Sanchez-Navarro, MJ;Borner, T;Reiner, BC;Crist, RC;Samson, WK;Yosten, GLC;Stein, L;Hayes, MR;
PMID: 37242151 | DOI: 10.3390/nu15102268
The g-protein coupled receptor GPR-160, recently identified as a putative receptor for the cocaine and amphetamine-regulated transcript (CART) peptide, shows abundant expression in the energy-balance control nuclei, including the dorsal vagal complex (DVC). However, its physiological role in the control of food intake has yet to be fully explored. Here, we performed a virally mediated, targeted knockdown (KD) of Gpr160 in the DVC of male rats to evaluate its physiological role in control of feeding. Our results indicate that DVC Gpr160 KD affects meal microstructure. Specifically, DVC Gpr160 KD animals consumed more frequent, but shorter meals during the dark phase and showed decreased caloric intake and duration of meals during the light phase. Cumulatively, however, these bidirectional effects on feeding resulted in no difference in body weight gain. We next tested the role of DVC GPR-160 in mediating the anorexigenic effects of exogenous CART. Our results show that DVC Gpr160 KD partially attenuates CART's anorexigenic effects. To further characterize Gpr160+ cells in the DVC, we utilized single-nucleus RNA sequencing data to uncover abundant GPR-160 expression in DVC microglia and only minimal expression in neurons. Altogether, our results suggest that DVC CART signaling may be mediated by Gpr160+ microglia, which in turn may be modulating DVC neuronal activity to control food intake.
Davis MI, Crittenden JR, Feng AY, Kupferschmidt DA, Naydenov A, Stella N, Graybiel AM, Lovinger DM.
PMID: 29466446 | DOI: 10.1371/journal.pone.0191436
Presynaptic cannabinoid-1 receptors (CB1-R) bind endogenous and exogenous cannabinoids to modulate neurotransmitter release. CB1-Rs are expressed throughout the basal ganglia, including striatum and substantia nigra, where they play a role in learning and control of motivated actions. However, the pattern of CB1-R expression across different striatal compartments, microcircuits and efferent targets, and the contribution of different CB1-R-expressing neurons to this pattern, are unclear. We use a combination of conventional techniques and novel genetic models to evaluate CB1-R expression in striosome (patch) and matrix compartments of the striatum, and in nigral targets of striatal medium spiny projection neurons (MSNs). CB1-R protein and mRNA follow a descending dorsolateral-to-ventromedial intensity gradient in the caudal striatum, with elevated expression in striosomes relative to the surrounding matrix. The lateral predominance of striosome CB1-Rs contrasts with that of the classical striosomal marker, the mu opioid receptor (MOR), which is expressed most prominently in rostromedial striosomes. The dorsolateral-to-ventromedial CB1-R gradient is similar to Drd2 dopamine receptor immunoreactivity and opposite to Substance P. This topology of CB1-R expression is maintained downstream in the globus pallidus and substantia nigra. Dense CB1-R-expressing striatonigral fibers extend dorsally within the substantia nigra pars reticulata, and colocalize with bundles of ventrally extending, striosome-targeted, dendrites of dopamine-containing neurons in the substantia nigra pars compacta (striosome-dendron bouquets). Within striatum, CB1-Rs colocalize with fluorescently labeled MSN collaterals within the striosomes. Cre recombinase-mediated deletion of CB1-Rs from cortical projection neurons or MSNs, and MSN-selective reintroduction of CB1-Rs in knockout mice, demonstrate that the principal source of CB1-Rs in dorsolateral striosomes is local MSN collaterals. These data suggest a role for CB1-Rs in caudal dorsolateral striosome collaterals and striosome-dendron bouquet projections to lateral substantia nigra, where they are anatomically poised to mediate presynaptic disinhibition of both striosomal MSNs and midbrain dopamine neurons in response to endocannabinoids and cannabinomimetics.
