Systematic review of the relationship between bladder and bowel function: implications for patient management.

BACKGROUND: The complex relationship between bladder and bowel function has implications for treating pelvic disorders. In this systematic review, we discuss the relationship between bladder and bowel function and its implications for managing coexisting constipation and overactive bladder (OAB) symptoms. METHODS: Multiple PubMed searches of articles published in English from January 1990 through March 2011 were conducted using combinations of terms including bladder, bowel, crosstalk, lower urinary tract symptoms, OAB, incontinence, constipation, hypermotility, pathophysiology, prevalence, management and quality of life. Articles were selected for inclusion in the review based on their relevance to the topic. RESULTS: Animal studies and clinical data support bladder-bowel cross-sensitization, or crosstalk. In the rat, convergent neurons in the bladder and bowel as well as some superficial and deeper lumbosacral spinal neurons receive afferent signals from both bladder and bowel. On a functional level, in animals and humans, bowel distention affects bladder activity and vice versa. Clinically, the bladder-bowel relationship is evident through the presence of urinary symptoms in patients with irritable bowel syndrome and bowel symptoms in patients with acute cystitis. Functional gastrointestinal disorders, such as constipation, can contribute to the development of lower urinary tract symptoms, including OAB symptoms, and treatment of OAB with antimuscarinics can worsen constipation, a common antimuscarinic adverse effect. The initial approach to treating coexisting constipation and OAB should be to relieve constipation, which may resolve urinary symptoms. CONCLUSIONS: The relationship between bladder and bowel function should be considered when treating patients with urinary symptoms, bowel symptoms, or both.

A subset of gonadotropin-releasing hormone neurons in the ovine medial basal hypothalamus is activated during increased pulsatile luteinizing hormone secretion.

GnRH neurons active in the preovulatory LH surge have been identified in several species using the early intermediate gene product, Fos, but the GnRH neurons active during episodic LH secretion remain unknown. In this study, we have used Fos and Fos-related antigens (FRA) to determine whether a subset of GnRH neurons is active when pulsatile LH secretion is acutely stimulated in sheep. In experiment 1, episodic LH secretion was stimulated in five of six ewes by injection of an opioid antagonist to luteal phase ewes. These five ewes had a 6-fold increase in the percentage of GnRH neurons in the medial basal hypothalamus (MBH) expressing Fos/FRA, compared with control ewes that had no LH pulses before death. Fos/FRA expression was not increased in GnRH neurons found in any other area. In experiment 2, episodic LH secretion was induced in rams by introduction of estrous ewes. This treatment increased Fos/FRA expression in MBH GnRH neurons approximately 10-fold compared with control rams. Again, this increase in Fos/FRA expression in GnRH neurons was limited to the MBH. This selective activation of MBH GnRH neurons could reflect the preferential inhibition of these perikarya by endogenous opioid peptides. It also raises the possibility that a subset of GnRH neurons in the MBH may be responsible for episodic GnRH secretion in sheep.

The GnRH system of seasonal breeders: anatomy and plasticity.

Seasonal breeders, such as sheep and hamsters, by virtue of their annual cycles of reproduction, represent valuable models for the study of plasticity in the adult mammalian neuroendocrine brain. A major factor responsible for the occurrence of seasonal reproductive transitions is a striking change in the responsiveness of gonadotropin-releasing hormone (GnRH) neurons to the inhibitory effects of gonadal steroids. However, the neural circuitry mediating these seasonal changes is still relatively unexplored. In this article, we review recent findings that have begun to define that circuitry and its plasticity in a well-studied seasonal breeder, the ewe. Tract tracing studies and immunocytochemical analyses using Fos and FRAs as markers of activation point to a subset of neuroendocrine GnRH neurons in the MBH as potential mediators of pulsatile GnRH secretion. Because the vast majority of GnRH neurons lack estrogen receptors, seasonal changes in responsiveness to estradiol are most probably conveyed by afferents. Two possible mediators of this influence are dopaminergic cells in the A14/A15 cell groups of the hypothalamus, and estrogen receptor-containing cells in the arcuate nucleus that project to the median eminence. The importance of GnRH afferents in the regulation of season breeding is underscored by observations of seasonal changes in the density of synaptic inputs onto GnRH neurons. Thyroid hormones may participate in this remodeling, because they are important in seasonal reproduction, influence the morphology of other brain systems, and thyroid hormone receptors are expressed within GnRH neurons. Finally, in the hamster, neonatal hypothyroidism affects the number of caudally placed GnRH neurons in the adult brain, suggesting that thyroid hormones may influence development of the GnRH system as well as its reproductive functions in the adult brain.

