In this context, a higher recruitment of pacemakers will increase the strength of the locomotor outputs, while their depolarization will speed up the locomotor rhythm. Finally, our results support a hybrid pacemaker network concept for generation of the locomotor rhythm in which INaP-dependent pacemaker properties of CPG interneurons may be switched on by activity-dependent changes in [Ca2+]o and [K+]o and finely tuned by neurotransmitters or neuromodulators

such as glutamate or 5-HT. These results obtained in vitro represent a major conceptual advance that remains to be tested in vivo. Experiments were performed on neonatal (1- to 5-day-old) Wistar rats (n = 97) and Hb9:eGFP transgenic selleckchem mice (n = 47). We performed experiments in accordance with French regulations (Ministry of Food, Agriculture and Fisheries; Division of Health and Protection of Animals). Electrophysiological experiments were performed on either whole spinal cord preparations or spinal cord slices. We performed dissections under continuous perfusion with an oxygenated

aCSF (details in the Supplemental Experimental see more Procedures). In the whole spinal cord preparation, the locomotor-like activity was recorded (bandwidth 70 Hz–1 kHz) using extracellular stainless steel electrodes placed in contact with lumbar ventral roots and insulated with Vaseline. During locomotor-like activity, [Ca2+]o and [K+]o were recorded by means of ion-sensitive microelectrodes manufactured from double-barreled theta glass capillaries (protocol described in the Supplemental Experimental Procedures). Slice preparations were used for whole-cell patch-clamp recordings from interneurons in the ventromedial laminae VII-VIII (neonatal rats) or Hb9 interneurons. Electrophysiological procedures used to characterize INaP are described in

the Supplemental Experimental Procedures. We simulated the effects of [Ca2+]o and [K+]o on INaP-dependent pacemaker properties at the level of either a single neuron or a population of 50 uncoupled neurons with randomized parameters. The detailed description of the computational model is provided in the Supplemental Experimental Procedures. Data are presented as means ± SEM. Nonparametric statistical analyses were employed with a Wilcoxon much matched-pairs test when two groups were compared and a one-way ANOVA test for multiple group comparisons (GraphPad Software). The level of significance was set at p < 0.05. Detailed methodology is described in the Supplemental Experimental Procedures. This work was supported by the French Agence Nationale pour la Recherche (ANR to L.V.), the Institut pour la Recherche sur la Moelle épinière et l’Encéphale (IRME to L.V. and F.B.). S.T. received a grant from the Fondation pour la Recherche Médicale (FRM). I.A.R. and N.A.S. were supported by the National Institutes of Health grant R01 NS081713. F.B. designed and supervised the overall project, performed and analyzed in vitro experiments, and wrote the manuscript. S.T.

Further, NMDA receptors play a crucial role in the modification of neural connectivity during or following experiences. NMDA antagonists attenuate experience-driven reorganization of the body map in S1 of awake animals (Jablonska

et al., 1999) and retard value-related changes of neural firing in orbitofrontal cortex of behaving animals (van Wingerden et al., 2012). These data suggest that neural reactivation causes formation of long-term memories via NMDA-dependent changes in synaptic strength. The pattern reactivation phenomena we describe RG7204 concentration here is also dependent on NMDA receptors and is therefore consistent with the mechanisms of memory consolidation in the awake state. Previous studies have suggested that “reverberating” patterns are similar to spontaneous patterns that precede specific sensory experience. This phenomenon is termed “preplay” and was elegantly shown in hippocampal cortex by Dragoi and Tonegawa (2011). Similarly, in Euston et al. (2007) in Figure 1, the pretask spiking patterns in medial prefrontal cortex have obvious similarity

to patterns during the task and patterns replayed after the task. The data presented here are consistent with these results and suggest that repeated stimulation induces only gradual changes to existing spiking patterns (note that, in Figures 2D and 6A–6E, similarity of evoked patterns to preceding spontaneous activity is consistently above 0). Y-27632 datasheet For that, the relationship between stimulus-evoked (or reverberating) sequences to prior patterns occurring spontaneously is a very important question. We have previously shown that

