Morphologic and quantitative evaluation of the myenteric plexuses and neurons in the large colon of horses.
OBJECTIVE
To determine the number of myenteric plexuses and neurons in the large colon of clinically normal horses and whether the number was decreased in the large colon of horses with colon disease.


METHODS
Prospective study.


METHODS
Colon samples from 15 clinically normal horses and 31 horses with colon disease.


METHODS
Samples were obtained, fixed, and stained with H&E. The number of myenteric plexuses and neurons and longitudinal muscle thickness were determined in each segment of colon for clinically normal horses. Counts for segments were compared with each other and with counts in the same segment from horses with colon disease.


RESULTS
Myenteric plexus and neuron densities and longitudinal muscle thickness in clinically normal horses were significantly greater in the pelvic flexure and left dorsal and transverse colons. Horses with chronic obstruction (> 24 hours' duration) or with previous obstruction had significantly lower neuron density in the pelvic flexure. Myenteric plexus density in horses with strangulating large colon torsion/volvulus was significantly less in the right ventral, right dorsal, and transverse colons, and neuron density in these horses was significantly less in all segments of colon, except the left ventral colon. Horses with colon strangulation that survived had significantly greater neuron density than horses with colon strangulation that died. Enteroglial cell numbers were increased in myenteric plexuses of horses with acute and chronic obstruction.


CONCLUSIONS
Myenteric plexus and neuron densities can be estimated by evaluating linear counts of H&E-stained colon samples. Enteroglial cells may increase in number in response to myenteric plexus inflammation, which may affect bowel function.
Schusser
G E
GE
Marion duPont Scott Equine Medical Center, Virginia-Maryland Regional College of Veterinary Medicine, Leesburg, USA.
White
N A
NA
D000818:Animals; D003085:Colic / Q000473:pathology / Q000662:veterinary; D003106:Colon / Q000166:cytology / Q000294:innervation* / Q000473:pathology; D003108:Colonic Diseases / Q000473:pathology / Q000662:veterinary*; D005260:Female; D006734:Horse Diseases / Q000473:pathology*; D006736:Horses / Q000033:anatomy & histology*; D007415:Intestinal Obstruction / Q000473:pathology / Q000662:veterinary; D008297:Male; D009197:Myenteric Plexus / Q000033:anatomy & histology* / Q000473:pathology; D009474:Neurons / Q000166:cytology* / Q000473:pathology; D012016:Reference Values