Downstream projection of Barrington's nucleus to the spinal cord in mice.

Barrington's nucleus (Bar), which controls micturition behavior through downstream projections to the spinal cord, contains two types of projection neurons, BarCRH and BarESR1, that have different functions and target different spinal circuitry. Both types of neurons project to the L6-S1 spinal intermediolateral (IML) nucleus, whereas BarESR1 neurons also project to the dorsal commissural nucleus (DCN). To obtain more information about the spinal circuits targeted by Bar, we used patch-clamp recording in spinal slices from adult mice in combination with optogenetic stimulation of Bar terminals. Recording of opto-evoked excitatory postsynaptic currents (oEPSCs) in 1,1'-dilinoleyl-3,3,3',3'-tetramethylindocarbocyanine, 4-chlorobenzenesulfonate (DiI)-labeled lumbosacral preganglionic neurons (LS-PGNs) revealed that both Bar neuronal populations make strong glutamatergic monosynaptic connections with LS-PGNs, whereas BarESR1 neurons also elicited smaller-amplitude glutamatergic polysynaptic oEPSCs or polysynaptic opto-evoked inhibitory postsynaptic currents (oIPSCs) in some LS-PGNs. Optical stimulation of BarCRH and BarESR1 terminals also elicited monosynaptic oEPSCs and polysynaptic oIPSCs in sacral DCN neurons, some of which must include interneurons projecting to either the IML or ventral horn. Application of capsaicin increased opto-evoked firing during repetitive stimulation of Bar terminals through the modulation of spontaneous postsynaptic currents in LS-PGNs. In conclusion, our experiments have provided insights into the synaptic mechanisms underlying the integration of inputs from Bar to autonomic circuitry in the lumbosacral spinal cord that may control micturition.NEW & NOTEWORTHY Photostimulation of BarCRH or BarESR1 axons in the adult mouse spinal cord elicits excitatory or inhibitory postsynaptic responses in multiple cell types related to the autonomic nervous system including preganglionic neurons (PGNs) in the lumbosacral intermediolateral nucleus and interneurons in the lumbosacral dorsal commissure nucleus. Integration of excitatory inputs from Bar and from visceral primary afferents in PGNs may be important in the regulation of micturition behavior.

Cholinergic modulation of CRH and non-CRH neurons in Barrington's nucleus of the mouse.

Corticotropin-releasing hormone (CRH) is expressed in Barrington's nucleus (BarN), which plays an essential role in the regulation of micturition. To control the neural activities of BarN, glutamatergic and GABAergic inputs from multiple sources have been demonstrated; however, it is not clear how modulatory neurotransmitters affect the activity of BarN neurons. We have employed knock-in mice, CRH-expressing neurons of which are labeled with a modified yellow fluorescent protein (Venus). Using whole cell patch-clamp recordings, we examined the responses of Venus-expressing (putative CRH-expressing) neurons in BarN (BarCRH), as well as non-CRH-expressing neurons (BarCRH-negative), following bath application of cholinergic agonists. According to the present study, the activity of BarCRH neurons could be modulated by dual cholinergic mechanisms. First, they are inhibited by a muscarinic receptor-mediated mechanism, most likely through the M2 subclass of muscarinic receptors. Second, BarCRH neurons are excited by a nicotinic receptor-mediated mechanism. BarCRH-negative neurons also responded to cholinergic agents. Choline transporter-immunoreactive nerve terminals were observed in close proximity to the neurites, as well as the somata of BarCRH. The present results suggest that BarN neurons are capable of responding to cholinergic input.NEW & NOTEWORTHY This study investigates the effects of bath-applied cholinergic agonists on Barrington's nucleus (BarN) neurons in vitro. They were either excitatory, through nicotinic receptors, or inhibitory, through muscarinic receptors. Putative corticotropin-releasing hormone (CRH)-expressing neurons in BarN, as well as putative non-CRH-expressing neurons, responded to cholinergic agonists.

Serotonergic regulation of distention-induced ATP release from the urothelium.

