Maturational changes in sympathetic and sensory innervation of the rat uterus: effects of neonatal capsaicin treatment

The effects of Bisphenol A (BPA) on sympathetic nerve fibers in the uterine wall of the domestic pig

Bisphenol A (BPA), used in the production of plastic, shows multidirectional negative effects on the living organism. BPA may affect the reproductive and nervous systems; however, its influence on the nerves supplying the uterus has not been studied. During the present study, the impact of BPA on the sympathetic nerves in the uterus was investigated using a double immunofluorescence technique. The results have shown that even low doses of BPA may change the neurochemical characterization of uterine sympathetic nerves, and the severity of these changes depends on the part of the uterus and the dose of the toxic substance. Probably the changes observed during the present study resulted from the neurotoxic and/or pro-inflammatory activity of BPA, but the exact mechanism for the observed fluctuation still remains unknown. The fluctuations of the neurochemical characterization of the uterine intramural nerves may be the first subclinical signs of harmful exposure to BPA.

The opioid neuropeptides in uterine fibroid pseudocapsules: a putative association with cervical integrity in human reproduction

The myoma pseudocapsule (MP) is a fibro-vascular network rich of neurotransmitters, as a neurovascular bundle, surrounding fibroid and separating myoma from myometrium. We investigated the distribution of the opioid neuropeptides, as enkephalin (ENK) and oxytocin (OXT), in the nerve fibers within MP and their possible influence in human reproduction in 57 women. An histological and immunofluorescent staining of OXT and ENK was performed on nerve fibers of MP samples from the fundus, corpus and isthmian-cervical regions, with a successive morphometric quantification of OXT and ENK. None of the nerve fibers in the uterine fundus and corpus MPs contained ENK and the nerve fibers in the isthmian-cervical region demonstrated an ENK value of up to 94 ± 0.7 CU. A comparatively lower number of OXT-positive nerve fibers were found in the fundal MP (6.3 ± 0.8 CU). OXT-positive nerve fibers with OXT were marginally increased in corporal MP (15.0 ± 1.4 CU) and were substantially higher in the isthmian-cervical region MP (72.1 ± 5.1 CU) (p < 0.01). The distribution of OXY neurofibers showed a slight into the uterine corpus, while are highly present into the cervico-isthmic area, with influence on reproductive system and sexual disorders manifesting after surgical procedures on the cervix.

Distribution and chemical coding of sympathetic neurons in the caudal mesenteric ganglion projecting to the ovary in sexually mature gilts

The distribution and co-localisation patterns of dopamine-beta-hydroxylase (DβH), neuropeptide Y (NPY), somatostatin (SOM) and galanin (GAL) were investigated by use of retrograde neuronal tracing and double-labelling immunofluorescence techniques in the caudal mesenteric ganglion (CaMG) neurons supplying the ovary of adult pigs. The existence and density of nerve fibres that are immunoreactive (IR) for the above-mentioned neuroactive substances were also evaluated. Injections of a fluorescent tracer (Fast Blue; FB) into the ovaries revealed the presence of small- (76.38%) and large-sized (23.62%) FB-positive postganglionic neurons in the CaMG. Noradrenergic FB-positive cells were simultaneously NPY- (43.38%), SOM- (18.77%) and GAL- (18.31%) IR. Of the examined FB-positive neurons, 53.49% were DβH-IR but NPY-immunonegative (IN), 79.06% were DβH-IR but SOM-IN, and 77.16% were DβH-IR but GAL-IN. Small- or large-sized subsets of traced neurons were supplied by only one or a few nerve fibres, exhibiting DβH-, NPY-, SOM- and/or GAL-IR. Our data show the specific morphological as well as immunochemical structural organisation of the sympathetic neurons in the CaMG in adult gilts. The occurrence of an abundant population of noradrenergic perikarya in the CaMG may suggest their important physiological role in the regulation of gonadal function(s) in these animals.

