Metabotropic glutamate receptor subtype 1 participates in synergy of bladder and external urethral sphincter in mice with spinal cord injury
Dr. Mitsuharu Yoshiyama (1,2), Prof. Masayuki Takeda (2)
(1) Shintotsuka Hospital, Yokohama, Japan, (2) University of Yamanashi Graduate School of Medicine, Chuo, Japan
Metabotropic glutamate receptor (mGluR) subtype 1, which is greatly expressed in Onuf's nucleus , is suggested to exert an inhibitory effect on external urethral sphincter (EUS)- electromyogram (EMG) activity during micturition in spinal intact rats . The aim of this study was to determine if this receptor is involved in EUS-EMG activity after chronic spinal cord injury (SCI), by comparing SCI wild-type (WT) and SCI mGluR1-knockout (KO) mice.
Complete spinal cord transection was performed by sectioning at the T9-T10 level in female C57BL/6 mice (9 week-old), and simultaneous recordings of continuous infusion cystometry (30 μl/min) and EUS-EMG were conducted under decerebrate, unanesthetized conditions at 4 weeks post-spinalization. Values are expressed as means ± SD.
Evacuation of intravesical fluid occurred during silence of EUS-EMG activity accompanying sudden decrease (presented as notches) in bladder contraction pressure. The number of notches (# notches) and the sum of evacuation duration (SED) per a bladder contraction were compared between SCI-WT and SCI-KO. Marked differences between SCI-WT and SCI-KO were found in # notches and SED as shown in Table 1.
The results showed that mGluR1 is involved in inactivation of EUS-EMG during bladder contraction in SCI mice, indicating that this receptor is necessary for an inhibition of EUS activity. Dysfunction of mGluR1 transmission in the spinal circuit may underlie the mechanism exacerbating or inducing detrusor-sphincter dyssynergia subsequent to SCI.