Introduction: Spinal cord injury (SCI) usually results in urinary dysfunction. Normally, stimulation of the pontine micturation center produces relaxation of the external urethral sphincter (EUS) via direct projections to GABAergic neurons in the sacral dorsal gray commissure (DGC), which inhibit the EUS motor neurons (Onuf’s Nucleus). Previously, we demonstrated that the light activated channels, Channelrhodopsin-2 (CHR2) and Halorhodopsin (HaloR), can manipulate neuronal spiking to create or inhibit action potentials in neurons following light exposure in SCI settings. Thus, we hypothesize that expression of ChR2 or HaloR and subsequent photostimulation in the DCG GABAergic neurons will affect neuronal excitability and produce or inhibit action potentials in the EUS motor neurons after injury and restore proper urinary function following SCI.
Methods: Bladder behavior activity was recorded, and evaluated between experimental groups, before and after photostimulation. These groups include non-injured and T8 contused (200KD, IH Impactor) rats expressing the depolarizer ChR2, the hyperpolarizer HaloR, or control GFP alone. Additionally, recordings were performed before injury and after injury in the injured rat groups. GFP expression was examined in DGC GABAergic neurons and their projecting axons to EUS motor neurons.
Results: Our preliminary results show that animals that were transfected with ChR2 demonstrated a return of urination (recordable urine volume and frequency) on the day of stimulation. HaloR was tested in non-injured rats. These rats demonstrated a very typical pattern of voiding and volume of urine during the recording period. Following transfection with HaloR, photostimulation resulted in a temporary loss of this micturition pattern. Immunocytochemistry showed that these light activated channels were expressed in DGC neurons with GABAergic projections to Onuf’s nucleus.
Conclusions: We have demonstrated that targeting the spinal cord DGC GABAergic neurons with optogenetic photostimulation strategies can manipulate EUS spinal cord motor neurons, as well as, induce some urinary functional recovery in experimentally SC injured rats.
Patient Care: Optogenetic technologic has the impact for translational use for control of the lower urinary tract in patients following SCI.
Learning Objectives: By the conclusion of this session, participants should be able to know that:
1)Spinal cord DGC GABAergic neurons and EUS motor neurons can be targeted with optogenetic photostimulation to restore proper urinary function following SCI.
2)Photostimulation of injured animals transfected with CHR2 demonstrated a temporary return of urination.
3)While, photostimulation of non-injured animal transfected with HaloR resulted in a temporary loss of the micturition pattern.