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Histaminergic and non-histamine-immunoreactive mast cells within the cat lateral geniculate complex examined with
K A Manning1, T P Pienkowski, D J Uhlrich
1Department of Anatomy, University of Wisconsin Medical School, Madison 53706.
Insights
Mast cells containing histamine are abundant in the cat lateral geniculate complex, influencing neural and vascular functions. These cells are located near blood vessels and neural elements within the thalamus.
Area of Science:
- Neuroscience
- Cell Biology
- Immunology
Background:
- Mast cells are immune cells known for their role in allergic reactions and inflammation.
- Their presence and function within the central nervous system, particularly in sensory processing areas like the lateral geniculate complex, are less understood.
- The lateral geniculate complex is a key structure in the thalamus involved in visual information processing.
Purpose of the Study:
- To investigate the presence, distribution, and ultrastructural characteristics of mast cells in the cat lateral geniculate complex.
- To determine the association of mast cells with blood vessels and neural elements in this brain region.
- To assess the histamine content of mast cells in the lateral geniculate complex.
Main Methods:
- Histamine immunohistochemistry and pinacyanol erythrosinate staining were used to identify mast cells.
- Light and electron microscopy were employed to examine mast cell morphology and location.
- Brain sections from seven normal adult pigmented cats were analyzed.
Main Results:
- Mast cells were widespread throughout the dorsal and ventral lateral geniculate nuclei and surrounding areas, with higher concentrations rostrally and in specific laminae.
- Mast cells were consistently found associated with blood vessels, particularly arterioles, and in close proximity to thalamic neuropil and astrocytes.
- Electron microscopy revealed mast cells located on the brain side of the blood-brain barrier, containing histamine within amorphous or restricted granular areas, and showed a potentially underestimated total mast cell population.
Conclusions:
- Mast cells are a significant cellular component of the cat lateral geniculate complex, with a distinct distribution pattern.
- Their intimate association with vasculature and neural elements suggests a potential role in modulating local vascular and neural functions.
- The presence and histamine content of mast cells indicate their possible involvement in sensory processing within the visual thalamus.
Abstract:
Mast cells and their location in the cat lateral geniculate complex of the thalamus were examined by means of histamine immunohistochemistry and the mast cell stain pinacyanol erythrosinate. Brain sections from seven normal adult pigmented cats were processed for light or electron microscopy. Histamine-containing and pinacyanol erythrosinate-stained mast cells were widespread throughout the dorsal and ventral lateral geniculate nuclei and the surrounding regions. Mast cells were especially numerous rostrally in the complex and in the geniculate C laminae. The cells were found consistently in association with blood vessels, ranging from capillary size to vessels c. 150 microns diameter, and twice as often with arterioles as with venules. Large clusters of many mast cells associated with single blood vessels were seen. Individual mast cells were typically 8 microns in diameter and somewhat oval, although multipolar and crescent-shaped cells were also seen, up to twice as long. The amount of histamine labeling varied across cells. When histamine-labeled material was secondarily stained with pinacyanol erythrosinate, many mast cells were double labeled. In addition, there was a small population of mast cells that stained only with pinacyanol erythrosinate, but was otherwise identical to the histamine-immunoreactive mast cells. Electron microscopic examination showed that the mast cells lie on the brain side of the blood-brain barrier. Mast cells were found in close proximity to the thalamic neuropil, primarily apposed to the processes of astrocytes, but also apposed to neural elements. The distinctive electron-dense cytoplasmic granules in the fully granulated, mature state were largely amorphous in appearance and as large as 700 nm in diameter. Histamine was dispersed throughout some granules and contained within restricted areas of other granules. In degranulated mast cells, large, irregularly shaped, electron-lucent granules were seen fused with the cell membrane on the neuropil side, as well as the lumen side of the mast cell. More mast cells were observed at the electron microscopic level than were expected from the light level observations, which suggests that, despite the numbers of mast cells labeled, these results may still underestimate the total mast cell population present in this region of the thalamus. Mast cells, by their numbers, their distribution and the potent chemical substances they contain, may significantly influence vascular and neural function, directly and indirectly, in the cat lateral geniculate complex.