A Non-spinal Neural Circuit for Transmitting Information of Bladder Conditions

The bladder is essential for the body's fluid balance to ensure normal physiological conditions; thus, a non-pathological bladder-that is, one sustaining internal homeostasis-is critical for this function. However, the neuro-network maintaining the bladder's intrinsic homeostasis is much less well-known compared with that for urination. Here, we identified that vagal nodose ganglion-pseudounipolar neurons project down to the bladder, up to the nucleus of the solitary tract, and further to multiple brain regions. The components of this network and those revealed by direct tracing from the bladder with herpes simplex virus (HSV) have significant overlaps and differences. Chemogenetic activation coupled with functional magnetic resonance imaging (fMRI) and c-Fos staining verified that the components in the vagal network were functionally connected. Strikingly, this vagal network did not include the primary motor cortex (M1), suggesting a role distinct from conscious urination control, and a cystitis model therefore revealed its potential role in transmitting bladder inflammation. Taken together, we have identified a non-spinal bladder-brain network not for urination but potentially for homeostasis of the bladder itself.