title: Gain Modulation of Cholinergic Neurons in the Medial Septum-Diagonal Band of Broca Through Hyperpolarization.
abstract: Hippocampal network oscillations are important for learning and memory. Theta rhythms are involved in attention, navigation, and memory encoding, whereas sharp wave-ripple complexes are involved in memory consolidation. Cholinergic neurons in the medial septum-diagonal band of Broca (MS-DB) influence both types of hippocampal oscillations, promoting theta rhythms and suppressing sharp wave-ripples. They also receive frequency-dependent hyperpolarizing feedback from hippocamposeptal connections, potentially affecting their role as neuromodulators in the septohippocampal circuit. However, little is known about how the integration properties of cholinergic MS-DB neurons change with hyperpolarization. By potentially altering firing behavior in cholinergic neurons, hyperpolarizing feedback from the hippocampal neurons may, in turn, change hippocampal network activity. To study changes in membrane integration properties in cholinergic neurons in response to hyperpolarizing inputs, we used whole-cell patch-clamp recordings targeting genetically labeled, choline acetyltransferase-positive neurons in mouse brain slices. Hyperpolarization of cholinergic MS-DB neurons resulted in a long-lasting decrease in spike firing rate and input-output gain. Additionally, voltage-clamp measures implicated a slowly inactivating, 4-AP-insensitive, outward K+conductance. Using a conductance-based model of cholinergic MS-DB neurons, we show that the ability of this conductance to modulate firing rate and gain depends on the expression of an experimentally verified shallow intrinsic spike frequency-voltage relationship. Together, these findings point to a means through which negative feedback from hippocampal neurons can influence the role of cholinergic MS-DB neurons. © 2016 Wiley Periodicals, Inc.
authors: Department of Bioengineering, University of Utah, Salt Lake City, Utah.
authors: Eric D
authors: 0000-0002-3643-9838
authors: ED
authors: Melonakos
authors: Department of Bioengineering, University of Utah, Salt Lake City, Utah.|Department of Biomedical Engineering, Boston University, Boston, Massachusetts.
authors: John A
authors: JA
authors: White
authors: Department of Bioengineering, University of Utah, Salt Lake City, Utah.|Department of Biomedical Engineering, Boston University, Boston, Massachusetts.
authors: Fernando R
authors: FR
authors: Fernandez
mesh_terms: D000818:Animals; D002414:Cations, Monovalent / Q000378:metabolism; D059329:Cholinergic Neurons / Q000187:drug effects / Q000502:physiology*; D003198:Computer Simulation; D020667:Diagonal Band of Broca / Q000187:drug effects / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D057507:Mice, 129 Strain; D008822:Mice, Transgenic; D008959:Models, Neurological; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D020665:Septum of Brain / Q000187:drug effects / Q000502:physiology*; D046509:Tissue Culture Techniques
chemical_list: D002414:Cations, Monovalent; D011188:Potassium
keywords: acetylcholine; electrophysiology; exponential integrate-and-fire model; spike firing; voltage-gated K+ conductance