Central nervous system innervation of the penis as revealed by the transneuronal transport of pseudorabies virus

Physiology of Erection and Pathophysiology of Erectile Dysfunction

The science of penile erection, including recent advances in its molecular physiology and neuroanatomic pathways, is described. The pathophysiology of erectile dysfunction is presented, acknowledging associated disease states, and accordingly follows a practical classification scheme: vasculogenic, neurogenic, endocrine, and psychogenic.

Differences in polysomnographic, nocturnal penile tumescence and penile doppler ultrasound findings in men with stuttering priapism and sleep-related painful erections

Men with Stuttering Priapism (SP) and sleep-related painful erections (SRPE) experience bothersome nocturnal painful erections resulting in poor sleep. The aim of this study is to observe common features and differences between men with SP and SRPE based on polysomnography, nocturnal penile tumescence (NPT), and penile doppler ultrasound (PDU). This is a prospective cohort study of 20 participants divided into two groups (Group 1 = SP [n = 12]; Group 2 = SRPE [n = 8]) with bothersome painful nocturnal erections. All participants were referred to the sleep disorder clinic to be assessed and consented for overnight polysomnography with simultaneous NPT recording and to complete validated sleep, sexual dysfunction and health-related quality of life questionnaires. Unstimulated PDU was also performed. Abnormal Polysomnographic findings (reduced sleep efficiency, total sleep time, and awake after sleep onset) were identified in both groups suggesting poor sleep. Men with SP had significantly longer erections (60.0 vs 18.5; p = 0.002) and took longer to detumesce once awake (25.7 vs 5.4 min; p = 0.001) than men with SRPE. They also had significantly higher peak systolic and end diastolic velocities on unstimulated PDU with an abnormal low resistance waveform identified. No sleep pathology was identified in men with SP. This implies a local (penile) etiology in men with SP. Men with SRPE had a normal resting PDU and abnormal sleep architecture with REM awakenings and significantly more Periodic limb movements (p = 0.04) than men with SP suggesting a central (sleep-related) cause in men with SRPE. Sexual dysfunction and poor HR-QoL was identified on validated questionnaires in both groups. SP and SRPE are rare entities that share similar symptoms (painful nocturnal erections and poor sleep) but dissimilar features of nocturnal erection onset, duration and resolution with different polysomnographic features which may allude to a different pathophysiology.

Spinal cord involvement in Lewy body-related α-synucleinopathies

Context: Lewy body (LB)-related α-synucleinopathy (LBAS) is the neuropathological hallmark of several neurodegenerative diseases such as Parkinson disease (PD), but it is also found in neurologically asymptomatic subjects. An abnormal accumulation of α-synuclein has been reported also in the spinal cord, but extent and significance of the spinal cord involvement are still poorly defined. Objective: We aimed to review the studies addressing the spinal cord involvement of LBAS in healthy subjects and in patients with PD or other neurodegenerative diseases. Methods: A MEDLINE search was performed using following terms: "spinal cord", " α-synucleinopathy", "α-synuclein", "Lewy body", "Parkinson's disease", "multiple system atrophy", "neurodegenerative disorder". Results: LBAS in the spinal cord is associated with that of the medullary reticular formation and locus ceruleus in the brainstem but not with that in the olfactory bulb and amygdala. The intermediolateral columns of the thoracic and sacral cord are the most frequently and severely affected region of the spinal cord. LBAS occurs in centrally projecting spinal cord neurons integrating pain, in particular from lower body periphery. It also involves the sacral parasympathetic nucleus innervating the smooth muscles of the bladder and distal colon and the Onuf's nucleus innervating the striated sphincters. The spinal cord lesions may thus play a crucial role in the genesis of frequent non-motor symptoms such as pain, urinary symptoms, bowel dysfunction, autonomic failure including orthostatic hypotension and sexual disturbances. Moreover, these may also contribute to the motor symptoms, since α-synuclein inclusions have been observed in the pyramidal tracts of patients with PD and multiple system atrophy. Conclusion: Recognition of this peculiar spinal cord pathology may help in the management of the related symptoms in subjects affected by α-synucleinopathies.

Recent advances in neuroimaging of bladder, bowel and sexual function

PURPOSE OF REVIEW

In this review, we summarize recent advances in the understanding of the neural control of the bladder, bowel and sexual function, in both men and women.

RECENT FINDINGS

Evidence of supraspinal areas controlling the storage of urine and micturition in animals, such as the pontine micturition centre, emerged in the early 20th century. Neurological stimulation and lesion studies in humans provided additional indirect evidence for additional bladder-related brain areas. Thereafter, functional neuroimaging in humans with PET and fMRI provided more direct evidence of the involvement of these brain areas. The areas involved in the storage and expulsion of urine also seem to be involved in the central control of storage and expulsion of feces. Furthermore, most knowledge on the brain control of sexual function is obtained from dynamic imaging in human volunteers. Relatively little is known about the dysfunctional central circuits in patients with pelvic organ dysfunction.

SUMMARY

fMRI has been the most widely used functional neuroimaging technique in the last decade to study the central control of bladder function, anorectal function and sexual function. The studies described in this review show which sensory and motor areas are involved, including cortical and subcortical areas. We propose the existence of a switch-like phenomenon located in the pons controlling micturition, defecation and orgasm.

Oxytocin Neurons Enable Melanocortin Regulation of Male Sexual Function in Mice

The melanocortin pathway has been implicated in both metabolism and sexual function. When the melanocortin 4 receptor (MC4R) is knocked out globally, male mice display obesity, low sexual desire, and copulatory difficulties; however, it is unclear whether these phenotypes are interdependent. To elucidate the neuronal circuitry involved in sexual dysfunction in MC4R knockouts, we re-expressed the MC4R in these mice exclusively on Sim1 neurons (tbMC4RSim1 mice) or on a subset of Sim1 neurons, namely oxytocin neurons (tbMC4Roxt mice). The groups were matched at young ages to control for the effects of obesity. Interestingly, young MC4R null mice had no deficits in sexual motivation or erectile function. However, MC4R null mice were found to have an increased latency to reach ejaculation compared to control mice, which was restored in both tbMC4RSim1 and tbMC4Roxt mice. These results indicate that melanocortin signaling via the MC4R on oxytocin neurons is important for normal ejaculation independent of the male's metabolic health.

