title: Medial septum-diagonal band of Broca (MSDB) GABAergic regulation of hippocampal acetylcholine efflux is dependent on cognitive demands.
abstract: The septohippocampal pathway contains cholinergic, GABAergic, and glutamatergic projections and has an established role in learning, memory, and hippocampal theta rhythm. Both GABAergic and cholinergic neurons in the medial septum-diagonal band of Broca (MSDB) have been associated with spatial memory, but the relationship between the two neuronal populations is not fully understood. The present study investigated the effect of selective GABAergic MSDB lesions on hippocampal acetylcholine (ACh) efflux and spatial memory during tasks that varied in memory demand. Male Sprague Dawley rats were given GABAergic lesions of the MSDB using GAT1-saporin (GAT1-SAP) and examined on spontaneous exploration (Experiment 1) and non-matching to position without (NMTP; Experiment 2) and with a delay (DNMTP; Experiment 3), while concurrently using in vivo microdialysis to measure hippocampal ACh efflux. Intraseptal GAT1-SAP treatment did not alter baseline or behaviorally stimulated hippocampal ACh efflux or maze exploration (Experiment 1). Moreover, GAT1-SAP did not alter evoked hippocampal ACh efflux related to NMTP nor did it impair working memory in NMTP (Experiment 2). In contrast, both ACh efflux and performance in DNMTP were impaired by intraseptal GAT1-SAP. Thus, GABAergic MSDB neurons are important for spatial working memory and modulate hippocampal ACh efflux under conditions of high memory load. The relationship between the septohippocampal cholinergic and GABAergic systems and working memory will be discussed.
authors.affiliation: Neurobehavioral Research Laboratory, Department of Veterans Affairs Medical Center-New Jersey Health Care System, East Orange, New Jersey 07018, Stress and Motivated Behavior Institute and Graduate School of Biomedical Sciences, New Jersey Medical School-Rutgers University, Newark, New Jersey 07103, Center for Molecular and Behavioral Neuroscience, Rutgers University, Newark, New Jersey 07102, and Behavioral Neuroscience Program, Binghamton University, Binghamton, New York 13902.
authors.forename: Jessica J
authors.initials: JJ
authors.lastname: Roland
authors.forename: Amanda L
authors.initials: AL
authors.lastname: Stewart
authors.forename: Kellie L
authors.initials: KL
authors.lastname: Janke
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Gielow
authors.forename: John A
authors.initials: JA
authors.lastname: Kostek
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Savage
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Servatius
authors.forename: Kevin C H
authors.initials: KC
authors.lastname: Pang
mesh_terms: D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003071:Cognition / Q000502:physiology*; D006624:Hippocampus / Q000378:metabolism*; D007150:Immunohistochemistry; D008297:Male; D017551:Microdialysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D012686:Septal Nuclei / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D005680:gamma-Aminobutyric Acid; D000109:Acetylcholine
keywords: GAT1-saporin; T-maze; hippocampus; learning; microdialysis; working memory