stereotypical patterns of population activity are associated mostly with the beginning of UP states (Luczak and Barthó, 2012 and Luczak et al., 2007) and that stimulus-evoked patterns have strikingly similar temporal structure to such spontaneous patterns (Luczak et al., 2009). Furthermore, even in desynchronized brain states, population activity is composed of bursts of population activity with similar temporal structure to secondly patterns during UP states in synchronized states (Luczak et al., 2013). Similar sequential patterns with stereotyped spatiotemporal dynamics have been also observed in vitro (Mao et al., 2001, Cossart et al., 2003, Ikegaya et al., 2004 and MacLean et al., 2005), suggesting that network UP states could be circuit attractors. Together, these in vitro and in vivo studies suggest that connectivity patterns at the local level impose significant constraints on activity propagation (Luczak and Maclean, 2012), thus leading to formation of similar sequential population patterns both spontaneously and during stimulation (although different stimuli produce slightly different variations of that sequential pattern; Luczak et al., 2013).

Three additional lines of evidence suggest that the Brm remodeler is specifically required for ddaC dendrite pruning. First, overexpression of BrmDN or loss of brm did not apparently disturb initial development and elaboration of larval ddaC dendrite arbors, because their primary and secondary dendrites at the white prepupal (WP) stage resembled the wild-type neurons in numbers and morphology ( Figures 1C, 1D, and 1F; wild-type, Figure 1B). Dendrite outgrowth and elaboration of ddaC neurons were largely normal in

brm2 and brmT362 mutant embryos at 18–20 hr after egg laying (AEL; n = 6 and n = 7, respectively; wild-type, n = 6; Figure S1D). Second, BI-6727 overexpression of BrmDN did not affect the cell fate/identity of ddaC neurons because the levels of

two important ddaC markers, Cut ( Grueber et al., 2003) and Knot ( Hattori et al., 2007 and Jinushi-Nakao et al., 2007), remained unchanged (n = 11 and n = 11, respectively; Figure S1E). Third, overexpression of BrmDN did not inhibit ddaC dendrite regrowth at the late pupal stages (n = 4; Figure S1F), suggesting that Brm is not important for ddaC dendrite regrowth per se. selleck chemicals llc However, the role of Brm in dendritic morphology/connectivity of adult ddaCs remains unclear. Taken together, our data show that Brm, but not ISWI, Mi-2, or Dom, plays an important and specific role in dendrite pruning of ddaC neurons. Given that the pruning defects in BrmDN and brm MARCM resembled EcRDN (n = 19; Figure 1G), usp, sox14, and mical mutant phenotypes ( Kirilly et al., 2009 and Kuo et al., 2005), we explored whether Brm regulates their normal expression in ddaCs. The Brm remodeler is not required for EcR-B1 expression because EcR-B1 upregulation occurred in both BrmDN-expressing (n = 8; Figures 2D and 2J) and brmT362 MARCM (n = 6; Figures 2G and 2J) ddaC neurons. Usp, the EcR-B1 conuclear receptor, also remained abundant in BrmDN-expressing ddaC neurons (n = nearly 13; Figure S2C). We then investigated whether Brm modulates the expression of sox14, the

key effector gene of EcR-B1/Usp controlling dendrite pruning ( Kirilly et al., 2009). In contrast to the abundant expression of Sox14 in wild-type (n = 11; Figure 2B), Sox14 levels were absent or strongly reduced in the majority of 2X BrmDN-expressing ddaCs (83.3%, n = 36; Figures 2E and 2K) or brmT362 MARCM ddaCs (90%, n = 10; Figures 2H and 2K). Similarly, Sox14 expression was also strongly reduced in the BrmDN-expressing ddaF neurons (n = 36; Figure 2E, arrow). Thus, the Brm remodeler is specifically required for the expression of Sox14, but not EcR-B1. Consistently, Mical expression that normally depends on Sox14 was also strongly reduced in BrmDN-expressing (75.6%, n = 41; Figures 2F and 2L) and brmT362 MARCM (80%, n = 5; Figures 2I and 2L) ddaC neurons, as compared to that in wild-type (n = 22; Figures 2C and 2L).

