The sensation of not being able to ‘go’ when you really need to could soon be a thing of the past as two recent papers describe populations of brain cells important for the control of voluntary urination.
Urination (or micturition) is a natural and necessary process important for removing waste products from our bodies and for maintaining a healthy fluid balance. For
Needless to say, the voiding of the bladder and the act of urination needs to be appropriate for the situation and is tightly controlled by the brain. Inappropriate urination could lead to social embarrassment or, in the case of an animal, unwanted attention from predators, for example. Despite this, it is thought that one in three people worldwide
In their recent paper, Yao et al. have identified a subset of layer 5 neurons in the primary motor cortex region of the brain that control the initiation of urination.
They initially identified the neurons by injecting a modified rabies virus encoding a green fluorescent protein (
However, they also discovered a bilateral expression of GFP in neurons in a specific region of the primary motor (M1) cortex.
Performing three-dimensional reconstruction of the region, they counted around 970 GFP positive neurons in layer 5 of the M1 cortex and a further 643 GFP positive neurons in layer 5 of the primary sensory cortex.
To test if the activity of these neurons coincided with urination, the scientists labelled the neurons with a calcium indicator whose fluorescence increases with cellular activity, enabling them to perform
To be sure they captured the neuronal activity in real time with the urination, the scientists made their
Using this setup, the scientists discovered the role of the layer 5 M1 neurons is specifically for the initiation of
A NETWORK CONTROL MECHANISM
Recent work from the Stower’s lab at the Scripps Research Institute, La Jolla,
Whether there is a link between the estrogen receptor-expressing cells in the Barrington’s nucleus of the brainstem and M1 layer 5 neurons of the primary motor cortex remains to be seen. But, together these studies reveal incredible functional insight into the control of urination. And, could possibly one day lead to a therapy that reduces the problem of incontinence or even help people overcome stage-fright at the urinal.