Role of spinal metabotropic glutamate receptors in regulation of lower urinary tract function in the decerebrate unanesthetized rat

The role of spinal metabotropic glutamate receptors (mGluRs) in control of lower urinary tract functions was evaluated in rats using an mGluR antagonist administered via the intrathecal route. Cystometrograms in combination with external urethral sphincter (EUS) EMG recordings were performed on 13 decerebrate unanesthetized Sprague–Dawley female rats (n = 6 for spinal cord intact rats; n = 7 for spinal cord transected rats). In spinal cord intact rats, a group I/II mGluR antagonist, (±)-alpha-methyl-4-carboxyphenylglycine (MCPG), at doses of 3–30 μg, changed neither bladder nor EUS EMG activity, whereas a larger dose (100 μg) produced a significant facilitation of EUS EMG activity (41% increase in the peak activity) with little effect on bladder contractions. In chronically spinal cord transected rats, MCPG (3–100 μg) had no effect on bladder and EUS EMG activity. The results suggest that group I/II mGluRs are likely to be involved in inhibition of the excitatory pathway to the EUS but not involved in the control of the bladder. The lack of effect of MCPG on the EUS EMG activity in chronic spinal cord transected rats indicates that mGluR-mediated inhibitory control of the EUS was eliminated after spinal cord injury.