Statistical analyses are described in the figure legends. Imaging of individual IR protein complexes in Xenopus oocyte membranes by total internal reflection fluorescence microscopy was performed essentially as described ( Sonnleitner et al., 2002 and Ulbrich and Isacoff, 2007); details

are provided in the Supplemental Experimental Procedures. Red (mCherry) and green (EGFP) spots were considered to be colocalized when their center positions were closer than 3 pixels (150 nm). However, most colocalization events reflect much shorter separation ( Figure S3B). The expectation value for colocalization of red and green spots from random spot distributions was calculated by the formula: f = a∗dg∗dr/(dg+dr), where a = π∗r2 is the area http://www.selleckchem.com/products/RO4929097.html of the disk around a spot with r = 150 nm, dg and dr are the green and red spot densities, respectively, and f is the resulting fraction of overlapping

spots. Rucaparib mw For spot densities as observed in the EGFP:IR84a+mCherry:IR25a coexpression experiment, the resulting expectation values for red/green colocalization was 1.4%–6.9% (mean 3.6% ± 0.7%). To analyze the influence of coexpression of the partner subunit on plasma membrane expression density (Figure S3A), we injected a total volume of 50 nl per cell, with 0.1 μg/μl cRNA for the EGFP-tagged subunit and, where included, 0.25 μg/μl cRNA for the mCherry-tagged subunit. For each condition, we counted surface-localized spots of EGFP in two randomly selected 13 × 13 μm plasma membrane areas in each of eight different cells. To deduce the fraction, f, of dimers from the average integrated intensity, x, we assumed that a fraction, p = 0.8, of the Megestrol Acetate EGFP tags were fluorescent ( Ulbrich and Isacoff, 2007). The relation between x, f, and p is: x=(∗(1−f)p+f∗∗(pp∗2+2∗p∗(1−p))/(∗(1−f)∗p+f∗(p∗p+2p∗(1−p)),x=((1−f)∗p+f∗(p∗p∗2+2∗p∗(1−p))/((1−f)∗p+f∗(p∗p+2∗p∗(1−p)),where the numerator is the total fluorescence

from all complexes and the denominator the fraction that is fluorescent. Not all complexes are fluorescent, because some monomers have a nonfluorescent EGFP and some dimers have two nonfluorescent EGFPs. Solving for f results in: f=(x−1)/(1−x+p∗x),f=(x−1)/(1−x+p∗x),which yields f = 0.70 for x = 1.49 and f = 0.83 for x = 1.57. We thank Yael Grosjean for sharing the IR84a mutant prior to publication, Raphael Rytz for generating the tree in Figure 1A, and Michael Saina for analyzing IR8a expression in axon termini. We acknowledge Kazushige Touhara for use of pXpress, Roger Tsien for use of mCherry, the Bloomington Stock Center for Drosophila strains, and the Developmental Studies Hybridoma Bank for monoclonal antibodies. We are grateful to Sophie Martin, Chun Tang, and members of the Benton group for discussions and comments on the manuscript. Research in S.K.