Serotonin [5-hydroxytryptamine (5-HT)] is involved in both motor and sensory functions in hollow organs, especially in the gastrointestinal tract. However, the involvement of 5-HT in visceral sensation of the urinary bladder remains unknown. Because distention-induced ATP release from the urothelium plays an essential role in visceral sensation of the urinary bladder, we investigated the regulation of urothelial ATP release by the 5-HT signaling system. RT-PCR and immunohistochemical analyses of the urothelium revealed specific expression of 5-HT1D and 5-HT4 receptors. The addition of 5-HT did not affect urothelial ATP release without bladder distention, but it significantly reduced distention-induced ATP release by physiological pressure during urine storage (5 cmH2O). The inhibitory effect of 5-HT on distention-elicited ATP release was blocked by preincubation with the 5-HT1B/1D antagonist GR-127935 but not by the 5-HT4 antagonist SB-204070. mRNA encoding tryptophan hydroxylase 1 was detected in the urinary bladder by nested RT-PCR amplification, and l-tryptophan or the selective serotonin reuptake inhibitor citalopram also inhibited ATP release, indicating that 5-HT is endogenously synthesized and released in the urinary bladder. The addition of GR-127935 significantly enhanced the distention-elicited ATP release 40 min after distention, whereas SB-204070 reduced the amount of ATP release 20 min after distention. These data suggest that 5-HT4 facilitates the distention-induced ATP release at an earlier stage, whereas 5-HT1D inhibits ATP release at a later stage. The net inhibitory effect of 5-HT indicates that the action of 5-HT on the urothelium is mediated predominantly by 5-HT1D.

Store-operated Ca2+ entry suppresses distention-induced ATP release from the urothelium.

Epithelial cells in the urinary bladder (urothelium) trigger sensory signals in micturition by releasing ATP in response to distention of the bladder wall. Our previous study revealed the distinct roles of extracellular Ca(2+) and the Ca(2+) stores in the endoplasmic reticulum (ER) in urothelial ATP release. In the present study, we investigated the regulation of urothelial ATP release by Ca(2+) influx from the extracellular space and Ca(2+) release from the ER using a distention assay of the mouse bladder wall in a small Ussing chamber. Stimulation of Ca(2+) release from the ER in the mucosal side of the bladder induced significant ATP release without distention. Blockade of the inositol 1,4,5-triphosphate receptor reduced distention-induced ATP release, suggesting that Ca(2+) release from the ER is essential for the induction of urothelial ATP release. On the other hand, blockade of store-operated Ca(2+) entry (SOCE) from the extracellular space significantly enhanced distention-induced ATP release. Thus Ca(2+) release from the ER causes urothelial ATP release and depletion of Ca(2+) stores in the ER, which in turn causes the depletion-inducing SOCE to suppress the amount of urothelial ATP released.

The nitric oxide-cyclic guanosine monophosphate pathway inhibits the bladder ATP release in response to a physiological or pathological stimulus.

The release of ATP from the epithelium of the urinary bladder (urothelium) in response to mechanical/chemical stimuli contributes to the visceral sensation in the micturition reflex. The nitric oxide (NO)-mediated induction of cyclic guanosine monophosphate (cGMP) has been detected in urothelial cells and may inhibit the micturition reflex. However, the function of the NO-cGMP pathway in the regulation of urothelial ATP release remains poorly understood in contrast to its effects on smooth muscles or primary afferent nerves. Therefore, we investigated the relevance of the NO-cGMP pathway to ATP release on the mucosal side in the present study. The administration of l-arginine (NO precursor) or NOC 12 (NO donor) significantly reduced ATP release to the mucosal side at a physiologically normal urine storage pressure (5 cmH2 O). L-NAME (NO synthase inhibitor) significantly increased the distention-induced release of ATP. The phosphodiesterase-5 inhibitor, sildenafil, which increases cGMP levels, inhibited distention-induced ATP release. Furthermore, sildenafil significantly reduced ATP release in response to the administration of lipopolysaccharide. These results suggest that the NO-cGMP pathway inhibited urothelial ATP release during the storage phase under both physiological and pathological conditions.

