Postnatal maturational changes in rat pelvic autonomic ganglion cells: a mixture of steroid-dependent and -independent effects

The influence of castration on intramural neurons of the urinary bladder trigone in male pigs

The present study investigated the influence of castration performed at neonatal age on neuronal elements in the intramural ganglia of the urinary bladder trigone (UBT) in male pigs using double-labeling immunohistochemistry. The ganglia were examined in intact (IP) 7-day-old (castration day) pigs, and at 3 and 6 months after surgery. In IP and control (3- and 6-month-old noncastrated pigs) groups, virtually, all neurons were adrenergic (68%) or cholinergic (32%) in nature. Many of them (32%, 51%, and 81%, respectively; 56%, 75%, and 85% adrenergic; and 32%, 52%, and 65% cholinergic, respectively) stained for the androgen receptor (AR), and only a small number of nerve cells were caspase-3 (CASP-3)-positive. In 3- and 6-month-old castrated pigs, an excessive loss (87.6% and 87.5%, respectively) of neurons and intraganglionic nerve fibers was observed. The majority of the surviving adrenergic (61% and 72%, respectively) and many cholinergic (41% and 31%, respectively) neurons expressed CASP-3 and were also AR-positive (61% and 66%, and 40% and 36%, respectively). This study revealed for the first time the excessive loss of intramural UBT neurons following castration, which could have resulted from apoptosis induced by androgen deprivation.

The Effect of Castration on Peripheral Autonomic Neurons Supplying Mammalian Male Genitourinary System

This review paper deals with the influence of androgens (testosterone) on pelvic autonomic pathways in male mammals. The vast majority of the relevant information has been gained in experiments involving castration (testosterone deprivation) performed in male rats, and recently, in male pigs. In both species, testosterone significantly affects the biology of the pathway components, including the pelvic neurons. However, there are great differences between rats and pigs in this respect. The most significant alteration is that testosterone deprivation accomplished a few days after birth results some months later in the excessive loss (approximately 90%) of pelvic and urinary bladder trigone intramural neurons in the male pig, while no changes in the number of pelvic neurons are observed in male rats (rats do not have the intramural ganglia). In the castrated pigs, much greater numbers of pelvic neurons than in the non-castrated animals express CGRP, GAL, VIP (peptides known to have neuroprotective properties), and caspase 3, suggesting that neurons die due to apoptosis triggered by androgen deprivation. In contrast, only some morpho-electrophysiological changes affecting neurons following castration are found in male rats. Certain clinicopathological consequences of testosterone deprivation for the functioning of urogenital organs are also discussed.

Changes in excitability and ion channel expression in neurons of the major pelvic ganglion in female type II diabetic mice

Bladder cystopathy and autonomic dysfunction are common complications of diabetes, and have been associated with changes in ganglionic transmission and some measures of neuronal excitability in male mice. To determine whether type II diabetes also impacts excitability of ganglionic neurons in females, we investigated neuronal excitability and firing properties, as well as underlying ion channel expression, in major pelvic ganglion (MPG) neurons in control, 10-week, and 21-week Lepr^db/db mice. Type II diabetes in Lepr^db/db animals caused a non-linear change in excitability and firing properties of MPG neurons. At 10 weeks, cells exhibited increased excitability as demonstrated by an increased likelihood of firing multiple spikes upon depolarization, decreased rebound spike latency, and overall narrower action potential half-widths as a result of increased depolarization and repolarization slopes. Conversely, at 21 weeks MPG neurons of Lepr^db/db mice reversed these changes, with spiking patterns and action-potential properties largely returning to control levels. These changes are associated with numerous time-specific changes in calcium, sodium, and potassium channel subunit mRNA levels. However, Principal Components Analysis of channel expression patterns revealed that rectification of excitability is not simply a return to control levels, but rather a distinct ion channel expression profile in 21-week Lepr^db/db neurons. These data indicate that type II diabetes can impact the excitability of post-ganglionic, autonomic neurons of female mice, and suggest that the non-linear progression of these properties with diabetes may be the result of compensatory changes in channel expression that act to rectify disrupted firing patterns of Lepr^db/db MPG neurons.

