Neurohormonal and glutamatergic neuronal control of the cardioarterial valves in the isopod crustaceanBathynomus doederleini

Abstract

SUMMARYThe heart of Bathynomus doederleini gives rise to an anterior median artery (AMA), one pair of anterior lateral arteries (ALAs) and five pairs of lateral arteries (LAs). Cardioarterial valves are located at the junctions between the heart and arteries, each composed of a pair of muscular flaps. All valves of the AMA and the ALAs receive valve excitatory(constrictor) nerves (VEs). The valves of the ALAs receive dual innervation from both constrictor and inhibitor (dilator) nerves, while the valves of the AMA receive innervation from a constrictor nerve alone. The effects of candidate neurohormones on cardioarterial valves were examined by measuring the pressure in each artery at which haemolymph flows out of the heart through the valve. Serotonin, octopamine, norepinephrine, glutamate (Glu) and proctolin constricted the cardioarterial valves and thus decreased the arterial pressure in all the arteries. Dopamine also decreased the arterial pressure of arteries except for the ALAs, in which pressure was increased. Among the neurohormones exerting excitatory effects on the valves, only Glu depolarized the membrane potential of valve muscle cells. The glutamatergic agonists kainate and quisqualate also depolarized the valve muscle cells of the AMA. Excitatory junctional potentials produced in the valves of the AMA in response to the stimulation of a VE were blocked by the glutamatergic antagonists Joro spider toxin and MK-801. Glu is the likeliest candidate for a neurotransmitter for the VEs.

Neuronal and neurohormonal control of the heart in the stomatopod crustacean,Squilla oratoria

“…JSTX (10 -5 ·mol·l -1 ), known as a glutamate antagonist (Kawai et al, 1982;Chiba and Tazaki, 1992;F.-Tsukamoto and Kuwasawa, 2003), blocked cardioacceleratory effects of stimulation of the CA1 and CA2 axon (Fig.·8). Acceleratory effects of stimulation of CA1 or CA2 decreased to 38.5±12.7% of control value for CA1 and 24.5±17.5% for CA2 (means ± S.D., N=3).…”

“…Glutamate-like immunoreactivity was observed in both the CA1 and CA2 axons (Fig.·11). JSTX is known to antagonize glutamatergic actions on the skeletal muscle of the lobster Palinurus japonicus (Kawai et al, 1982), on the stomach muscle of S. oratoria (Chiba and Tazaki, 1992), the heart of L. exotica and on the arterial valve in B. doederleini (F.-Tsukamoto and Kuwasawa, 2003). These results may indicate that, in S. oratoria, both the CA1 and CA2 neurons are glutamatergic.…”

“…In immunocytochemistry using anti-GABA and anti-glutamate, preparations were processed as described for the isopod by F. Tsukamoto and Kuwasawa (2003). For controls, preparations were processed in the same manner but without treatment with the primary antibodies.…”

“…Neurotransmitters for cardioregulatory neurons and cardiac ganglion neurons have been proposed for some crustaceans. It has been proposed that GABA may be a neurotransmitter of the CI neuron in the isopod, B. doederleini (Tanaka et al, 1992;F.-Tsukamoto and Kuwasawa, 2003), and in the decapods, A. aniculus (Yazawa and Kuwasawa, 1994) and Panulirus argus (Delgado et al, 2000). It is concluded that GABA may be commonly a cardio-inhibitory neurotransmitter in all those crustacean taxa.…”

“…cardio inhibitory activity on the heart of an isopod, Bathynomus doederleini, 5-TH, OA and Glu are reported to produce cardio-acceleratory activity (Tanaka et al, 1992;Yazawa et al, 1998;F.-Tsukamoto and Kuwasawa, 2003).…”