Mechanisms involved in contractile differences among cremaster muscles according to localization of testis

BACKGROUND/PURPOSE

Evidence suggests differences in contractility in cremaster muscles (CM) associated with undescended testis caused by alterations of autonomic innervation. Contractile responses of CM to various pharmacologic agents were evaluated and compared according to the localization of testis.

METHODS

Samples of CM from boys with undescended testis or inguinal hernia were obtained. Twitch and tetanic contractions were recorded isometrically at 37 degrees C. Effects of verapamil, isoprenaline, calcitonin gene-related peptide (CGRP), substance P (SP) and N(omega)-nitro-L-arginine (L-NNA) were investigated. Results were compared through 2-way analysis of variance, and P values less than.05 were considered to be different.

RESULTS

Verapamil alone significantly (P <.05) decreased contraction amplitudes in CM from both sources; the decrease was more pronounced in CM from boys with inguinal hernia (P <.05). Although isoprenaline increased contraction amplitudes in CM associated with undescended testis (P <.05), CGRP and SP increased contraction amplitudes in CM associated with descended testis (P <.05). L-NNA increased contraction amplitudes in both groups (P <.05). The decrease of contraction amplitudes after verapamil displayed a similar pattern after isoprenaline, SP, and L-NNA. Verapamil-induced contractility decrease was more pronounced after CGRP in both groups (P <.05).

CONCLUSIONS

Sensitivity of CM to verapamil differs according to localization of testis. Isoprenaline enhances contractility by stimulating Na(+)-K(+)ATPase in undescended testis without altering voltage-sensitive channel sensitivity to verapamil. CGRP and SP increase contractility in inguinal hernia, and CGRP increases the sensitivity of voltage-sensitive Ca(2+) channels to verapamil in CM from both groups. Nitric Oxide (NO) exerts inhibitory action on CM contractility, and it is less pronounced in undescended testis. These differences may contribute to pathophysiology of undescended testis.

Sympathetic hyperinnervation of the uterus in the estrogen receptor alpha knock-out mouse

Uterine innervation undergoes cyclical remodeling in the adult virgin rat. Previous studies showed that ovariectomy leads to increased uterine sympathetic nerve density, and this can be reduced by estrogen administration. However, the receptor mechanism by which estrogen modulates sympathetic innervation is unknown. The present study assessed the role of the estrogen receptor alpha in establishing levels of uterine innervation by comparing the nerve abundance in mice with a null mutation of the estrogen receptor alpha with those of the wild-type cycling mouse. Immunostaining for total uterine innervation using antibodies against the pan-neuronal marker protein gene product 9.5 showed that nerve numbers in normally cycling wild-type mice were high in diestrus when circulating estrogen is at its nadir, and low at estrus, coincident with high plasma estrogen. Uteri of the estrogen receptor alpha knock-out mice were smaller than those of wild-type mice, but even when corrected for differences in size, total innervation was 188% and 355% greater than that of wild-type mice at diestrus and estrus, respectively. This hyperinnervation is associated with increased numbers of nerves immunoreactive for the noradrenergic enzyme dopamine beta-hydroxylase, without obvious differences in those containing calcitonin gene-related peptide or the vesicular acetylcholine transporter. While estrogen supplementation of the ovariectomized wild-type mice significantly reduced total uterine innervation, neither ovariectomy nor estrogen supplementation affected uterine nerve density in estrogen receptor alpha knock-out mice.We conclude that estrogen acting through the estrogen receptor alpha determines the number of sympathetic nerve terminal branches within uterine smooth muscle target. In mice with low circulating estrogen, or high estrogen but lacking the functional estrogen receptor alpha, the uterus contains abundant sympathetic nerves, whereas estrogen acts via the estrogen receptor alpha to regulate uterine innervation by reducing numbers of intact sympathetic nerves. Although it is not known whether estrogen acts on the target or neuron to initiate these changes, the estrogen receptor alpha apparently plays a major role in the cyclical modulation of uterine sympathetic innervation.

