Fast Inhibition Slows and Desynchronizes Mouse Auditory Efferent Neuron Activity.

The encoding of acoustic stimuli requires precise neuron timing. Auditory neurons in the cochlear nucleus (CN) and brainstem are well suited for accurate analysis of fast acoustic signals, given their physiological specializations of fast membrane time constants, fast axonal conduction, and reliable synaptic transmission. The medial olivocochlear (MOC) neurons that provide efferent inhibition of the cochlea reside in the ventral brainstem and participate in these fast neural circuits. However, their modulation of cochlear function occurs over time scales of a slower nature. This suggests the presence of mechanisms that reduce MOC inhibition of cochlear function. To determine how monaural excitatory and inhibitory synaptic inputs integrate to affect the timing of MOC neuron activity, we developed a novel in vitro slice preparation ("wedge-slice"). The wedge-slice maintains the ascending auditory nerve root, the entire CN and projecting axons, while preserving the ability to perform visually guided patch-clamp electrophysiology recordings from genetically identified MOC neurons. The "in vivo-like" timing of the wedge-slice demonstrates that the inhibitory pathway accelerates relative to the excitatory pathway when the ascending circuit is intact, and the CN portion of the inhibitory circuit is precise enough to compensate for reduced precision in later synapses. When combined with machine learning PSC analysis and computational modeling, we demonstrate a larger suppression of MOC neuron activity when the inhibition occurs with in vivo-like timing. This delay of MOC activity may ensure that the MOC system is only engaged by sustained background sounds, preventing a maladaptive hypersuppression of cochlear activity.

Impact of anesthesia and sex on sympathetic efferent and hemodynamic responses to renal chemo- and mechanosensitive stimuli.

Activation of renal sensory nerves by chemo- and mechanosensitive stimuli produces changes in efferent sympathetic nerve activity (SNA) and arterial blood pressure (ABP). Anesthesia and sex influence autonomic function and cardiovascular hemodynamics, but it is unclear to what extent anesthesia and sex impact SNA and ABP responses to renal sensory stimuli. We measured renal, splanchnic, and lumbar SNA and ABP in male and female Sprague-Dawley rats during contralateral renal infusion of capsaicin and bradykinin or during elevation in renal pelvic pressure. Responses were evaluated with a decerebrate preparation or Inactin, urethane, or isoflurane anesthesia. Intrarenal arterial infusion of capsaicin (0.1-30.0 µM) increased renal SNA, splanchnic SNA, or ABP but decreased lumbar SNA in the Inactin group. Intrarenal arterial infusion of bradykinin (0.1-30.0 µM) increased renal SNA, splanchnic SNA, and ABP but decreased lumbar SNA in the Inactin group. Elevated renal pelvic pressure (0-20 mmHg, 30 s) significantly increased renal SNA and splanchnic SNA but not lumbar SNA in the Inactin group. In marked contrast, SNA and ABP responses to every renal stimulus were severely blunted in the urethane and decerebrate groups and absent in the isoflurane group. In the Inactin group, the magnitude of SNA responses to chemo- and mechanosensory stimuli were not different between male and female rats. Thus, chemo- and mechanosensitive stimuli produce differential changes in renal, splanchnic, and lumbar SNA. Experimentally, future investigations should consider Inactin anesthesia to examine sympathetic and hemodynamic responses to renal sensory stimuli.NEW & NOTEWORTHY The findings highlight the impact of anesthesia, and to a lesser extent sex, on sympathetic efferent and hemodynamic responses to chemosensory and mechanosensory renal stimuli. Sympathetic nerve activity (SNA) and arterial blood pressure (ABP) responses were present in Inactin-anesthetized rats but largely absent in decerebrate, isoflurane, or urethane preparations. Renal chemosensory stimuli differentially changed SNA: renal and splanchnic SNA increased, but lumbar SNA decreased. Future investigations should consider Inactin anesthesia to study SNA and hemodynamic responses to renal sensory nerve activation.