The European journal of neuroscience
Quirion, B;Beaulieu, C;Côté, L;Parent, JL;Gendron, L;
PMID: 35674691 | DOI: 10.1111/ejn.15733
Primary afferents are responsible for transmitting signals produced by noxious stimuli from the periphery to the spinal cord. Mu and delta opioid receptors (MOP and DOP) have analgesic properties and are highly expressed in dorsal root ganglia (DRG) neurons. In humans, spinal DOP is almost exclusively located on central terminals of DRG neurons, whereas in rodents, it is expressed both on presynaptic terminals and spinal neurons. In this study, we aimed to assess the distribution of MOP and DOP in the DRGs of mice and rats. Using in situ hybridization and immunofluorescence, we visualized MOP and DOP mRNA together with various neuronal markers. In rats and mice, we show that both receptors are expressed, albeit to different extents, in all types of neurons, namely, large and medium myelinated neurons (NF200-positive), small nonpeptidergic (IB4- or P2X3R-positive) and peptidergic C fibres (Tac1-positive). Overall, DOP mRNA was found to be mainly expressed in large and medium myelinated neurons, whereas MOP mRNA was mainly found in C fibres. The distribution of MOP and DOP, however, slightly differs between rats and mice, with a higher proportion of small nonpeptidergic C fibres expressing DOP mRNA in mice than in rats. We further found that neither morphine nor inflammation affected the distribution of the receptor mRNA. Because of their location, our results confirm that MOP and DOP have the potential to alleviate similar types of pain and that this effect could slightly differ between species.
bioRxiv : the preprint server for biology
François, M;Delgado, IC;Lafond, A;Lewis, EM;Kuromaru, M;Hassouna, R;Deng, S;Thaker, VV;Dölen, G;Zeltser, LM;
PMID: 36824966 | DOI: 10.1101/2023.02.15.528679
Females are more sensitive to social exclusion, which could contribute to their heightened susceptibility to anxiety disorders. Chronic social isolation stress (CSIS) for at least 7 weeks after puberty induces anxiety-related behavioral adaptations in female mice. Here, we show that Arginine vasopressin receptor 1a ( Avpr1a )-expressing neurons in the central nucleus of the amygdala (CeA) mediate these sex-specific effects, in part, via projections to the caudate putamen. Loss of function studies demonstrate that AVPR1A signaling in the CeA is required for effects of CSIS on anxiety-related behaviors in females but has no effect in males or group housed females. This sex-specificity is mediated by AVP produced by a subpopulation of neurons in the posterodorsal medial nucleus of the amygdala that project to the CeA. Estrogen receptor alpha signaling in these neurons also contributes to preferential sensitivity of females to CSIS. These data support new therapeutic applications for AVPR1A antagonists in women.
Yao, Y;Chen, J;Li, X;Chen, ZF;Li, P;
PMID: 36750092 | DOI: 10.1016/j.cub.2023.01.019
Increased ventilation is a critical process that occurs when the body responds to a hypoxic environment. Sighs are long, deep breaths that prevent alveolar collapse, and their frequency is significantly increased by hypoxia. In this study, we first show that sighing is induced by hypoxia as a function of increased hypoxic severity and that hypoxia-induced sighing is capable of increasing the oxygen saturation in a mouse model. We next found that the gastrin-releasing peptide (Grp) expressing neurons in the nucleus of the solitary tract (NTS) are important in mediating hypoxia-induced sighing. Retrograde tracing from these Grp neurons reveals their direct afferent input from the petrosal ganglion neurons that innervate the carotid body, the major peripheral chemoreceptor that senses blood oxygen. Acute hypoxia preferentially activates these Grp neurons in the NTS. Photoactivation of these neurons through their projections in the inspiratory rhythm generator in the ventral medulla induces sighing, whereas genetic ablation or chemogenetic silencing of these neurons specifically diminishes the sighs, but not other respiratory responses, induced by hypoxia. Finally, the mice with reduced sighing in hypoxia exhibit an elevated heart-rate increase, which may compensate for maintaining the blood oxygen level. Therefore, we identified a neural circuit that connects the carotid body to the breathing control center in the ventral medulla with a specific function for hypoxia-induced sighing, which restores the oxygen level.