Role of supraspinal and spinal alpha1-adrenergic receptor subtypes in micturition reflex in conscious rats.

α(1)-Adrenergic receptor subtypes are widely distributed in the central nervous system and are involved in autonomic functions such as micturition. We investigated the presence and the role of supraspinal and/or spinal α(1)-adrenergic receptors in modulating the micturition reflex in conscious female Wistar rats. The expression of α(1)-adrenergic receptor subtypes in rat brain and lumbosacral spinal cord was studied using RT-PCR. Continuous-infusion cystometrograms were obtained in conscious rats, and α(1)-adrenergic receptor antagonists were administered via intracerebroventricular or intrathecal routes. The mRNA expression of α(1A)-, α(1B)-, and α(1D)-adrenergic receptors was detected in rat brain (midbrain and pons) and lumbosacral spinal cord (dorsal and ventral parts of spinal cord). In addition, intracerebroventricular injection of the α(1)-adrenergic receptor antagonist tamsulosin (1-10 µg), the selective α(1A)-adrenergic receptor antagonist silodosin (1-10 µg), and the selective α(1D)-adrenergic receptor antagonist BMY 7378 (1-10 µg) significantly prolonged the intercontraction interval (ICI) but did not alter maximum voiding pressure (MVP). Although intrathecal injection of BMY 7378 (0.0001-10 µg) did not affect ICI, tamsulosin and silodosin prolonged ICI in a dose-dependent manner. MVP was significantly reduced by intrathecal injection of tamsulosin (10 µg) but not by silodosin or BMY 7378 (0.0001-10 µg). Supraspinal α(1A)- and α(1D)-adrenergic receptors are apparently important for the regulation of reflex-bladder activity in conscious rats. Noradrenergic projection from the brain stem to the lumbosacral spinal cord may promote the afferent limb rather than the efferent limb of the micturition reflex pathway via α(1A)-adrenergic receptors.

Peripheral nerve injury in rats induces alternations in choice behavior associated with food reinforcement.

Operant methods that allow animals to avoid painful stimuli are interpreted to assess the aversive quality of pain; however, such measurements require investigator-initiated stimuli to animals. Here we developed a shuttle maze test to repeatedly assess activity associated nociception without forced stimulation. Rats ambulate back and forth between two treat feeders by taking either a short route with a prickly surfaced arch or a longer route with a smooth floor. L5-L6 spinal nerve ligation (SNL) reduced the preference for the short route with the arch, correlated with hypersensitivity in the hind paw. Oral gabapentin restored the short route preference and reduced hypersensitivity in SNL rats, and blockade of spinal α2-adrenoceptors reduced gabapentin's effects on hypersensitivity but not on preference index. These results suggest that SNL injury alters behavior in the shuttle maze test and that the shuttle maze test shows comparable results to reflexive hypersensitivity after SNL in magnitude and response to gabapentin.

Micro-CT imaging analysis for the effects of ibandronate and eldecalcitol on secondary osteoporosis and arthritis in adjuvant-induced arthritis rats.

We investigated the effects of ibandronate, a bisphosphonate; eldecalcitol, an active vitamin D3 analogue; and combination treatment with both agents on secondary osteoporosis and arthritis using rats with adjuvant-induced arthritis. Arthritis was induced in 8-week-old male Lewis rats. Rats were randomized into four treatment groups and an untreated normal control group: ibandronate, eldecalcitol, ibandronate + eldecalcitol, vehicle, and control. Paw thickness was measured to evaluate arthritis. Joint destruction was evaluated histomorphometrically by the ankle joint stained with Fast Green and safranin O. The femur and lumbar spine were scanned using dual-energy X-ray absorptiometry, and the distal femur was scanned using micro-computed tomography for bone mineral density (BMD) and trabecular microstructural evaluations. Ibandronate and/or eldecalcitol increased BMD in both the lumbar vertebrae and femur and improved several microstructural parameters (bone volume/total volume, structure model index, trabecular number, and trabecular separation of the distal femur). In addition, there was an additive effect of combination treatment compared with single treatments for most trabecular parameters, including BMD and bone volume. However, ibandronate and/or eldecalcitol did not inhibit arthritis and joint destruction. Combination treatment with ibandronate and eldecalcitol may be effective for secondary osteoporosis associated with arthritis.

