Marker Of Neuronal Activation Research Articles

Attention-deficit/hyperactivity disorder-related psychomotor activity and altered neuronal activity in the medial prefrontal cortex and striatum in the A53T mouse model of Parkinson's disease and other synucleinopathies: Findings from an "endophenotype" approach.

Attention-Deficit/Hyperactivity Disorder (ADHD) is associated with an increased risk of Parkinson's disease (PD) and other synucleinopathies later in life. The severity of the ADHD phenotype may play a significant role in this association. There is no indication that any of the existing animal models can unify these disorders. Using the Open Field Test, amphetamine-challenge test, Western blot and immunohistochemical analysis of neuronal activity markers (c-Fos, FosB and ΔFosB) we performed a deliberate neurobehavioral characterization of 6-month-old hemizygous A53T carriers (A53T+) of the JAX006823 strain, evaluating the utility of this transgenic mouse model of PD and other synucleinopathies in ADHD/PD continuum research. Adhering to the "endophenotype" approach, non-transgenic littermates (A53T-) and C57BL/6 J mice (used to maintain the colony) were examined with A53T+ mice, to differentiate between biomarkers of transgenicity and endophenotypic traits related to the genetic background of the strain. Obtained results revealed that increased behavioral and acute striatal response to novelty, increased basal neuronal activity of the ventromedial prefrontal cortex and rate-dependent calming effect of amphetamine were endophenotypic characteristics of the strain. Increased acute response of the medial prefrontal cortex to novelty and chronic increase in neuronal activity of the striatum appeared as the mark of transgenicity. To the best of our knowledge, this is the first study to indicate external validity of a transgenic mouse model of PD and other synucleinopathies with the neurobehavioral pathology associated with ADHD, hinting at its potential in preclinical research of ADHD/PD continuum. The full capacity of the model remains to be explored.

Dynamic Dysregulation of Ribosomal Protein Genes in Mouse Brain Stress Models

Emphasizing their evolutionarily conserved role in stress adaptation mechanisms, ribosomal protein genes (RPGs) are observed to be downregulated in various stressors and across phyla. However, this evolutionarily conserved stress response is not well explored in mouse models of neurobiological stress. This study investigates the dysregulation patterns of RPGs in various murine preclinical stress paradigms across different brain regions using available transcriptomic data and identifies the non-canonical ribosomal functions using synaptic gene-ontology terms. Without a discernible structure across different brain areas, we observed heterogeneous dysregulation, encompassing either up or downregulation in both cytoplasmic and mitochondrial RPGs. However, downregulation was more prominent than upregulation, and the overall dysregulation seems more prevalent in the chronic stress paradigm compared to stress paradigms involving acute and early-life stress. Enrichment analysis significantly associates dysregulated RPGs with post-synaptic gene ontology terms, emphasizing their involvement in synaptic modulation. Overall, the study demonstrates ribosomal dysregulation as an evolutionarily conserved stress response mechanism during different mouse stress paradigms. We discuss the possibility that the variability in the directionality of dysregulation may emerge as a potential marker of neuronal activity in response to diverse stress paradigms and the involvement of paradigm-specific RPG dysregulation either in the process of global downscaling of ribosome biogenesis or in the process of ribosomal heterogeneity, each leading to a different effect.

Zolmitriptan niosomal transdermal patches: combating migraine via epigenetic and endocannabinoid pathways and reversal of migraine hypercoagulability.