Leithead, AB;Godino, A;Barbier, M;Harony-Nicolas, H;
PMID: 37245781 | DOI: 10.1016/j.biopsych.2023.05.016
The posterior intralaminar (PIL) complex of the thalamus is a multimodal nucleus that has been implicated in maternal behaviors and conspecific social behaviors in male and female rodents. Glutamatergic neurons are a major component of the PIL; however, their specific activity and role during social interactions has not yet been assessed.We used immunohistochemistry for the immediate early gene c-fos as a proxy for neuronal activity in the PIL of mice exposed to a novel social stimulus, a novel object stimulus, or no stimulus. We then used fiber photometry to record neural activity of glutamatergic neurons in the PIL in real-time during social and non-social interactions. Finally, we used inhibitory DREADDs in glutamatergic PIL neurons and tested social preference and social habituation-dishabituation.We observed significantly more c-fos-positive cells in the PIL of mice exposed to social versus object or no stimuli. Neural activity of PIL glutamatergic neurons was increased when male and female mice were engaged in social interaction with a same-sex juvenile or opposite-sex adult, but not a toy mouse. Neural activity positively correlated with social investigation bout length and negatively correlated with chronological order of bouts. Social preference was unaffected by inhibition; however, inhibiting activity of glutamatergic neurons in the PIL delayed the time it took female mice to form social habituation.Together these findings suggest that glutamatergic PIL neurons respond to social stimuli in both male and female mice and may regulate perceptual encoding of social information to facilitate recognition of social stimuli.
Polgár, E;Dickie, AC;Gutierrez-Mecinas, M;Bell, AM;Boyle, KA;Quillet, R;Rashid, EA;Clark, RA;German, MT;Watanabe, M;Riddell, JS;Todd, AJ;
PMID: 35543635 | DOI: 10.1097/j.pain.0000000000002677
Neurons in the superficial dorsal horn that express the gastrin-releasing peptide receptor (GRPR) are strongly implicated in spinal itch pathways. However, a recent study reported that many of these correspond to vertical cells, a population of interneurons that are thought to transmit nociceptive information. In this study, we have used a GRPRCreERT2 mouse line to identify and target cells that possess Grpr mRNA. We find that the GRPR cells are highly concentrated in lamina I and the outer part of lamina II, that they are all glutamatergic, and that they account for ∼15% of the excitatory neurons in the superficial dorsal horn. We had previously identified 6 neurochemically distinct excitatory interneuron populations in this region based on neuropeptide expression and the GRPR cells are largely separate from these, although they show some overlap with cells that express substance P. Anatomical analysis revealed that the GRPR neurons are indeed vertical cells, and that their axons target each other, as well as arborising in regions that contain projection neurons: lamina I, the lateral spinal nucleus and the lateral part of lamina V. Surprisingly, given the proposed role of GRPR cells in itch, we found that most of the cells received monosynaptic input from Trpv1-expressing (nociceptive) afferents, that the great majority responded to noxious and pruritic stimuli, and that chemogenetically activating them resulted in pain- and itch-related behaviours. Together, these findings suggest that the GRPR cells are involved in spinal cord circuits that underlie both pain and itch.
Kamitakahara A, Wu HH, Levitt P.