The regulation of total body fat: lessons learned from lipectomy studies

Surgical removal of body fat (partial lipectomy) is a means of directly reducing fat such that metabolic and behavioral responses can be readily attributed to the lipid deficit. If total body fat is regulated, then lipectomy should trigger compensatory increases in nonexcised white adipose tissue (WAT) mass and/or regrowth at excision sites. Many species, including laboratory rats and mice, show lipectomy-induced compensatory recovery of body fat. Those animals exhibiting naturally occurring annual adiposity cycles, such as ground squirrels and hamsters, do so most impressively reaching seasonally appropriate body fat levels indistinguishable from controls. Reparation of the lipid deficit occurs without an increase in food intake, and generally through enlargement of non-excised WAT mass, rather than regrowth of excised WAT. A body fat regulatory system involving humoral and sensory neural inputs to the brain as well as sympathetic neural outputs from brain to adipose tissue is presented. Collectively, the lipectomy model appears useful for testing mechanisms controlling adiposity, or individual depot growth, and offers insight into how lipid stores fluctuate naturally.

The evaluation of sympathetic system-related contractile activity of the rat vas deferens after ligation and intra-abdominal placement of the testis

OBJECTIVE

To evaluate the contractile response of the vas deferens in a model of stress, to determine any changes in sympathetic activity as a result of stress in the ipsilateral testis, which decreases blood flow to the contralateral testis.

MATERIALS AND METHODS

The study comprised two groups of six rats each; group 1 underwent a sham operation, and in group 2 the right testis was placed into the abdominal cavity and the vas deferens ligated. After 30 days, the vasa deferentia were resected bilaterally and their isometric contractions recorded. Electrical-field stimulation (EFS) was applied through a pair of platinum electrodes and concentration-response curves constructed for noradrenaline at 37 degrees C and to a solution containing 80 mmol/L K+.

RESULTS

The vasa deferentia in both groups showed similar contractile responses to EFS, which were frequency-dependent and maximal at 80 Hz. Noradrenaline-induced contractile activity was lower in amplitude in the vasa deferentia of group 2 than in the contralateral and ipsilateral vasa deferentia of group 1, which were not significantly different from each other. All groups responded similarly to high K+.

CONCLUSION

Intra-abdominal placement of the testes with vas deferens ligation decreased the contractile response to noradrenaline in the ipsilateral vas deferens without altering the contractile response to EFS and high K+. This difference could be caused by a reduction in the number of postjunctional alpha-adrenergic receptors or decreased receptor sensitivity. Both possibilities suggest that the vas deferens may initiate sympathetic activity, which may be responsible for contralateral testicular deterioration.

Neurogenic and non-neurogenic responses in the urinary bladder of hibernating hamster

1. Purinergic and cholinergic components of parasympathetic neurotransmission and contractile responses to exogenous alpha,beta-methylene ATP, acetylcholine, substance K, substance P, calcitonin gene-related peptide, vasoactive intestinal polypeptide and capsaicin have been investigated in the urinary bladder of hibernating hamsters (4 weeks), cold exposed (4 weeks) and age-matched controls. 2. Electrical field stimulation (EFS) evoked increased frequency-dependent contractions in the detrusor strips from hibernating hamsters compared with those obtained from cold-exposed and age-matched animals. Tetrodotoxin (10(-6) M) completely blocked the frequency-dependent contractions in all groups. 3. The purinergic component of the parasympathetic neurotransmission was not affected in hibernating and cold-exposed animals while the cholinergic component was increased with respect to age-matched animals. The neurogenic response to EFS, still present after incubation with atropine (10(-6) M) and suramin (10(-4) M), was attenuated by indomethacin (10(-6) M) and blocked by tetrodotoxin (10(-6) M). 4. Exogenous administration of alpha,beta-methylene ATP elicited a significantly reduced contraction in strips from hibernating and cold-exposed hamsters relative to age-matched animals. The contractile response to exogenous acetylcholine was greater in the detrusors from hibernating hamsters than in cold-exposed and age-matched animals. Substance K elicited reduced contractions in preparations from hibernating animals compared with cold-exposed and control animals. Calcitonin gene-related peptide, vasoactive intestinal polypeptide, substance P and capsaicin did not elicit any relaxant or contractile response either at resting tone or in carbachol (5 x 10(-7) M)-precontracted tissues. 5. In summary, our findings indicate that 4 weeks of hibernation can significantly increase neurogenic responses in the hamster urinary bladder. This appears to be due to an increase in postjunctional responses to acetylcholine. In contrast, there was a decrease of the postjunctional responses to the parasympathetic cotransmitter ATP and also to the sensory-motor neurotransmitter substance K.

