Meeting Abstract
P3.46 Sunday, Jan. 6 Octopamine Has a Dual Effect on Heart Rate of Crassostrea virginica HOQUE, R.*; JEANLOUIS, A.; CARROLL, M.A.; CATAPANE, E.J.; Medgar Evers College; Medgar Evers College; Medgar Evers College; Medgar Evers College catapane@mec.cuny.edu
Octopamine (OA) a biogenic amine first identified in octopus has been well studied in arthropods and gastropods being as a neurotransmitter and hormone. Functions of OA have rarely been reported in bivalves. Previously, we identified OA in cerebral and visceral ganglia (VG), gill, palps and hemolymph of the oyster Crassostrea virginica. We found OA is cardio-acceleratory when applied to whole animals and speculated it is a neuro or endocrine agent. We tested OA on heart rate of C. virginica by applying OA to VG of whole animals (in situ) or isolated hearts. Rate was monitored with a Narco Systems Physiograph. Data were collected and analyzed with a DATAQ DI-700 Data Acquisition System. Average basal heart rate of whole animal preparations was 5.5 beats/min. Superfusion of OA (10-6 – 10-3 M) to VG increased rates to 9.3 beats/minutes in a dose dependent manner. Average beating rates of isolated heart preparations was 13.4 beats/min. Bath applications of OA (10-6 – 10-3 M) decreased rates to 0 in a does dependent manner. Actions of OA were prevented by the OA antagonist phentolamine. The study shows OA affects heart rate in 2 different fashions, depending on site of application. Bath applications to isolated heart reveals it decreases heart rate at that site. When applied to VG OA increases rates. A possible explanation for the divergent results is if OA is activating different receptors in the different locations. Superfusing OA to VG causes it to stimulate receptors on different neurons at the same time. The end result would be due to the various nerves being simultaneously stimulated, which is not what happens in the animal’s normal physiological actions. Under normal conditions OA would be discretely released to stimulate discrete neuronal circuits at a particular time.