PMID: 28758209 | DOI: 10.1002/cne.24294
Detailed anatomical tracing and mapping of the viscerotopic organization of the vagal motor nuclei has provided insight into autonomic function in health and disease. To further define specific cellular identities, we paired information based on visceral connectivity with a cell-type specific marker of a subpopulation of neurons in the dorsal motor nucleus of the vagus (DMV) and nucleus ambiguus (nAmb) that express the autism-associated MET receptor tyrosine kinase. As gastrointestinal disturbances are common in children with autism spectrum disorder (ASD), we sought to define the relationship between MET-expressing (MET+) neurons in the DMV and nAmb, and the gastrointestinal tract. Using wholemount tissue staining and clearing, or retrograde tracing in a METEGFP transgenic mouse, we identify three novel subpopulations of EGFP+ vagal brainstem neurons: 1) EGFP+ neurons in the nAmb projecting to the esophagus or laryngeal muscles, 2) EGFP+ neurons in the medial DMV projecting to the stomach, and 3) EGFP+ neurons in the lateral DMV projecting to the cecum and/or proximal colon. Expression of the MET ligand, hepatocyte growth factor (HGF), by tissues innervated by vagal motor neurons during fetal development reveal potential sites of HGF-MET interaction. Furthermore, similar cellular expression patterns of MET in the brainstem of both the mouse and nonhuman primate suggest that MET expression at these sites is evolutionarily conserved. Together, the data suggest that MET+ neurons in the brainstem vagal motor nuclei are anatomically positioned to regulate distinct portions of the gastrointestinal tract, with implications for the pathophysiology of gastrointestinal comorbidities of ASD.
Sodium leak channel contributes to neuronal sensitization in neuropathic pain
Zhang, D;Zhao, W;Liu, J;Ou, M;Liang, P;Li, J;Chen, Y;Liao, D;Bai, S;Shen, J;Chen, X;Huang, H;Zhou, C;
PMID: 33766679 | DOI: 10.1016/j.pneurobio.2021.102041
Neuropathic pain affects up to 10% of the total population and no specific target is ideal for therapeutic need. The sodium leak channel (NALCN), a non-selective cation channel, mediates the background Na+ leak conductance and controls neuronal excitability and rhythmic behaviors. Here, we show that increases of NALCN expression and function in dorsal root ganglion (DRG) and dorsal spinal cord contribute to chronic constriction injury (CCI)-induced neuropathic pain in rodents. NALCN current and neuronal excitability in acutely isolated DRG neurons and spinal cord slices of rats were increased after CCI which were decreased to normal levels by NALCN-siRNA. Accordingly, pain-related symptoms were significantly alleviated by NALCN-siRNA-mediated NALCN knockdown and completely prevented by NALCN-shRNA-mediated NALCN knockdown in rats or by conditional NALCN knockout in mice. Our results indicate that increases in NALCN expression and function contribute to CCI-induced neuronal sensitization; therefore, NALCN may be a novel molecular target for control of neuropathic pain.
Polinski NK, Gombash SE, Manfredsson FP, Lipton JW, Kemp CJ, Cole-Strauss A, Kanaan NM, Steece-Collier K, Kuhn NC, Wohlgenant SL, Sortwell CE.
PMID: http
Clinical trials are examining the efficacy of viral vector-mediated gene delivery for treating Parkinson’s disease (PD). While viral vector strategies have been successful in preclinical studies, to date clinical trials have disappointed. This may be due to the fact that preclinical studies fail to account for aging. Aging is the single greatest risk factor for developing PD and age alters cellular processes utilized by viral vectors. We hypothesized that the aged brain would be relatively resistant to transduction when compared to the young adult. We examined recombinant adeno-associated virus 2/5 mediated green fluorescent protein (rAAV2/5 GFP) expression in the young adult and aged rat nigrostriatal system. GFP overexpression was produced in both age groups. However, following rAAV2/5 GFP injection to the substantia nigra (SN) aged rats displayed 40-60% less GFP protein in the striatum, regardless of rat strain or duration of expression. Further, aged rats exhibited 40% fewer cells expressing GFP and 4-fold less GFP mRNA. rAAV2/5-mediated gene transfer is compromised in the aged rat midbrain, with deficiencies in early steps of transduction leading to significantly less mRNA and protein expression.
MOLECULAR THERAPY — METHODS & CLINICAL DEVELOPMENT
Polinski NK, Manfredsson FP, Benskey MJ, Fischer DL, Kemp CJ, Steece-Collier K, Sandoval IM, Paumier KL, Sortwell CE.