These findings were supported by recent studies demonstrating that IGF2BP3 prevents miRNA-dependent inhibition of HMGA2-expression [16]. Also in HCC, we recently demonstrated that IGF2BP1 and IGF2BP3 are among the ten most upregulated RBPs, as revealed by microarray and RT-PCR analyses [33]. Like proposed for IGF2BP3, IGF2BP1 was found to act as an oncogenic factor promoting the survival and proliferation of HCC-derived cells in vitro and in vivo by enhancing the expression of MYC and Ki67 [33]. In pancreatic cancer, IGF2BP3 expression was exclusively assessed by IHC-analyses

with three studies using the DAKO-supplied antibody [82], [83], [84], [85] and [86]. In agreement with other analyses, IGF2BP expression was determined in the vast majority of pancreatic ductal adenocarcinomas (PDAC) and selleck kinase inhibitor was proposed for 97% of invasive PDACs [83]. In contrast, the vast majority (>74%) of inflamed pancreatic tissue was negative supporting the view that IGF2BPs, in particular IGF2BP1 and IGF2BP3, are potent biomarkers of aggressive and invasive pancreatic carcinomas [83]. In prostate cancer (PC), exclusively analyzed by the pan-IGF2BP antibody supplied by DAKO, the expression of IGF2BP3 was observed in 18–83% of analyzed samples [87], [88] and [89] but considered to be of low prognostic value [88].

However, a significant upregulation of IGF2BP expression was HA-1077 clinical trial observed in only 15% of localized but strikingly 65% of palliatively treated metastatic PCs supporting the pro-invasive/-metastatic role of IGF2BP1/3 [87]. Notably, upregulated IGF2BP3 expression was not correlated with elevated IGF2 mRNA or protein abundance. next However, increased IGF2BP serum levels were independently correlated with poor survival in patients

treated with radical prostatectomy [87] and [89]. In studies focusing on IGF2BP3 expression in renal cell carcinoma (RCC), all using the DAKO-supplied antibody, the expression of IGF2BPs was correlated with an overall poor prognosis and metastasis [90], [91], [92] and [93]. The vast majority (86%) of IGF2BP-positive patients developed metastases whereas this was only observed for 14% of negative tumors [92]. In agreement, IGF2BP expression was reported for about 50% of metastasizing RCCs but approximately only 4% of non-disseminating RCCs [91]. Notably, IGF2BP expression was also observed in approximately 62% of analyzed metastases of RCC-origin [91]. In testicular cancer and male teratoma, IGF2BP3 expression was observed in the vast majority of analyzed samples [94] and [95]. The study by Hammer et al. used a highly paralogue-specific set of peptide-directed polyclonal antibodies targeting the C-terminus of IGF2BPs [94], similar to the MBL-supplied antibody (Fig. 1c).

GUVs were composed of a 5:2:1:1 molar ratio of brain L-α-phosphatidylcholine, L-α-phosphatidylethanolamine, L-α-phosphatidylserine, cholesterol (Avanti Polar Lipids),

and 2 mol% DiO (Invitrogen). We dried 1 μl of 1 mg/ml lipid in chloroform at 70°C followed by passive rehydration in PBS with 3 ng/μl EndoA (or mutant EndoA) (van den Bogaart et al., 2007); fly EndoA was prepared as outlined DAPT ic50 in the Supplemental Experimental Procedures. Blinded confocal microscopy was used to determine tubulation (Yoon et al., 2010). GUVs prepared by electroswelling (data not shown) yielded similar results. Liposome composition in flotations (Schuette et al., 2004) was identical to GUVs. We loaded 30 mM lipids in 25 μl HP150 buffer (20 mM HEPES [pH 7.4]; 150 mM KCl) and 3% (w/v) Na-cholate on a sephadex-G50 (Sigma-Aldrich) column. We formed ∼35-nm-sized liposomes by size exclusion chomatography (van den Bogaart et al., 2010). Liposome

