Computational studies on bladder small dorsal root ganglion neurons: Modelling BK channels

The urinary bladder afferent neurons called the dorsal root ganglion (DRG) neurons carry information on diverse modalities such as stretch, pressure and nociception to the spinal cord. This information is carried in the form of electrical activity called action potentials (AP). The bladder small diameter DRG neurons that are considered to be putative nociceptors express several ion channels and active mechanisms which are responsible for generating this electrical activity. One of the channels that has been suggested to play a role in cell excitability is the large conductance calcium activated potassium channel (BK) channel. Its activation is governed by cell membrane potential and intracellular calcium concentration. Here, we present a computational model of the BK channel along with other ion channels and mechanisms present in the bladder small DRG neuron cell body. The BK channel simulations show properties that are similar to those shown by Isolectin B4 (IB4) negative cutaneous small DRG neurons. The bladder small DRG neurons have also been found to show some of these properties. Thus, we hypothesize that the bladder small DRG neurons are IB4 negative. This hypothesis is supported by experimental studies which suggest that about 80% of bladder small DRG neurons are IB4 negative. The model of bladder small DRG neuron also faithfully reproduced some of the electrical properties that have been reported experimentally. This model can thus be used to predict abnormal behaviour of the DRG neuron during pathological conditions.