Mimicking efferent nerves using a graphdiyne-based artificial synapse with multiple ion diffusion dynamics.

A graphdiyne-based artificial synapse (GAS), exhibiting intrinsic short-term plasticity, has been proposed to mimic biological signal transmission behavior. The impulse response of the GAS has been reduced to several millivolts with competitive femtowatt-level consumption, exceeding the biological level by orders of magnitude. Most importantly, the GAS is capable of parallelly processing signals transmitted from multiple pre-neurons and therefore realizing dynamic logic and spatiotemporal rules. It is also found that the GAS is thermally stable (at 353 K) and environmentally stable (in a relative humidity up to 35%). Our artificial efferent nerve, connecting the GAS with artificial muscles, has been demonstrated to complete the information integration of pre-neurons and the information output of motor neurons, which is advantageous for coalescing multiple sensory feedbacks and reacting to events. Our synaptic element has potential applications in bioinspired peripheral nervous systems of soft electronics, neurorobotics, and biohybrid systems of brain-computer interfaces.

Nicotine evoked efferent transmitter release onto immature cochlear inner hair cells.

Olivocochlear neurons make temporary cholinergic synapses on inner hair cells of the rodent cochlea in the first 2 to 3 wk after birth. Repetitive stimulation of these efferent neurons causes facilitation of evoked release and increased spontaneous release that continues for seconds to minutes. Presynaptic nicotinic acetylcholine receptors (nAChRs) are known to modulate neurotransmitter release from brain neurons. The present study explores the hypothesis that presynaptic nAChRs help to increase spontaneous release from efferent terminals on cochlear hair cells. Direct application of nicotine (which does not activate the hair cells' α9α10-containing nAChRs) produces sustained efferent transmitter release, implicating presynaptic nAChRs in this response. The effect of nicotine was reduced by application of ryanodine that reduces release of calcium from intraterminal stores.NEW & NOTEWORTHY Sensory organs exhibit spontaneous activity before the onset of response to external stimuli. Such activity in the cochlea is subject to modulation by cholinergic efferent neurons that directly inhibit sensory hair cells (inner hair cells). Those efferent neurons are themselves subject to various modulatory mechanisms. One such mechanism is positive feedback by released acetylcholine onto presynaptic nicotinic acetylcholine receptors causing further release of acetylcholine.

Stem cell-derived cranial and spinal motor neurons reveal proteostatic differences between ALS resistant and sensitive motor neurons.

In amyotrophic lateral sclerosis (ALS) spinal motor neurons (SpMN) progressively degenerate while a subset of cranial motor neurons (CrMN) are spared until late stages of the disease. Using a rapid and efficient protocol to differentiate mouse embryonic stem cells (ESC) to SpMNs and CrMNs, we now report that ESC-derived CrMNs accumulate less human (h)SOD1 and insoluble p62 than SpMNs over time. ESC-derived CrMNs have higher proteasome activity to degrade misfolded proteins and are intrinsically more resistant to chemically-induced proteostatic stress than SpMNs. Chemical and genetic activation of the proteasome rescues SpMN sensitivity to proteostatic stress. In agreement, the hSOD1 G93A mouse model reveals that ALS-resistant CrMNs accumulate less insoluble hSOD1 and p62-containing inclusions than SpMNs. Primary-derived ALS-resistant CrMNs are also more resistant than SpMNs to proteostatic stress. Thus, an ESC-based platform has identified a superior capacity to maintain a healthy proteome as a possible mechanism to resist ALS-induced neurodegeneration.

Acute bladder decentralization in hound dogs: Preliminary results of effects on hypogastric nerve electroneurograms and detrusor pressure responses to spinal root and hypogastric nerve stimulation.

