The myenteric plexus of the large intestine of the mouse: observations with supravital staining with methylene blue

ABSTRACT

Morphologic and morphometric studies of the myenteric plexus of the large intestine of the mouse were performed using supravital methylene blue staining. Male albino mice (70-80 days odl) were sacrificed after ether anaesthesia and the large intestine immediately removed and immersed in 0.1 per cent methylene blue solution in saline at 37 degrees Celsius and bubbled with air. After 25 minutes the intestine was rinsed and the lumen perfused with warm saline to remove the faeces. The caecum was sectioned and the colon was divided into three segments of the same length. The fragments, without opening the lumen, were mounted on slides and covered with coverglass for microscopic examination (4X and 10X objectives). At least 10 micrographs of each segment of intestine were used for the point counting method for evaluation of the surface area of the plexus (4x micrographs). For neuron count 10X micrographs were used. Neuron (pericaron0 volume and area were evaluated on 40X micrographs. The results shouwed (a) the myenteric plexus in the large intestine of mouse is more dense in the proximal third of the colon than in the caecum and in the distal third of the colon; the number of neurons/cm2 is significantly less in caecum (24,352 + 4,807 neurons/cm2) and distal segment of the colon (6,5767 + 10,341 neurons/cm2) than in the proximal and intermediate segments (93,242 + 9,185 neurons/cm2 and 85,188 + 5154 neurons/cm2, respectively). The mean volume of the neurons was similar in the diferent segments of the colon (4549 + 3493 mum3).