Chronic Spinal Cord Injury Reduces Gastrin-Releasing Peptide in the Spinal Ejaculation Generator in Male Rats

Spinal cord injury (SCI) causes sexual dysfunction, including anejaculation in men. Likewise, chronic mid-thoracic contusion injury impairs ejaculatory reflexes in male rats. Ejaculation is controlled by a spinal ejaculation generator (SEG) comprised of a population of lumbar spinothalamic (LSt) neurons. LSt neurons co-express four neuropeptides, including gastrin-releasing peptide (GRP) and galanin and control ejaculation via release of these peptides in lumbar and sacral autonomic and motor nuclei. Here, we tested the hypothesis that contusion injury causes a disruption of the neuropeptides that are expressed in LSt cell bodies and axon terminals, thereby causing ejaculatory dysfunction. Male Sprague Dawley rats received contusion or sham surgery at spinal levels T6-7. Five to six weeks later, animals were perfused and spinal cords were immunoprocessed for galanin and GRP. Results showed that numbers of cells immunoreactive for galanin were not altered by SCI, suggesting that LSt cells are not ablated by SCI. In contrast, GRP immunoreactivity was decreased in LSt cells following SCI, evidenced by fewer GRP and galanin/GRP dual labeled cells. However, SCI did not affect efferent connections of LSt, cells as axon terminals containing galanin or GRP in contact with autonomic cells were not reduced following SCI. Finally, no changes in testosterone plasma levels or androgen receptor expression were noted after SCI. In conclusion, chronic contusion injury decreased immunoreactivity for GRP in LSt cell soma, but did not affect LSt neurons per se or LSt connections within the SEG. Since GRP is essential for triggering ejaculation, such loss may contribute to ejaculatory dysfunction following SCI.

Neuronal nitric oxide synthase activity mediates Lycium barbarum polysaccharides-enhanced sexual performance without stimulating noncontact erection in rats

RATIONALE

Lycium barbarum polysaccharide (LBP) is known to promote reproductive functions. However, its role in noncontact erection (NCE) of penis initiated by brain regions including medial preoptic area (MPOA) and paraventricular nucleus (PVN) regions responsible for sexual behavior has not been investigated.

OBJECTIVES

Therefore, this study initially investigated the effects of LBP on male sexual function, and subsequently, the mechanistic insight was investigated through assessing the expression of neuronal nitric oxide synthase (nNOS) in the MPOA and PVN.

METHODS

The adult male rats were treated with 100 mg/kg of LBP or vehicle by oral gavage. Before and after 14 days of treatment, copulatory behavior and noncontact erection (NCE) were recorded. After the last behavioral test, the brain was isolated to measure nNOS expression in the MPOA and PVN.

RESULTS

Data showed that LBP treatment significantly increased both the frequencies of intromission as well as ejaculation, compared to the control group. Whereas, a reduced post-ejaculatory interval was observed compared to same group on day 0. Furthermore, the treatment led to an increased intromission ratio, inter-intromission interval, and the number of MPOA nNOS-immunoreactive cells (nNOS-ir). Additionally, a significantly positive correlation between ejaculation frequency and MPOA nNOS-ir cells was recorded. Of note, LBP treatment had no effects on NCE and PVN nNOS-ir expression.

CONCLUSION

These findings suggest that LBP enhances sexual behavior through increased nNOS expression in the MPOA in male rats.

Neuroanatomical Framework of the Metabolic Control of Reproduction

A minimum amount of energy is required for basic physiological processes, such as protein biosynthesis, thermoregulation, locomotion, cardiovascular function, and digestion. However, for reproductive function and survival of the species, extra energy stores are necessary. Production of sex hormones and gametes, pubertal development, pregnancy, lactation, and parental care all require energy reserves. Thus the physiological systems that control energy homeostasis and reproductive function coevolved in mammals to support both individual health and species subsistence. In this review, we aim to gather scientific knowledge produced by laboratories around the world on the role of the brain in integrating metabolism and reproduction. We describe essential neuronal networks, highlighting key nodes and potential downstream targets. Novel animal models and genetic tools have produced substantial advances, but critical gaps remain. In times of soaring worldwide obesity and metabolic dysfunction, understanding the mechanisms by which metabolic stress alters reproductive physiology has become crucial for human health.

Reflex erection in the rat: reciprocal interplay between hemodynamic and somatic events

Background

Penile erection is a complex reflex under spinal control and modulated by the brain. The hemodynamic events under autonomic control and the perineal muscles somatic activity are interconnected during the reflex erection at the spinal level, however if the afferent feedback on the corpus cavernosum pressure during an erection affects the somatic activity (perineal muscles contractions) and vice versa is not known. This study was aimed to test this hypothesis using a rat model.

Methods

Intracavernous pressure (ICP) and bulbocavernosus (BC) muscle EMG were recorded during reflex erections elicited with dorsal penile nerve (DNP) electrical stimulation in anaesthetized acutely spinalized SD rats with surgically (bilateral cavernous nerve section, CnX, n = 8) and pharmacologically (trimetaphan infusion, TMPh, n = 8) abolished pressor response, or with surgically (bilateral section of the motor branch of the pudendal nerve, PnX, n = 7) and pharmacologically (1 mg/kg d-tubocurarine, n = 8) blocked perineal muscles contractions, or with interrupted afferent input from the penis (bilateral crush of the dorsal penile nerve, DPnX, n = 7). Control rats (n = 8) received no intervention.

Results

Moderate positive correlations were found between net parameters of pressor and somatic activity during DNP-stimulation induced reflex erection in spinal rats, particularly the speed of pressor response development was positively correlated to EMG parameters. No changes of EMG activity were found in CnX rats, while the decrease of BC EMG in TMPh-treated males can be attributed to direct inhibitory action of TMPh on neuromuscular transmission. Pressor response latency was increased and ICP front slope decreased in dTK and PnX rats, indicating that perineal muscles contraction augment pressor response. DPN crush had little effect on ICP and EMG.

Conclusion

Afferent input on the level of intracavernous pressure and the perineal muscles activity has minimal impact on, correspondingly, the somatic and the autonomic components of the reflex erection in spinal males, once the reflex has been initiated.

Electronic supplementary material

The online version of this article (10.1186/s12894-018-0352-5) contains supplementary material, which is available to authorized users.

Sim1 Neurons Are Sufficient for MC4R-Mediated Sexual Function in Male Mice

Sexual dysfunction is a poorly understood condition that affects up to one-third of men around the world. Existing treatments that target the periphery do not work for all men. Previous studies have shown that central melanocortins, which are released by pro-opiomelanocortin neurons in the arcuate nucleus of the hypothalamus, can lead to male erection and increased libido. Several studies specifically implicate the melanocortin 4 receptor (MC4R) in the central control of sexual function, but the specific neural circuitry involved is unknown. We hypothesized that single-minded homolog 1 (Sim1) neurons play an important role in the melanocortin-mediated regulation of male sexual behavior. To test this hypothesis, we examined the sexual behavior of mice expressing MC4R only on Sim1-positive neurons (tbMC4Rsim1 mice) in comparison with tbMC4R null mice and wild-type controls. In tbMC4Rsim1 mice, MC4R reexpression was found in the medial amygdala and paraventricular nucleus of the hypothalamus. These mice were paired with sexually experienced females, and their sexual function and behavior was scored based on mounting, intromission, and ejaculation. tbMC4R null mice showed a longer latency to mount, a reduced intromission efficiency, and an inability to reach ejaculation. Expression of MC4R only on Sim1 neurons reversed the sexual deficits seen in tbMC4R null mice. This study implicates melanocortin signaling via the MC4R on Sim1 neurons in the central control of male sexual behavior.