OBJECTIVE: We aimed to refine electroneurogram techniques for monitoring hypogastric nerve activity during bladder filling, and then examined nerve activity in normal intact versus acutely decentralized bladders. METHODS: Effects of electrical stimulation of hypogastric nerves or lumbar ventral roots on detrusor pressure were examined, as were effects of isoflurane versus propofol anesthetics on hypogastric nerve stimulation evoked pressure. Hypogastric nerve activity was then recorded using custom-made bipolar cuff electrodes during bladder filling before and after its transection between the spinal cord and electrode to eliminate efferent nerve signals. RESULTS: Electrical stimulation of hypogastric nerves evoked low amplitude detrusor pressures that did not differ between the two anesthetics. Upper lumbar (L2) ventral root stimulation evoked detrusor pressures were suppressed, yet not eliminated, after transection of hypogastric nerves and all spinal roots below L5. Afferent and efferent hypogastric nerve activity did not change with bladder filling in neuronally intact bladders yet decreased in decentralized bladders. No change in afferent activity was observed during bladder filling in either intact or decentralized bladders. CONCLUSIONS: These findings indicate that a more complete decentralized bladder model should include transection of lumbosacral spinal roots innervating the bladder as well as hypogastric nerves. These refined electroneurogram recording methods may be suitable for evaluating the effectiveness of nerve transfer surgeries for bladder reinnervation by monitoring sensory activity in the transferred nerve.

Posterior ventral tegmental area-nucleus accumbens shell circuitry modulates response to novelty.

Dopamine release in the nucleus accumbens from ventral tegmental area (VTA) efferent neurons is critical for orientation and response to novel stimuli in the environment. However, there are considerable differences between neuronal populations of the VTA and it is unclear which specific cell populations modulate behavioral responses to environmental novelty. A retroDREADDs (designer drugs exclusively activated by designer receptors) technique, comprising designer G protein-coupled receptors exclusively activated by designer drugs and modulated by retrograde transported Cre, was used to selectively stimulate neurons of the VTA which project to the nucleus accumbens shell (AcbSh). First, the selectivity and expression of the human M3 muscarinic receptor-based adeno-associated virus (AAV-hM3D) was confirmed in primary neuronal cell cultures. Second, AAV-CMV-GFP/Cre was infused into the AcbSh and AAV-hSyn-DIO-hM3D(Gq)-mCherry (a presynaptic enhancer in the presence of its cognate ligand clozapine-N-oxide) was infused into the VTA of ovariectomized female Fisher 344 rats to elicit hM3D(Gq)-mCherry production specifically in neurons of the VTA which synapse in the AcbSh. Finally, administration of clozapine-N-oxide significantly altered rodents' response to novelty (e.g. absence of white background noise) by activation of hM3D(Gq) receptors, without altering gross locomotor activity or auditory processing per se. Confocal imaging confirmed production of mCherry in neurons of the posterior aspect of the VTA (pVTA) suggesting these neurons contribute to novelty responses. These results suggest the pVTA-AcbSh circuit is potentially altered in motivational disorders such as apathy, depression, and drug addiction. Targeting the pVTA-AcbSh circuit, therefore, may be an effective target for pharmacological management of such psychopathologies.

Adenosine A1-Dopamine D1 Receptor Heteromers Control the Excitability of the Spinal Motoneuron.

While the role of the ascending dopaminergic system in brain function and dysfunction has been a subject of extensive research, the role of the descending dopaminergic system in spinal cord function and dysfunction is just beginning to be understood. Adenosine plays a key role in the inhibitory control of the ascending dopaminergic system, largely dependent on functional complexes of specific subtypes of adenosine and dopamine receptors. Combining a selective destabilizing peptide strategy with a proximity ligation assay and patch-clamp electrophysiology in slices from male mouse lumbar spinal cord, the present study demonstrates the existence of adenosine A1-dopamine D1 receptor heteromers in the spinal motoneuron by which adenosine tonically inhibits D1 receptor-mediated signaling. A1-D1 receptor heteromers play a significant control of the motoneuron excitability, represent main targets for the excitatory effects of caffeine in the spinal cord and can constitute new targets for the pharmacological therapy after spinal cord injury, motor aging-associated disorders and restless legs syndrome.

