Meeting Abstract
P1.20 Tuesday, Jan. 4 Pharmacological Study of the Effects of Octopamine on Heart Rate of Crassostrea viginica PRYCE, K.*; KNIGHT, J.; CATAPANE, E.J.; CARROLL, M.A.; Medgar Evers College; Kingsborough Community College; Medgar Evers College; Medgar Evers College catapane@mec.cuny.edu
Octopamine (OA) is a biogenic amine first identified in the octopus. It has been well studied in arthropods and a few gastropods, serving as a neurotransmitter and hormone. The presence and possible functions of OA have rarely been reported in bivalves. Previously, we identified OA in cerebral ganglia, visceral ganglia, gill, palps and hemolymph of Crassostrea virginica. We also found OA was a cardio-acceleratory agent and postulated it may have a neuroendocrine role in C. virginica. The present pharmacological study examined OA agonist and antagonists to determine if OA is activating an OA receptor in the oyster heart or if the previous results were due to nonspecific stimulation of another receptor, possibly a dopamine (DA) receptor because DA is known to speed up bivalve hearts. C. virginica heart preparations were prepared in situ by removing the oyster’s right shell and connecting the ventricle and atria to isotonic transducers with small stainless steel hooks. Electrodes were used to record EKGs. Heart rate and EKG were monitored with a Narco Systems Physiograph. Data were collected and analyzed with a DATAQ DI-700 Data Acquisition System. Basal heart rates averaged 4.2 beats/min. Superfusion of OA (10-6 – 10-2 M) more than doubled heart rates in a dose dependent manner. The OA agonists, synephrine and phenylephrine were tested and both were slightly more potent than OA in increasing heart rates. The antagonists, phentolamine, metaclopramide and yohimbine (10-4 M) each blocked the cardio-acceleratory effects of OA, however, they did not block the cardio-acceleratory effects of DA. The study provides further evidence that OA may have a neuroendocrine role as a cardio-regulatory hormone.