The treatment of erectile dysfunction in patients with neurogenic disease

Erectile dysfunction (ED) related to compromise of the nervous system is an increasingly common occurrence. This may be due to the multifactorial nature of ED, the myriad of disorders affecting the neurotransmission of erectogenic signals, and improved awareness and diagnosis of ED. Nevertheless, neurogenic ED remains poorly understood and characterized. Disease related factors such as depression, decreased physical and mental function, the burden of chronic illness, and loss of independence may preclude sexual intimacy and lead to ED as well. The amount of data regarding treatment options in subpopulations of differing neurologic disorders remains scarce except for men with spinal cord injury. The treatment options including phosphodiesterase inhibitors, intracavernosal or intraurethral vasoactive agents, vacuum erection devices (VED) and penile prosthetic implantation remain constant. This review discusses the options in specific neurologic conditions, and briefly provides insight into new and future developments that may reshape the management of neurogenic ED.

Sympathetic preganglionic neurons: properties and inputs

The sympathetic nervous system comprises one half of the autonomic nervous system and participates in maintaining homeostasis and enabling organisms to respond in an appropriate manner to perturbations in their environment, either internal or external. The sympathetic preganglionic neurons (SPNs) lie within the spinal cord and their axons traverse the ventral horn to exit in ventral roots where they form synapses onto postganglionic neurons. Thus, these neurons are the last point at which the central nervous system can exert an effect to enable changes in sympathetic outflow. This review considers the degree of complexity of sympathetic control occurring at the level of the spinal cord. The morphology and targets of SPNs illustrate the diversity within this group, as do their diverse intrinsic properties which reveal some functional significance of these properties. SPNs show high degrees of coupled activity, mediated through gap junctions, that enables rapid and coordinated responses; these gap junctions contribute to the rhythmic activity so critical to sympathetic outflow. The main inputs onto SPNs are considered; these comprise afferent, descending, and interneuronal influences that themselves enable functionally appropriate changes in SPN activity. The complexity of inputs is further demonstrated by the plethora of receptors that mediate the different responses in SPNs; their origins and effects are plentiful and diverse. Together these different inputs and the intrinsic and coupled activity of SPNs result in the rhythmic nature of sympathetic outflow from the spinal cord, which has a variety of frequencies that can be altered in different conditions.

Anatomy and physiology of genital organs - men

Male sexual functions involve a number of organs and structures in genitalia whose role is to produce fertilizing gametes and to allow female-partner insemination. The testes belong to the reproductive and endocrine systems as they synthesize spermatozoa and androgens, and are under finely regulated hormonal control by the hypothalamopituitary axis. Sexual responses are controlled by a complex and coordinated interplay of both the somatic and the autonomic nervous system in multiple components of the brain, spinal cord, and relevant peripheral organs. Erectile bodies are an essential element of the penis and engorgement of the penis with blood leads to penile tumescence. Blood engorgement is due to relaxation of smooth-muscle cells of erectile tissue and endothelium of the penile arteries. The penis gains additional rigidity when the ischiocavernosus muscles contract. Stimuli from peripheral and/or central origins activate particular spinal nuclei, causing penile erection. Ejaculation consists of two phases, emission and expulsion, which correspond, respectively, to secretion of the different components of the semen by sex glands and forceful expulsion of semen due to rhythmic contractions of the bulbospongiosus muscle. A spinal generator of ejaculation integrates genital stimuli and sexual cues and, when the excitatory threshold is reached, triggers ejaculation by orchestrating the activation of autonomic and somatic pathways commanding the peripheral events of ejaculation.

Connections of the magnocellular medial preoptic nucleus (MPN mag) in male Syrian hamsters. II. The efferents

The magnocellular medial preoptic nucleus (MPN mag) plays a critical role in the regulation of male copulatory behavior in the Syrian hamster. Our study of the afferents are consistent with the hypothesis that the MPN mag receives input from areas in the chemosensory pathway and nuclear groups that contain receptors for gonadal steroids (Wang and Swann, 2006). The goal of the present study is to identify targets of the MPN mag by describing the location of labeled fibers following an injection of biotinylated dextran amine (BDA) into the MPN mag. Our results indicate that targets of the MPN mag include: (1) brainstem nuclei implicated in regulating male mating behavior in other species, such as the periaqueductal gray, deep mesencephalic nucleus, retrorubral field, ventral tegmental area and lateral paragigantocellular nucleus and (2) steroid-concentrating nuclei in the septum, preoptic area and hypothalamus. The lack of projections from the MPN mag to its chemosensory afferents indicate that the connections of the MPN mag with the posterior medial bed nucleus of the stria terminalis, medial and anterior cortical nuclei of the amygdala are unidirectional, and that chemosensory information flows from the medial amygdala and bed nucleus of the stria terminalis (BST) to the MPN mag. The bidirectional nature of the connections between the MPN mag and steroid-concentrating nuclei suggest that the MPN mag may influence the function of a steroid-concentrating network that regulates behaviors. Together these results support the hypothesis that the MPN mag regulates male mating behavior by integrating chemosensory and hormonal signals and relaying this information to brainstem areas that control motor output.

The role of oxytocin in male and female reproductive behavior

Oxytocin (OT) is a nonapeptide with an impressive variety of physiological functions. Among them, the 'prosocial' effects have been discussed in several recent reviews, but the direct effects on male and female sexual behavior did receive much less attention so far. As our contribution to honor the lifelong interest of Berend Olivier in the control mechanisms of sexual behavior, we decided to explore the role of OT in the present review. In the successive sections, some physiological mechanisms and the 'pair-bonding' effects of OT will be discussed, followed by sections about desire, female appetitive and copulatory behavior, including lordosis and orgasm. At the male side, the effects on erection and ejaculation are reviewed, followed by a section about 'premature ejaculation' and a possible role of OT in its treatment. In addition to OT, serotonin receives some attention as one of the main mechanisms controlling the effects of OT. In the succeeding sections, the importance of OT for 'the fruits of labor' is discussed, as it plays an important role in both maternal and paternal behavior. Finally, we pay attention to an intriguing brain area, the ventrolateral part of the ventromedial hypothalamic nucleus (VMHvl), apparently functioning in both sexual and aggressive behavior, which are at first view completely opposite behavioral systems.

Identification of CNS neurons innervating the levator ani and ventral bulbospongiosus muscles in male rats

INTRODUCTION

The pelvic striated muscles play an important role in mediating erections and ejaculation, and together these muscles compose a tightly coordinated neuromuscular system that is androgen sensitive and sexually dimorphic.