Pharmacological potentiation of the efferent vagus nerve attenuates blood pressure and renal injury in a murine model of systemic lupus erythematosus.

Recent evidence suggests hypertension may be secondary to chronic inflammation that results from hypoactive neuro-immune regulatory mechanisms. To further understand this association, we used systemic lupus erythematosus (SLE) as a model of inflammation-induced hypertension. In addition to prevalent inflammatory kidney disease and hypertension, SLE patients suffer from dysautonomia in the form of decreased efferent vagal tone. Based on this, the cholinergic anti-inflammatory pathway, an endogenous vagus-to-spleen mechanism that, when activated results in decreases in systemic inflammation, may be compromised in SLE. We hypothesized that stimulation of the cholinergic anti-inflammatory pathway via pharmacological potentiation of the efferent vagus nerve would reduce inflammation and halt the development of hypertension and renal injury in SLE. Female NZBWF1 mice, an established model of murine SLE, and female control mice were treated with galantamine (4 mg/kg daily ip), an acetylcholinesterase inhibitor, or saline for 14 days. At the end of therapy, carotid catheters were surgically implanted and were used to measure mean arterial pressure before the animals were euthanized. Chronic galantamine administration attenuated both splenic and renal cortical inflammation, which likely explains why the hypertension and renal injury (i.e., glomerulosclerosis and fibrosis) typically observed in murine SLE was attenuated following therapy. Based on this, the anti-inflammatory, antihypertensive, and renoprotective effects of galantamine may be mediated through activation of the cholinergic anti-inflammatory pathway. It is possible that dysfunction of the cholinergic anti-inflammatory pathway exists in SLE at the level of the efferent vagus nerve and promoting restoration of its activity through central cholinergic receptor activation may be beneficial.

Calcium imaging of CPG-evoked activity in efferent neurons of the stick insect.

The stick insect is a well-established experimental animal to study the neural basis of walking. Here, we introduce a preparation that allows combining calcium imaging in efferent neurons with electrophysiological recordings of motor neuron activity in the stick insect thoracic nerve cord. The intracellular free calcium concentration in middle leg retractor coxae motor neurons and modulatory octopaminergic DUM neurons was monitored after backfilling lateral nerve nl5 that contains the axons of these neurons with the calcium indicator Oregon Green BAPTA-1. Rhythmic spike activity in retractor and protractor motor neurons was evoked by pharmacological activation of central pattern generating neuronal networks and recorded extracellularly from lateral nerves. A primary goal of this study was to investigate whether changes in the intracellular free calcium concentration observed in motor neurons during oscillatory activity depend on action potentials. We show that rhythmic spike activity in leg motor neurons induced either pharmacologically or by tactile stimulation of the animal is accompanied by a synchronous modulation in the intracellular free calcium concentration. Calcium oscillations in motor neurons do not appear to depend on calcium influx through voltage-sensitive calcium channels that are gated by action potentials because Calcium oscillations persist after pharmacologically blocking action potentials in the motor neurons. Calcium oscillations were also apparent in the modulatory DUM neurons innervating the same leg muscle. However, the timing of calcium oscillations varied not only between DUM neurons and motor neurons, but also among different DUM neurons. Therefore, we conclude that the motor neurons and the different DUM neurons receive independent central drive.

The Degeneration of the Vestibular Efferent Neurons After Intratympanic Gentamicin Administration.

