Browsing by Subject "Tachykinins"

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    Molecular Segmentation of the Spinal Trigeminal Nucleus in the Adult Mouse Brain
    (Frontiers Media, 2021-12-10) García-Guillén, Isabel M.; Martínez-de-la-Torre, Margaret; Puelles, Luis; Aroca Tejedor, Pilar; Marín San Leandro, Faustino; Anatomía Humana y Psicobiología
    The trigeminal column is a hindbrain structure formed by second order sensory neurons that receive afferences from trigeminal primary (ganglionic) nerve fibers. Classical studies subdivide it into the principal sensory trigeminal nucleus located next to the pontine nerve root, and the spinal trigeminal nucleus which in turn consists of oral, interpolar and caudal subnuclei. On the other hand, according to the prosomeric model, this column would be subdivided into segmental units derived from respective rhombomeres. Experimental studies have mapped the principal sensory trigeminal nucleus to pontine rhombomeres (r) r2-r3 in the mouse. The spinal trigeminal nucleus emerges as a plurisegmental formation covering several rhombomeres (r4 to r11 in mice) across pontine, retropontine and medullary hindbrain regions. In the present work we reexamined the issue of rhombomeric vs. classical subdivisions of this column. To this end, we analyzed its subdivisions in an AZIN2-lacZ transgenic mouse, known as a reference model for hindbrain topography, together with transgenic reporter lines for trigeminal fibers. We screened as well for genes differentially expressed along the axial dimension of this structure in the adult and juvenile mouse brain. This analysis yielded genes from multiple functional families that display transverse domains fitting the mentioned rhombomeric map. The spinal trigeminal nucleus thus represents a plurisegmental structure with a series of distinct neuromeric units having unique combinatorial molecular profiles.
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    Substance P: A neurotransmitter of amacrine and ganglion cells in the vertebrate retina
    (Murcia : F. Hernández, 1995) Kolb, H.; Fernández, E.; Ammermüller, J.; Cuenca, N.
    A short history and summary of the occurrence of substance P in the vertebrate body is presented. Substance P is now generally accepted to be a neurotransmitter and can be visualized by immunocytochemistry to occur in various nerve cells in the CNS. In the retina, substance P-immunoreactivity (SP-IR) occurs in amacrine cell populations in al1 the species so far studied. In some vertebrates retinas SP is also apparent in one or more ganglion cell types. Anatomical investigations have revealed the morphology and connectivity of SP-IR amacrine cells: they branch in severa1 strata of the inner plexiform layer receiving input from bipolar and amacrine cells and making synapses upon bipolar and ganglion cells. Most commonly SP-IR amacrines emit axon-like process that pass to both the outer plexiform layer and the ganglion cell and nerve fiber layers. These processes often end upon the retina1 vasculature. SP-IR ganglion cells have been described in turtle, rabbit and human retinas. In turtle, intracellular dye injection has revealed the morphology of one type of SPIR ganglion cell as being a large-field monostratified cell with a branches in the outer stratum of the inner plexiform layer. It may correspond to a «Dogiel cell» type. Intracellular investigation of SP-IR amacrine cells in turtle reveal their physiological responses to be ONOFF in nature with some color-coding characteristics. In general SP acts as an excitatory neurotransmitter raising the spontaneous activity leve1 of ganglion cell responses. The SP-IR ganglion cell is an OFF-center unit in the turtle retina and may be driven in the center of its receptive field by luminosity bipolar cells and in its surround by amacrine cells with color-opponent properties.