www.ijcmr.com International Journal of Contemporary Medical Research ISSN (Online): 2393-915X; (Print): 2454-7379 | ICV: 50.43 | Volume 3 | Issue 4 | April 2016 1023 Segments of Spinal Cord Harbouring Motor Neuron Somata of Median Nerve in Rabbit Israr Ahmad Khan 1 , Farhan Kirmani 2 , Mohd Imran 3 ORIGINAL RESEARCH ABSTRACT Introduction: Median nerve is the main nerve of forearm. With knowledge of location of motor roots we can explain motor loss of different muscles of forearm. The study was conducted with an aim to see the segments of spinal cord har- bouring motor neuron somata of median nerve in rabbit. Material and methods: Six New Zealand white adult rabbits were used in the study. Retrograde changes, chromatolysis in- cluding cell body response were induced in the motor neuron somata of median nerve by sectioning the nerve of left side under general anaesthesia. The right side was used as control. The animals were sacriiced at an interval of 8 to 28 days after operation and perfusion ixed in 10% buffered formalin. Cer- vical spinal cord segments (C4-C8) and thoracic spinal cord segments (T1 and T2) were processed for parafin embedding. 40-micron thick serial transverse sections were obtained and stained with thionine. The stained sections were examined microscopically to identify the neuron somata showing retro- grade changes including chromatolysis. Results: Chromatolysis (or cell body response) was observed in the caudal part of ifth cervical (C-5) segment, the whole length of sixth to eighth cervical (C6-C8) segment and up to the middle of irst thoracic (T-1) segment. Conclusion: The length of the spinal cord harbouring motor neuron somata of median nerve extends from the caudal part of ifth cervical (C-5) segment up to the middle of irst thorac- ic (T-1) segment. Keywords: motor neuron somata, spinal cord segment, medi- an nerve, chromatolysis INTRODUCTION Nervous system is the system that controls and co-ordinates other systems of body. It consist of highly specialized cells called neuron and neuroglia cells which are supporting cells. Most neurons consist of a central mass of cytoplasm within a limiting cell membrane, the cell body, perikaryon or soma, from which extend a number of branched processes, or neu- rites. One of these, the axon, is usually much longer than the others and conducts information away from the cell body. The other processes are termed dendrites and these typically conduct information towards the soma (cell body). Nerve cell bodies stained with basophilic dyes such as thio- nine, cresyl violet, toluidine blue etc. show numerous mi- croscopic clumps of Nissl granules or Nissl bodies, which consists of rough endoplasmic reticulum and associated ri- bosomal RNA. 1 When the axon is cut (axotomy), typical morphological changes can be seen in the cell body. There is swelling of the cell and the apparent disappearance of Nissl granules. All these changes are termed as Chromatolysis. 2 There is migra- tion of the nucleus towards the periphery of the cell and an increase in the size of the nucleus, nucleolus, and cell body. However, it has become increasingly clear that the morpho- logical manifestations of this response are different in dif- ferent cells, and the chromatolysis itself is not invariably seen. 3 Hence the term "axon reaction", "retrograde reaction" or "cell body response"(CBR) have come to be considered more appropriate to designate the whole range of alterations that may occur. 4-6 We can see the location of motor neuron somata of different nerves by producing chromatolysis or cell body response (CBR) in different animals. Location of motor neuron somata of different nerves supplying forelimb muscles have been studied by retrograde cell degeneration technique, by electrophysiological method, and by retro- grade axonal transport of horseradish peroxidase (HRP). 3,7-18 These studies have shown the locations of motor neuron so- mata of major forelimb nerves in the cervical enlargement of spinal cord. The aim of present study is to ind out cranio-caudal extent of spinal cord that harbours the motor neuron somata of the median nerve in rabbit. MATERIAL AND METHODS Six adult New Zealand white rabbits were used in this study. Three of them were females and three of them were males. The median nerve was cut in axilla just after where the two roots are meeting together to form the trunk of median nerve, on left side. The right side was used as control. The operations were performed under general anaesthesia and aseptic conditions. Ether was used for general anaes- thesia and inhalation route was used. The median nerve was exposed in left axilla and cut. A part of the trunk of nerve was also removed from the site of the cut to prevent reunion. Then the animals were sacriiced with an overdose of chlo- roform at intervals of 8 to 28 days after operation. They were immediately perfused, irstly by about 500 ml of normal sa- line (0.9% sodium chloride solution) followed by about 1500 ml of 10% formal saline. On next day rabbit was dissected. Vertebral column was ex- posed after removing skin and muscles of the back. Spine and laminae of vertebrae were cut through bone cutter and spinal cord was exposed. Complete spinal cord including hindbrain was taken out. Segments of spinal cord was count- ed with the help of emerging spinal nerves. Fourth cervical 1 Senior Resident, 2 Associate Professor, 3 Assistant Professor, De- partment of Anatomy, JNMC, AMU, Aligarh (U.P.) India Corresponding author: Israr Ahmad Khan, Department of Anato- my, JNMC, AMU, Aligarh (U.P.) India How to cite this article: Israr Ahmad Khan, Farhan Kirmani, Mohd Imran. Segments of spinal cord harbouring motor neuron somata of median nerve in rabbit. International Journal of Contemporary Med- ical Research 2016;3(4):1023-1025.