Expression of beta-adrenergic receptors in the rat uterus: effects of puberty and oestrogen treatment during prepubertal development

The expression of beta-adrenoceptors in the rat uterus has been analysed during the peripubertal transition and following acute and chronic oestradiol treatment during prepubertal development. The distribution and density of beta-adrenoceptors was assessed autoradiographically on cryostat tissue sections using [3H]-dihydroalprenolol ([3H]-DHA). Binding sites were localised in all ages and experimental situations examined and showed the following intensity of labelling: endometrial epithelium > longitudinal muscle layer > circular myometrial layer > endometrial stroma. Competition experiments with the selective antagonists ICI 118,551 and atenolol, showed that most of the beta-adrenoceptors in the uterus belong to the beta(2) receptor subclass. In prepubertal animals, the density of [3H]-DHA binding sites was extremely low. Following puberty the density of binding sites showed a generalised increase. Acute administration of oestradiol at the end of the prepubertal period provoked an increase in the density of [3H]-DHA binding sites in all uterine regions, but the levels of labelling were lower than in peripubertal animals at proestrus and oestrus. Following chronic oestrogen treatment during postnatal development, oestradiol increased further the density of [3H]-DHA binding sites. Results are discussed considering both the endocrine and neural changes accompanying puberty and oestradiol treatment.

Plasticity in adult and ageing sympathetic neurons

The nature of neural plasticity and the factors that influence it vary throughout life. Adult neurons undergo extensive and continual adaptation in response to demands that are quite different from those of early development. We review the main influences on the survival, growth and neurotransmitter expression in adult and ageing sympathetic neurons, comparing these influences to those at work in early development. This "developmental" approach is proposed because, despite the contrasting needs of different phases of development, each phase has a profound influence on the mechanisms of plasticity available to its successors. Interactions between neurons and their targets, whether effector cells or other neurons, are vital to all of these aspects of neural plasticity. Sympathetic neurons require access to target-derived diffusible neurotrophic factors such as NGF, NT3 and GDNF, as well as to bound elements of the extracellular matrix such as laminin. These factors probably influence plasticity throughout life. In adult life, and even in old age, sympathetic neurons are relatively resistant to cell death. However, they continue to require target-derived diffusible and bound factors for their maintenance, growth and neurotransmitter expression. Failure to maintain appropriate neuronal function in old age, for example in the breakdown of homeostasis, may result partly from a disturbance of the dynamic, trophic relationship between neurons and their targets. However, there is no clear evidence that this is due to a failure of targets to synthesize neurotrophic factors. On the neural side of the equation, altered responsiveness of sympathetic neurons to neurotrophic factors suggests that expression of the trk and p75 neurotrophin receptors contributes to neuronal survival, maintenance and growth in adulthood and old age. Altered receptor expression may therefore underlie the selective vulnerability of some sympathetic neurons in old age. The role of neural connectivity and activity in the regulation of synthesis of target-derived factors, as well as in neurotransmitter dynamics, is reviewed.