AIM

To identify spinal and brains neurons involved in the control of the levator ani (LA) and bulbospongiosus (BS) in the male adult and preadolescent rat.

METHODS

Rats were anesthetized, and the transsynaptic retrograde tracer pseudorabies virus (PRV) was injected into the LA muscle of adults or the ventral BS muscle in 30-day-old rats. After 3-5 days rats were sacrificed, and PRV-labeled neurons in the spinal cords and brains were identified using immunohistochemistry. The presence of gastrin-releasing peptide (GRP) in the lumbar spinal neurons was examined.

MAIN OUTCOMES MEASURES

The location and number of PRV-labeled neurons in the spinal cord and brain and GRP colocalization in the lumbar spinal cord.

RESULTS

PRV-labeled spinal interneurons were found distributed throughout T11-S1 of the spinal cord, subsequent to dorsal medial motoneuron infection. The majority of spinal interneurons were found in the lumbosacral spinal cord in the region of the dorsal gray commissure and parasympathetic preganglionic neurons. Preadolescent rats had more PRV-labeled spinal interneurons at L5-S1 where the motoneurons were located but relatively less spread rostrally in the spinal cord compared with adults. Lumbar spinothalmic neurons in medial gray of L3-L4 co-localized PRV and GRP. In the brain consistent labeling was seen in areas known to be involved in male sexual behavior including the ventrolateral medulla, hypothalamic paraventricular nucleus, and medial preoptic area.

CONCLUSION

Common spinal and brain pathways project to the LA and BS muscles in the rat suggesting that these muscles act together to coordinate male sexual reflexes. Differences may exist in the amount of synaptic connections/neuronal pathways in adolescents compared with adults.

The Possible Neuronal Mechanism of Acupuncture: Morphological Evidence of the Neuronal Connection between Groin A-Shi Point and Uterus

Somatovisceral reflex suggested that the somatic stimulation could affect visceral function like acupuncture which treats diseases by stimulating acupoints. The neuronal connection between somatic point and visceral organ was not clear. Uterine pain referred to the groin region has long been recognized clinically. Wesselmann, using neurogenic plasma extravasation method, showed that uterine pain was referred to the groin region through a neuronal mechanism (Wesselmann and Lai 1997). This connection could be considered through the somatovisceral reflex pathway. However, the relay center of this pathway is still not clearly identified. In the present study, bee venom was injected in the groin region to induce central Fos expression to map the sensory innervation of groin region. Pseudorabies virus (PrV), a transneuronal tracer, was injected in the uterus to identify the higher motor control of the uterus. Immunohistochemistry staining revealed the Fos expression and PrV-infected double-labeled neurons in the nucleus of solitary tract (NTS), the dorsal motor nucleus of vagus (DMX), and the paraventricular hypothalamic nucleus (PVN). These results suggest a somatoparasympathetic neuronal connection (groin-spinal dorsal horn-NTS/DMX-uterus) and a somatosympathetic neuronal connection (groin-spinal dorsal horn-NTS-PVN-uterus). These two neuronal connections could be the prerequisites to the neuronal basis of the somatovisceral reflex and also the neuronal mechanism of acupuncture.

A pivotal role of lumbar spinothalamic cells in the regulation of ejaculation via intraspinal connections

INTRODUCTION

A population of lumbar spinothalamic cells (LSt cells) has been demonstrated to play a pivotal role in ejaculatory behavior and comprise a critical component of the spinal ejaculation generator. LSt cells are hypothesized to regulate ejaculation via their projections to autonomic and motor neurons in the lumbosacral spinal cord.

AIM

The current study tested the hypothesis that ejaculatory reflexes are dependent on LSt cells via projections within the lumbosacral spinal cord.

METHODS

Male rats received intraspinal injections of neurotoxin saporin conjugated to substance P analog, previously shown to selectively lesion LSt cells. Two weeks later, males were anesthetized and spinal cords were transected. Subsequently, males were subjected to ejaculatory reflex paradigms, including stimulation of the dorsal penile nerve (DPN), urethrogenital stimulation or administration of D3 agonist 7-OH-DPAT. Electromyographic recordings of the bulbocavernosus muscle (BCM) were analyzed for rhythmic bursting characteristic of the expulsion phase of ejaculation. In addition, a fourth commonly used paradigm for ejaculation and erections in unanesthetized, spinal-intact male rats was utilized: the ex copula reflex paradigm.

MAIN OUTCOME MEASURES

LSt cell lesions were predicted to prevent rhythmic bursting of BCM following DPN, urethral, or pharmacological stimulation, and emissions in the ex copula paradigm. In contrast, LSt cell lesions were not expected to abolish erectile function as measured in the ex copula paradigm.

RESULTS

LSt cell lesions prevented rhythmic contractions of the BCM induced by any of the ejaculatory reflex paradigms in spinalized rats. However, LSt cell lesions did not affect erectile function nor emissions determined in the ex copula reflex paradigm.

CONCLUSIONS

These data demonstrate that LSt cells are essential for ejaculatory, but not erectile reflexes, as previously reported for mating animals. Moreover, LSt cells mediate ejaculation via projections within the spinal cord, presumably to autonomic and motor neurons.

Function and pharmacology of spinally-projecting sympathetic pre-autonomic neurones in the paraventricular nucleus of the hypothalamus

The paraventricular nucleus (PVN) of the hypothalamus has been described as the "autonomic master controller". It co-ordinates critical physiological responses through control of the hypothalamic-pituitary-adrenal (HPA)-axis, and by modulation of the sympathetic and parasympathetic branches of the central nervous system. The PVN comprises several anatomical subdivisions, including the parvocellular/ mediocellular subdivision, which contains neurones projecting to the medulla and spinal cord. Consensus indicates that output from spinally-projecting sympathetic pre-autonomic neurones (SPANs) increases blood pressure and heart rate, and dysfunction of these neurones has been directly linked to elevated sympathetic activity during heart failure. The influence of spinally-projecting SPANs on cardiovascular function high-lights their potential as targets for future therapeutic drug development. Recent studies have demonstrated pharmacological control of these spinally-projecting SPANs with glutamate, GABA, nitric oxide, neuroactive steroids and a number of neuropeptides (including angiotensin, substance P, and corticotrophin-releasing factor). The underlying mechanism of control appears to be a state of tonic inhibition by GABA, which is then strengthened or relieved by the action of other modulators. The physiological function of spinally-projecting SPANs has been subject to some debate, and they may be involved in physiological stress responses, blood volume regulation, glucose regulation, thermoregulation and/or circadian rhythms. This review describes the pharmacology of PVN spinally-projecting SPANs and discusses their likely roles in cardiovascular control.

