Action of biogenic amines on crustacean chromatophores—IV. Analysis of the synergistic erythrophoric pigment dispersion evoked by 5-hydroxytryptamine and lysergic acid diethylamide in the dwarf crayfish, Cambarellus shufeldti

Abstract

1. 1. The effects of injection of 5-hydroxytryptamine (5-HT, serotonin) and D-lysergic acid diethylamide (LSD) on the erythrophores of the dwarf crayfish, Cambarellus shufeldti, were determined. 2. 2. 5-HT and LSD evoked synergistic pigment-dispersing responses in the erythrophores of intact crayfish. 3. 3. 5-HT and LSD failed to evoke red pigment dispersion when tested in vitro on isolated pieces of carapace. In contrast, an extract of the eyestalks evoked red pigment dispersion in vitro. 4. 4. Injection of the acetone-soluble fraction of the eyestalks evoked red pigment concentration in eyestalkless crayfish. 5-HT and LSD were both capable of antagonizing the action of the red pigment-concentrating hormone. 5. 5. The red pigment-concentrating hormone from Cambarellus eyestalks and a synthetic red pigment-concentrating octapeptide ( Pandalus hormone) were able to antagonize the action of LSD in intact crayfish. 6. 6. It is concluded that 5-HT and LSD act primarily on the neuroendocrine system to stimulate the release of a red pigment-dispersing hormone. The latter stimulates the erythrophores directly and antagonizes the action of the red pigment-concentrating hormones tested.