Conventional zolmitriptan (ZOL) has limited oral bioavailability, many adverse effects, and poor membrane penetrability that negatively influences its accessibility to its 5-HT1B/1D receptor binding pocket, located transmemberanous. This work aimed at preparing transdermal ZOL-nanoformulation (niosomes) to surpass these limitations and to explore novel antimigraine mechanisms for ZOL via modulation of the epigenetically-altered chronification genes (RAMP-1, NPTX-2) or microRNAs and affecting the endocannabinoid CB-1/MAPK pathway. The prepared ZOL niosomes (Fsp60/6-1:1) exhibited %EE of 57.28%, PS of 472.3nm, PDI of 0.366, and ZP of -26 mV were cast into patch with content uniformity of 93.12%, maintained endurance after 200-times folding, no interaction between its components (FT-IR), a biphasic release pattern and good stability after storage at 4°C for 6 months. In-vivo ZOL-patch application in rats with nitroglycerin-induced migraine showed significant management of migraine pain symptoms and photophobia assessed behaviorally, decreased brain levels of the trigeminal neuronal activation marker (c-fos), the migraine pain neurotransmitter (CGRP) and the serum levels of different migraine pain markers (substance P, nitric-oxide, and TNF-α). It also significantly decreased RAMP-1, NPTX-2, miR-382-5p, and CB-1/MAPK gene expression reflecting improved efficacy and brain receptors delivery to a much greater extent than conventional ZOL has done. Additionally, this nanoformulation significantly opposed migraine-induced platelet activation and hypercoagulable status in both central and peripheral circulations as evidenced by the significant decrease in adenosine diphosphate, thrombin, factor X, CD41, and Von-Willebrand factor levels assessed peripherally and centrally. TPFsp60/6-1:1 significantly improved ZOL efficacy and accessibility to brain-receptors to a much greater extent than conventional ZOL-solution.KeywordsEndocannabinoid receptors; Epigenetically-altered genes; Hemostatic pathways; Niosomal patch; Transdermal; Zolmitriptan.

Chronic unpredictable stress during adolescence exerts sex-specific effects on depressive-like behavior and neural activation triggered by tail suspension test

During adolescence, acute stress can modify neuronal excitability in various brain regions, leading to negative behavioral outcomes. However, the impact of chronic stress during adolescence on neuronal responses to acute stimuli remains unclear. To address this, we subjected adolescent mice to 12 days of chronic unpredictable stress (CUS). Anxiety and depressive behaviors were evaluated, along with changes in c-Fos expression, which is one of the most widely used markers of neuronal activation. By comparing c-Fos immunoreactivity between the CUS and control groups both before and after the tail suspension test (TST), we found that adolescent CUS induced depressive behaviors in male mice, but not in female mice. Adolescent CUS primarily affected the excitability of neurons in the infralimbic cortex (IL), the dorsomedial and dorsolateral area of the bed nucleus of the stria terminalis (BNST), and the ventral hippocampus CA3. TST exerted a significant main effect on the density of c-Fos+ neurons in the prelimbic cortex (PL), infralimbic cortex (IL), cingulate areas 1 and 2 (Cg1, Cg2), the lateral septum (LS), BNST, and lateral habenular (LHb). Furthermore, the excitability of neurons in the paraventricular thalamic nucleus (PVT) was impacted by sex. These data suggest that adolescent CUS elicits region- and sex-specific modifications in TST-induced c-Fos expression, establishing a theoretical basis for understanding the pathophysiological alterations in mood disorders following adolescent stress.

Role of Membrane Estrogen Receptor Alpha on the Positive Feedback of Estrogens on Kisspeptin and GnRH Neurons.

Estrogens act through nuclear and membrane-initiated signaling. Estrogen receptor alpha (ERα) is critical for reproduction, but the relative contribution of its nuclear and membrane signaling to the central regulation of reproduction is unclear. To address this question, two complementary approaches were used: estetrol (E4) a natural estrogen acting as an agonist of nuclear ERs, but as an antagonist of their membrane fraction, and the C451A-ERα mouse lacking mERα. E4 dose- dependently blocks ovulation in female rats, but the central mechanism underlying this effect is unknown. To determine whether E4 acts centrally to control ovulation, its effect was tested on the positive feedback of estradiol (E2) on neural circuits underlying luteinizing hormone (LH) secretion. In ovariectomized females chronically exposed to a low dose of E2, estradiol benzoate (EB) alone or combined with progesterone (P) induced an increase in the number of kisspeptin (Kp) and gonadotropin-releasing hormone (GnRH) neurons coexpressing Fos, a marker of neuronal activation. E4 blocked these effects of EB, but not when combined to P. These results indicate that E4 blocked the central induction of the positive feedback in the absence of P, suggesting an antagonistic effect of E4 on mERα in the brain as shown in peripheral tissues. In parallel, as opposed to wild-type females, C451A-ERα females did not show the activation of Kp and GnRH neurons in response to EB unless they are treated with P. Together these effects support a role for membrane-initiated estrogen signaling in the activation of the circuit mediating the LH surge.

