Convergence of multiple pelvic organ inputs in the rat rostral medulla

Abstract

Electrophysiological recordings were used to investigate the degree of pelvic/visceral convergent inputs onto single medullary reticular formation (MRF) neurons. A total of 94 MRF neurons responsive to bilateral electrical stimulation of the pelvic nerve (PN) in 12 urethane-anaesthetized male rats were tested for responses to mechanical stimulation of the urinary bladder, urethra, colon and penis, and electrical stimulation of the dorsal nerve of the penis (DNP) and abdominal branches of the vagus. Responses to distension of the bladder were found for 51% (n = 48) of the MRF neurons tested. Of these 48, 71% responded to urethral infusion, 81% responded to colon distension, 100% responded to penile stimulation (and DNP), and 85% responded to vagal stimulation, with 62% responding to stimulation of all four of these territories. This high degree of visceral convergence (i.e. 62%) in a subset of PN-responsive MRF neurons is significantly greater than for the subset of PN-responsive MRF neurons that did not respond to urinary bladder distension (i.e. out of the 46 remaining neurons, none responded to all four of the other pelvic/visceral stimuli combined). These results suggest that the neurons processing information from the urinary bladder at this level of the neural axis are likely to be important for mediating interactions between different visceral organs for the coordination of multiple pelvic/visceral functions. Normal functions related to the male pelvic/visceral organs, such as urination, defaecation, and ejaculation, involve coordination between the different organ systems. One example of a process in which coordination is important is ejaculation, which consists of emission of the seminal fluid from the ejaculatory ducts to the proximal urethra, bladder neck closure and anterograde ejaculation out of the proximal urethra (Seftel et al. 1991;Truitt & Coolen, 2002). Disruption of this coordination, such as following spinal cord injury, results in the failure of bladder neck closure and thus a subsequent retrograde ejaculation leading to infertility (Heruti et al. 2001).Another example in which coordination between the pelvic organs is important is during voiding of the urinary bladder, which requires contraction of the external anal sphincter, thereby preventing defaecation. In humans, distension of the urinary bladder produces contractions of the anal sphincter (Basinski et al. 2003). Experimental studies using cats have shown that distension of the urinary bladder both inhibits colonic contractions (Bouvier et al. 1990) and produces simultaneous contraction of the anal sphincter (Bouvier & Grimaud, 1984). The reverse also occurs, i.e. the urinary system is inhibited during defaecation. In humans, functional stimulation of the anal sphincter inhibits detrusor muscle contraction (Cheng et al. 2002). In animal studies, distension of the rectum has been shown to inhibit urinary bladder activity in female rats (Sugaya et al. 1998), and stimulation of colonic branches of the pelvic nerve in cats has been shown ...

Activation and inhibition of the micturition reflex by penile afferents in the cat

“…There is also evidence of supraspinal convergence of pelvic and pudendal afferents in regions associated with control of lower urinary tract function. Penile afferents project to the paragigantocellularis region of the medial reticular formation (20), and afferents activated by DNP stimulation, urethral infusion, and bladder distension converge on neurons in the medullary reticular formation (26). The ventral medullary gigantocellular reticular nuclei (which consists partially of the lateral paragigantocellular nucleus) projects to the intermediate gray and sacral parasympathetic nucleus of the sacral spinal cord (23).…”

Cross-organ interactions between reproductive, gastrointestinal, and urinary tracts: modulation by estrous stage and involvement of the hypogastric nerve

“…3, C-E) and rely on three published facts. First, there is extensive convergence of pelvic organ input on neurons in the spinal cord and brain (7,24,38). Second, preganglionic fibers in the hypogastric nerve synapse not only on neurons in the inferior mesenteric ganglion but also on neurons in the pelvic ganglion (23, 68), i.e., the pelvic ganglion receives preganglionic input from fibers traveling in both the hypogastric nerve derived from T13/L1 and the pelvic nerve derived from L6-S2.…”

Effects of exercise training on urinary tract function after spinal cord injury

“…92 and 93 for justification) after ϳ10 wk of training (or equivalent time frame) for all groups. For catheter placement (47,54,63), a 1.5-cm midline abdominal incision was made under brief gas anesthesia (2% isoflurane). The catheter (PE-60 tubing), with previously heated tip to form a collar of ϳ2 mm from the end, was inserted into the bladder through the dome.…”