Porcine dorsal root ganglia ovarian neurons are affected by long lasting testosterone treatment

We studied the effect of testosterone overdose on the number, distribution and chemical coding of ovarian neurons in the dorsal root ganglia (DRGs) in pigs. On day 3 of the estrous cycle, the ovaries of both the control and experimental gilts were injected with retrograde tracer Fast Blue. From day 4 of the estrous cycle to the expected day 20 of the second studied cycle, the experimental gilts were injected with testosterone, while the control gilts received oil. After the completion of the protocol the Th16-L5 DRGs were collected. Injections of testosterone increased the testosterone (~3.5 fold) and estradiol-17beta (~1.6 fold) levels in the peripheral blood, and reduced the following in the DRGs: the total number of the Fast Blue-positive perikarya, the population of perikarya in the L2-L4 ganglia, and the numbers of SP(+)/CGRP(+), SP(+)/PACAP(+), SP(+)/nNOS(+) and SP(-)/nNOS(+) perikarya. In the testosterone-injected gilts, the populations of SP(+)CGRP(-), small and large androgen receptors-expressing perikarya were increased. These results suggest that elevated androgen levels during pathological states may regulate the transmission of sensory modalities from the ovary to the spinal cord, and antidromic regulation of the ovarian functions.

Developing a functional urinary bladder: a neuronal context

The development of organs occurs in parallel with the formation of their nerve supply. The innervation of pelvic organs (lower urinary tract, hindgut, and sexual organs) is complex and we know remarkably little about the mechanisms that form these neural pathways. The goal of this short review is to use the urinary bladder as an example to stimulate interest in this question. The bladder requires a healthy mature nervous system to store urine and release it at behaviorally appropriate times. Understanding the mechanisms underlying the construction of these neural circuits is not only relevant to defining the basis of developmental problems but may also suggest strategies to restore connectivity and function following injury or disease in adults. The bladder nerve supply comprises multiple classes of sensory, and parasympathetic or sympathetic autonomic effector (motor) neurons. First, we define the developmental endpoint by describing this circuitry in adult rodents. Next we discuss the innervation of the developing bladder, identifying challenges posed by this area of research. Last we provide examples of genetically modified mice with bladder dysfunction and suggest potential neural contributors to this state.

Bladder outlet obstruction causes up-regulation of nicotinic acetylcholine receptors in bladder-projecting pelvic ganglion neurons

Pelvic ganglion (PG) neurons relay sympathetic and parasympathetic signals to the lower urinary tract, comprising the urinary bladder and bladder outlet, and are thus essential for both storage and voiding reflexes. Autonomic transmission is mediated by activation of the nicotinic acetylcholine receptor (nAChR) in PG neurons. Previously, bladder outlet obstruction (BOO), secondary to benign prostatic hyperplasia, was found to increase soma sizes of bladder-projecting PG neurons. To date, however, it remains unknown whether these morphological changes are accompanied by functional plasticity in PG neurons. In the present study, we investigated whether BOO alters acetylcholine receptor (nAChR) transcript expression and current density in bladder PG neurons. Partial ligation of the rat urethra for six weeks induced detrusor overactivity (DO), as observed during cystometrical measurement. In rats exhibiting DO, membrane capacitance of parasympathetic bladder PG neurons was selectively increased. Real-time PCR analysis revealed that BOO enhanced the expression of the transcripts encoding the nAChR α3 and β4 subunits in PG neurons. Notably, BOO significantly increased ACh-evoked current density in parasympathetic bladder PG neurons, whereas no changes were observed in sympathetic bladder and parasympathetic penile PG neurons. In addition, other ligand-gated ionic currents were immune to BOO in bladder PG neurons. Taken together, these data suggest that BOO causes upregulation of nAChR in parasympathetic bladder PG neurons, which in turn may potentiate ganglionic transmission and contribute to the development of DO.