Bilateral bulbospinal projections to pudendal motoneuron circuitry after chronic spinal cord hemisection injury as revealed by transsynaptic tracing with pseudorabies virus

Complications of spinal cord injury in males include losing brainstem control of pudendal nerve-innervated perineal muscles involved in erection and ejaculation. We previously described, in adult male rats, a bulbospinal pathway originating in a discrete area within the medullary gigantocellularis (GiA/Gi), and lateral paragigantocellularis (LPGi) nuclei, which when electrically microstimulated unilaterally, produces a bilateral inhibition of pudendal motoneuron reflex circuitry after crossing to the contralateral spinal cord below T8. Microstimulation following a long-term lateral hemisection, however, revealed reflex inhibition from both sides of the medulla, suggesting the development or unmasking of an injury-induced bulbospinal pathway crossing the midline cranial to the spinal lesion. In the present study, we investigated this pathway anatomically using the transsynaptic neuronal tracer pseudorabies virus (PRV) injected unilaterally into the bulbospongiosus muscle in uninjured controls, and ipsilateral to a chronic (1-2 months) unilateral lesion of the lateral funiculus. At 4.75 days post-injection, PRV-labeled cells were found bilaterally in the GiA/Gi/LPGi with equal side-to-side labeling in uninjured controls, and with significantly greater labeling contralateral to the lesion/injection in lesioned animals. The finding of PRV-labeled neurons on both sides of the medulla after removing the mid-thoracic spinal pathway on one side provides anatomical evidence for the bilaterality in both the brainstem origin and the lumbosacral pudendal circuit termination of the spared lateral funicular bulbospinal pathway. This also suggests that this bilaterality may contribute to the quick functional recovery of bladder and sexual functions observed in animals and humans with lateral hemisection injury.

Distinct patterns of neuronal inputs and outputs of the juxtaparaventricular and suprafornical regions of the lateral hypothalamic area in the male rat

We have analyzed at high resolution the neuroanatomical connections of the juxtaparaventricular region of the lateral hypothalamic area (LHAjp); as a control and in comparison to this, we also performed a preliminary analysis of a nearby LHA region that is dorsal to the fornix, namely the LHA suprafornical region (LHAs). The connections of these LHA regions were revealed with a coinjection tract-tracing technique involving a retrograde (cholera toxin B subunit) and anterograde (Phaseolus vulgaris leucoagglutinin) tracer. The LHAjp and LHAs together connect with almost every major division of the cerebrum and cerebrospinal trunk, but their connection profiles are markedly different and distinct. In simple terms, the connections of the LHAjp indicate a possible primary role in the modulation of defensive behavior; for the LHAs, a role in the modulation of ingestive behavior is suggested. However, the relation of the LHAjp and LHAs to potential modulation of these behaviors, as indicated by their neuroanatomical connections, appears to be highly integrative as it includes each of the major functional divisions of the nervous system that together determine behavior, i.e., cognitive, state, sensory, and motor. Furthermore, although a primary role is indicated for each region with respect to a particular mode of behavior, intermode modulation of behavior is also indicated. In summary, the extrinsic connections of the LHAjp and LHAs (so far as we have described them) suggest that these regions have a profoundly integrative role in which they may participate in the orchestrated modulation of elaborate behavioral repertoires.

Men versus women on sexual brain function: prominent differences during tactile genital stimulation, but not during orgasm

Biological differences in male and female sexuality are obvious in the behavioral domain, but the central mechanisms that might explain these behavioral gender differences remain unclear. In this study, we merged two earlier positron emission tomography data sets to enable systematic comparison of the brain responses in heterosexual men and women during sexual tactile genital (penile and clitoral) stimulation and during orgasm. Gender commonalities were most evident during orgasm, a phase which demonstrated activations in the anterior lobe of the cerebellar vermis and deep cerebellar nuclei, and deactivations in the left ventromedial and orbitofrontal cortex in both men and women. During tactile genital stimulation, deactivations in the right amygdala and left fusiform gyrus were found for both genders. Marked gender differences were seen during this phase: left fronto-parietal areas (motor cortices, somatosensory area 2 and posterior parietal cortex) were activated more in women, whereas in men, the right claustrum and ventral occipitotemporal cortex showed larger activation. The only prominent gender difference during orgasm was male-biased activation of the periaqueductal gray matter. From these results, we conclude that during the sexual act, differential brain responses across genders are principally related to the stimulatory (plateau) phase and not to the orgasmic phase itself. These results add to a better understanding of the neural underpinnings of human sexuality, which might benefit treatment of psychosexual disorders.

Neural regulation of ejaculation

INTRODUCTION

Delineation of the underlying neurophysiological mechanisms of ejaculatory behavior is crucial for the treatment of male sexual dysfunction, including premature ejaculation. Recent studies provide compelling evidence that a population of lumbar spinothalamic (LSt) cells may play a role in the regulation of the ejaculatory response. Subsequent to ejaculation, LSt cells exhibit markers of activation that are not only highly correlated with ejaculatory behavior, but are also absent following the expression of other components of sexual behavior, such as mounts or intromissions. Similarly, targeted chemical lesion of LSt cells using substance P-saporin abolishes ejaculatory behavior explicitly. Early evidence suggests that pharmacological manipulation of LSt cells may offer additional evidence of crucial LSt cell involvement in the generation of ejaculation.

AIM

This review is intended to summarize what has currently been revealed regarding the role of LSt cells in the regulation and generation of ejaculatory behavior, and also to discuss the direction of future behavioral investigations.

METHODS

Information presented in this discussion was derived from analysis of numerous recent articles detailing the delineation of anatomical and physiological correlates of sexual behavior, as well as numerous literature searches using the National Library of Medicine PubMed Services.

RESULTS

A great deal of the work that has led to the implication of LSt cells in ejaculatory behavior is reviewed in the present article, including clinical data, as well as anatomical, physiological, and behavioral examinations. The rationale for ongoing pharmacological studies is also discussed.

CONCLUSION

LSt cells appear to play a vital role in the generation and regulation of ejaculatory behavior. Additional elucidation of this "ejaculation generator" could prove invaluable for the future treatment of male sexual dysfunction. Studies are currently in progress to further reveal the precise function of these cells and mechanisms of action through which they operate.