Intratympanic gentamicin (ITG) has been used to treat refractory Ménière's disease. Disequilibrium after ITG was still a challenge for some patients, and the underlying mechanism is poorly understood. Our previous study demonstrated that gentamicin distributed in the bilateral vestibular efferent neurons (VEN) after ITG; however, does it lead to VEN damage and cause further disequilibrium in patients following ITG? In this study, we observed severe damaged gentamicin-positive neurons of VEN and severe fractured myelin layer plates around neural fibers when viewed under transmission electron microscopy at day 3 after ITG. At day 30, neurons of VEN presented with relatively normal structures. Compared with the control group, the total number of choline acetyltransferase (CHAT) immunolabeling neurons in bilateral VEN showed a significant decrease both at day 3 and day 30. However, there was no significant difference in the total number of CHAT immunolabeling neurons between day 3 and day 30. It indicates that gentamicin is not only retrogradely transported into bilateral VEN, but also results in the degeneration of VEN after ITG. These findings may be related to patients' disequilibrium symptom after ITG. Furthermore, we speculate that VEN may play a role in vestibular compensation.

Reflex arc of the teeth clenching-induced pressor response in rats.

Although "teeth clenching" induces pressor response, the reflex tracts of the response are unknown. In this study, dantrolene administration inhibited teeth clenching generated by electrical stimulation of the masseter muscles and completely abolished the pressor response. In addition, trigeminal ganglion block or hexamethonium administration completely abolished the pressor response. Local anesthesia of molar regions significantly reduced the pressor response to 27 ± 10%. Gadolinium (mechanoreceptor blocker of group III muscle afferents) entrapment in masticatory muscles also significantly reduced the pressor response to 62 ± 7%. Although atropine methyl nitrate administration did not change the pressor response, a significant dose-dependent augmentation of heart rate was observed. These results indicate that both periodontal membrane and mechanoreceptors in masticatory muscles are the receptors for the pressor response, and that the afferent and efferent pathways of the pressor response pass through the trigeminal afferent nerves and sympathetic nerves, respectively.

Muscarinic Acetylcholine Receptors and M-Currents Underlie Efferent-Mediated Slow Excitation in Calyx-Bearing Vestibular Afferents.

Stimulation of vestibular efferent neurons excites calyx and dimorphic (CD) afferents. This excitation consists of fast and slow components that differ >100-fold in activation kinetics and response duration. In the turtle, efferent-mediated fast excitation arises in CD afferents when the predominant efferent neurotransmitter acetylcholine (ACh) activates calyceal nicotinic ACh receptors (nAChRs); however, it is unclear whether the accompanying efferent-mediated slow excitation is also attributed to cholinergic mechanisms. To identify synaptic processes underlying efferent-mediated slow excitation, we recorded from CD afferents innervating the turtle posterior crista during electrical stimulation of efferent neurons, in combination with pharmacological probes and mechanical stimulation. Efferent-mediated slow excitation was unaffected by nAChR compounds that block efferent-mediated fast excitation, but were mimicked by muscarine and antagonized by atropine, indicating that it requires ACh and muscarinic ACh receptor (mAChR) activation. Efferent-mediated slow excitation or muscarine application enhanced the sensitivity of CD afferents to mechanical stimulation, suggesting that mAChR activation increases afferent input impedance by closing calyceal potassium channels. These observations were consistent with suppression of a muscarinic-sensitive K+-current, or M-current. Immunohistochemistry for putative M-current candidates suggested that turtle CD afferents express KCNQ3, KCNQ4, and ERG1-3 potassium channel subunits. KCNQ channels were favored as application of the selective antagonist XE991 mimicked and occluded efferent-mediated slow excitation in CD afferents. These data highlight an efferent-mediated mechanism for enhancing afferent sensitivity. They further suggest that the clinical effectiveness of mAChR antagonists in treating balance disorders may also target synaptic mechanisms in the vestibular periphery, and that KCNQ channel modulators might offer similar therapeutic value.SIGNIFICANCE STATEMENT Targeting the efferent vestibular system (EVS) pharmacologically might prove useful in ameliorating some forms of vestibular dysfunction by modifying ongoing primary vestibular input. EVS activation engages several kinetically distinct synaptic processes that profoundly alter the discharge rate and sensitivity of first-order vestibular neurons. Efferent-mediated slow excitation of vestibular afferents is of considerable interest given its ability to elevate afferent activity over an extended time course. We demonstrate for the first time that efferent-mediated slow excitation of vestibular afferents is mediated by muscarinic acetylcholine receptor (mAChR) activation and the subsequent closure of KCNQ potassium channels. The clinical effectiveness of some anti-mAChR drugs in treating motion sickness suggest that we may, in fact, already be targeting the peripheral EVS.

