Author(s): M. Naushad A Dilkash, Syed Sayeed Ahmed and Aijaz Ahmed Khan
Trigeminal ganglion (TRG) consists of collection of primary sensory neurons. The different subsets of neurons have been identified on the basis of morphological and neurochemical characteristics. It remains to be resolved as to whether the various neuronal subsets remain alike across the mammalian species and if there exists some species specific characteristic neurons. The present study was conducted on adult mammals (rat, rabbit, and goat) of either sex. TRG of both sides were procured and fixed in 10% buffered formalin and processed for paraffin embedding. 10 μm thick sections stained with Haematoxylin and Eosin were examined under light microscope and relevant findings were recorded in photomicrographs. It was noticed that the main cellular constituents (neuron and glia) of TRG could be easily identified and features of most of the neurons matched with earlier light microscopic descriptions [1, 2]. However, few neurons in the present study revealed certain additional features. For example – in the medium size neuron, large Nissl granules formed single peripheral ring; in the medium and large sized neurons, coarse Nissl granules formed two concentric (perinuclear and peripheral) rings; and a couple of neurons appeared to share common sheath – a kin to binucleate neurons. In addition, the neuronal somatic size appeared to have direct relationship with the body size of the animal. The number of nucleoli and Cajal bodies per neuron and the number of cells involved in the formation of satellite glial cell (SGC)-sheath could be correlated with the size of neuronal somata. It was concluded that the neuronal subgroups of mammalian TRG remain fairly similar across the species. However some less common neurons with single and double rings of coarse Nissl granules need suitable categorization with respect to their neurochemical and functional characteristics.