Animals were maintained on a 12 hr light/dark cycle in the Georgia this website Health Sciences University animal care facility. Except for when specified in experiment, such as when food pellets were used as rewards, food and water were given ad libitum. All procedures relating to animal care and treatment conform to the Institutional and NIH guidelines. For behavioral tests in the study, we used male mice around

1 year old in age. These animals have been prescreened to make sure that they have normal vision and hearing capacity. Mice were perfused transcardially with 4% paraformaldehyde (PFA) in 1× PBS followed by a postfixation in 4% PFA overnight. Coronal sections (50 μm thick) were cut on a vibratome and collected in 0.5% PFA in 1× PBS and stored at 4°C before use. For double-immunofluorescent staining of β-galactosidase and TH, sections were incubated at 4°C overnight with gentle shaking in primary Selleck 3-Methyladenine antibody (anti-β-galactosidase [pAb] 1/5,000, Invitrogen; anti-TH [monoclonal antibody] 1/1,000) in a buffer containing 0.05% Tween 20, 10% normal goat serum, and 1× PBS following preincubation in 10% normal goat serum and 1× PBS at room temperature for 2 hr. The sections were then incubated with Alexa-conjugated secondary antibodies (1/200; Invitrogen) at room temperature for 2 hr. β-Galactosidase IR was visualized by Alexa 568 and TH IR by Alexa 488. A similar

procedure was employed to double stain NMDAR1 and TH except that anti-NR1 (polyclonal antibody 1:100; Chemicon, Temecula, CA, USA) was used as the primary antibody for NMDAR1. The sections were incubated with ever Alexa-conjugated secondary antibodies (1/200; Invitrogen) at room temperature for 2 hr. NMDAR1 was visualized by Alexa 488 and TH IR by Alexa 594. Fluorescent images were captured with a confocal

laser-scanning microscope and an epifluorescence microscope. This apparatus consists of a center platform (5 × 5 cm) 37 cm off the ground with four branching arms (30 cm long and 5 cm wide). Two of the four arms are open, and the other two arms are enclosed by black walls (20 cm high). Testing was performed during light phase in a dimly lit room (50 lux). Animals were placed on the center platform and scored for arm entries and time spent in each arm. Percentages of time animals spent in the open arms were calculated as the final readout of anxiety. Unpaired t tests were used to compare the significance between the different genotypes. RotaRod analysis was performed using the mouse version of ROTA-ROD manufactured by San Diego Instruments (San Diego, CA, USA). Mice were trained by allowing them to run on a rotarod rotating at 30 rpm for a total time span of 5 min. (Time counting was stopped when mice dropped until they were put back onto the rotarod again.) During the tests mice were again placed on top of the rotarod, which rotated at 30 rpm. Durations of each mouse that stayed on the rotarod (latency to fall) were recorded.

, 1998, Burt, 2004 and Gutierrez et al., 2009). EOs are volatile, natural and complex compounds characterized by a strong odor and are formed by aromatic plants as secondary metabolites. Galunisertib concentration In addition to being used as flavoring agents in foods, EOs exhibit antibacterial, antifungal and antioxidant properties (Bakkali et al., 2008). Satureja montana L., commonly known as winter savory or mountain savory, belongs to the Lamiaceae family, Nepetoideae subfamily and Mentheae tribe and is a perennial semi-shrub (20 cm–30 cm) that inhabits arid, sunny and rocky regions. S. montana

L. is native to the Mediterranean and is found throughout Europe, Russia and Turkey. S. montana L. is a strong aromatic herb and has been used for centuries as a spice for food and teas; is used in Mediterranean cooking, mainly as a seasoning for meats and fish and in flavoring agents for soups, sausages, canned meats and spicy sauces ( Slavkovska et al., 2001, Mastelić and Jerković, PARP inhibitor 2003, Bezbradica et al., 2005, Ćetković et al., 2007 and Silva et al., 2009). S. montana L. has biological properties that are related to the presence of its major EO chemical compounds thymol and carvacrol ( Radonic and Milos, 2003 and Mirjana and Nada, 2004). This research was aimed to evaluate the antimicrobial effect of winter savory (S. montana L.) EO (0.0%, 0.78%, 1.56% and 3.125%) on C. perfringens type A (ATCC

3624) added in mortadella-type sausages formulated with different levels of NaNO2 (0 ppm, 100 ppm Endonuclease and 200 ppm) stored at 25 °C for 30 days. This study was also aimed to determine the feasibility of reducing the levels of nitrite used in the product formulation through the combined use of savory EO to control C. perfringens. The bacterium used in this research was C. perfringens type A ATCC