The pan-Kv7 (KCNQ) Channel Opener Retigabine Inhibits Striatal Excitability by Direct Action on Striatal Neurons In Vivo.

Central Kv7 (KCNQ) channels are voltage-dependent potassium channels composed of different combinations of four Kv7 subunits, being differently expressed in the brain. Notably, striatal dopaminergic neurotransmission is strongly suppressed by systemic administration of the pan-Kv7 channel opener retigabine. The effect of retigabine likely involves the inhibition of the activity in mesencephalic dopaminergic neurons projecting to the striatum, but whether Kv7 channels expressed in the striatum may also play a role is not resolved. We therefore assessed the effect of intrastriatal retigabine administration on striatal neuronal excitability in the rat determined by c-Fos immunoreactivity, a marker of neuronal activation. When retigabine was applied locally in the striatum, this resulted in a marked reduction in the number of c-Fos-positive neurons after a strong excitatory striatal stimulus induced by acute systemic haloperidol administration in the rat. The relative mRNA levels of Kv7 subunits in the rat striatum were found to be Kv7.2 = Kv7.3 = Kv7.5 > >Kv7.4. These data suggest that intrastriatal Kv7 channels play a direct role in regulating striatal excitability in vivo.

Potential Future Pharmacological Treatment of Bladder Dysfunction.

In the last decades, a number of new antimuscarinic drugs have been introduced for treatment of the overactive bladder (OAB), defined symptomatically (OAB syndrome) or urodynamically (detrusor overactivity). Recently, three new drug principles have been approved for clinical use, the ß3 -adrenoceptor agonist, mirabegron, the phosphodiesterase-5 inhibitor, tadalafil and the blocker of afferent and efferent nerves, botulinum toxin. However, new alternatives are continuously being explored. OAB is a filling disorder, and ATP is involved in the generation of afferent impulses. One way of blocking the ATP afferent pathway is through the use of P2X3 receptor antagonists. In animal models, this strategy appears to work very well, but whether it translates effectively to man remains to be established. Evidence suggests that components of the endocannabinoid system are involved in regulation of bladder function. Clinical studies of cannabinoid extracts on LUTS are scarce and essentially restricted to patients with MS, and the results have so far not been convincing. Amplification of endocannabinoid activity by inhibiting their degradation via fatty acid amide hydrolase inhibitors may be an attractive approach, but no clinical experiences in OAB have been reported. Studies of the lower urinary tract have indicated that several transient receptor potential (TRP) channels, including TRPV1, TRPV2, TRPV4, TRPM8 and TRPA1, are expressed in the bladder and may act as sensors of stretch and/or chemical irritation. Animal studies have shown that inhibition of these pathways can be effective for the reduction in bladder activity. However, the roles of these channels for normal function and in pathological states have not been established, and so far adverse effects (hyperthermia) have hampered development of antagonists.

Contralateral Hyperalgesia from Injection of Endothelin-1 into the Ipsilateral Paw Requires Efferent Conduction into the Contralateral Paw.