Age-related changes in purinergic and adrenergic components of sympathetic neurotransmission in guinea-pig seminal vesicles

1. Purinergic and adrenergic components of sympathetic neurotransmission and contractile responses to exogenous alpha,beta-methylene ATP and noradrenaline have been investigated in the seminal vesicles of 1-day (new-born), 2-weeks (young), 12-weeks (adult) and 2-years old (aged) guinea-pigs. 2. In seminal vesicles of new-born guinea-pigs electrical field stimulation (EFS; 80 V, 0.5 ms for 30 s, 2-32 Hz) evoked tonic frequency-related contractions. In 2-weeks old guinea-pigs the tonic contraction masked an initial phasic component of the neurogenic responses, whereas in 12-weeks and 2-years old guinea-pigs, neurogenic responses were biphasic, a phasic response being followed by a tonic contraction. In all experimental groups, prazosin (10(-6) M) blocked the tonic contraction while desensitization of P2X receptors by alpha,beta-methylene ATP (10(-4) M) abolished the phasic responses. 3. The phasic purinergic component of the neurogenic response was significantly higher in 12-weeks and 2-years old animals, compared with 2-weeks old guinea-pigs. At 32 Hz phasic contractions were (mN mg(-1) tissue): 0.047+/-0.012, 0.018+/-0.040 and 0.147+/-0.026 in 2-weeks, 12-weeks and 2-years old guinea-pigs, respectively. In contrast, the tonic adrenergic component of the neurogenic contraction significantly declined at 12-weeks and 2-years compared with 2-weeks old guinea-pigs. 4. Contractile responses (mN mg(-1) tissue) to the highest concentration of alpha,beta-methylene ATP tested were significantly higher in 2-weeks (0.248+/-0.022) than in 1-day old animals (0.113+/-0.012) and decreased in 12-weeks (0.163+/-0.016) and 2-years old guinea-pigs (0.200+/-0.008). The pD2 values for the purinoceptor agonist were also significantly lower in adult (4.74+/-0.20) and aged guinea-pigs (5.22+/-0.08) compared with 2-weeks old animals (5.91+/-0.27). Conversely, responses to the highest concentration of noradrenaline gradually decreased with age, without significant changes in the pD2 values. Contractile responses to KCl (240 mM) did not differ significantly between the experimental groups. 5. These results demonstrate age-related changes in purinergic and adrenergic components of sympathetic neurotransmission in the guinea-pig seminal vesicles. The purinergic component is absent in new-born animals and it appears fully developed in adult and old guinea-pigs, while the adrenergic component decreases with age. Pre- and postjunctional mechanisms contributing to the age-related changes of sympathetic neurotransmission are discussed.

Development and maturation of noradrenaline-containing nerves of the rat uterine artery. Effects of acute and chronic oestrogen treatment

The development and maturation of noradrenaline-containing nerves of the rat uterine artery was investigated, histochemically and biochemically, at seven different postnatal age-stages and following acute and chronic treatment with oestradiol. Morphological changes in the vessel were quantitatively evaluated on Toluidine Blue-stained semithin sections and low magnification electronmicrographs. In summary, the uterine artery is innervated at birth; the adult pattern of innervation is established at two weeks of age; the innervation density increases progressively between the infantile and prepubertal periods, accompanying proliferation and growth of smooth muscle cells in the tunica media; changes in the innervation are followed by an increase in the tissue concentration of noradrenaline and neither the endocrine changes characterizing puberty nor acute or chronic treatment with oestradiol have an effect on the pattern of development of the uterine artery and associated noradrenaline-containing nerves. Results are interpreted considering the differential susceptibility of urinogenital organs to sex hormones.

Effects of chronic and acute oestrogen treatment on the developing noradrenaline-containing nerves of the rat uterus

