title: Whisker-related circuitry in the trigeminal nucleus principalis: ultrastructure.
abstract: Trigeminal (V) nucleus principalis (PrV) is the requisite brainstem nucleus in the whisker-to-barrel cortex model system that is widely used to reveal mechanisms of map formation and information processing. Yet, little is known of the actual PrV circuitry. In the ventral "barrelette" portion of the adult mouse PrV, relationships between V primary afferent terminals, thalamic-projecting PrV neurons, and gamma-aminobutyric acid (GABA)-ergic terminals were analyzed in the electron microscope. Primary afferents, thalamic-projecting cells, and GABAergic terminals were labeled, respectively, by Neurobiotin injections in the V ganglion, horseradish peroxidase injections in the thalamus, and postembedding immunogold histochemistry. Primary afferent terminals (Neurobiotin- and glutamate-immunoreactive) display asymmetric and multiple synapses predominantly upon the distal dendrites and spines of PrV cells that project to the thalamus. Primary afferents also synapse upon GABAergic terminals. GABAergic terminals display symmetric synapses onto primary afferent terminals, the somata and dendrites (distal, mostly) of thalamic-projecting neurons, and GABAergic dendrites. Thus, primary afferent inputs through the PrV are subject to pre- and postsynaptic GABAergic influences. As such, circuitry exists in PrV "barrelettes" for primary afferents to directly activate thalamic-projecting and inhibitory local circuit cells. The latter are synaptically associated with themselves, the primary afferents, and with the thalamic-projecting neurons. Thus, whisker-related primary afferent inputs through PrV projection neurons are pre- and postsynaptically modulated by local circuits.
authors.affiliation: Department of Neurology, Washington University School of Medicine , St Louis, MO , USA.
authors.forename: Chuanxi
authors.initials: C
authors.lastname: Xiang
authors.forename: Joop J A
authors.initials: JJ
authors.lastname: Arends
authors.forename: Mark F
authors.initials: MF
authors.lastname: Jacquin
mesh_terms: D000344:Afferent Pathways / Q000502:physiology* / Q000648:ultrastructure*; D000818:Animals; D001710:Biotin / Q000031:analogs & derivatives / Q000378:metabolism; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism; D008297:Male; D051379:Mice; D016253:Microscopy, Immunoelectron; D009415:Nerve Net / Q000000981:diagnostic imaging*; D013569:Synapses / Q000378:metabolism / Q000648:ultrastructure; D014278:Trigeminal Nuclei / Q000648:ultrastructure*; D014463:Ultrasonography; D014738:Vibrissae / Q000294:innervation*; D018998:Wheat Germ Agglutinin-Horseradish Peroxidase Conjugate / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D018998:Wheat Germ Agglutinin-Horseradish Peroxidase Conjugate; C070614:neurobiotin; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D001710:Biotin
keywords: Barrel; GABA; glutamate; principal trigeminal nucleus; synapse; thalamus; vibrissa