Orbitofrontal cortex to dorsal striatum circuit is critical for incubation of oxycodone craving after forced abstinence.

Relapse is a major challenge in treating opioid addiction, including oxycodone. During abstinence, oxycodone seeking progressively increases, a phenomenon termed incubation of oxycodone craving. We previously demonstrated a causal role of orbitofrontal cortex (OFC) in this incubation. Here, we studied the interaction between glutamatergic projections from OFC and dopamine 1-family receptor (D1R) signaling in dorsal striatum (DS) in this incubation in male rats. We first examined the causal role of D1R signalling in DS in incubated oxycodone seeking. Next, we combined fluorescence-conjugated cholera toxin subunit B (CTb-555, a retrograde tracer) with Fos (a neuronal activity marker) to assess whether the activation of OFC→DS projections was associated with incubated oxycodone seeking. We then used a pharmacological asymmetrical disconnection procedure to examine the role of the interaction between projections from OFC and D1R signalling in DS in incubated oxycodone seeking. We also tested the effect of unilateral pharmacological inactivation of OFC or unilateral D1R blockade of DS on incubated oxycodone seeking. Finally, we assessed whether contralateral disconnection of OFC→DS projections impacted non-incubated oxycodone seeking on abstinence day 1. We found that D1R blockade in DS decreased incubated oxycodone seeking and OFC→DS projections were activated during incubated oxycodone seeking. Moreover, anatomical disconnection of OFC→DS projections, but not unilateral inactivation of OFC or unilateral D1R blockade in DS, decreased incubated oxycodone seeking. Lastly, contralateral disconnection of OFC→DS projections had no effect on oxycodone seeking on abstinence day 1. Together, these results demonstrated a causal role of OFC→DS projections in incubation of oxycodone craving.

Neuromedin U Neurons in the Edinger–Westphal Nucleus Respond to Alcohol Without Interfering with the Urocortin 1 Response

The Edinger–Westphal nucleus (EW) is a midbrain nucleus composed of a preganglionic, cholinergic subpopulation and a densely clustered peptidergic subpopulation (EWcp). The EWcp is one of the few brain regions that show consistent induction of FOS following voluntary alcohol intake. Previous results in rodents point to urocortin 1 (UCN1) as one of the peptides most involved in the control of ethanol intake and preference. Notably, the functions described for UCN1, such as reward processing, stress coping or the regulation of feeding behavior are similar to those described for the neuropeptide neuromedin U (NMU). Interestingly, NMU has been recently associated with the modulation of alcohol-related behaviors. However, little is known about the expression and functionality of NMU neurons in alcohol-responsive areas. In this study, we used the recently developed Nmu-Cre knock-in mouse model to examine the expression of NMU in the subaqueductal paramedian zone comprising the EWcp. We delved into the characterization and co-expression of NMU with other markers already described in the EWcp. Moreover, using FOS as a marker of neuronal activity, we tested whether NMU neurons were sensitive to acute alcohol administration. Overall, we provided novel insights on NMU expression and functionality in the EW region. We showed the presence of NMU within a subpopulation of UCN1 neurons in the EWcp and demonstrated that this partial co-expression does not interfere with the responsivity of UCN1-containing cells to alcohol. Moreover, we proposed that the UCN1 content in these neurons may be influenced by sex.

