title: Study of projections from the entopeduncular nucleus to the thalamus of the rat.
abstract: The entopeduncular nucleus (EP) is a major outflow nucleus of the basal ganglia and innervates the lateral habenula, parafascicular, pedunculopontine, ventrolateral (VL), ventromedial (VM), and mediodorsal thalamic nuclei. This study investigated the morphology of single axons of entopeduncular neurons projecting to the motor thalamus by placing small injections of dextran biotin into the EP and reconstructing drawings of single axons from serial sections. There were two populations of entopeduncular-thalamic projection axons: those that projected only to the motor thalamus (VL and VM) and those that projected to both the motor thalamus and other nuclei (e.g., the habenula). The neurochemistry of EP neurons projecting to the thalamus was investigated by injecting the retrograde tracer FluoroGold into the VL and VM thalamic nuclei to retrogradely fill entopeduncular projection neurons. These were subsequently immunohistochemically labeled for choline acetyl transferase, gamma-aminobutyric acid (GABA), and glutamate. Consistent with previous studies, significant proportions of these neurons were GABA immunoreactive. In addition, approximately half of the entopeduncular-thalamic projecting neurons were found to be cholinergic. This excitatory input is most likely derived from axons that branch as they pass through the motor thalamus to the lateral habenula.
authors.affiliation: Department of Medicine, Monash Medical Centre, Clayton 3168, Victoria, Australia.
authors.forename: H T
authors.initials: HT
authors.lastname: Kha
authors.forename: D I
authors.initials: DI
authors.lastname: Finkelstein
authors.forename: D V
authors.initials: DV
authors.lastname: Pow
authors.forename: A J
authors.initials: AJ
authors.lastname: Lawrence
authors.forename: M K
authors.initials: MK
authors.lastname: Horne
mesh_terms: D000818:Animals; D001369:Axons / Q000502:physiology; D002352:Carrier Proteins / Q000378:metabolism; D002795:Choline O-Acetyltransferase / Q000378:metabolism; D020392:Entopeduncular Nucleus / Q000166:cytology / Q000502:physiology*; D005456:Fluorescent Dyes; D018698:Glutamic Acid / Q000378:metabolism; D007150:Immunohistochemistry; D008297:Male; D026901:Membrane Transport Proteins; D009474:Neurons / Q000502:physiology; D051381:Rats / Q000502:physiology*; D017208:Rats, Wistar; D013266:Stilbamidines; D009435:Synaptic Transmission / Q000502:physiology*; D013788:Thalamus / Q000502:physiology*; D050494:Vesicular Acetylcholine Transport Proteins; D033921:Vesicular Transport Proteins; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: C049774:2-hydroxy-4,4'-diamidinostilbene, methanesulfonate salt; D002352:Carrier Proteins; D005456:Fluorescent Dyes; D026901:Membrane Transport Proteins; C493461:Slc18a3 protein, rat; D013266:Stilbamidines; D050494:Vesicular Acetylcholine Transport Proteins; D033921:Vesicular Transport Proteins; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D002795:Choline O-Acetyltransferase