Electrophysiological identification of tonic and phasic neurons in sensory dorsal root ganglion and their distinct implications in inflammatory pain

In the mammalian autonomic nervous system, tonic and phasic neurons can be differentiated on firing patterns in response to long depolarizing current pulse. However, the similar firing patterns in the somatic primary sensory neurons and their functional significance are not well investigated. Here, we identified two types of neurons innervating somatic sensory in rat dorsal root ganglia (DRG). Tonic neurons fire action potentials (APs) in an intensity-dependent manner, whereas phasic neurons typically generate only one AP firing at the onset of stimulation regardless of intensity. Combining retrograde labeling of somatic DRG neurons with fluorescent tracer DiI, we further find that these neurons demonstrate distinct changes under inflammatory pain states induced by complete Freund's adjuvant (CFA) or bee venom toxin melittin. In tonic neurons, CFA and melittin treatments significantly decrease rheobase and AP durations (depolarization and repolarization), enhance amplitudes of overshoot and afterhyperpolarization (AHP), and increase the number of evoked action potentials. In phasic neurons, however, the same inflammation treatments cause fewer changes in these electrophysiological parameters except for the increased overshoot and decreased AP durations. In the present study, we find that tonic neurons are more hyperexcitable than phasic neurons after peripheral noxious inflammatory stimulation. The results indicate the distinct contributions of two types of DRG neurons in inflammatory pain.

Distribution of androgen and oestrogen receptors-α in the seminal vesicle-related spinal neurones in male rats

The seminal vesicles are male accessory sex glands that contribute much of the seminal fluid volume. Previous studies have suggested that the majority of autonomic innervations to the rat seminal vesicles originate from the bilateral major pelvic ganglia. Many preganglionic autonomic neurones innervating the pelvic ganglion were expressed androgen receptors (AR) or oestrogen receptor (ER)-α immunoreactivity. However, direct neuroanatomic data regarding the distribution of AR and ER-α in seminal vesicle related-spinal neurones are lacking. In the present study, a nonvirulent pseudorabies virus (PRV-152 strain) was used in a retrograde tracing experiment. Four days after PRV injection into the seminal vesicles of male rats, spinal cord sections were prepared. Double- and triple-fluorescence techniques using AR and ER-α with choline acetyltransferase (ChAT) and PRV were used to investigate the AR and ER-α distribution in the seminal vesicles related spinal neurones in male rats. In lamina X, 14% of the PRV-labelled neurones in the L1-L4 segments and 43% in the L5-S1 segments were double-labelled with AR. In the L1-L4 segments, 6% of PRV-labelled neurones and 26% in the L5-S1 segments were double-labelled with ER-α. In the intermedial cell column area, 10% of PRV-labelled neurones in the L1-L4 segments and 47% of PRV-labelled neurones in the L5-S1 segments were double-labelled with AR. Up to 16% of PRV-labelled neurones in the L5-S1 segments were double-labelled with ER-α. No PRV-labelled neurones in the L1-L4 segments were double-labelled with ER-α. However, for the AR and ER-α/PRV/ChAT triple-fluorescence experiments, very few seminal vesicle preganglionic neurones expressed AR or ER-α. Our data suggests that many spinal interneurones but not preganglionic neurones involved in the seminal vesicle control in male rats were double-labelled with AR or ER-α, and they were mainly located at the parasympathetic level in the spinal cord.

Changes in the number and volume of NPY and VIP neurons from periprostatic accessory vegetative ganglia in pre- and peripubertal rats. A stereological study

The amount of neurons of periprostatic accessory ganglia in pre- and peripubertal rats was studied to ascertain whether the development of these autonomic ganglia is androgen-dependent. Stereological estimates of the volumes and number of neurons immunoreactive to protein gene product 9.5 (PGP 9.5), neuropeptide Y (NPY), and vasoactive intestinal polypeptide (VIP) were carried out. Immunostaining of androgen receptors (AR) in the ganglia was also performed. The ganglionic neurons from the two groups studied were immunoreactive to PGP 9.5, NPY, and VIP. Almost all the neurons were immunostained for AR. The ganglionic volume showed a significant increase in peripubertal prostate in comparison with the prepubertal gland. No significant changes were observed with respect to the absolute number of neurons immunoreactive to all the antigens. The neuronal volume was significantly increased in peripubertal rats in comparison with prepubertal animals. These findings led us to the following conclusions: There is no evidence of neurogenesis during pubertal development in the periprostatic accessory ganglia of the rat. The increase of ganglionic volume in puberty is due to the growth in neuronal volume. There were no differences between the sizes of NPY and VIP neurons in pubertal periprostatic accessory ganglia. The development of periprostatic vegetative neurons is androgen-dependent.

