Serotonin-induced short- and long-term sensitization in the crab Chasmagnathus.
On sudden presentation of a passing shadow (a visual danger stimulus), the crab Chasmagnathus granulatus responds with a running reaction that we term an escape response (ER). A single administration of 5-HT in a dose range between 0.005 and 0.1 microgram/g enhances the ER at 30 min, and a dose of 10-15 micrograms/g has a similar effect for at least 24 h. The classical 5-HT antagonist cyproheptadine (CYP) given within a dose range 0.01-2.0 micrograms/g has no effect on ER at 30 min, but 0.5 microgram/g blocks the 5-HT-induced short-term sensitization. An enhancing effect of CYP on the ER is shown at 24 h with 1.0-2.0 micrograms/g doses. An explanation of this results in terms of a model similar to that proposed for Aplysia, that is two sensitizing processes linked in parallel and mediated by two different types of 5-HT receptors is discussed. Results indicate that the sensitizing effect of 5-HT is confined to high responders, thus suggesting that crabs of a same population have different degrees of sensitivity to the drug according to their different degrees of reactivity to the visual danger stimulus.
Aggio
J
J
Departamento de Biología, Ciudad Universitaria, Buenos Aires, Argentina.
Rakitín
A
A
Maldonado
H
H
D000818:Animals; D003386:Brachyura / Q000502:physiology*; D003533:Cyproheptadine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004924:Escape Reaction / Q000187:drug effects*; D007206:Individuality; D008297:Male; D012701:Serotonin / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology*; D013268:Stimulation, Chemical
D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D003533:Cyproheptadine; D012701:Serotonin