Micturition reflex

Capsaicin-sensitive nerves sense bladder fullness and form the afferent limb of the micturition reflex [132]. In conditions of bladder hypersensitivity, TRPVl is up-regulated on these nerves (presumably via NGL [133, 134]) and deafferentation of the bladder by intravesical capsaicin or RTX was proven beneficial [135-137]. Parenthetically, intravesical RTX is also an effective analgesic agent during experimental cystitis in the rat [138]. By... 

Enhancing the positive effects of serotonin and norepinephrine in the afferent and efferent pathways of the micturition reflex... 

The goal of treatment of SUI is to improve urethral closure by stimulating a-adrenergic receptors in the smooth muscle of the bladder neck and proximal urethra, enhancing supportive structures underlying the urethral epithelium, or enhancing serotonin and norepinephrine effects in the micturition reflex pathways. 

Other recent studies have reported that the 5-HT7 receptor is involved in mediating the effects of 5-HT on ileum peristalsis (107). the micturition reflex (108), and relaxation of the oviduct (109). 

Read KE, Sanger GJ, Ramage AG. Evidence for the involvement of central 5-HT7 receptors in the micturition reflex in anaesthetized female rats. Br J Pharmacol 2003 140 53-60. 

Maggi CA, Santicioli P, Furio M, Meli A (1985) Dual effects of clonidine on micturition reflex in urethane anesthetized rats. J Pharmacol Exper Ther 235 528-536... 

Maggi CA, Giuliani S, Santicioli P et al. (1987) Further studies on the mechanisms of the tachykinin-induced activation of the micturition reflex in rats evidence for the involvement of the capsaicin-sensitive bladder mechanoreceptors. Eur J Pharmacol 136 189-205... 

Maggi CA, Santicioli P, Furio M, Meli A (1985) Dual effects of clonidine on micturition reflex in urethane anesthetized rats. J Pharmacol Exper Ther 235 528-536 Mapp CE, Chitano P, Fabbri LM et al. (1990) Pharmacological modulation of the contractile response to toluene diisocyanate in the rat isolated urinary bladder. Br J Pharmacol 100 886-888... 

Neurokinin A and B are both decapeptides discovered by Kimura et al. (142) from the porcine spinal cord. Both have very similar amino acid composition and sequence homology to the undecapeptide substance P, and they also have similar biological activities as substance P. They are potent bronchoconstrictors, constrict smooth muscle, and activate the micturition reflex. 

In vitro experiments demonstrated that menthol (0.1-1.0 mM) inhibited carbachol-induced contraction of the detrusor smooth muscle of rat. Intravesical infusion of menthol (3.0 mM) facilitated the micturition reflex since it caused a reduction in voided volume (by 20%), volume threshold for inducing micturition (19%), and pressure threshold for inducing micturition (31%). This effect on micturition reflex was not modified by pretreatment with capsaicin. This was interpreted to suggest that intravesically infused menthol cannot relax detrusor muscle, and acts on capsaicin-resistant afferents (probably through TRPM8 in urothelium or sensory nerve endings) to facilitate the micturition reflex [15]. 

Nomoto Y, Yoshida A, Dceda S, Kamikawa Y, Harada K, Ohwatashi A, Kawahira K (2008) Effect of menthol on detrusor smooth-muscle contraction and the micturition reflex in rats. Urology 72 701... 

Afferent cholinergic and adrenergic autonomic fibers are similarly present in detrusor and lissosphincter units and include micturition triggers linked with stretch receptors and urinary flow receptors (Gil Ver-net, 1968 Hutch, 1972 Elbadawi, 1973, 1982, 1983 Elbadawi and Schenk, 1974 de Groat and Kawatani, 1985). Some of the afferent fibers connect to reflex circuits in the sacral cord for bladder and rectum while connecting in the sacral and thoracic cord for sexual reflex circuits. 

Maggi CA (1992) Prostanoids as local modulators of reflex micturition. Pharmacol Res 25 13-20... 

When the detrusor relaxes and the sphincters close, urine is stored this is achieved by central inhibition of parasympathetic tone accompanied by a reflex increase in a-adrenergic activity. Voiding requires contraction of the detrusor, accompanied by relaxation of the sphincters. These acts are coordinated by a micturition centre probably in the pons. 

A basic study of the urinary tract should start with an explanation to the parents, and to the child if he or she is old enough to understand. The bladder is studied first, especially in infants, since reflex micturition is frequent when the transducer is placed on the abdominal wall (avoid unheated jelly). Examination of the full bladder includes analysis of urine echogenicity and the bladder wall. It is extremely important to look for dilated ureters(s) behind the... 

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