concentration was 240 nM (by FCS; Cypionka et al., 2009). We mixed 750 nM EndoA with two volumes of liposome suspension and 40% (w/v) nycodenz (Axis-Shield; also in HP150), overlaid with 30% (w/v) nycodenz and HP150, and centrifuged check details for 3 hr at 259,000 × g in a swinging bucket. We retrieved 20 μl fractions for western blotting. LRRK2 phosphorylation in the presence of liposomes was prepared in kinase buffer (50 mM Tris [pH 7.5], 1 mM EGTA, 10 mM MgCl2, 2 mM DTT; no detergents) and 2 mM total lipids with 250 nM EndoA were preincubated and then mixed with 1 ng/μl LRRK2G2019S or kinase-dead LRRK2KD (LRRK2D1994A) and 200 μM ATP for 2 hr at 37°C. This reaction was mixed with nycodenz and centrifuged. Fly heads collected on ice were crushed in lysis buffer (10 mM HEPES, 150 mM NaCl, 1% triton) (pH 7.4) with complete protease (Roche) and phosphatase inhibitor cocktail 2 and 3 (Sigma) followed by clearing at 10,000 × g for 10 min. Proteins separated on Bis-Tris 4%–12% precast gels (Life Technologies) were transferred to nitrocellulose. Primary antibodies were the following:

Ab-EndoAGP69 guinea pig (1:5,000); Ab-EndoAS75 rabbit (1:200); Ab-NsybR29 rat (1:2,000); anti-ATPA1 (Novus Biologicals); anti-Flag M2 (Sigma); and anti-alpha Tubulin (1:2,000). Recombinant LRRK2 (5 ng LRRK2, LRRK2G2019S, or kinase-dead LRRK2KD [LRRK2D1994A]; however Life Technologies), Drosophila LRRK ( Supplemental Experimental Procedures) and 50 ng human EndoA1-3 (SH3GL1, SH3GL2 [Origene]; SH3GL3 [Abnova]), or Drosophila EndoA were incubated in kinase buffer (Tris 50 mM [pH 7.5]; EGTA 1 mM; MgCl2 10 mM; DTT 2 mM; Tween 0.01%) with 1 μM ATP and 1 μCi AT33P (Perkin Elmer) at 37°C. SDS PAGE sample buffer stopped the reactions. EndoA or EndoA1 phosphorylation (Typhoon, Amersham, GE Healthcare) and total protein (colloidal gold, Aurodye, Biorad) were quantified. We transfected 500,000 CHO cells/well with V5-tagged LRRK2 with or without Flag-tagged EndoA1 (Origene).

Blood samples for analysis of afoxolaner concentration were collected as either part of the samples collected for clinical chemistry analysis or were collected separately 3 h after treatment on Day 112. Plasma samples were analyzed quantitatively find more to determine afoxolaner concentrations using a method based on 96-well solid phase extraction of afoxolaner from canine plasma and a proprietary internal standard followed by LC–MS analysis as described in Letendre et al. (2014). The physical exam, continuous clinical pathology values, and urinalysis were analyzed over the full

study. The analysis of these variables used repeated measures analysis of covariance (RMANCOVA), including treatment, sampling day, sex, and their interaction terms as fixed effects. The covariate was the most recent pre-treatment value. If the three-way interaction, “treatment by sex by sampling

day”, was significant at the p = 0.05 level, then no further evaluation was done. If the “treatment by sex by sampling day” interaction was not significant, then “treatment by sex” and “treatment by Dolutegravir cell line sampling day” were evaluated. If either two-way interaction was significant, then the treatment means were compared to the control group within each level of the corresponding factor. If neither was significant, the effect of treatment was evaluated and if significant, the treatment means were compared to the control group. Other than the test of the three-way interaction, all statistical analyses used p = 0.10 significance isothipendyl level. When compared to efficacy testing of molecules where a significance level <0.05 is needed, the choice of 0.10 significance level for animal safety study increases the safety margin by highlighting effects that would not appear at p < 0.05. During the study, commercial food was offered at least twice daily and total daily consumption was analyzed. Organ weights (absolute, per 100 g body

weight and per 100 g brain weight) were analyzed using analysis of variance (ANOVA). Abnormal health findings were summarized by treatment group using Veterinary Medicinal Dictionary for Drug Regulatory Authorities (VEDDRA) terms (EMA, 2013). For the analysis of health abnormalities, the analysis endpoint was the number of dogs within each treatment group that experienced that abnormality at least once during the study. If a treatment group other than control had at least 4 animals experiencing the abnormality, then the three treated groups were compared to the control group using the Pearson Chi-Square test on a pair-wise basis. The only abnormalities analyzed in this manner were emesis and diarrhea. Nine plasma samples over 126 days from each treated dog were collected in order to establish afoxolaner plasma concentrations during the study.

