Article

The histaminergic innervation of the lateral geniculate complex in the cat.

Department of Anatomy, University of Wisconsin Medical School, Madison 53706.
Visual Neuroscience (impact factor: 2.23). 10(2):225-35. pp.225-35
Source: PubMed

ABSTRACT The histaminergic innervation of the thalamic dorsal and ventral lateral geniculate nuclei and the perigeniculate nucleus of the cat was examined immunohistochemically by means of an antibody to histamine. We find histamine-immunoreactive neurons in the cat brain are concentrated in the ventrolateral portion of the posterior hypothalamus, confirming a previous report. However, this cell group also spreads into medial, dorsal, and extreme lateral regions of the posterior hypothalamus and extends as far rostral as the optic chiasm. Histamine-labeled fibers cover all regions of the lateral geniculate complex, but the density of labeling varies. The ventral lateral geniculate nucleus (vLGN) is most densely labeled, the A laminae of the dorsal lateral geniculate are sparsely labeled, and the geniculate C laminae and the perigeniculate nucleus show intermediate amounts of label. Thus, histaminergic fibers demonstrate a predilection for zones innervated by the W-cell system. Labeled fibers exhibit few branchings and numerous en passant swellings, lending a beaded appearance. The vLGN showed more instances of fibers with larger-sized swellings (up to 2 microns). Following injections of biotinylated tracers into the hypothalamus, we find labeled fibers throughout the lateral geniculate complex. The anterogradely labeled fibers resemble the histaminergic fibers in morphology, distribution, and relative bouton size. Thus, the hypothalamus appears to be the source of the histaminergic fibers in the lateral geniculate complex. Histamine-labeled fibers in the dorsal lateral geniculate nucleus (dLGN) exhibit uncommon ultrastructural morphology. Many extremely large, round, or elliptical vesicles fill the fiber swellings. Swellings are directly apposed to a variety of other dendritic and axonal profiles, but thus far no convincing synaptic contacts have been seen. The distribution and appearance of these histaminergic fibers resembles those reported for serotonergic fibers. Our results support the idea that histamine works nonsynaptically as a neuromodulator in the lateral geniculate complex, affecting the level of visual arousal.

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    Article: Histamine immunoreactive axons in the macaque retina.
    M J Gastinger, J J O'Brien, N B Larsen, D W Marshak
    [show abstract] [hide abstract]
    ABSTRACT: The goal of these experiments was to identify the neurotransmitter in centrifugal axons of the macaque retina. Macaca mulatta retinas and optic nerves were fixed overnight in carbodiimide and labeled with an antiserum to histamine with the use of an immunofluorescence technique. Several large histamine-immunoreactive axons ran from the optic nerve head to the peripheral retina, where they branched extensively and terminated in the inner plexiform layer, occasionally alongside retinal blood vessels. Other axons that emerged from the optic nerve head ran in the optic fiber layer to the central retina, circled the fovea, and then returned to the optic disc. These may be the source of histamine-immunoreactive axons that have been observed in central visual areas. No labeled cell bodies were present in the retina. Because perikarya in the posterior hypothalamus are the only known source of histamine in the primate central nervous system and because neurons there can be retrogradely labeled from the cut optic nerve, the histamine-immunoreactive axons must have originated there. Centrifugal axons in the macaque retina are part of the system of axons containing histamine that originate in the hypothalamus and project throughout the brain. Because the activity of these neurons is highest during the morning, histamine might play a role in preparing the retina to operate in daylight. The contacts of histamine-immunoreactive axons with blood vessels suggest that histamine may also play a role in regulating the retinal microvasculature.
    Investigative Ophthalmology &amp Visual Science 03/1999; 40(2):487-95. · 3.60 Impact Factor
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.

Keywords

convincing synaptic contacts
 
dorsal lateral geniculate
 
dorsal lateral geniculate nucleus
 
elliptical vesicles
 
fiber swellings
 
histamine works nonsynaptically
 
histamine-immunoreactive neurons
 
histaminergic innervation
 
larger-sized swellings
 
lateral geniculate complex
 
numerous en passant swellings
 
optic chiasm
 
perigeniculate nucleus
 
previous report
 
results support
 
serotonergic fibers
 
ventral lateral geniculate nucleus
 
ventrolateral portion
 
visual arousal
 
zones innervated
 

D J Uhlrich