How do fetal grafts of the suprachiasmatic nucleus communicate with the host brain?

Fetal grafts containing the hypothalamic suprachiasmatic nucleus (SCN), the site of an endogenous circadian pacemaker, can reinstate behavioral rhythms in lesioned recipients but the precise routes of communication between the graft and the host brain remain unknown. Grafts containing the SCN may convey temporal information to the host brain via neural efferents, diffusible factors, or a combination of both. We examined graft-host connections in anterior hypothalamic homografts (hamster-to hamster) and heterografts (rat-to hamster) implanted in the third ventricle by: (a) applying the carbocyanine dye, diI, directly onto homo- and heterografts in fixed tissue sections; and (b) using a donor-specific neurofilament (NF) antibody to immunocytochemically visualize heterograft efferents. DiI applied onto either homografts or heterografts labeled relatively few graft efferents which could be followed only short distances into the host brain. In contrast, NF-labeled heterograft efferents were both more numerous and extended for longer distances into the host brain than anticipated on the basis of diI tract tracing. The results suggest that anterior hypothalamic grafts implanted in the third ventricle provide substantial input to the adjacent host hypothalamus although it is not known whether these projections arise from SCN cells or from other extra-SCN hypothalamic tissue within these grafts. Nor is it known whether these projections are functional. To determine if neural efferents are required for the restoration of rhythmicity after grafting, we have encapsulated fetal anterior hypothalamus in a permselective polymer which prevents neurite outgrowth but allows diffusible signals to reach the host brain.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of Fos-like proteins in gonadotropin-releasing hormone neurons of Syrian hamsters: effects of estrous cycles and metabolic fuels.

In female mammals, reproduction is sensitive to the availability of metabolic fuels, and food deprivation has been shown to suppress pulsatile LH secretion, attenuate the preovulatory LH surge, and prevent ovulation. It has been suggested that food deprivation impairs fertility by reducing the secretion of GnRH by GnRH-producing neurons in the forebrain. A series of experiments tested this hypothesis by examining the effects of estrous cycles and manipulations of metabolic fuel availability on the expression of Fos-like proteins (Fos-IR) in GnRH-immunoreactive (GnRH-IR) neurons in the forebrain of Syrian hamsters. GnRH-IR neurons were detected in several areas, including the diagonal band of Broca (DBB), medial septum (MS), rostral medial preoptic area (mPOA), and caudal POA. In the more rostral regions (DBB and MS/mPOA), GnRH-IR neurons expressed Fos-IR almost exclusively on day 4 of the cycle, just after the preovulatory LH surge. However, in the caudal POA, GnRH-IR neurons expressed Fos-IR across the entire cycle, including days 1-3, when LH secretion is pulsatile. Food deprivation on days 1 and 2 of the cycle, which attenuates the LH surge and blocks ovulation in hamsters, significantly reduced the proportion of GnRH-IR neurons that expressed Fos-IR on days 2 and 4 (caudal POA) or only on day 4 (DBB and MS/mPOA). Suppression of fuel availability with insulin or 2-deoxy-D-glucose on day 1 of the cycle mimicked the effects of food deprivation and reduced the proportion of caudal POA GnRH-IR neurons that expressed Fos-IR. The results of these experiments suggest that in Syrian hamsters, there are separate populations of GnRH-IR neurons associated with pulsatile and surge modes of LH secretion. In addition, the fact that manipulations of metabolic fuel availability cause changes in the expression of Fos-IR in both populations of GnRH-IR neurons provides strong support for the hypothesis that nutritional infertility is due in part to decreased GnRH secretion.