Histological and Lectin Histochemical Studies on the Main and Accessory Olfactory Bulbs in the Japanese Striped Snake, <i>Elaphe quadrivirgata</i>

Abstract

ABSTRACT. The main and accessory olfactory bulbs were examined by histological methods and lectin histochemistry in the Japanese striped snake. As the results, the histological properties are similar between the main olfactory bulb and the accessory olfactory bulb. In lectin histochemistry, 21 lectins used in this study showed similar binding patterns in the main olfactory bulb and the accessory olfactory bulb. In detail, 15 lectins stained these olfactory bulbs with similar manner, and 6 lectins did not stain them at all. Two lectins, Lycopersicon esculentum lectin (LEL) and Solanum tuberosum lectin (STL), stained the nerve and glomerular layers and did not stain any other layers in both olfactory bulbs. Four lectins, Soybean agglutinin (SBA), Vicia villosa agglutinin (VVA), Peanut agglutinin (PNA) and Phaseolus vulgaris agglutinin-L (PHA-L) stained the nerve and glomerular layers more intensely than other layers in both olfactory bulbs. In addition, VVA showed the dot-like stainings in the glomeruli of both olfactory bulbs. These findings suggest that the degree of development and the properties of glycoconjugates are similar between the main olfactory bulb and the accessory olfactory bulb in the Japanese striped snake.

Subpopulations of Projection Neurons in the Olfactory Bulb

“…Whether a single OSN of reptiles projects unbranched axon to a single glomerulus has not been clearly described. The MOB of reptiles also exhibits a distinct layer structure in which the GL, EPL, MCL, and GCL are clearly visible, however, they may have a thicker IPL than mammalian OB ( Kirillova and Lin, 1998 ; Pinato and Midtgaard, 2003 ; Kondoh et al, 2013 ). Mitral cells are distributed throughout the MCL in the turtle OB ( Kirillova and Lin, 1998 ).…”

“…In fact, the mitral cells observed in the EPL of the lizard OB are described as displaced mitral cells ( Llahi et al, 1985 ). Cells varying in soma size were identified in the EPL and MCL of the snake MOB ( Kondoh et al, 2013 ), and the Japanese striped snake has two mitral cell types that are morphologically distinct based on the somata locations within the MCL ( Iwahori et al, 1989 ). These support a concept suggestive of a transition between mitral cells and tufted cells.…”

“…However, in contrast to the mammalian OB projection neurons, some axons from the snake MOB enter the ipsilateral stria medullaris thalami, cross the midline in the habenular commissure, enter the contralateral stria medullaris thalami and terminate in the contralateral lateral pallium ( Halpern, 1976 ; Lanuza and Halpern, 1998 ). The accessory olfactory system becomes more noticeable in reptiles compared to amphibians considering that the AOB is caudally located and clearly separated from the MOB ( Martínez-Marcos and Halpern, 2009 ; Ubeda-Banon et al, 2011 ; Kondoh et al, 2013 ). The AOB mitral cells in the reptile give rise to more than one primary dendrite with multiple tufts in the GL ( Llahi et al, 1985 ).…”

Phylogenic Studies on the Olfactory System in Vertebrates

“…The dorsomedial and the most of the dorsolateral wall of the nasal cavity is covered with the OE, while the ventral wall and a part of the dorsolateral wall of the nasal cavity are covered with the non-sensory epithelium. The projection pattern of the OE to the MOB is almost the same as in lizards and mammals; and the MOB also shows the similar cytoarchitecture to lizards and mammals and corresponds to the mammal-type MOB [15]. That is, the MOB in snakes corresponds to mammal-type MOB.…”