VGLUT1 and VGLUT2 innervation in autonomic regions of intact and transected rat spinal cord

Fast excitatory neurotransmission to sympathetic and parasympathetic preganglionic neurons (SPN and PPN) is glutamatergic. To characterize this innervation in spinal autonomic regions, we localized immunoreactivity for vesicular glutamate transporters (VGLUTs) 1 and 2 in intact cords and after upper thoracic complete transections. Preganglionic neurons were retrogradely labeled by intraperitoneal Fluoro-Gold or with cholera toxin B (CTB) from superior cervical, celiac, or major pelvic ganglia or adrenal medulla. Glutamatergic somata were localized with in situ hybridization for VGLUT mRNA. In intact cords, all autonomic areas contained abundant VGLUT2-immunoreactive axons and synapses. CTB-immunoreactive SPN and PPN received many close appositions from VGLUT2-immunoreactive axons. VGLUT2-immunoreactive synapses occurred on Fluoro-Gold-labeled SPN. Somata with VGLUT2 mRNA occurred throughout the spinal gray matter. VGLUT2 immunoreactivity was not noticeably affected caudal to a transection. In contrast, in intact cords, VGLUT1-immunoreactive axons were sparse in the intermediolateral cell column (IML) and lumbosacral parasympathetic nucleus but moderately dense above the central canal. VGLUT1-immunoreactive close appositions were rare on SPN in the IML and the central autonomic area and on PPN. Transection reduced the density of VGLUT1-immunoreactive axons in sympathetic subnuclei but increased their density in the parasympathetic nucleus. Neuronal cell bodies with VGLUT1 mRNA occurred only in Clarke's column. These data indicate that SPN and PPN are densely innervated by VGLUT2-immunoreactive axons, some of which arise from spinal neurons. In contrast, the VGLUT1-immunoreactive innervation of spinal preganglionic neurons is sparse, and some may arise from supraspinal sources. Increased VGLUT1 immunoreactivity after transection may correlate with increased glutamatergic transmission to PPN.

Differential brain processing of audiovisual sexual stimuli in men: Comparative positron emission tomography study of the initiation and maintenance of penile erection during sexual arousal

The human male psychosexual cycle consists of four phases: excitation, plateau, orgasm, and resolution. Identification of the specific neural substrates of each phase may provide information regarding the brain's pathophysiology of sexual dysfunction. We previously analyzed regional cerebral blood flow (rCBF) with H(2)15O-positron emission tomography (PET) during the excitation phase (initiation of penile erection) induced by audiovisual sexual stimuli (AVSS) and identified activation of the cerebellar vermis, the bilateral extrastriate cortex, and right orbitofrontal cortex, suggesting a role of cognition/emotion in the excitement phase. In the present study, we analyzed rCBF of the same six healthy volunteers during the plateau phase (maintenance of penile erection) induced by AVSS and compared the results with those of the excitation phase. Penile rigidity was monitored in real time with RigiScan Plus during PET scanning. Images were analyzed by statistical parametric mapping (SPM) software, and rCBF in the amygdala, hypothalamus, anterior cingulate, and insula was measured. During the plateau phase, primary subcortical activation was noted in the right ventral putamen, indicating motivational factors in the sexual response via the limbic reward circuit. A significant increase in rCBF in the left hypothalamus was also observed during the plateau phase. The right anterior cingulate and left insula were specifically activated during the excitation phase but not during the plateau phase. These results indicate a significant role of the ventral putamen and the hypothalamus in the plateau phase and confirm that paralimbic and limbic components of the human brain differentially coordinate the sexual response in a psychosexual phase-dependent manner.

Oxytocin Involvement in SSRI-Induced Delayed Ejaculation: A Review of Animal Studies

INTRODUCTION

Selective serotonin reuptake inhibitors (SSRIs) differ in the severity of induced ejaculation delay. Various studies indicate that oxytocin is involved in sexual behavior.

AIM

To review and evaluate the involvement of oxytocin in SSRI-induced ejaculation delay.

MAIN OUTCOME MEASURES

Oxytocine release, 5-hydroxytryptamine (5-HT) neurotransmission, and desensitization of 5-HT(1A) receptors.

METHODS

A review and critical analysis of animal studies investigating the interaction of serotonergic and oxytocinergic neurotransmission in relation to the ejaculation process.

RESULTS

Although acute treatment with the SSRIs fluoxetine and paroxetine immediately causes increased serotonin levels, delayed ejaculation does not occur. The increased serotonin levels induce oxytocin release via activation of 5-HT(1A) receptors, and this might compensate for the inhibitory actions of serotonin on sexual behavior. Chronic treatment with fluoxetine and paroxetine desensitizes 5-HT(1A) receptors on oxytocin neurons, and that might in part determine the onset of delayed ejaculation. Desensitization of 5-HT(1A) receptors is less strong following chronic treatment with the SSRIs fluvoxamine or citalopram, which may attenuate the degree of delayed ejaculation.

CONCLUSIONS

Preliminary data suggest that the severity of chronic SSRI treatment-induced delayed ejaculation and the differences between the various SSRIs in inducing ejaculation delay is related to gradual desensitization of 5-HT(1A) receptors on oxytocin neurons.

A comparison of the neurotropism of Theiler's virus and poliovirus in CBA mice

Theiler's murine encephalomyelitis virus (TMEV) and poliovirus infect the central nervous system (CNS) and cause neurological damage. The exact route by which TMEV and polioviruses enter the CNS remains, for the most part, unknown, although the neural and/or the hematogenous pathway have both been postulated. To explore these hypotheses, this research focuses on both the site of entry and the pathway used to invade the CNS. Following different inoculation sites of the GDVII strain of Theiler's virus or Lansing Type 2 poliovirus in CBA mice, the incidence of paralysis and/or encephalitis was evaluated on the basis of clinical signs and histopathology. The forms of paralysis displayed corresponded to the site of viral inoculation. Following intramuscular (i.m.), intraperitoneal (i.p.), and footpad routes of injection, bilateral and or contralateral paralyses were observed for both TMEV and poliovirus. In mice injected intratongue and in the hypoglossal nerve, tongue paralysis or paralysis of the forelimb, which progressed to bilateral forelimb paralysis, was observed, additionally the penis of most infected males was protruded. Intracranial (i.c.) injections with type II poliovirus strain resulted in forelimb paralysis. Intravenous (i.v.), injections with TMEV also resulted in forelimb paralysis. Thus Lansing Type II poliovirus and TMEV infections of CBA mice, result in similar incidence of paralysis and histopathological findings.

Convergence of multiple pelvic organ inputs in the rat rostral medulla

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.

Expression of corticotropin-releasing factor and CRF receptors in micturition pathways after cyclophosphamide-induced cystitis

Corticotropin-releasing factor (CRF) is a prominent neuropeptide involved in micturition reflexes, and different roles in these reflexes have been suggested. These studies examined the expression of CRF in the urinary bladder and lumbosacral sacral parasympathetic nucleus (SPN) in response to cyclophosphamide (CYP)-induced cystitis (4 h, 48 h, or chronic) in rats. The expression of CRF receptors, CRF(1) and CRF(2), was examined in urinary bladder from control and CYP-treated rats. Urinary bladder and lumbosacral spinal cord were harvested from rats killed by isoflurane (4%) and thoracotomy. CRF protein expression in whole urinary bladders significantly (P < or = 0.01) increased with 48 h or chronic CYP treatment. CRF immunoreactivity (IR) was increased significantly (P < or = 0.01) in the urothelium and SPN after CYP treatment. CRF IR nerve fibers increased in density in the suburothelial plexus and detrusor smooth muscle whole mounts with CYP-induced cystitis. CRF(2) receptor transcript was expressed in the urothelium or detrusor smooth muscle, and CRF(2) receptor expression increased in whole bladder with CYP-treatment, whereas no CRF(1) receptor transcript was expressed in either urothelium or detrusor. Immunohistochemical studies demonstrated CRF(2) IR in urinary bladder nerve fibers and urothelial cells from control animals, whereas no CRF(1) IR was observed. These studies demonstrated changes in the expression of CRF in urinary bladder and SPN region with CYP-induced cystitis and CRF receptor (CRF(2)) expression in nerve fibers and urothelium in control rats. CRF may contribute to urinary bladder overactivity and altered sensory processing with CYP-induced cystitis.

