Cardiac reflexes and their neural pathways in lepidopterous insects

Previously described salines for lepidoptera did not maintain a constant he art rate for a very long. We have been successful in maintaining a normal h eartbeat for many hours in a newly designed saline. This saline was also su itable for maintaining normal neuromuscular junctional potentials. The card iac reflexes studied in larvae of Bombyx and Agrius were five types of card iac responses induced by mechanical stimuli to sensillar setae. The cardiac responses were caused by electrical stimulation of nerves in the reflex pa thways. The antidromic heartbeat was triggered even in larvae before the 5t h instar by stimulation of axons in the visceral nerve arising from the fro ntal ganglion and terminating at the aorta, while spontaneous heartbeat rev ersal started to occur in wandering larvae. Other axons in the visceral ner ve terminate at the rear end of the heart. Electrical stimuli to the nerves caused cardiac inhibition of the orthodromic heartbeat. Nerves extending f rom the visceral nerve to the alary muscles of the 2nd abdominal segment co ntain axons to increase the tone of the muscles. Nerves extending from the 7th abdominal ganglion to the most posterior alary muscles also contain axo ns to increase the tone of the muscles, and were responsible for accelerati on of the antidromic and orthodromic heartbeat, respectively. (C) 1999 Else vier Science Inc. All rights reserved.