Glucagon-like peptide-1 (GLP-1) action in the mouse area postrema neurons.

Glucagon-like peptide-1 (GLP-1) is a peptide hormone and member of the incretin family. GLP-1 related drugs, such as liraglutide, are widely used to treat diabetic patients and work by stimulating pancreatic ß cells to increase glucose-dependent insulin secretion. However, extrapancreatic effects, such as appetite suppression or emesis, are observed in response to GLP-1 receptor agonists. In this study we used the in vitro patch-clamp method in acute brainstem preparations of mice and demonstrated that GLP-1 acts directly on area postrema neurons. It is known that activation of the area postrema is related to the induction of homeostatic autonomic nervous systems, including nausea. Approximately,half of the neurons tested in the area postrema were excited by GLP-1 in the presence of tetrodotoxin, and is thought to be through adenylate cyclase-cAMP pathways. Excitation was not frequently observed in nucleus tractus solitaries neurons or in area postrema neurons from GLP-1 receptor knock-out mice. These results indicate that GLP-1 receptor agonists excite area postrema neurons and potentially leading to the expression of extra-pancreatic effects. This is the first study to show that GLP-1 directly activates area postrema neurons.

Novel agonist of α4ß2* neuronal nicotinic receptor with antinociceptive efficacy in rodent models of acute and chronic pain.

OBJECTIVE: To demonstrate the antinociceptive and antihypersensitivity mechanisms of Cris-104 (1-{2-[5-(4-fluorophenyl)-1H-pyrazol-4-yl]ethyl}piperidine), a novel selective α4ß2* nicotinic acetylcholine receptor (nAChR) agonist, in rodent acute/inflammatory and chronic pain models. MATERIALS AND METHODS: Hot-plate and formalin tests in mice were used to examine Cris-104-induced antinociceptive effects on thermal/inflammatory pain. Cris-104 effects on hypersensitivity, norepinephrine (NE) release in the spinal dorsal horn, and neuronal activity in the locus coeruleus (LC) were examined in rats with lumbar spinal nerve ligation using behavioral, microdialysis, and extracellular recording methods. Cris-104 effects on spontaneous locomotion were examined in an open-field test. RESULTS: Cris-104 induced dose-dependent antinociception effects in hot-plate and formalin tests, and these effects were blocked by the general nAChR antagonist mecamylamine, the selective α4ß2* nAChR antagonist dihydro-beta-erythroidine, and the α2-adrenoceptor antagonist yohimbine, but not by the α1-adrenoceptor antagonist prazosin. Systemic and spinally perfused Cris-104 increased NE concentrations in microdialysates from the spinal cord in both normal and SNL rats. Systemic Cris-104 increased neuronal activity in the LC of normal rats. Mecamylamine blocked the effects of Cris-104 on spinal NE release and LC neuronal activity. Systemic Cris-104 did not affect locomotor activity significantly. CONCLUSION: The α4ß2 neuronal nAChR agonist, Cris-104, was effective for treatment of pain via descending noradrenergic inhibition of pain signaling.

Noradrenergic effects in rat sacral autonomic nucleus using in vitro slice patch-clamp recordings.

