T. Yazawa et K. Kuwasawa, DOPAMINERGIC ACCELERATION AND GABAERGIC INHIBITION IN EXTRINSIC NEURAL CONTROL OF THE HERMIT-CRAB HEART, Journal of comparative physiology. A, Sensory, neural, and behavioral physiology, 174(1), 1994, pp. 65-75
The acceleratory and inhibitory cardio-regulatory nerves of hermit cra
bs (Aniculus aniculus, Dardanus crassimanus) were studied using histoc
hemical, immunocytochemical and pharmacological tests. Glyoxylic acid-
induced fluorescence was observed in two of three axons of the dorsal
cardiac nerve. One axon of the nerve showed gamma-aminobutyric acid-li
ke immunoreactivity. Effects of stimulation of cardio-acceleratory axo
ns were blocked by the dopaminergic antagonists, haloperidol and chlor
promazine, but not by cholinergic, adrenergic or serotonergic blockers
, suggesting that dopamine is the primary potential candidate for the
neurotransmitter of cardio-accelerator neurons. Picrotoxin antagonized
inhibition of the cardiac ganglion induced by gamma-aminobutyric acid
and by cardio-inhibitory axons. Both small and large ganglionic cells
may receive dopaminergic and GABAergic extrinsic neural control.