Synaptic transmission parallels neuromodulation in a central food-intake circuit

NeuromedinU is a potent regulator of food intake and activity in mammals. In Drosophila, neurons producing the homologous neuropeptide hugin regulate feeding and locomotion in a similar manner. Here, we use EM-based reconstruction to generate the entire connectome of hugin-producing neurons in the Drosophila larval CNS. We demonstrate that hugin neurons use synaptic transmission in addition to peptidergic neuromodulation and identify acetylcholine as a key transmitter. Hugin neuropeptide and acetylcholine are both necessary for the regulatory effect on feeding. We further show that subtypes of hugin neurons connect chemosensory to endocrine system by combinations of synaptic and peptide-receptor connections. Targets include endocrine neurons producing DH44, a CRH-like peptide, and insulin-like peptides. Homologs of these peptides are likewise downstream of neuromedinU, revealing striking parallels in flies and mammals. We propose that hugin neurons are part of an ancient physiological control system that has been conserved at functional and molecular level.SFB 645 and 704, DFG Cluster of Excellence ImmunoSensation, DFG grant PA 787, HHMI Janeli

Oxygen supply of the heart and electrocardiogram potentials with reversed polarity in sleeping and resting honey bees

International audienceA novel active ventilatory mechanism of the dorsal air sacs in the abdomen of forager honey bees is described. These air sacs supply the heart with oxygen. During sleep and rest, the air sacs undergo frequent volume changes. The dilation of the air sacs is caused by the activity of hitherto unidentified muscles. Their subsequent collapse is probably due to elastic components in the walls of the sacs. The volume changes also occur when, during discontinuous resting ventilation, ventilatory movements of the abdomen are absent. They are always combined with an increase in heart rate. The heart thus receives oxygen when it needs it and can therefore function effectively during sleep, to supply the brain with nutrients necessary for energy-demanding sleep-specific functions. During sleep, rest, and induction of chill coma, periodic heartbeat reversals were also discovered. The biological significance of these heartbeat reversals remains to be elucidated