Noradrenergic modulation has been frequently discussed in the context of neural activities that are related to pelvic organs. The sacral preganglionic nucleus (SPN) is a spinal nucleus containing parasympathetic preganglionic neurons that send fibers to pelvic nerves. In spite of the abundant presence of noradrenergic fibers around the SPN, the effects of noradrenaline (NA) remain obscure. To explore this issue, NA (50 µM) was applied to parasympathetic preganglionic neurons in the SPN during whole-cell patch clamp recording. The SPN was labeled with the retrograde tracer, DiI. These neurons demonstrated two classes of firing patterns (delayed and regular) in terms of initiation of firing. Independent of these firing patterns, NA induced inward (56%) or outward (32%) currents in labeled SPN neurons. Phenylephrine, an α1 receptor agonist, induced an inward current, and clonidine, an α2 receptor agonist, induced an outward current, indicating the existence of both α1 and α2 adrenoreceptors in DiI-labeled SPN neurons. NA also modulated synaptic currents according to the firing patterns. In delayed firing neurons, NA inhibited both spontaneous excitatory post-synaptic currents (sEPSCs) and spontaneous inhibitory post-synaptic currents (sIPSCs). Hence, NA facilitated sEPSCs and sIPSCs in about a half of regular firing neurons. Bath application of phenylephrine facilitated sEPSCs and sIPSCs, and clonidine inhibited them. These results support the hypothesis of multiple effects of NA in the SPN, and may suggest functional differences among SPN neurons.

Dynamic movement of center of gravity with hand grip.

We studied the movement of center of gravity (CG) in young and aged subjects during maximum grip of right or left hand. Body-sway was recorded with stabilometry in rest-stand position and in maximum grip. The data from right-or left-handed young subjects were analyzed. Maximum grip power was not different between dominant hand and un-dominant hands. Total length (LNG) and total movement area of CG (REC AREA) during the measurements were significantly larger in maximum grip than in rest-stand. In right-handed subjects, LNG increased to 245% and 250% of rest-stand value, and REC AREA increased to 589% and 633% in right and left hand grip, respectively. In left-handed subjects, LNG increased to 186% and 188% of rest-stand value, and REC AREA increased to 400% and 533% in right and left hand grip, respectively. No significant difference of LNG and REC AREA was observed between right and left hand grip in either hand dominant subject Maximum grip did not affect CG in rest-stand. In aged subjects, maximum grip power was significantly less than in young subjects (48%). LNG and REC AREA in rest-stand were significantly larger in aged subjects than in young subjects (220% and 400%, respectively). They were not different during maximum grip with either hand. While aged subjects have difficulty of controlling CG in rest-stand, they have less problems to stabilize CG during maximum grip. These data indicated that dynamic movement of CG might be important to understand person's activity of daily living.

Prostaglandin facilitates afferent nerve activity via EP1 receptors during urinary bladder inflammation in rats.

We examined the effects of loxoprofen, a cyclooxygenase inhibitor, and ONO-8711, an EP1-receptor antagonist, on afferent nerve activity during acetic acid (AA, 0.1% v/v)-induced inflammation of the rat urinary bladder. Distension stimulation was performed (vesical pressure of 30 cm H2O) for 2 min. The neuronal discharge was recorded from L6 dorsal root filaments. The discharge was observed just after the beginning of distension and increased gradually thereafter. When the vesical pressure returned to control value, the discharge diminished abruptly. AA infusion increased the total number of spikes to 198 +/- 38.8% of control values. AA infusion also produced asynchronous discharge in 39% of the animals. Loxoprofen administration (1 mg/kg, i.v.) reduced the number of spikes to 40.3 +/- 14.8% of control values. ONO-8711 administration (1 and 3 mg/kg, i.v.) reduced the number of spikes to 81.6 +/- 1.6% and 32.2 +/- 7.4% of control values, respectively. These data indicate that loxoprofen or EP1-receptor antagonist inhibit the inflammation-related neuronal activity. EP1 receptors in the peripheral afferent nerve terminal and/or urothelium may facilitate the primary afferent nerve activity, which elicits the inflammation-induced micturition reflex.

Reduction of muscle fatigue by catchlike-inducing intermittent electrical stimulation in rat skeletal muscle.

