In vitro motility disorders associated with displaced abomasum in dairy cows

The objective of this study was to investigate in vitro abomasal motility i n dairy cows diagnosed with displaced abomasum. Longitudinal muscle myenter ic plexus preparations originating from the abomasal antrum of control cows , and cows diagnosed with left displaced abomasum (LDA), right displaced ab omasum (RDA) or abomasal volvulus (AV) were used. In control preparations e lectrical field stimulation evoked an immediate cholinergic contractile res ponse exceeding amplitude of basal contractions by 60%. In contrast, contra ctile activity was significantly inhibited during electrical stimulation in LDA, RDA and AV by 47%, 66% and 45%, respectively. This inhibition was rev ersed in the presence of L-NAME. The staining intensity of NADPH-positive m yenteric neurones was significantly higher in displaced abomasa than in con trols. Concentration-response curves indicated that preparations from dis p laced abomasa showed reduced sensitivity to acetylcholine. This study demon strated motility disorders in displaced abomasa in vitro. The results sugge sted that abomasal displacement is associated with malfunctions at the leve l of the intrinsic nervous system combined with impaired cholinergic muscle responses. There appeared to be a predominance of nitrergic inhibitory mec hanisms over excitatory mechanisms. These results might be of significance for diseases associated with gastric hypomotility and emptying disorders.