Identification of neurogenic intestinal motility patterns in silver perch (Bidyanus bidyanus) that persist over wide temperature ranges.

Abstract

Fish are increasingly being utilized as a model species for genetic manipulation studies related to gastrointestinal (GI) motility. Our aim was to identify whether patterns of GI motility in fish and the mechanisms underlying their generation are similar to those recorded from mammals (including humans). The entire intestine was removed from euthanized adult Silver Perch (n=11) and lesioned at the midway point to obtain two equal lengths. Proximal and distal segments were studied separately in organ baths with oxygenated Krebs solution, maintained at either 15°C (n=5) or 25°C (n=6). Motility was analyzed during rest, after oral infusion of Krebs solution, and after application of hexamethonium (100µM) and tetrodotoxin (TTX) (0.6µM). Antegrade and retrograde propagating contractions (PC) were recorded in all preparations. In the proximal intestine, at 15 and 25°C, retrograde PCs occurred at 2.7 [1.7-4.5] and 3.1 [1.6-6.5] times the frequency of antegrade PCs, respectively. Colder temperatures did not inhibit PC frequency. Hexamethonium did not inhibit PC, and however, TTX abolished all contractile activity. Both neurogenic antegrade and retrograde propagating contractions occur throughout the intestine of Silver Perch. However, unlike the mammalian colon, these motor patterns do not require enteric nicotinic transmission and they are not inhibited by cold temperatures (15°C). Therefore, while the GI motility patterns in Silver Perch resemble those recorded from the colon of mammals, there may be differences in the mechanisms that underlying their generation.