We performed HPLC analysis of hemolymph of a crayfish (Procambarus clarkii) and the American lobster (Homarus americanus). Blood samples were obtained from either animals anesthetized with ice for 30 min or agitated for 10 min.
In the crayfish, anesthetized animal and fighting animal showed, respectively, lower and higher 5-HT levels (5.3 +/- 1.0 and 17.3 +/- 3.0 pg/10 ul HPLC sample). We found that 5-HIAA, a metabolite of 5-HT, also shows the same trend in the crayfish, lower and higher levels, respectively, for anesthetized and fighting animals (71.1 +/- 14.5 and 29.8+-14.1 pg/10 ul blood HPLC sample). Other substances in blood were not changed in concentration between anesthetized and fighting animals : mean concentrations were 20 ug/l noradrenaline, 3 ug/l HVA (a dopamine metabolite), 0.01 mg/l GABA, 6 mg/l aspartate, and 12 mg/l glutamate.
In the lobster, concentrations of 5-HT and 5-HIAA were found to be lower than the detection limit of HPLC, 0.5 pg/10 ul sample. However, we found that anesthetized and fighting lobster shows, respectively, lower and higher dopamine levels, performing the comparison in the same lobster (n=5 animals).
The present investigation revealed that neurohormones in the blood are significantly changed by behavioral state, that is, fighting or resting.