BACKGROUND: Contralateral hyperalgesia, occurring after unilateral injury, is usually explained by central sensitization in spinal cord and brain. We previously reported that injection of endothelin-1 (ET-1) into one rat hindpaw induces prolonged mechanical and chemical sensitization of the contralateral hindpaw. Here, we examined the role of contralateral efferent activity in this process. METHODS: ET-1 (2 nmol, 10 µL) was injected subcutaneously into the plantar surface of right (ipsilateral) hindpaw (ILP), and the thermal response latency and mechanical threshold for nocifensive withdrawal were determined by the use of, respectively, plantar radiant heating and von Frey filaments, for both ILP and contralateral hindpaws (CLP). Either paw was anesthetized for 60 minutes by direct injection of bupivacaine (0.25%, 40 µL), 30 minutes before ET-1. Alternatively, the contralateral sciatic nerve was blocked for 6 to 12 hours by percutaneous injection of bupivacaine-releasing microspheres 30 minutes before injection of ET-1. Systemic actions of these bupivacaine formulations were simulated by subcutaneous injection at the nuchal midline. RESULTS: After the injection of ET-1, the mechanical threshold of both ILP and CLP decreased by 2 hours, appeared to be lowest around 24 hours, and recovered through 48 hours to preinjection baseline at 72 hours. These hypersensitive responses were suppressed by bupivacaine injected into the ipsilateral paw before ET-1. Injection of the CLP by bupivacaine also suppressed the hypersensitivity of the CLP at all test times, and that of the ILP, except at 2 hours when it increased the sensitivity. This same pattern of change occurred when the contralateral sciatic nerve was blocked by bupivacaine-releasing microspheres. The systemic actions of these bupivacaine formulations were much smaller and only reached significance at 24 hours post-ET-1. Thermal hypersensitivity after ET-1 injection also occurred in both ILP and CLP and showed the same pattern in response to the 2 contralateral anesthetic procedures. CONCLUSIONS: These results show that efferent transmission through the contralateral innervation into the paw is necessary for contralateral sensitization by ET-1, suggesting that the release of substances by distal nerve endings is involved. The release of substances in the periphery is essential for contralateral sensitization by ET-1 and may also contribute to secondary hyperalgesia, occurring at loci distant from the primary injury, that occurs after surgery or nerve damage.

Therapeutic modulation of urinary bladder function: multiple targets at multiple levels.

Storage dysfunction of the urinary bladder, specifically overactive bladder syndrome, is a condition that occurs frequently in the general population. Historically, pathophysiological and treatment concepts related to overactive bladder have focused on smooth muscle cells. Although these are the central effector, numerous anatomic structures are involved in their regulation, including the urothelium, afferent and efferent nerves, and the central nervous system. Each of these structures involves receptors for­and the urothelium itself also releases­many mediators. Moreover, hypoperfusion, hypertrophy, and fibrosis can affect bladder function. Established treatments such as muscarinic antagonists, ß-adrenoceptor agonists, and onabotulinumtoxinA each work in part through their effects on the urothelium and afferent nerves, as do α1-adrenoceptor antagonists in the treatment of voiding dysfunction associated with benign prostatic hyperplasia; however, none of these treatments are specifically targeted to the urothelium and afferent nerves. It remains to be explored whether future treatments that specifically act at one of these structures will provide a therapeutic advantage.

Efferent pathways of the mouse lateral habenula.

The lateral habenula (LHb) is part of the habenula complex of the dorsal thalamus. Recent studies of the LHb have focused on its projections to the ventral tegmental area (VTA) and rostromedial tegmental nucleus (RMTg), which contain γ-aminobutyric acid (GABA)ergic neurons that mediate reward prediction error via inhibition of dopaminergic activity. However, older studies in the rat have also identified LHb outputs to the lateral and posterior hypothalamus, median raphe, dorsal raphe, and dorsal tegmentum. Although these studies have shown that the medial and lateral divisions of the LHb have somewhat distinct projections, the topographic specificity of LHb efferents is not completely understood, and the relative extent of these projections to brainstem targets is unknown. Here we have used anterograde tracing with adeno-associated virus-mediated expression of green fluorescent protein, combined with serial two-photon tomography, to map the efferents of the LHb on a standard coordinate system for the entire mouse brain, and reconstruct the efferent pathways of the LHb in three dimensions. Using automated quantitation of fiber density, we show that in addition to the RMTg, the median raphe, caudal dorsal raphe, and pontine central gray are major recipients of LHb efferents. By using retrograde tract tracing with cholera toxin subunit B, we show that LHb neurons projecting to the hypothalamus, VTA, median raphe, caudal dorsal raphe, and pontine central gray reside in characteristic, but sometimes overlapping regions of the LHb. Together these results provide the anatomical basis for systematic studies of LHb function in neural circuits and behavior in mice. J. Comp. Neurol. 523:32-60, 2015. © 2014 Wiley Periodicals, Inc.