Androgen receptors in coeliac ganglion in late pregnant rat

The ovarian function is controlled by endocrine factors and neural influence. In late pregnant rat, androstenedione, from the coeliac ganglion, has a luteotrophic effect in the ex vivo coeliac ganglion-superior ovarian nerve-ovary system. In this work we investigate the presence of androgen receptors in the coeliac ganglion of late pregnant rats by immunohistochemistry. We also explore, from a physiological point of view, the potential participation of these receptors in the androstenedione ganglionic action on progesterone release and metabolism, as well as on nitrites release in the ovary compartment. The coeliac ganglion was isolated after being fixed in situ and immunohistochemistry was performed. In the system, three experimental groups were used with the addition of (a) androstenedione, (b) flutamide, and (c) androstenedione plus flutamide in the ganglion compartment. Progesterone and nitrite concentrations were determined in the ovary compartment at different incubation times. Corpora lutea samples isolated at the end of incubation were used to determine the expressions and activities of the progesterone synthesis (3beta-hydroxysteroid-dehydrogenase, 3beta-HSD) and degradation (20alpha-hydroxysteroid-dehydrogenase, 20alpha-HSD) enzymes. Immunohistochemistry revealed cytoplasmatic androgen receptor immunoreactivity in neural somas in the coeliac ganglion. In the coeliac ganglion-superior ovarian nerve-ovary system, androstenedione addition increased 3beta-HSD and decreased 20alpha-HSD, showed a tendency to decrease 20alpha-HSD expression, and increased nitrites release in relation to control. Androstenedione plus flutamide decreased progesterone and nitrites release in relation to the androstenedione group. This work demonstrates the presence of androgen receptors in neurons of celiac ganglion and provides evidence for the luteotrophic action of androstenedione via a neural pathway that may be mediated by these receptors.

Anatomical and physiological properties of pelvic ganglion neurons in female mice

Most neurons that regulate motility and blood flow in female pelvic organs are located within pelvic (paracervical) ganglia. In this study we investigated the anatomical and physiological properties of neurons within mouse (C57/Bl/6) paracervical ganglia. Most neurons showed immunoreactivity for choline acetyl transferase (CHAT) and were presumably cholinergic. Few neurons (approximately 5%) were tyrosine hydroxylase (TH) positive. Immunohistochemical labelling for microtubule associated protein 2 showed most neurons had small somata (cross sectional area approximately 300 microm(2)) and lacked dendrites. Action potential (AP) discharge characteristics, determined by depolarising current step injection, revealed most neurons (70%) adapted rapidly to depolarising current injection and were classified as "phasic". The remaining neurons discharged APs throughout the current step and were classified as "tonic". Membrane properties and current-voltage relationships were similar in phasic and tonic neurons, however the afterhyperpolarisation was significantly smaller in tonic neurons. Stimulation of preganglionic axons usually evoked a single strong preganglionic input (21/27 and 9/10 for pelvic and hypogastric nerves, respectively). In 19 preparations where we tested for inputs from both nerves pelvic inputs predominated (23/45 neurons) and inputs via the hypogastric nerve were rarely observed (3/45 neurons). Together, our data indicate that most neurons within mouse paracervical ganglia are cholinergic and parasympathetic. As there is little anatomical or functional evidence for integration of preganglionic inputs we propose that the role of paracervical neurons is restricted to one of spatial amplification or filtering of preganglionic inputs.

Androgen and estrogen receptor-mediated mechanisms of testosterone action in male rat pelvic autonomic ganglia

Although male reproductive function is primarily androgen dependent, many studies suggest that estrogens have direct actions on the male reproductive organs. Pelvic autonomic neurons provide the motor control of the internal reproductive organs and the penis and various properties of these neurons are affected by endogenous androgens. However, the possible role of estrogens at this site has not been examined. Here we have investigated the significance of estrogens produced by aromatization of testosterone (T) in the physiological actions of androgens on adult male rat pelvic ganglion neurons. Reverse transcriptase polymerase chain reaction (RT-PCR) studies showed that aromatase and both estrogen receptors (ERalpha and ERbeta) are expressed in these ganglia. Western blotting also showed that aromatase is expressed in male pelvic ganglia. Using immunohistochemical visualization, ERalpha was predominantly expressed by nitric oxide synthase (NOS)-positive parasympathetic pelvic ganglion neurons. In vivo studies showed that the decrease in pelvic ganglion soma size caused by gonadectomy could be prevented by administration of T or dihydrotestosterone (DHT), but not 17beta-estradiol (E2), showing that this maintenance action of testosterone is mediated entirely by androgenic mechanisms. However, in vitro studies of cultured pelvic ganglion neurons revealed that T, DHT and E each stimulated the growth of longer and more complex neurites in both noradrenergic and cholinergic NOS-expressing neurons. The effects of T were attenuated by either androgen or estrogen receptor antagonists, or by inhibition of aromatase. Together these studies demonstrate that estrogens are likely to be synthesized in the male pelvic ganglia, produced from T by local aromatase. The effects of androgens on axonal growth are likely to be at least partly mediated by estrogenic mechanisms, which may be important for understanding disease-, aging- and injury-induced plasticity in this part of the nervous system.

