The regulation of neuroendocrine release in the eyestalk of the fiddler crab Uca pugilator (dopamine, fmrfamide)
Description
Crustaceans, like many other invertebrates and some vertebrates, are capable of altering their color by altering the degree of pigment concentration or dispersion in specialized integumental cells known as chromatophores. Pigment translocation in the fiddler crab, Uca pugilator, is regulated by hormones released from the animal's eyestalk neuroendocrine gland, the X-organ-sinus gland complex. This complex contains no fewer than four pigment effector hormones. The release of these hormones is thought to be regulated by neurons impinging directly on the secretory cells, or on cells somewhere along the chain of neurons leading to the X-organ-sinus gland (Fingerman, 1985) Biogenic amines, including dopamine, octopamine, 5-hydroxytryptamine, and norepinephrine, have been shown to have hormone-releasing effects when injected into U. pugilator. Whether or not endogenous stores of these compounds act as neurotransmitters, however, has not been fully illustrated In the following work, I have documented the presence of dopamine, octopamine, norepinephrine and 5-hydroxytryptamine in various tissues of U. pugilator. In addition, I have provided evidence for a mechanism of synthesis of one (5-hydroxytryptamine) using pharmacological blockers against enzymes involved in its synthesis. I have also demonstrated a mechanism whereby the action of one (norepinephrine) is terminated by re-uptake and metabolism of this putitive neurotransmitter. In the final chapter, the relationship of biogenic amines and eyestalk neuropeptides, was examined