title: Distribution and intrinsic membrane properties of basal forebrain GABAergic and parvalbumin neurons in the mouse.
abstract: The basal forebrain (BF) strongly regulates cortical activation, sleep homeostasis, and attention. Many BF neurons involved in these processes are GABAergic, including a subpopulation of projection neurons containing the calcium-binding protein, parvalbumin (PV). However, technical difficulties in identification have prevented a precise mapping of the distribution of GABAergic and GABA/PV+ neurons in the mouse or a determination of their intrinsic membrane properties. Here we used mice expressing fluorescent proteins in GABAergic (GAD67-GFP knock-in mice) or PV+ neurons (PV-Tomato mice) to study these neurons. Immunohistochemical staining for GABA in GAD67-GFP mice confirmed that GFP selectively labeled BF GABAergic neurons. GFP+ neurons and fibers were distributed throughout the BF, with the highest density in the magnocellular preoptic area (MCPO). Immunohistochemistry for PV indicated that the majority of PV+ neurons in the BF were large (>20 μm) or medium-sized (15-20 μm) GFP+ neurons. Most medium and large-sized BF GFP+ neurons, including those retrogradely labeled from the neocortex, were fast-firing and spontaneously active in vitro. They exhibited prominent hyperpolarization-activated inward currents and subthreshold "spikelets," suggestive of electrical coupling. PV+ neurons recorded in PV-Tomato mice had similar properties but had significantly narrower action potentials and a higher maximal firing frequency. Another population of smaller GFP+ neurons had properties similar to striatal projection neurons. The fast firing and electrical coupling of BF GABA/PV+ neurons, together with their projections to cortical interneurons and the thalamic reticular nucleus, suggest a strong and synchronous control of the neocortical fast rhythms typical of wakefulness and REM sleep.
authors.affiliation: Laboratory of Neuroscience, VA Boston Healthcare System and Harvard Medical School, Department of Psychiatry, Brockton, Massachusetts, 02301, USA.
authors.forename: James T
authors.initials: JT
authors.lastname: McKenna
authors.forename: Chun
authors.initials: C
authors.lastname: Yang
authors.forename: Serena
authors.initials: S
authors.lastname: Franciosi
authors.forename: Stuart
authors.initials: S
authors.lastname: Winston
authors.forename: Kathleen K
authors.initials: KK
authors.lastname: Abarr
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Rigby
authors.forename: Yuchio
authors.initials: Y
authors.lastname: Yanagawa
authors.forename: Robert W
authors.initials: RW
authors.lastname: McCarley
authors.forename: Ritchie E
authors.initials: RE
authors.lastname: Brown
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism*; D059330:GABAergic Neurons / Q000737:chemistry / Q000378:metabolism*; D055879:Gene Knock-In Techniques; D005968:Glutamate Decarboxylase / Q000032:analysis / Q000096:biosynthesis; D008297:Male; D051379:Mice; D010320:Parvalbumins / Q000032:analysis / Q000378:metabolism*; D016548:Prosencephalon / Q000737:chemistry / Q000378:metabolism*
chemical_list: D010320:Parvalbumins; D005968:Glutamate Decarboxylase; C402565:glutamate decarboxylase 1