TNFα causes thrombin-dependent vagal neuron apoptosis in inflammatory bowel disease.

BACKGROUND: The role of peripheral tumor necrosis factor alpha (TNFα) in inflammatory bowel disease (IBD) is well established, but its central nervous system (CNS) effects are not understood. Thrombin, another mediator of inflammation in IBD, has been implicated in CNS vagal neuron apoptosis in the dorsal motor nucleus of the vagus (DMV). This study evaluates DMV TNFα exposure, characterizes effects of TNFα on DMV neurons, and identifies a relationship between DMV TNFα and thrombin in IBD. METHODS: 2,4,6-Trinitrobenzene sulfonic acid was administered via enema to induce colonic inflammation in rats. TNFα in serum, cerebrospinal fluid (CSF), and DMV tissues were determined by ELISA and DMV TNFα expression by quantitative reverse transcription PCR (RT-PCR). TNFα was administered into the fourth intracerebral ventricle (4 V) adjacent to the DMV, with and without blockade of TNF receptor 1 (TNFR1) and the thrombin receptor proteinase-activated receptor 1 (PAR1). Immunofluorescence was used to evaluate microglial activation (Cd11b) and prothrombin presence in DMV sections. Apoptosis was examined using terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling (TUNEL) and activated caspase-3 immunofluorescence. RESULTS: IBD is associated with increased TNFα protein in serum, CSF, and DMV tissue; DMV TNFα transcription is also increased. TNFα (4 V) caused a 54 % increase in microglial activation, a 27 % increase in DMV prothrombin protein, and a 31 % increase in vagal neuron apoptosis by TUNEL. There was a 52 % increase in activated caspase-3 immunofluorescence in TNFα-treated animals (p < 0.05). All effects of 4 V TNFα were prevented by TNFR1 blockade. TNFα-induced apoptosis was prevented by PAR1 blockade. CONCLUSIONS: IBD is associated with DMV exposure to TNFα, causing excess DMV prothrombin and vagal apoptosis.

Coronary responses to cold air inhalation following afferent and efferent blockade.

Cardiac ischemia and angina pectoris are commonly experienced during exertion in a cold environment. In the current study we tested the hypotheses that oropharyngeal afferent blockade (i.e., local anesthesia of the upper airway with lidocaine) as well as systemic ß-adrenergic receptor blockade (i.e., intravenous propranolol) would improve the balance between myocardial oxygen supply and demand in response to the combined stimulus of cold air inhalation (-15 to -30°C) and isometric handgrip exercise (Cold + Grip). Young healthy subjects underwent Cold + Grip following lidocaine, propranolol, and control (no drug). Heart rate, blood pressure, and coronary blood flow velocity (CBV, from Doppler echocardiography) were continuously measured. Rate-pressure product (RPP) was calculated, and changes from baseline were compared between treatments. The change in RPP at the end of Cold + Grip was not different between lidocaine (2,441 ± 376) and control conditions (3,159 ± 626); CBV responses were also not different between treatments. With propranolol, heart rate (8 ± 1 vs. 14 ± 3 beats/min) and RPP responses to Cold + Grip were significantly attenuated. However, at peak exercise propranolol also resulted in a smaller ΔCBV (1.4 ± 0.8 vs. 5.3 ± 1.4 cm/s, P = 0.035), such that the relationship between coronary flow and cardiac metabolism was impaired under propranolol (0.43 ± 0.37 vs. 2.1 ± 0.63 arbitrary units). These data suggest that cold air breathing and isometric exercise significantly influence efferent control of coronary blood flow. Additionally, ß-adrenergic vasodilation may play a significant role in coronary regulation during exercise.