Brainstem neurons coordinate the bladder and urethral sphincter for urination

Urination, a fundamental biological function in mammals, necessitates a finely tuned interplay between the urinary bladder and the external urethral sphincter (EUS). This process is regulated by a complex network of neurons, but the precise neuronal subpopulations involved have remained elusive, hindering the development of targeted therapies for certain bladder or urinary control disorders such as detrusor–sphincter dyssynergia.

A recent study has identified a specific population of brainstem neurons as the key coordinators of this process.

The cells in question are those expressing estrogen receptor 1 (ESR1+) within the pontine micturition center (PMC). Upon activation, these neurons reliably initiate the voiding process, ensuring the emptying of urine from the bladder. Conversely, when suppressed, they effectively halt ongoing urination. Remarkably, these neurons maintain their control over the EUS via the pudendal nerve despite the transection of the pelvic nerve, and they continue to regulate the bladder via the pelvic nerve even after the pudendal nerve has been transected.

Anatomically, the PMC ESR1+ neurons are classified into three distinct subpopulations based on their spinal projections. One group targets the sacral parasympathetic nucleus, another innervates the dorsal gray commissure, while a third projects to both regions. This strategic spatial arrangement allows the neurons to orchestrate the complex temporal sequence required for coordinating both bladder contraction and EUS relaxation.

The identification of this specific brainstem neuronal population marks a significant step forward in understanding the mechanisms underlying urination. With this knowledge, researchers can now explore the development of therapies that target these cells, potentially offering new treatment options for individuals suffering from disorders affecting bladder and urethral coordination.