3624 (history I.C. Hall: L.S. Mc Clung 1997; A.J. Wildson type A, cep26; INCQS 00053), which was kindly provided by the National Institute of Quality Control in Health (INCQS) of the Oswaldo Cruz Foundation (Rio de Janeiro, Brazil). The bacterial strain was reactivated in a specific medium semisolid Clostridium Broth (Biolife Italiana Srl, Italy) under anaerobic conditions at 37 °C for 24 h. After the strain grew, the bacterial cells were pelleted by centrifugation (5000 g for 5 min at 24 °C), covered by freezing culture medium (15% glycerol Vetec, Brazil; 0.5% bacteriological peptone and 0.3% of yeast extract, Biolife Italiana Srl, Italy; and 0.5% of NaCl, final pH of 7.2 ± 0,2) and maintained under a freezing temperature (− 20 °C) throughout the experiment. For bacterial reactivation and use, an aliquot of the freezing culture medium was transferred to test tubes containing the Clostridium Broth medium and grown with two subcultures (last in Brain Heart Infusion broth) at 37 °C for 24 h under anaerobic conditions. The standardization of cell counts was carried out by the growth curve.

5%, p < 0.01; sixth, 145% ± 6.6%, p < 0.01; tenth, 140 ± 6.4%, p < 0.01) but not the first NMDA-fEPSP (105% ± 0.5%, n = 8, p =

0.8) (Figure S5, right), indicating that only when consecutive synaptic responses cause sufficient Ca2+ buildup for CaCC activation does NFA exert an effect on the synaptic response. Next, we recorded the pharmacologically isolated NMDA-EPSPs in CA1 pyramidal neurons while stimulating Schaffer collaterals at 10 Hz and asked whether CaCC plays a role in NMDA-EPSP-spike coupling. In the presence of 10 mM internal Cl−, 100 μM NFA enhanced NMDA-EPSP-spike coupling; NMDA-EPSPs summate to spike much later (first spike occurring most frequently at the tenth synaptic response) when CaCC is intact than when CaCC is blocked by 100 μM NFA (first spike occurring most frequently at the fourth or fifth responses) (Figure S6A). Thus, when CaCC is blocked by NFA, neurons fire spikes more readily with click here reduced average latency to first spike and increased average number of spikes per train (Figure S6B; n = 10, p < 0.001). The CaCC function depends on the Cl− concentration gradient because when we elevated the internal Cl− level to 130 mM (ECl ∼0 mV), reducing CaCC with 100 μM NFA delayed spike initiation, increased the average latency to first spike and reduced

the average number of spikes generated (Figures S6C and S6D; n = 10, p < 0.001). Thus, whereas CaCC normally acts as an inhibitory brake Lenvatinib on NMDA-EPSP to spike coupling, elevating internal Cl− concentration during neuronal activity or dysfunction could cause CaCC to provide positive feedback and enhance excitation. To further explore the physiological contribution of CaCCs to synaptic responses,

we stimulated Schaffer collaterals at 100–200 microns from the CA1 pyramidal cell body layer every 30 s and recorded from CA1 pyramidal neurons at 35°C in physiological solution plus picrotoxin to block GABAA receptors. Reducing CaCC with 100 μM NFA increased the amplitude of large but not small synaptic potentials (Figure 6A), most likely because the former involved NMDA receptor activation. Indeed, in the presence of 100 μM Tryptophan synthase APV to block NMDA receptors, the EPSP was no longer affected by 100 μM NFA (Figure 5I), regardless the stimulus intensity (Figure 5J). Under physiological condition with 10 mM [Cl−]in (Figure 6B, left panel), reducing CaCC with 100 μM NFA amplified EPSPs of large amplitude. In 130 mM [Cl−]in (Figure 6B, middle panel), however, reducing CaCC with 100 μM NFA dampened EPSPs of large amplitude. NFA had no effect on EPSP amplitude when BAPTA was included with 10 mM [Cl−]in to chelate Ca2+ (Figure 6B, right panel). These controls reinforce the notion that the NFA block of CaCC affects the large synaptic potentials that involve activation of NMDA-Rs (6 mV EPSP: 147% ± 2.9%, n = 10, p < 0.05). To test whether CaCCs also play a role in EPSP summation to regulate synaptic integration, we delivered 3 nerve stimuli at 40 Hz.

