The effects of thyrotropin-releasing hormone (TRH) on the sexual and defecatory reflexes regulated by pudendal motoneurons were investigated. Intrathecal TRH (10 μl volume; 0.0, 0.01, 1.0, or 100 μM concentration) at lumbosacral spinal segments (L4-S1) in acute preparations produced a dose-dependent increase in external anal sphincter (EAS), but not bulbospongiosus (BS), electromyographic (EMG) activity. Intraspinal (L6) injection of 100 μM TRH (1 μl/micropipette), significantly increased EAS EMG activity in acute preparations. Electromyographic activity of the BS muscle was unchanged. All doses of intrathecal TRH (10 μl volume; 0, 10, 50, 100, or 500 μM concentration) in awake animals significantly reduced the proportion of responders to a penile reflex test. Subsequently, all measures of penile reflexes were significantly reduced. Glans tumescence and defecation bouts before or during penile reflex testing were unaffected by intrathecal TRH as were indices of behavioral and motor hyper-reactivity analogous to that produced by serotonin. These data indicate that pudendal motoneurons, in the dorsomedial nucleus, are differentially regulated by neuropeptides present in the lumbosacral spinal cord.
All Science Journal Classification (ASJC) codes
- Experimental and Cognitive Psychology
- Behavioral Neuroscience