As typically only 30% of patients respond to even the gold standard FDA approved treatments (Finnerup et al., 2010), identification of the pattern of mechanisms

present in an individual should be a useful approach for identifying patients more likely to respond to a particular treatment and establishing individualized pain treatment. The pattern of expression of pain-related sensory abnormalities, the individual sensory phenotype, should reveal clues of the underlying pathophysiological dysfunction. Since one specific symptom (e.g., burning pain) may be generated by several different underlying pathophysiological mechanisms (e.g., peripheral sensitization, gain of function c-Met inhibitor mutations in

Nav1.7, or ectopic activity due to alteration in HCN2), it is more likely that a specific constellation of many sensory symptoms and signs might ABT-199 mouse better predict underlying mechanisms. Patient reported outcomes, as well as quantitative sensory testing, or a combination of both, are beginning to be used to analyze sensory profiles in neuropathic pain patients and distinct subgroups of patients can be detected who are characterized by different specific sensory profiles (Baron et al., 2009, Bouhassira et al., 2005 and Scholz et al., 2009). In a large group of patients with diabetic peripheral neuropathy and postherpetic neuralgia, a sensory profiling approach revealed five subgroups of patients with distinct pain-related sensory phenotypes (Baron et al., 2009). For example, patients who suffer from considerable burning crotamiton pain and paresthesias but

minimal mechanical allodynia and thermal hyperalgesia and who additionally show numbness as a prominent finding probably have sensory terminal deafferentation in the skin with little or no central sensitization. A length-dependent dying-back or atrophy of sensory terminals innervating the extremities together with ectopic activity in heat nociceptors, best explains these findings. Patients with spontaneous burning pain in combination with dynamic mechanical allodynia and minimal negative symptoms (no reduced thermal threshold), reflects the presence of relatively preserved and sensitized nociceptors in the skin together with central sensitization (Baron et al., 2009). A major goal is to identify the most relevant and discriminatory aspects of the pain phenotype that most robustly reflect different mechanisms or combinations of mechanisms.

We did not notice significantly different seizure stages in WT and AKAP150−/− mice as previously reported by Tunquist et al. (2008), except in response to the first dose of KA ( Figure S2). Hippocampi were isolated from mice 16–20 hr after intrapleural administration of either pilocarpine or KA, or only vehicle as a control, total RNA was extracted, and qPCR was performed. Indeed, a profound augmentation of both KCNQ2 and KCNQ3 mRNA was observed in mice after

this website seizures induced by pilocarpine (27.9 ± 6.7-fold and 9.3 ± 2.2-fold, n = 18) or KA (8.7 ± 2.3-fold and 3.1 ± 0.6-fold, n = 25), compared with control mice injected with vehicle (1.1 ± 0.05-fold and 1.1 ± 0.10-fold, n = 17) ( Figures 10D and 10E). This profoundly increased mRNA of both KCNQ2 and KCNQ3 in hippocampi from mice subjected to seizures is much greater than that seen from 50 K+ or ACh treatment in cultured sympathetic neurons, suggesting that seizures induce exaggeration of this transcriptional regulation and could be conserved throughout the nervous system as a protective mechanism against hyperexcitability disorders such as epilepsy. Our mechanism predicts that this profound increase induced by seizures should selleckchem likewise be dependent on AKAP150. Indeed, in AKAP150−/− mice, there was almost

no upregulation of KCNQ2 and KCNQ3 mRNA after pilocarpine-induced (1.5 ± 0.1 and 1.4 ± 0.1, n = 14) or KA-induced (1.8 ± 0.4 and 1.6 ± 0.2, n = 18) seizures ( Figures 10D and 10E), confirming the central role of

