Catecholamines in adult lampreys: Baseline levels and stress-induced changes, with a note on cardiac cannulation

The circulating levels of dopamine, norepinephrine, and epinephrine (about 1300, 1300, and 3600 pg/ml, respectively) of the adult sea lamprey are very high when compared with the levels in teleosts and mammals, but similar to the levels found in the shark. Contrary to the situation in the shark, teleosts, and mammals, however, epinephrine has the highest plasma levels of the three catecholamines studied, and dopamine seems to be released mainly outside the brain. We find two types of responses: agitation causes a decrease of circulating dopamine, whereas decapitation causes an enormous increase of norepinephrine release. Details of a technique of heart cannulation for repeated blood sampling from individual lampreys are also given.