The developing noradrenaline-containing (NA-C) sympathetic nerves of the rat uterus were analyzed following acute and chronic treatment with oestrogen. Histochemical methods were used in association with nerve density measurements and biochemical assays. For comparative purposes, noradrenaline (NA) levels were measured in the urinary bladder and right auricle following chronic oestrogen treatment. Acute treatment was performed by s.c. administration of a single dose of 40 micrograms oestradiol cypionate on the 25th day of age. Chronic treatment consisted of four doses of 10 micrograms oestradiol on days 10, 15, 20 and 25 of postnatal development. Both acute- and chronic-treated animals were killed at 28 days of age. The main biochemical findings were the following: (a) both acute and chronic oestrogen treatment increased the weight of the uterine horn, parametrial tissue and uterine cervix; (b) in the uterine horn, the total content of NA was reduced following both oestrogen treatments. However, the degree of reduction was greater after chronic treatment; (c) in the parametrial tissue, the NA levels were reduced only after chronic treatment; (d) in the cervix, the NA total content was increased after both treatments; (e) in the urinary bladder, there was a parallel increase between organ growth and NA content following chronic oestrogen treatment; (e) in the auricle neither the tissue weight nor the total content of NA were changed by chronic estrogen treatment. Histochemical studies showed that: (a) acute treatment with one single dose of oestradiol, provoked a marked reduction in the density of NA-C nerves associated with the myometrial and parametrial smooth muscle, without affecting the innervation of blood vessels; (b) following chronic treatment, the only fibers we were able to recognize were those associated with blood vessels. These fibers were thinner and less intensely fluorescent than in controls. Results are interpreted considering the differential sensitivity of uterine nerves to sex hormones. A possible involvement of oestrogen in changes of noradrenergic innervation of the uterus following puberty is discussed.

Nerve growth factor treatment of adult rats selectively enhances innervation of urinogenital tract rather than vascular smooth muscle

Following treatment of adult rats with nerve growth factor (0.5 mg/rat, three times a week for 3 weeks), the innervation of cardiovascular and urinogenital tract smooth muscle was investigated using immunoassay and immunohistochemical techniques. Substance P and calcitonin gene-related peptide levels were increased in the vas deferens, but not in the atria or femoral artery. Neuropeptide Y and vasoactive intestinal polypeptide levels were unchanged. In penile tissues, there was a marked increase in the density of substance P-, calcitonin gene-related peptide-, neuropeptide Y-, tyrosine hydroxylase- and vasoactive intestinal polypeptide-containing nerves innervating the urethra and in SP-containing nerves in the tunica with little changes in the innervation of the deep dorsal vein and artery and corpus cavernosum. In the bladder, there was increased innervation of the detrusor by neuropeptide Y- and vasoactive intestinal polypeptide-containing nerves, but a decrease in innervation by substance P-containing nerves in the trigone. There were no changes in the density of innervation of the femoral artery after nerve growth factor treatment. Thus, in the mature rat, sensory and sympathetic nerve innervating urinogenital tract smooth muscle appear to be more responsive to exogenous nerve growth factor than those innervating cardiovascular smooth muscle. This may reflect an ongoing requirement of plasticity of innervation in the urinogenital tract of the sexually mature animal.

Plasticity of autonomic nerves: differential effects of long-term guanethidine sympathectomy on the sensory innervation of the rat uterus during maturation

The sensory nerves, containing substance P and calcitonin gene-related peptide, and noradrenaline-containing sympathetic nerves of the rat uterus were analyzed following long-term sympathectomy with guanethidine in prepubertal (four weeks), young adult (eight weeks) and fully adult animals (18 weeks). Immunohistochemical and histochemical methods were used in association with nerve density measurements and biochemical assays. The main findings were as follows: (1) long-term guanethidine treatment completely abolished the noradrenergic innervation of the uterine horn and parametrial tissue and markedly reduced the tissue levels of noradrenaline in both regions at the three ages analysed; (2) in the uterine horn guanethidine treatment had no effect on the tissue levels of either calcitonin gene-related peptide or substance P or on the density of calcitonin gene-related peptide-containing nerves, at any of the three ages studied; (3) in the parametrial tissue increased levels of calcitonin gene-related peptide were observed at 8 and 18 weeks of age, together with a significant increase in the density of calcitonin gene-related peptide-containing nerves. Substance P levels showed a transient increase in this tissue at eight weeks. In conclusion, long-term sympathectomy with guanethidine resulted in an increase in calcitonin gene-related peptide and substance P in sensory nerves in the parametrial tissue, but not in the uterine horn. The changes in the parametrial tissue only occurred after puberty. It is suggested that sensory nerves in the uterine horn may be less responsive to sympathetic denervation since loss of sympathetic nerves occurs as part of a normal physiological process during pregnancy in this region.