mTORC1 includes regulatory-associated protein of mTOR (Raptor) and proline-rich AKT substrate 40 kDa and promotes protein synthesis and cell growth through phosphorylation of two main substrates, eukaryotic initiation factor 4E-binding protein 1 (4EBP1) and p70 ribosomal S6 kinase 1 (p70S6K). This complex is sensitive to inhibition by rapamycin and is activated in response to several stimuli including nutrients and amino phosphatase inhibitor library acids. In contrast, mTORC2 specifically contains rapamycin-insensitive companion of mTOR (Rictor), mammalian stress-activated protein

kinase interacting protein, and protein observed with rictor-1, and phosphorylates the hydrophobic motif (HM) of multiple kinases including AKT,

protein kinase Cα (PKCα), and serum- and glucocorticoid-inducible kinase 1. mTORC2 activity was originally implicated in cytoskeletal remodeling (Sarbassov et al., 2004), and recent evidence suggests a role in cell survival and growth as well; however, the upstream activators are poorly understood (Pearce et al., 2010). Results of the present study show that the morphine-induced decrease in VTA DA soma size occurs concomitantly with an increase in the Nutlin 3a intrinsic excitability of these neurons, and that the net functional effect of chronic morphine is to decrease DA output to target regions. This net effect is consistent with morphine reward tolerance observed under these conditions. We go on to show that these adaptations induced by chronic morphine—including decreased soma size, increased excitability, and reward tolerance—are mediated via downregulation of IRS2-AKT and mTORC2 activity in this brain region. These results are surprising since our starting hypothesis was that chronic morphine might decrease mTORC1 activity, in concert with downregulation of IRS2-AKT, based on several reports that tie mTORC1 activity to regulation of neuronal growth and size (Kwon et al., 2003 and Zhou et al., 2009). Counter to this hypothesis, mTORC1 signaling was increased in VTA by chronic morphine, Digestive enzyme an effect

not related to the other actions of morphine on VTA DA neurons. Together, the findings reported here describe a fundamentally novel molecular pathway, involving decreased mTORC2 signaling, possibly as a result of decreased IRS2 signaling, through which chronic opiates alter the phenotype of VTA DA neurons to produce reward tolerance. We set out to characterize the effects of chronic morphine on several phenotypic characteristics of VTA DA neurons. We first determined whether morphine induces a morphological change in the mouse VTA similar to that seen in rats. We found an ∼25% decrease in the mean surface area of mouse VTA DA neurons in response to chronic morphine (Figure 1A), very similar to the magnitude of soma size decrease observed in rats (Russo et al., 2007 and Sklair-Tavron et al., 1996).

In the latter case, no correlation is expected between initial state, end state, and duration. Our data support the first hypothesis in the case of sleep spindles. We found a robust correlation between the participation probability of nRT cells in the first cycle and the length of the spindle (Figure 7A). A similar, though weaker

relationship existed between spindle duration and both the participation probability and spike/burst of TC cells. We also observed a strong correlation between the participation probability of nRT cells in the first and the last cycles (Figure 7C). These data indicate that the initial state of the network has strong influence DAPT concentration on spindle duration, and, once a spindle is launched,

it does not evolve randomly but follows a rigid trajectory between fixed start and end points. The optogenetic experiments, however, indicated that there is no fixed correlation between the magnitude of nRT activation and the evoked spindle length. This suggests that spindle duration is determined by more complex variables, such as the precise state of neuromodulators selleck inhibitor and/or degree of cortical drive present at spindle initiation. Such variables would affect both the nRT firing pattern seen on the first cycle, and phenomena controlling spindle duration, such as the speed at which nRT cells become hyperpolarized as the spindle progresses. Our data indicate that quantitative cycle-by-cycle analysis of excitatory and inhibitory activity can be used to test hypotheses regarding what determines the duration of transient network events. Because short, transient oscillations with widely different frequencies are abundant in the

brain (e.g., type II theta activity, alpha waves, transient gamma oscillations, sharp wave ripples, etc.), similar analyses may help to determine the mechanisms of these oscillations. The duration of transient oscillatory events is plastic, changing both under healthy conditions (e.g., following learning) and also in case of neurological diseases. Thus, defining the mechanism underlying the duration of these transients can lead to better understanding of the temporal organization of neuronal activity in both healthy and diseased states. All animal procedures were approved by the Institute Isotretinoin of Experimental Medicine Protection of Research Subjects Committee as well as the Food-Safety and Animal-Health Office of the Pest District Government Bureau, which is in line with the European Union regulation of animal experimentations. For general surgical procedures, see Barthó et al. (2004). Briefly, 41 male Wistar rats were used in the study. For anesthetized experiments (n = 36), rats were administered 1.5 g/kg urethane, the skull was opened over somatosensory cortex and thalamus (−3.0 AP, 2.8 ML from Bregma), dura was removed, and silicon microelectrodes (Neuronexus Technologies) were lowered into the brain.