Projections from bed nuclei of the stria terminalis, magnocellular nucleus: implications for cerebral hemisphere regulation of micturition, defecation, and penile erection

The basic structural organization of axonal projections from the small but distinct magnocellular and ventral nuclei (of the bed nuclei of the stria terminalis) was analyzed with the Phaseolus vulgaris leucoagglutinin anterograde tract tracing method in adult male rats. The former's overall projection pattern is complex, with over 80 distinct terminal fields ipsilateral to injection sites. Innervated regions in the cerebral hemisphere and brainstem fall into nine general functional categories: cerebral nuclei, behavior control column, orofacial motor-related, humorosensory/thirst-related, brainstem autonomic control network, neuroendocrine, hypothalamic visceromotor pattern-generator network, thalamocortical feedback loops, and behavioral state control. The most novel findings indicate that the magnocellular nucleus projects to virtually all known major parts of the brain network that controls pelvic functions, including micturition, defecation, and penile erection, as well as to brain networks controlling nutrient and body water homeostasis. This and other evidence suggests that the magnocellular nucleus is part of a corticostriatopallidal differentiation modulating and coordinating pelvic functions with the maintenance of nutrient and body water homeostasis. Projections of the ventral nucleus are a subset of those generated by the magnocellular nucleus, with the obvious difference that the ventral nucleus does not project detectably to Barrington's nucleus, the subfornical organ, the median preoptic and parastrial nuclei, the neuroendocrine system, and midbrain orofacial motor-related regions.

Identification of neural circuits involved in female genital responses in the rat: a dual virus and anterograde tracing study

The spinal and peripheral innervation of the clitoris and vagina are fairly well understood. However, little is known regarding supraspinal control of these pelvic structures. The multisynaptic tracer pseudorabies virus (PRV) was used to map the brain neurons that innervate the clitoris and vagina. To delineate forebrain input on PRV-labeled cells, the anterograde tracer biotinylated dextran amine was injected in the medial preoptic area (MPO), ventromedial nucleus of the hypothalamus (VMN), or the midbrain periaqueductal gray (PAG) 10 days before viral injections. These brain regions have been intimately linked to various aspects of female reproductive behavior. After viral injections (4 days) in the vagina and clitoris, PRV-labeled cells were observed in the paraventricular nucleus (PVN), Barrington's nucleus, the A5 region, and the nucleus paragigantocellularis (nPGi). At 5 days postviral administration, additional PRV-labeled cells were observed within the preoptic region, VMN, PAG, and lateral hypothalamus. Anterograde labeling from the MPO terminated among PRV-positive cells primarily within the dorsal PVN of the hypothalamus, ventrolateral VMN (VMNvl), caudal PAG, and nPGi. Anterograde labeling from the VMN terminated among PRV-positive cells in the MPO and lateral/ventrolateral PAG. Anterograde labeling from the PAG terminated among PRV-positive cells in the PVN, ventral hypothalamus, and nPGi. Transynaptically labeled cells in the lateral hypothalamus, Barrington's nucleus, and ventromedial medulla received innervation from all three sources. These studies, together, identify several central nervous system (CNS) sites participating in the neural control of female sexual responses. They also provide the first data demonstrating a link between the MPO, VMNvl, and PAG and CNS regions innervating the clitoris and vagina, providing support that these areas play a major role in female genital responses.

Sympathetic genital responses induced by p-chloroamphetamine in anaesthetized female rats

In urethane-anesthetized female rats, a branch of the hypogastric nerve equivalent to the vas deferens nerve in males was shown anatomically and electrophysiologically to supply the uterine horns and we have consequently termed this the uterine nerve. Administration of p-chloroamphetamine i.v. elicited patterned bursting uterine nerve activity responses together with contractions of the uterine horns and musculature of the vaginal wall. These responses are qualitatively similar to ejaculatory responses observed following p-chloroamphetamine administration to anesthetized male rats and the urethrogenital reflex in females, suggesting they represent responses occurring during sexual processes. This response to p-chloroamphetamine was still present after complete transection of the spinal cord at T8. These data indicate that common neurophysiological and pharmacological mechanisms regulate genital reflexes at the lumbosacral spinal level in both the female and the male rat.

Physiology of penile erection and pathophysiology of erectile dysfunction

This article reviews the physiology of penile erection, the components of erectile function, and the pathophysiology of erectile dysfunction. The molecular and clinical under-standing of erectile function continues to gain ground at a particularly fast rate. Advances in gene discovery have aided greatly in working knowledge of smooth muscle relaxation/contraction pathways. The understanding of the nitric oxide pathway has aided not only in the molecular understanding of the tumescence but also greatly in the therapy of erectile dysfunction.

Ascending spinal pathways from sexual organs: effects of chronic spinal lesions

A recent survey of paraplegics indicates that regaining sexual function is of the highest priority for both males and females (Anderson, K.D. (2004) Targeting recovery: priorities of the spinal cord-injured population J. Newrotrauma, 21: 1371-1383). Our understanding of the neural pathways and mechanisms underlying sexual behavior and function is limited at the present time. More studies are obviously needed to direct experiments geared toward developing effective therapeutic interventions. In this chapter, a review of studies on the processing of sensory inputs from the male and female reproductive organs is presented with a review of what is known about the location of ascending spinal pathways conveying this information. The effect of spinal cord injury on sexual function and the problems that ensue are discussed.

