: 4292791
references.citation: Proc Natl Acad Sci U S A. 1982 May;79(10):3355-9
references.pmid: 6124970
references.citation: Neuroscience. 1984 Oct;13(2):265-339
references.pmid: 6514182
references.citation: Anat Embryol (Berl). 1984;169(1):41-4
references.pmid: 6721220
references.citation: J Neurosci. 1993 Sep;13(9):3712-24
references.pmid: 7690065
references.citation: Neuroscience. 1994 Oct;62(4):1033-47
references.pmid: 7845584
references.citation: J Neurosci. 1996 Jul 15;16(14):4468-78
references.pmid: 8699257
references.citation: J Neurosci Methods. 1996 Apr;65(2):113-36
references.pmid: 8740589
references.citation: J Physiol. 1996 Jul 1;494 ( Pt 1):201-15
references.pmid: 8814616
references.citation: J Neurosci. 1996 Oct 1;16(19):6000-11
references.pmid: 8815883
references.citation: Synapse. 1996 Jan;22(1):15-27
references.pmid: 8822474
references.citation: J Neurophysiol. 1996 Sep;76(3):1657-66
references.pmid: 8890283
references.citation: Neuroscience. 1997 Jan;76(1):225-40
references.pmid: 8971774
references.citation: J Physiol. 1997 Apr 15;500 ( Pt 2):463-74
references.pmid: 9147330
references.citation: Exp Brain Res. 1997 May;114(3):442-53
references.pmid: 9187280
references.citation: Brain Res Mol Brain Res. 1997 Oct 3;49(1-2):82-8
references.pmid: 9387866
references.citation: J Neurosci. 1998 Feb 1;18(3):1056-71
references.pmid: 9437026
references.citation: J Neurophysiol. 1998 Mar;79(3):1230-8
references.pmid: 9497404
references.citation: J Neurophysiol. 1998 Apr;79(4):1633-42
references.pmid: 9535934
references.citation: J Neurosci. 1998 Jul 1;18(13):4938-45
references.pmid: 9634559
references.citation: Neuron. 1998 Jul;21(1):9-12
references.pmid: 9697847
references.citation: Eur J Neurosci. 1998 Feb;10(2):464-77
references.pmid: 9749709