AKAP150 in this phenomenon. Here, we show neuronal activity tuclazepam to closely regulate M-channel transcription, likely as a negative feedback loop that limits neuronal hyperexcitability. AKAP79/150 associates with L-type (CaV1.3) Ca2+ channels and orchestrates a signaling complex that includes bound PKA, CaM, and CaN in this microdomain. CaV1.3 channels serve as the critical “sensor” of activity and depolarization, and their opening creates an elevated local Ca2+i signal, which activates CaN bound to AKAP79/150 in the microdomain of elevated local [Ca2+]i. Upon Ca2+i/CaN signals, both NFATc1 and NFATc2 are dephosphorylated and translocate from the cytoplasm to the nucleus, where they act on KCNQ2 and KCNQ3 gene regulatory elements, upregulating IM, thus reducing excitability ( Figure 10F). In a variety of neurons, AKAP79/150 orchestrates PKA to phosphorylate and upregulate the activity of L-type Ca2+ channels, amplifying the responses to depolarization induced by neuronal activity. In the hippocampus, CaN counterbalances PKA actions since the Ca2+ ions that enter the cell through L channels participate in inactivating those same channels via CaN ( Hall et al., 2007; Oliveria et al., 2007).

In addition, we were able to integrate the functional and expression data and predict a function for one Gr ( Figure 9). While our data support the hypothesis that Gr59c encodes a bitter receptor for BER, DEN, and LOB, Gr59c is not sufficient for responses to these compounds in sugar neurons. It is also apparently not necessary, in the sense that physiological responses to these tastants

were observed in S-a sensilla that do not express the Gr59c driver. These observations suggest that there is another receptor for BER, DEN, and LOB that may recognize a different moiety of these tastants, providing multiple means of detecting some of the most behaviorally aversive bitter tastants in the panel. We note that 38 of the Gr-GAL4 drivers, slightly more than half, showed expression in the labellum. The other selleck chemicals Pfizer Licensed Compound Library order Grs are probably expressed in other chemosensory neurons of the adult and larva ( Dunipace et al., 2001, Jones et al., 2007, Kwon et al., 2007,

Scott et al., 2001 and Thorne and Amrein, 2008) (unpublished data, A.D., J.Y.K., L.A.W., F. Ling, and J.R.C.). Of the 38 labellar Gr-GAL4 drivers, 33 are expressed in bitter neurons, and only a few in sugar neurons. It seems probable that a high fraction of Grs are devoted to bitter perception because of the number and structural complexity of bitter compounds ( Schoonhoven et al., 2005 and Schwab, 2003). Sugars are simpler and more similar in structure. In order to detect the wide diversity of noxious bitter substances that an animal may encounter, a larger and more versatile repertoire of receptors is likely needed. We note that

in mice and rats, 36 bitter receptors have been identified ( Wu et al., 2005), but few sugar receptors ( Montmayeur et al., 2001 and Nelson et al., 2001). Among the Grs mapped to bitter neurons, five map to all bitter neurons: Gr32a, Gr33a, Gr39a.a, Gr66a, and Gr89a. Some or all of these “core bitter Grs” may function as coreceptors, perhaps forming multimers with other Grs. These core Grs might play a role analogous to Or83b, an Or that is however broadly expressed in olfactory receptor neurons and that functions in the transport of other Ors and as a channel, rather than conferring odor specificity per se (Benton et al., 2006, Sato et al., 2008 and Wicher et al., 2008). If so, the core Grs may be useful in deorphanizing other Grs in heterologous expression systems. We note that in mammals, T1R3 functions as a common coreceptor with either T1R1 or T1R2 to mediate gustatory responses to amino acids or sugars, respectively (Zhao et al., 2003). We note finally that the receptor-to-neuron map defines intriguing developmental problems.