PMID: - | DOI: 10.1038/mtm.2016.82
Therapeutic protein delivery using viral vectors has shown promise in preclinical models of Parkinson’s disease (PD) but clinical trial success remains elusive. This may partially be due to a failure to include advanced age as a covariate despite aging being the primary risk factor for PD. We investigated transgene expression following intracerebral injections of recombinant adeno-associated virus pseudotypes 2/2 (rAAV2/2), 2/5 (rAAV2/5), 2/9 (rAAV2/9), and lentivirus (LV) expressing green fluorescent protein (GFP) in aged versus young adult rats. Both rAAV2/2 and rAAV2/5 yielded lower GFP expression following injection to either the aged substantia nigra or striatum. rAAV2/9-mediated GFP expression was deficient in the aged striatonigral system but displayed identical transgene expression between ages in the nigrostriatal system. Young and aged rats displayed equivalent GFP levels following LV injection to the striatonigral system but LV-delivered GFP was deficient in delivering GFP to the aged nigrostriatal system. Notably, age-related transgene expression deficiencies revealed by protein quantitation were poorly predicted by GFP-immunoreactive cell counts. Further, in situ hybridization for the viral CβA promoter revealed surprisingly limited tropism for astrocytes compared to neurons. Our results demonstrate that aging is a critical covariate to consider when designing gene therapy approaches for PD.
Hennessy ML, Corcoran A, Brust RD, Nattie EE, Dymecki S.
PMID: 28073937 | DOI: 10.1523/JNEUROSCI.2316-16.2016
Homeostatic control of breathing, heart rate, and body temperature relies on circuits within the brainstem modulated by the neurotransmitter serotonin (5-HT). Mounting evidence points to specialized neuronal subtypes within the 5-HT system, which have borne out in functional studies, including the modulation of distinct facets of homeostatic control. These functional differences, read out at the organismal level, are likely subserved by differences among 5-HT neuron subtypes at the cellular and molecular levels, including differences in the capacity to co-express other neurotransmitters such as glutamate, GABA, thyrotropin releasing hormone, and substance P encoded by the Tachykinin-1 (Tac1) gene. Here we characterize in mice a 5-HT neuron subtype identified by expression of Tac1 and the transcription factor gene Pet1, thus referred to as the Tac1-Pet1 neuron subtype. Transgenic cell labeling showed Tac1-Pet1 soma resident largely in the caudal medulla. Chemogenetic (CNO-hM4Di) perturbation of Tac1-Pet1 neuron activity resulted in blunting of the respiratory CO2 chemoreflex, which normally augments ventilation in response to hypercapnic acidosis to restore normal pH and PCO2 Tac1-Pet1 axonal boutons were found localized to brainstem areas implicated in respiratory modulation, with highest density in motor nuclei. These findings demonstrate that the activity of a Pet1 neuron subtype with potential to release both 5-HT and substance P is necessary for normal respiratory dynamics, likely via motor outputs that maintain airway patency and engage muscles of respiration. These Tac1-Pet1 neurons may complement the activity of Egr2-Pet1 neurons, previously established in respiratory chemoreception, but which do not innervate respiratory motor nuclei.
SIGNIFICANCE STATEMENT:
5-HT neurons modulate outputs as diverse as body temperature, respiration, aggression, and mood. We characterize a 5-HT neuron subtype defined by expression of Tachykinin1 and Pet1 (Tac1-Pet1 neurons) which projects to respiratory motor nuclei, and when silenced, blunts the ventilatory response to inhaled carbon dioxide. We employ genetic tools to access this subset of 5-HT neurons to query function, anatomy, and connectivity. Localization of synaptic boutons from Tac1-Pet1 neurons, primarily within motor regions, contrasts with those from previously described Egr2-Pet1 neurons, which are chemosensitive and reside in the raphe magnus and project primarily to chemosensory integration, but not motor, regions of the brainstem.