Catchlike property is the force enhancement produced when a brief, high-frequency burst of pulses is added to a constant low-frequency stimulation. In functional electrical stimulation, constant low-frequency stimulation of approximately 20 Hz has primarily been used to reduce muscle fatigue. The purpose of this study was to investigate the effects of catchlike-inducing intermittent stimulation on muscle fatigue in relation to continuous intermittent low-frequency stimulation. Twenty-two adult male Wistar ST rats were randomly assigned into the constant frequency stimulation (CFS) group or the catchlike-inducing stimulation (CIS) group. In the CFS group, constant low-frequency stimulation of 20 Hz was applied intermittently (4 seconds "ON"/15 seconds "OFF"). In the CIS group, a single electrical burst of 100 Hz was applied at the start of the every 4-second period of stimulation. The muscle fatigue test lasted for 16 min and isometric muscle force, muscle fatigue, and muscular workload were evaluated. CIS significantly increased the maximum muscular force (under fatigued condition) and workload, and significantly decreased muscle fatigue (p < 0.05). The results of this study suggest that catchlike-inducing intermittent electrical stimulation is useful in the clinical administration of functional electrical stimulation.

Effects of therapeutic magnetic stimulation on acute muscle atrophy in rats after hindlimb suspension.

In most subjects with spinal cord injury, the spinal neurons below the level of injury are spared. Therefore, it is conceivable that the skeletal muscles innervated by these spinal nerves can be activated by applying therapeutic magnetic stimulation along the dorsal spine. The purpose of this study was to evaluate the ability of magnetic stimulation to prevent acute muscle atrophy in rats after hindlimb suspension. Forty adult male Wistar rats were randomly assigned to stimulated and non-stimulated (control) groups. Their hindlimbs were unweighted using a suspension method, causing muscle atrophy. In the stimulation group, magnetic stimulation (20 Hz, 60 min per day) was applied to the sciatic nerve for 10 days. After the stimulation period, the tibialis anterior (TA) and extensor digitorum longus (EDL) were surgically removed and histologically measured. The lesser diameters of type 1, 2A, and 2B muscle fibers were significantly greater in the stimulated group than in the non-stimulated group for both the TA and EDL (p < 0.05). The mean difference in lesser fiber diameter was 20% (range, 14%-27%). These results suggest that therapeutic magnetic stimulation is an effective method of preventing muscle atrophy.

ATP release from bladder urothelium and serosa in a rat model of partial bladder outlet obstruction.

Overactive bladder is one of the major health problem especially in elderly people. Adenosine triphosphate (ATP) is released from urinary bladder cells and acts as a smooth muscle contraction and sensory signal in micturition but little is known about the role of ATP release in the pathophysiology of overactive bladder. To assess the relationship between ATP and overactive bladder, we used a partial bladder outlet obstruction (pBOO) model in rats. The bladder caused several changes by pBOO: An increase in bladder weight, hypertrophy of sub-urothelium and sub-serosal area, and frequent non-voiding bladder contraction during urine storage. Basal ATP release from urothelium and serosa of pBOO rats was significantly higher than that of normal rats. Distentioninduced ATP release from urothelium of normal and pBOO rats had no significant change. However, distention-induced ATP release from serosa of pBOO rats was higher than that of normal. These findings may identify ATP especially released from serosa as one of causes of non-voiding contractions and overactive bladder symptoms.

Loxoprofen inhibits facilitated micturition reflex induced by acetic acid urinary bladder infusion of the rats.

Prostaglandins (PGs) are well known as one of the chemical mediators of inflammation. Nonsteroidal anti-inflammatory drugs (NSAIDs), PG synthesis inhibitors, are used for anti-nociception and/or anti-inflammation. We examine the effect of loxoprofen, an NSAID, on micturiton in acetic acid-induced bladder inflammation of the rats. In cystometrogram study with saline infusion into the urinary bladder, loxoprofen did not alter the interval of bladder contraction (IC, 107% of the control). IC was shortened by acetic acid infusion (65% of the control) and loxoprofen prolonged the IC (162% of acetic acid infused period). This prolonged IC was approximately same as the control. Loxoprofen did not alter the threshold pressure and the maximal voiding pressure. These data suggest that PGE2 might not play a part of normal micturition and may play a part of the micturition reflex during acetic acid infusion. That is, loxoprofen might be useful for pathological hyperreflex of the micturition.

The effect of magnetic stimulation on unloaded soleus muscle of rat: changes in myosin heavy chain mRNA isoforms.

