Histamine and Histamine Receptor Involvement in Sensory‐Motor Integration of Gill Lateral Cell Cilia Activity in the Bivalve Crassostrea viginica

Abstract

Gill lateral ciliated cells of Crassostrea virginica are innervated by serotonin and dopamine nerves. Motor aspects have been well studied, but the sensory side hasn't. Histamine (HIS) a neurotransmitter in a variety of invertebrates rarely has been reported in bivalves. We quantified HIS in C. virginica and found gill lateral cell cilia beating changed in response to mantle sensory inputs including HIS. The mechanism involves mantle rim sensory tentacles and visceral ganglia. HIS does not alter beating when applied to gill. We hypothesize HIS receptors are present in mantle and can be confirmed by Western Blot (WB). For WB, mantle body and rim lysates were prepared in NP-40 detergent buffer containing protease inhibitor followed by centrifuging to obtain supernatant with solubilized mantle body and rim membrane proteins. H2 receptor immunoreactivity was revealed by 1̊ antibody followed by HRP-conjugated 2̊ antibody. Mantle body and rim H2 receptor protein was resolved by colormetric development using CN/DAB substrate kit. We also did a dose response of HIS H1, H2 and H3 receptor agonists and antagonist at the mantle rim and observed cilia beating in gill. WB showed a 70 kD band corresponding to HIS H2 receptors in mantle body and rim, and H2 agonists and antagonists had the strongest effects on cilia beating. The study shows mantle body and rim have HIS H2 receptors and demonstrates a physiological role of HIS in sensory-motor integration of gill lateral cell cilia activity.