, 2005) a pharmacological

agent believed to reduce abnormally high glutamatergic activity. The interactions between circadian clocks and neurochemical mechanisms in the brain appear to be complex and may illustrate the pleiotropy of clock genes. This pleiotropy may be key to temporally coordinate and couple mechanistically unrelated physiological pathways such as weight and mood regulation, which once uncoupled may favor development of obesity and depression. Because the circadian system appears to be involved in a number of diseases including obesity and depression, it may be an entry point for the development of treatments for these diseases. As highlighted in this review, light and food can significantly impact the check details circadian system; this implies that lifestyle affects human health via the circadian system with nutrition, movement and light exposure as the key elements involved. Nuclear receptors, kinases, and molecules buy Vorinostat such as melatonin are a part of the circadian system. It is thus plausible that pharmacological agents acting on these components or mimicking their actions may serve as a conduit to ameliorate health problems associated with the circadian clock. One

modulator of kinase activity is lithium, which inhibits GSK3β activity. This kinase regulates clock components such as REV-ERBα (Yin et al., 2006) and PER2 (Iitaka et al., 2005), lengthens the circadian 3-mercaptopyruvate sulfurtransferase period (Li et al., 2012), and thus may relay the beneficial effects of lithium in the treatment of depressive disorders (Johnsson et al., 1983). However, its precise mechanism of action is not understood. Another

potential pharmacological target to alter the circadian clock is casein kinase 1δ (CK1δ). Application of a CK1δ inhibitor (PF-670462) to wild-type mice lengthened circadian period accompanied by nuclear retention of the clock protein PER2. This treatment lengthened the period in a phase specific manner, selectively extending the duration of PER2-mediated transcriptional feedback (Meng et al., 2010). This suggests that CK1δ inhibition might be effective in increasing the synchronization of disrupted circadian oscillators offering an avenue for therapeutic treatment of diseases caused by disrupted or desynchronized circadian rhythms. Recently, longdaysin, a molecule that targets three kinases, CK1α, CK1δ, and ERK2, was discovered during a large-scale chemical screen. Longdaysin inhibition of CK1α reduced PER1 phosphorylation and degradation. As a consequence, the clock periods in human cells and in zebrafish embryos became longer, pointing to a therapeutic potential of longdaysin in manipulating and synchronizing circadian clocks (Hirota et al., 2010b). Another approach to modulate clock activity is through delivery of substances that modulate the action of nuclear receptors.

2. Both DLW and HR analyses yielded similar results for the TEE, with a mean difference of −8.6 kcal/day. Forty-four (96%) out of 46 subjects fell within Tariquidar cost ±2SD of the mean difference in TEE comparisons, and there was no tendency towards under- or over-estimation. Since the REE is the largest component of the TEE and different methods and equations have been used to estimate the

REE in current years, we included REE estimations in the same subjects as a reference. We found that the GEA, Harris–Benedict equation and Cunningham equation used by bioimpedance assessment (BIA) all yielded similar REE estimates in middle-aged women and men. However, in young women, the Cunningham equation (BIA) gave significantly lower REE estimates than both GEA (p = 0.006) and the Harris–Benedict equation (p = 0.011)( Table 2). The mean difference between Bortezomib datasheet the GEA and Cunningham equation (BIA) was 1.4 kcal/day, and the correlation was r2 = 0.64 (p < 0.001, Fig. 1B). In this study we showed that the TEE estimated by HR monitoring compared well with that derived from the DLW method in young women, as well as in middle-aged men and women, but with large individual variations. HR monitoring is the most popular method for assessing free-living energy expenditure and the patterns of physical activity.30 It fulfills many of the criteria for providing continuous, indirect,

and objective measures of the TEE, being relatively inexpensive, simple to use and non-invasive. The TEE estimation from the HR is based on the fact that under most circumstances, the HR is correlated with the rate of oxygen consumption, and hence the Idoxuridine rate of energy expenditure.31 Unfortunately, the predictive power of HR monitoring as an index of energy expenditure at low levels of activity is poor,11 particularly in the critical HR range where resting and active conditions converge and overlap.32 As a result, the HR method

