Queens University, Kingston, Ontario - May 12, 2005

SARAH CHIANG & R. GARY CHIANG
Department of Biology, Redeemer University College, Ancaster, ON

Electrical activity recorded extracellularly from the cephalic aorta before and after feeding in the blood-sucking insect, Rhodnius prolixus.

Electrical activity of the cephalic aorta in the head of Rhodnius prolixus can be routinely recorded by pulling a short length of an intact aorta into an extracellular suction electrode.   This activity occurs spontaneously, and consists of a number of identifiable action potentials that vary according to their amplitude, duration, and shape. We now know that much of this activity originates from the retrocerebral complex, and that it may belong to axons of cell bodies located in the hypocerebral ganglion (HG).   This ganglion is involved in the act of feeding, which accounts for its nervous connections to the salivary glands. To determine if the cells of the HG associated with the cephalic aorta may also be involved in feeding, we describe the electrical activity of the cephalic aorta in unmated adult females before, and up to three days after, ingestion of a blood meal.   We have found only minor differences in electrical activity between fed and unfed animals.

R. GARY CHIANG & SARAH CHIANG
Department of Biology, Redeemer University College, Ancaster, ON

Electrophysiological evidence that neurosecretory cells in the hypocerebral ganglion send axons into the cephalic aorta of the blood-feeding insect, Rhodnius prolixus.

We report that a large portion of the electrical activity recorded extracellularly from the cephalic aorta of unfed male and female Rhodnius prolixus adults depends on an intact retrocerebral complex.   When the cephalic aorta is electrically active, mechanically disrupting the medial neurosecretory cells in the protocerebral lobes, transecting the NCC, or removing connections to the suboesophageal ganglion has little effect on this activity.   Even after the entire retrocerebral complex has been lifted out of the insect by the suction electrode attached to the cephalic aorta, much of the spontaneous activity remains.   Localizing the seat of this activity to the retrocerebral complex suggests that it originates from cells in the hypocerebral ganglion (HG).   The HG of Rhodnius prolixus is a cluster of cell bodies located between, and ventral to, the right and left nervus corpus cardiaca in the retrocerebral complex.   Compared to nearby nervous structures, such as the corpus cardiacum and the corpus allatum, this ganglion is insignificant, and it has been overlooked in many previous studies.