This study assessed the potential application and the effectiveness of functional magnetic stimulation (FMS) for preventing skeletal muscle atrophy in adult rats. FMS using magnetic stimulator was performed to rat soleus muscle by placing a round magnetic coil on the back of 3rd-5th lumbar vertebral level at 20 Hz frequency for 60 min/day up to 10 days. A reverse transcriptase-polymerase chain reaction was applied to evaluate relative amounts of mRNAs specific to four myosin heavy chain (MHC) isoforms [MHCIbeta, MHCIIa, MHCIIb, and MHCIId(x)] in rat soleus muscle during contractile activity by magnetic stimulation. Ten-day unloading by hindlimb suspension induced a drastic decrease of MHCIbeta and MHCIIa mRNA expressions, while MHCIIb and MHCIId(x) mRNA was not decreased. The magnetic stimulation resuscitated the down-regulation of the mRNA levels of MHCIbeta and MHCIIa. These results suggest that magnetic stimulation on acute atrophied muscles is useful for preventing the muscle atrophy.

Regulatory Effects of 5-Hydroxytryptamine Receptors on Voiding Function.

UNLABELLED: A growing body of evidence suggests that 5-hydroxytryptamine (5-HT; serotonin) has both physiological and pathological functions in the lower urinary tract. A wide variety of 5-HT receptor subtypes are variably expressed in different organs, both peripheral and central. On urinary bladder smooth muscle, 5-HT1A, 5-HT2, 5-HT3, and 5-HT7 subtypes could function as postjunctional receptors. Postjunctional 5-HT2 receptors induce detrusor contraction of the bladder body. 5-HT1A is suggested to have a similar effect to 5-HT2, while 5-HT3 might suppress detrusor contraction evoked by direct muscle stimulation. Postjunctional 5-HT7 is reported to induce relaxation of the bladder neck, which might be required for efficient voiding. 5-HT1A, 5-HT2A, 5-HT2C, 5-HT3, 5-HT4, and 5-HT7 subtypes also could act as prejunctional receptors in autonomic excitatory nerve terminals. 5-HT2A, 5-HT2C, 5-HT3, 5-HT4, and 5-HT7 subtypes facilitate the neurogenic contraction of the detrusor by enhancing cholinergic or purinergic transmission, whereas 5-HT1A receptors might inhibit the release of acetylcholine in the detrusor. Furthermore, 5-HT1D could be involved in the suppression of ATP release from the urothelium, aiding visceral sensation of the urinary bladder. In the central pathways controlling the micturition reflex, 5-HT1A, 5-HT2A, and 5-HT7 are involved in regulation of bladder and urethral sphincter activities. Their functions, especially that of 5-HT1A, vary in a species- and site (spinal or supraspinal)- dependent manner. In addition to urinary bladder, 5-HT could be involved in prostate contraction and cell proliferation. Evidence indicates that 5-HT receptor subtypes may be novel therapeutic targets for lower urinary tract symptoms. FUNDING: Grants-in-Aid for Scientific Research (C) (KAKENHI 23590707, 24590722, and 26460694) from the Japan Society for the Promotion of Science.

Effect of prostaglandins on parasympathetic neurons in the rat lumbosacral spinal cord.

Prostaglandin E(2)(PGE(2)) elicits a variety of effects by activating four subtypes of receptors, EP1, EP2, EP3 and EP4. We examined receptor subtypes mediating the effects of PGE(2) on parasympathetic preganglionic neurons that regulate the activity of pelvic visceral organs. In tonic parasympathetic preganglionic neurons in neonatal rat spinal slices, PGE(2) increased the firing frequency to depolarizing current pulses, induced after-discharges and inhibited spike after-hyperpolarization. PGE(2) did not affect phasic preganglionic neurons. An EP1 agonist inhibited after-hyperpolarizations and induced after-discharges, whereas EP4 agonist reduced after-hyperpolarization and increased evoked firing but did not induce after-discharges. EP2 and EP3 agonists were inactive. These results indicate that PGE(2) acting via EP1 and/or EP4 receptors modulates the excitability and/or excitatory synaptic input to tonic parasympathetic preganglionic neurons.