Eymael, A. | Search bioRxiv

bioRxiv2024

A PHOX2b+ PONTINE NUCLEUS ESSENTIAL FOR INGESTION.

The first phase of feeding consists in acquiring solid foods from the environment by biting, and their preparation for swallowing by chewing. These actions require the precise coordination of tens of orofacial muscles for the jaw and tongue. The siege for this motor patterning is known to be in the reticular formation, a complex and poorly mapped region of the hindbrain, but the neuron groups involved are still elusive. Here, we characterize a group of reticular interneurons located in the supratrigeminal area that express the homeodomain transcription factor Phox2b. This nucleus -- Sup5Phox2b-- is premotor to both jaw-closing and jaw-opener motoneurons and receives direct input from cranial sensory afferents, motor cortex and satiation related nuclei. Its activity differentially tracks lapping, biting and chewing movements, suggesting its involvement in the elaboration of distinct orofacial motor patterns in vivo. Acute global activation or inhibition of Sup5Phox2bby optogenetics both interrupt volitional feeding sequences. Thus, Sup5Phox2bis an obligatory subcortical node, topologically and genetically defined, in the neural circuits that control the oral phase of feeding. TeaserA genetically defined cluster of neurons in the hindbrain is an essential relay for biting and chewing food.

physiology↗

bioRxiv2023

The pelvic organs receive no parasympathetic innervation

The pelvic organs (bladder, rectum and sex organs) have been represented for a century as receiving autonomic innervation from two pathways -- lumbar sympathetic and sacral parasympathetic -- by way of a shared relay, the pelvic ganglion, conceived as an assemblage of sympathetic and parasympathetic neurons. Using single cell RNA sequencing, we find that the mouse pelvic ganglion is made of four classes of neurons, distinct from both sympathetic and parasympathetic ones, albeit with a kinship to the former, but not the latter, through a complex genetic signature. We also show that spinal lumbar preganglionic neurons synapse in the pelvic ganglion onto equal numbers of noradrenergic and cholinergic cells, both of which therefore serve as sympathetic relays. Thus, the pelvic viscera receive no innervation from parasympathetic or typical sympathetic neurons, but instead from a divergent tail end of the sympathetic chains, in charge of its idiosyncratic functions.

neuroscience↗