The relationship between serotonin, dopamine beta hydroxylase and GABA immunoreactive inputs and spinal preganglionic neurones projecting to the major pelvic ganglion of wistar rats

Preganglionic neurones in the lumbosacral spinal cord give rise to nerves providing the parasympathetic and sympathetic innervation of pelvic organs. These neurones are modulated by neurotransmitters released both from descending supra-spinal pathways and spinal interneurones. Though serotonin has been identified as exerting a significant influence on these neurones, few studies have investigated the circuitry through which it achieves this particularly in relation to sympathetic preganglionic neurones. Using a combination of neuronal tracing and multiple immunolabeling procedures, the current study has shown that pelvic preganglionic neurones receive a sparse, and probably non-synaptic, axosomatic/proximal dendritic input from serotonin-immunoreactive terminals. This was in marked contrast to dopamine beta hydroxylase-immunoreactive terminals, which made multiple contacts. However, the demonstration of both serotonin, and dopamine beta hydroxylase immunoreactive terminals on both parasympathetic and sympathetic preganglionic neurones provides evidence for direct modulation of these cells by both serotonin and norepinephrine. Serotonin-containing terminals displaying conventional synaptic morphology were often seen to contact unlabeled somata and dendritic processes in regions surrounding the labeled preganglionic cells. It is possible that these unlabeled structures represent interneurones that might allow the serotonin containing axons to exert an indirect influence on pelvic preganglionic neurones. Since many spinal interneurones employ GABA as a primary fast acting neurotransmitter we examined the relationship between terminals that were immunoreactive for serotonin or GABA and labeled pelvic preganglionic neurones. These studies were unable to demonstrate any direct connections between serotonin and GABA terminals within the intermediolateral or sacral parasympathetic nuclei. Colocalization of serotonin and GABA was very rare but terminals immunoreactive for each were occasionally seen to contact the same unlabeled processes in close proximity. These results suggest that in the rat, the serotonin modulation of pelvic preganglionic neurones may primarily involve indirect connections via local interneurones.

Enkephalin-immunoreactive interneurons extensively innervate sympathetic preganglionic neurons regulating the pelvic viscera

Enkephalin (ENK)-immunoreactive (IR) axons occur in regions containing spinal autonomic neurons and endogenous opiates contribute to spinal regulation of bladder function. To identify possible spinal sites of opiate action, we used immunocytochemistry for ENK with retrograde tracing from the major pelvic ganglion (MPG), a key location for postganglionic neurons controlling pelvic viscera, with cholera toxin B subunit (CTB) or CTB-horseradish peroxidase (CTB-HRP). We compared the relationship of ENK-IR axons with sympathetic preganglionic neurons (SPNs) projecting to the MPG between intact spinal cords and cords with 2- or 11-week complete transections between thoracic segments 4 and 5. By light microscopy, sections of intact cord showed dense networks of ENK-IR axons surrounding CTB-IR SPNs in the intermediolateral cell column (IML), intercalated nucleus, and central autonomic area of lower thoracic and upper lumbar cord. This staining pattern was similar in rats with 2- or 11-week transections. Ultrastructurally, ENK-IR axons formed synapses on SPNs in all three autonomic subnuclei of intact cord. In the IML, ENK-IR varicosities contributed 52% of the synapses on the somata of MPG-projecting SPNs. In 2-week transected cord, synapses from ENK-IR axons persisted on SPNs and the proportion of input to IML SPNs had increased to 67%, probably reflecting loss of supraspinal input. These results suggest that endogenous opioids could play a major role in controlling sympathetic outflow to the bladder through a direct action on SPNs. The persistence of the dense ENK innervation after complete cord transection indicates that the ENK-IR input to SPNs arises predominantly from intraspinal sources.

Corticotropin-releasing factor (CRF) expression in postnatal and adult rat sacral parasympathetic nucleus (SPN)

The neural control of micturition undergoes marked changes during the early postnatal development. During the first few postnatal weeks, the spinal micturition reflex is gradually replaced by a spinobulbospinal reflex pathway that is responsible for micturition in adult animals. Upregulation of brainstem regulation of spinal micturition pathways may contribute to development of mature voiding patterns. We examined the expression of corticotropin-releasing factor (CRF), present in descending projections from Barrington's nucleus to the sacral parasympathetic nucleus (SPN), in postnatal (P0-P36) and adult Wistar rats (P60-90). CRF-immunoreactivity (IR) was present predominantly in the SPN region, although some staining was also observed in the dorsal horn and dorsal commissure in L5-S1 spinal segments. CRF-IR in spinal cord regions was age dependent (R2=0.87-0.98). The majority of the CRF-IR in the lumbosacral spinal cord was eliminated by complete spinalization (2-3 weeks). Double-label immunohistochemistry was combined with quantitative confocal laser scanning microscopy to quantify the number and percentage of colocalization between CRF-immunoreactive varicosities and preganglionic somas or proximal neurites in the SPN in postnatal and adult rats. Results demonstrate an age-dependent upregulation of CRF-IR in the SPN region and specifically in association with preganglionic parasympathetic neurons identified with neuronal nitric oxide synthase (nNOS)-IR. CRF-immunoreactive varicosities on or within a 1 microm perimeter of nNOS-immunoreactive somas or proximal neurites also increased with postnatal age. The upregulation of CRF-IR in bulbospinal projections to the SPN may contribute to mature voiding reflexes.

Spinal cord control of ejaculation

Ejaculation is a reflex mediated by a spinal control center, referred to as a spinal ejaculation generator. During intercourse, the spinal ejaculation generator integrates the sensory inputs that are necessary to trigger ejaculation. At the time of ejaculation, it coordinates the sympathetic, parasympathetic, and somatic outflow to induce the two phases of ejaculation, i.e. emission and expulsion. It also provides the brain with signals related to the occurrence of ejaculation. Experimental and clinical data evidenced that these functions were devoted to neurons located in the lumbosacral cord. We recently characterized a population of spinothalamic neurons in the lumbar spinal cord of male rats (LSt cells) that constitutes an integral part of the spinal ejaculation generator. LSt cells send projections to the autonomic nuclei and motoneurons involved in the emission and expulsion phase, and they receive sensory projections from the pelvis. LSt cells are activated with ejaculation, but not following other components of sexual behavior, and lesions of LSt cells completely ablate ejaculatory function. These data support a pivotal role for the LSt cells in the control of ejaculation.

Is there a Relationship between Chronic Bladder Dysfunction and Somatic Symptoms in other Body Regions? 2. An Experimental Neuroanatomical Approach

OBJECTIVE

Based on clinical description of associated dysfunctional symptoms in patients with non-neurogenic lower urinary tract dysfunction an experimental setup was created in order to investigate the neuroanatomical basis for the clinical phenomena observed.

METHODS

Using 24 male adult Sprague-Dawley rats for retrograde mapping of the spinal cord and brain, a pseudorabies virus (PRV) tracer was subsequently injected into four pertinent locations; (a) the trigone, (b) the masseter muscle (c) the forepaw and (d) the hindpaw.

RESULTS

PRV tracing demonstrated clearly overlapping of labeled areas in the brain stem, diencephalon and thoracic-lumbar cord, from all injection sites of the rats.

CONCLUSION

There is a diffuse overlap within the brain stem and spinal cord, of autonomic innervation to peripheral tissues based on the presented animal experiments. The described autonomic network allows an understanding of the occurrence of symptoms in distant regions of the body associated to chronic bladder dysfunction.