P1.157 Wednesday, Jan. 4 Modulation and calcium sensitivity in rate and force of contraction of the crayfish gut HOLSINGER, Rachel C.*; POTENZA, Jensen B.; MERCIER, A. Joffre; COOPER, Robin L.; Univ. of Kentucky, Lexington, KY; Transylvania University, Lexington, KY; Brock University, St. Catherines, Canada; Univ. of Kentucky, Lexington, KY email@example.com
Although, the crayfish hindgut has been a research model for over a century, it is still an excellent model for investigating the generation and regulation of peristaltic rhythms and for describing the mechanisms underlying their modulation, both at the level of neural circuitry and at the level of ion channels within the neurons and muscles. The crayfish hindgut is unique when compared to the smooth muscle in the GI tract of vertebrates, as this invertebrate system not only contains striated muscle with gap junctions but also has the ability to generate intrinsic pacemaker activity. We first investigated the influence of the ventral nerve cord (VNC) and, in particular, the sixth abdominal ganglion on the innervation of the hindgut of Procambarus clarkia by measuring the force and frequency of GI contractions. Then we examined the influence of neuromodulators selectively on the drive to the hindgut from sixth abdominal ganglion as well as the whole chain of abdominal ganglia (A1-A6). In addition, we assessed the effects of neuromodulators selectively to the central brain on descending drive of the hindgut and direct application to the hindgut isolated from the VNC. Serotonin, octopamine and dopamine (1 uM) all enhance the rate of contractions when the VNC or the GI is directly exposed. Direct application of neuromodulators on the GI produced more forceful contractions and a faster rate than exposure only to the VNC.