ROLE OF GLUTAMATE AND NMDA RECEPTORS IN THE DESCENDING-LIMB OF THE SPINOBULBOSPINAL MICTURITION REFLEX PATHWAY OF THE RAT

MK-801, an NMDA receptor antagonist administered intravenously or intr athecally to the L6-S1 spinal cord inhibited in a dose dependent manne r the amplitude of isovolumetric bladder contractions evoked by electr ical stimulation in the pontine micturition center (PMC) in urethane a nesthetized rats, The mean threshold dose of MK-801 was 10 +/- 6 mu g/ kg i.v. and 10 +/- 1 mu g i.t. Bladder contractions were completely in hibited at doses ranging from 300 to 3000 mu g/kg i.v. and from 18 to 48 mu g i.t. These data indicate that NMDA glutamatergic receptors pla y an important role in excitatory transmission in the descending pathw ay from the PMC to the spinal segmental circuitry involved in the cont rol of the urinary bladder.