Morphological and Quantitative Study of Neurons in the Gracile Nucleus of the Camel Brain Stem

Abstract

Neurons in the gracile nucleus of the camel brain stem were studied by Golgi method. Neurons were classified based on soma size and shape, density of dendritic tree, morphology and distribution of appendages. Six types of neurons were identified. Type I neurons had very large somata with appendages on their somata and distal dendrites. Type II neurons had large somata and almost smooth dendrites. Type III neurons displayed medium size somata with dendritic appendages of different forms. Type IV neurons were small to medium spheroidal or triangular neurons. Somata and dendrites of these neurons had appendages of different forms. Type V medium-size neurons had bipolar, round or fusiform somata and poorly branching dendritic tree. Some spines and appendages were seen on somata and dendrites of these neurons. Neurons of type VI were medium-size unipolar, round or fusiform with spines on their dendrites. The radiating branching pattern was more common than the tufted for all types of neurons. Wide overlap between widths of dendrites of different orders was found for all neuronal types. Hopefully, this study will improve our understanding of the role of the gracile nucleus as major center for sensory information processing and contribute to our understanding of comparative neuroanatomy and neurophysiology

A Golgi Study of the Camel Cuneate Nucleus

“…In camel, at least six main types of nerve cells were found in the Cu in this study. Both similarities and differences were found between these neurons and neuronal types found in the Gr of the camel in our previous study (Al‐Hussain et al, 2012) and neuronal types described in previous studies in in the Cu of small mammals such as rat (Basbaum and Hand, 1973) and monkey (Biedenbach, 1972). Unfortunately, neurons in the Cu of large mammals were not described before.…”

“…In general, most of neuronal types observed in the Gr had larger somata and lesser somatic and dendritic appendages comparing to neuronal types observed in the Cu. Although, both of the Cu and Gr nuclei were processed together in the same sections, no very large neurons similar to the very large neurons (somata mean diameters greater than 45 μm and may reach 74 μm) found in the Gr (Al‐Hussain et al, 2012) were found in the Cu. Large neurons with somatic mean diameters ranging from 26 to 40 μm include type I and type IIa neurons of the Cu and type II neurons of the Gr.…”

“…Despite these studies, neuronal classifications according to dendritic pattern and presence or absence of different types of dendritic appandages in the Cu of certain species of large mammals were not described before. Recently, we described six types of neurons in the Gr of the camel (Al‐Hussain et al, 2012). No other published studies concerning neurons in the DCN of the camel or any other large mammal were found in published literature.…”

Functional and Anatomical Features of the Dorsal Column Nuclei in Mammals and Lower Animals

“…Golgi and/or Nissl studies of the DCN in rat [33,38], cat, [29,30,36,39] monkey [40] and camel [41,42] showed that it contain a heterogeneous neuronal population of various shapes and somata diameters (7µm -74µm). Using horseradish peroxidase (HRP) injection into ventropostero-lateral nucleus in the cat thalamus, gracilothalamic projection neurons identified as large cells (≥18µm in diameter) confined to a region known as the "cell nest region" [43,44].…”

“…The large size and heavy duties of the camel may create need to develop sophisticated balance system including well developed DCN (Figure 7). Recent Golgi studies on the camel Gr [41] and Cu [42] revealed the presence of a wide variety of neurons comprising a broad spectrum of sizes, shapes, dendritic density, dendritic branching pattern, somatic spines and appendages and dendritic spines and appendages. These studies demonstrated certain complex morphological features of neurons in the camel DCN such as wide variation of somatic and dendritic spines and appendages, flower-like dendritic ends, spiny axons and profusely branched axons.…”