for TEE estimation performs well under circumstances of moderate to vigorous exercise, but is much less accurate in sedentary people.8, 33 and 34 To overcome this shortcoming, combining HR monitoring with accelerometry has been suggested to improve energy expenditure estimation.2 However, a recent study using the Actiheart monitor showed that this combined accelerometry/HR method did not provide any better energy expenditure estimates than using HR monitoring alone.35 The accuracy of TEE estimation by HR depends on the accuracy of the manufacturer’s proprietary software, namely the algorithm used.36 In an Australian study using Suunto’s previous software, the TEE was underestimated in runners during a submaximal running test when compared to gas analysis data.37 Livingstone and colleagues32 and 38 reported that the mean difference in the TEE obtained from the HR and DLW methods varied between 24 and 98 kcal/day. Likewise in a Japanese study, the HR TEE was also higher by a mean difference of 57 kcal/day in contrast to the DLW method.

94 ± 0.1; not significantly different from 1, p = 0.54; peak EPSP at seven synapses = 97% ± 10% of linear sum; n = 5; Figures 2B and 2C). This shows that supralinear integration in layer 2/3 pyramidal cell dendrites crucially depends on NMDAR recruitment, which is facilitated CP 673451 by activation of both VGCCs and VGSCs. We next investigated how unitary EPSPs varied with distance from the branch point. Analysis of somatic EPSPs evoked by single spine uncaging revealed no significant correlation between somatic peak amplitude and distance along the dendritic branch (r = 0.13; p = 0.12; n = 139 synapses from

18 dendrites; peak of distal EPSPs = 97% ± 3% of proximal EPSPs, not significantly different; p = 0.73; laser power, plane of focus, and spine MK0683 supplier size kept constant; Figures 2D, 2E, and S1C). However, block of NMDARs revealed a larger

NMDA component for EPSPs arising at more distal synapses (22% ± 4% for distal, 5% ± 7% for proximal; p = 0.041; n = 8), and lead to smaller somatic EPSPs for inputs at distal locations (82% ± 2% of proximal; p = 0.032), suggesting that NMDAR recruitment can partially compensate for dendritic filtering in these dendrites. Inputs to cortical neurons can exhibit different degrees of temporal synchrony (Abeles, 1991, König et al., 1996 and Shadlen and Newsome, 1995), and the efficacy of each particular input pattern depends on how well the individual inputs summate over time (Magee, 2000 and Rall, 1964). We therefore investigated how temporal summation varies along basal and apical oblique branches. We stimulated groups of seven synapses

at different dendritic locations using different interstimulus intervals and monitored the somatic EPSP peak. While for proximal synapses the EPSP peak decreased as input became more asynchronous, distal synapses produced EPSPs that had remarkably similar sizes over a range Casein kinase 1 of stimulation intervals (Figure 3A). Distal EPSPs at 10 ms intervals were 95% ± 1% of the peak at 1 ms intervals, while for proximal EPSPs the peak decreased to 56% ± 4% (p < 0.0001, ANOVA, n = 19; Figure 3B), which was also seen for small EPSPs (Figures S2E and S2F) and for a smaller number of stimulated synapses (Figure S1D). Between the branch point and the tip of the dendrite, temporal summation gradually increased by almost 2-fold (Figure 3C). This shows that in parallel with the changes in gain described above, single dendritic branches also have a gradient of efficacy for summation of asynchronous synaptic input. Layer 2/3 pyramidal cells lack a significant density of Ih channels (Larkum et al., 2007). In hippocampal CA1 pyramidal cells, the presence of a dendritic Ih gradient has been shown to normalize temporal summation over the dendritic tree (Magee, 2000).

, 2005). Collectively, these results provide evidence that N-cadherin expression and neuroepithelial maintenance are controlled by both activating inputs provided by Sox2 and repressive inputs provided by Foxp4, mediated by distinct enhancer elements. If N-cadherin is the critical target for Foxp repression, then the same ectopic differentiation phenotype should be observed by learn more directly blocking N-cadherin activity. To this end, we misexpressed a dominant-negative form of N-cadherin (dn-N-Cad) lacking its extracellular domain, which disrupts adhesions between neighboring cells (Tanabe et al., 2006).