Electrical properties of neurons in the intact rat major pelvic ganglion

The aim of this investigation was to characterize the electrical properties of neurons in the rat major pelvic ganglia (MPG) using intracellular recording techniques. MPG were dissected from male rats euthanized by isoflurane and thoracotomy. Neurons were classified as "phasic" or "tonic" according to their rate of accommodation during a 500-ms depolarizing current pulse. Phasic cells were further subdivided into rapidly or slowly adapting. The firing pattern of tonic cells was divided into regular high frequency, low frequency or irregular firing. In tonic cells, onset spikes showed TTX-resistant discharges; whereas sustained spikes were TTX sensitive. Changing the current pulse amplitude or the stimulation interval could alter the firing pattern in both types of neurons. Subthreshold membrane potential oscillations (SMPOs) were primarily observed when neurons were depolarized. SMPOs were Na(+) dependent and TTX sensitive. The majority of tonic and phasic neurons generated rebound spikes, most of which were partially Na(+) dependent. A small percentage (<6%) of neurons exhibited spontaneous activity. Taken together these findings are consistent with the concept that neurons in the MPG exhibit heterogeneous electrical properties.

Plasticity of pelvic autonomic ganglia and urogenital innervation

Pelvic ganglia contain a mixture of sympathetic and parasympathetic neurons and provide most of the motor innervation of the urogenital organs. They show a remarkable sensitivity to androgens and estrogens, which impacts on their development into sexually dimorphic structures and provide an array of mechanisms by which plasticity of these neurons can occur during puberty and adulthood. The structure of pelvic ganglia varies widely among species, ranging from rodents, which have a pair of large ganglia, to humans, in whom pelvic ganglion neurons are distributed in a large, complex plexus. This plexus is frequently injured during pelvic surgical procedures, yet strategies for its repair have yet to be developed. Advances in this area will come from a better understanding of the effects of injury on the cellular signaling process in pelvic neurons and also the role of neurotrophic factors during development, maintenance, and repair of these axons.

Remodelling of connections in pelvic ganglia after hypogastric nerve crush

Pelvic ganglia innervate the urogenital organs and contain both sympathetic and parasympathetic neurons. Previous studies have shown that within days of cutting either the lumbar or sacral preganglionic axons that innervate pelvic ganglia, many axon collaterals grow and appear to form specific connections with denervated pelvic neurons. Here we have examined the longer term consequences of partial deafferentation by studying pelvic ganglia up to 7 weeks after hypogastric nerve (HGN) crush, a lesion which also allows faster regeneration of spinal axons. Noradrenergic neurons were denervated by HGN crush, as demonstrated by loss of varicosities immunostained for the synaptic proteins, synaptophysin and synapsin. A week after HGN crush, axon collaterals grew from parasympathetic pelvic ganglion neurons, shown by the presence of numerous varicose fibers immunostained for vasoactive intestinal peptide (VIP). These VIP fibers were poorly stained or unstained for synaptophysin, even after 7 weeks. At early post-operative times the VIP fibers grew irregularly; however, with longer post-operative times they appeared to target particular VIP-negative, noradrenergic neurons. Our results also indicate that some lumbar preganglionic axons regenerated during the post-operative period, although this only affected a minority of sympathetic neurons. These reinnervated sympathetic neurons were not associated with VIP fibers, suggesting that the new intrinsic connections may have precluded regeneration or targeting of preganglionic axons. Together these results demonstrate that there is considerable remodelling within pelvic ganglia after partial deafferentation. This occurs under conditions where spinal preganglionic axons can regenerate. New intra-ganglionic connectivity may be permanent and may impact on this regeneration.