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Functional Neuroanatomy of the Rat Nucleus Incertus–Medial Septum Tract: Implications for the Cell-Specific Control of the Septohippocampal Pathway

Authors :
Agata Szlaga
Patryk Sambak
Aleksandra Trenk
Anna Gugula
Caitlin E. Singleton
Gniewosz Drwiega
Tomasz Blasiak
Sherie Ma
Andrew L. Gundlach
Anna Blasiak
Source :
Frontiers in Cellular Neuroscience, Vol 16 (2022)
Publication Year :
2022
Publisher :
Frontiers Media S.A., 2022.

Abstract

The medial septum (MS) is critically involved in theta rhythmogenesis and control of the hippocampal network, with which it is reciprocally connected. MS activity is influenced by brainstem structures, including the stress-sensitive, nucleus incertus (NI), the main source of the neuropeptide relaxin-3 (RLN3). In the current study, we conducted a comprehensive neurochemical and electrophysiological characterization of NI neurons innervating the MS in the rat, by employing classical and viral-based neural tract-tracing and electrophysiological approaches, and multiplex fluorescent in situ hybridization. We confirmed earlier reports that the MS is innervated by RLN3 NI neurons and documented putative glutamatergic (vGlut2 mRNA-expressing) neurons as a relevant NI neuronal population within the NI–MS tract. Moreover, we observed that NI neurons innervating MS can display a dual phenotype for GABAergic and glutamatergic neurotransmission, and that 40% of MS-projecting NI neurons express the corticotropin-releasing hormone-1 receptor. We demonstrated that an identified cholecystokinin (CCK)-positive NI neuronal population is part of the NI–MS tract, and that RLN3 and CCK NI neurons belong to a neuronal pool expressing the calcium-binding proteins, calbindin and calretinin. Finally, our electrophysiological studies revealed that MS is innervated by A-type potassium current-expressing, type I NI neurons, and that type I and II NI neurons differ markedly in their neurophysiological properties. Together these findings indicate that the MS is controlled by a discrete NI neuronal network with specific electrophysiological and neurochemical features; and these data are of particular importance for understanding neuronal mechanisms underlying the control of the septohippocampal system and related behaviors.

Details

Language :
English
ISSN :
16625102
Volume :
16
Database :
Directory of Open Access Journals
Journal :
Frontiers in Cellular Neuroscience
Publication Type :
Academic Journal
Accession number :
edsdoj.80f2bb38e68e4b8a93b3657edcda2d7a
Document Type :
article
Full Text :
https://doi.org/10.3389/fncel.2022.836116