High levels of dn-N-cad disrupted the radial structure of the neuroepithelium, resulting in a cytoplasmic accumulation of Numb and ectopic formation of NeuN+ neurons in the VZ much like the defects seen after Foxp4 misexpression (Figures 5A, 5B, 5F, 5G, 5K, 5L, 5P, 5Q, 5U, 5V,

5Z, and 5AC). Interestingly, low-level misexpression of dn-N-cad also promoted neuronal differentiation, but under these conditions AJs and the radial structure of the neuroepithelium was preserved. The majority of these transfected cells settled in the IZ, though they rarely migrated further Antiinfection Compound Library into the MZ (Figures 5C, 5H, 5M, 5R, 5W). Misexpression of full-length N-cadherin had the opposite effect, retaining most of the transfected cells in a progenitor-like state within the VZ (Figures 5D, 5I, 5N, 5S, and 5X). Sox2 is known to activate N-cadherin expression in many regions of the CNS, and its elevation can block neuronal differentiation (Bylund et al., 2003, Graham et al., 2003 and Matsumata Org 27569 et al., 2005). We therefore examined whether Sox2 misexpression could increase N-cadherin and thereby offset the progenitor-suppressing actions of Foxp4. When Sox2 was elevated, apical staining for N-cadherin and other components of AJs such as aPKCζ and Numb was increased, reminiscent of the phenotype seen with

Foxp2 and Foxp4 knockdown (compare results in Figures 3S and 3T to Figures 5E, 5J, 5O, 5T, and 5Y). Moreover, the majority of transfected cells remained in the VZ and neuronal differentiation was blocked (Figures 5A and 5E). When Sox2 was coexpressed with Foxp4, N-cadherin levels and AJs were fully restored and cells were held in a NPC state (Figures 5Z–5AA, 5AC, 5AD, and 5AF). Identical results were obtained with the coexpression of Foxp4 with full-length N-cadherin (Figures 5AB, 5AE, 5AF). Thus, Foxp4 appears to work in opposition to Sox2 in setting the level of N-cadherin expression to balance progenitor maintenance with differentiation (Figure 5AG). We next set out to determine where Foxp4 functions in the neurogenic cascade that mediates neuronal differentiation.

Not surprisingly, chemotropism is complex:

the same ligand can be either attractive or repulsive depending on the receptor complexes expressed by the growth cone. Axons, in turn, usually express several guidance receptors. The combination of multiple guidance cues and receptors effectively constitutes a combinatorial “guidance code” that defines how an axon (or dendrite) will find its way. An intriguing hypothesis is that synaptic partners might share similar guidance codes, ensuring that their processes meet at specific locations within the developing nervous system, as a first step in forming a neural circuit. In this issue of Neuron, Wu et al. (2011) provide compelling evidence to support this hypothesis. CH5424802 clinical trial They show that a combinatorial code involving Semaphorins

and their Plexin receptors guides the construction of a central neural circuit in the Drosophila embryo, involving MAPK inhibitor sensory neurons and their interneuronal partners. The developing Drosophila CNS expresses three Semaphorins, a transmembrane Sema-1a protein that signals through the Plexin A (PlexA) receptor, and the secreted Sema-2a and -2b proteins. While Sema-2a was known to act as a chemorepellant, signaling through the Plexin B receptor (PlexB; Ayoob et al., 2006), much less was known about either Sema-2b or its receptor. Sensory innervation of the embryonic CNS is perhaps less well known than other model systems in Drosophila, such as the eye, CNS midline, olfactory neuropil, or neuromuscular junction. Nevertheless, this paper shows it to be enormously powerful. The authors examined a group

of mechanosensory neurons called chordotonal (ch) cells, that are born in the periphery and whose axons grow along peripheral nerves to innervate the CNS. Once there, the axons are faced with the daunting challenge of identifying the correct tracts to lead them to their synaptic partners. In the CNS, they find that the roadways are still under construction, with axon tracts and fascicles actively being established. Wu et al. (2011) show that the ch neurons and their interneuron partners use the same molecular guidance system to rendezvous at a specific site within the developing ventral nerve cord (VNC, akin to the vertebrate spinal cord). The embryonic and larval VNC is organized as a latticework of longitudinal axon tracts that link the local segment-specific circuits together, and transverse of tracts that enable communication between the left and right hemisegments. A subset of the longitudinal axon tracts can be selectively labeled by virtue of their expression of the NCAM homolog Fasciclin2 (Fas2). This IgCAM is expressed by the axons of three parallel longitudinal tracts, known as the medial, intermediate, and lateral bundles, located on either side of the midline. Work by the Goodman lab (UC Berkeley) and the Dickson lab (Vienna, Austria) had shown that the spacing of these bundles is due to various degrees of chemorepulsion by Slit, a protein secreted by glial cells at the midline.