| 20164207 |
Karicheti V, Langdale CL, Ukai M, Thor KB: Characterization of a "Spinal - Urine Storage Reflex - Inhibitory Center" (SUSRIC) and Its Regulation by Serotonin 5-HT1A Receptors in Female Cats. Am J Physiol Regul Integr Comp Physiol. 2010 Feb 17.
Urine storage is facilitated by somatic (pudendal nerve, PUD) and sympathetic (hypogastric nerve, HgN) reflexes to the urethral rhabdosphincter (URS) and urethral smooth muscle, respectively, initiated by primary afferent fibers in the pelvic nerve (PEL). Inhibition of storage reflexes is required for normal voiding. This study characterizes a urine storage reflex inhibitory network that can be activated by pelvic nerve afferent fibers concurrently with the reflexes themselves. Electrical stimulation of PEL nerves produced evoked potentials recorded by URS EMG electrodes (10 msec latency) or HgN nerve electrodes (60 msec latency) in chloralose-anesthetized cats. When a second (i.e. paired) pulse of the same stimulus intensity was applied to the PEL nerves 50 - 500 msec after the first, the reflexes evoked by the second stimulus were inhibited. The inhibition was maximal at paired pulse intervals of 50 - 100 msec and remained after acute spinal transection at T10, confirming the inhibitory center is located in the spinal cord. The 5-HT1A receptor agonist, 8-OH-DPAT (3 - 300 microg/kg, i.v.), consistently reduced the paired pulse inhibition from 20% to 60% of control in spinal intact animals but had no effect in acute spinal animals (i.e. supraspinal site of action). WAY-100635 (300 microg/kg) completely reversed 8-OH-DPAT's effects. The PEL-HgN reflex paired pulse inhibition was not affected by 8-OH-DPAT. These results indicate the presence of a "spinal, urine storage reflex, inhibitory center" SUSRIC that is activated within 50 msec after activation of the reflexes themselves. SUSRIC is inhibited (disfacilitated) by supraspinal 5-HT1A receptors. Key words: urethral rhabdosphinter, condition test stimulation, spinal inhibition, female feline. |
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