Emission of 50-kHz ultrasonic vocalizations stimulated by antiparkinsonian dopaminomimetic drugs in hemiparkinsonian rats is associated with neuronal activation in subcortical regions that regulate the affective state

Dopamine replacement therapy (DRT) of Parkinson's disease (PD) may trigger non-motor complications, some of which affect hedonic homeostatic regulation. Management of iatrogenic alterations in the affective state in PD is unsatisfactory, partly because of the limitations in the experimental models that are used in the preclinical investigation of the neurobiology and therapy of these alterations. In this connection, we recently employed a new experimental approach consisting in measuring the emission of 50-kHz ultrasonic vocalizations (USVs), a marker of positive affect, in hemiparkinsonian rats treated with drugs used in the DRT of PD. To further strengthen our approach, we here evaluated how the acute and repeated (× 5, on alternate days) administration of apomorphine (2 mg/kg, i.p.) or L-3,4-dihydroxyphenilalanine (L-DOPA, 12 mg/kg, i.p.) modified the immunoreactivity for Zif-268, a marker of neuronal activation, in the nucleus accumbens (NAc), caudate-putamen (CPu) and medial prefrontal cortex (mPFC), which are brain regions that regulate emotional states and drugs' affective properties. Acute and repeated treatment with either apomorphine or L-DOPA stimulated the emission of 50-kHz USVs in hemiparkinsonian rats, and this effect was paired with increased Zif-268 immunoreactivity in the NAc and CPu, but not mPFC. These findings indicate that subcortical and cortical regions may differently regulate the emission of 50-kHz USVs in hemiparkinsonian rats treated with dopaminergic drugs used in the DRT of PD. Moreover, they provide further evidence that measuring 50-kHz USV emissions in hemiparkinsonian rats may be a relevant approach to investigate at the preclinical level the affective properties of antiparkinsonian drugs.

Fasting-induced activity changes in MC3R neurons of the paraventricular nucleus of the thalamus.

The brain controls energy homeostasis by regulating food intake through signaling within the melanocortin system. Whilst we understand the role of the hypothalamus within this system, how extra-hypothalamic brain regions are involved in controlling energy balance remains unclear. Here we show that the melanocortin 3 receptor (MC3R) is expressed in the paraventricular nucleus of the thalamus (PVT). We tested whether fasting would change the activity of MC3R neurons in this region by assessing the levels of c-Fos and pCREB as neuronal activity markers. We determined that overnight fasting causes a significant reduction in pCREB levels within PVT-MC3R neurons. We then questioned whether perturbation of MC3R signaling, during fasting, would result in altered refeeding. Using chemogenetic approaches, we show that modulation of MC3R activity, during the fasting period, does not impact body weight regain or total food intake in the refeeding period. However, we did observe significant differences in the pattern of feeding-related behavior. These findings suggest that the PVT is a region where MC3R neurons respond to energy deprivation and modulate refeeding behavior.

Decoding Arc transcription: a live-cell study of stimulation patterns and transcriptional output.

Activity-regulated cytoskeleton-associated protein (Arc) plays a crucial role in synaptic plasticity, a process integral to learning and memory. Arc transcription is induced within a few minutes of stimulation, making it a useful marker for neuronal activity. However, the specific neuronal activity patterns that initiate Arc transcription have remained elusive due to the inability to observe mRNA transcription in live cells in real time. Using a genetically encoded RNA indicator (GERI) mouse model that expresses endogenous Arc mRNA tagged with multiple GFPs, we investigated Arc transcriptional activity in response to various electrical field stimulation patterns. The GERI mouse model was generated by crossing the Arc-PBS knock-in mouse, engineered with binding sites in the 3' untranslated region (UTR) of Arc mRNA, and the transgenic mouse expressing the cognate binding protein fused to GFP. In dissociated hippocampal neurons, we found that the pattern of stimulation significantly affects Arc transcription. Specifically, theta-burst stimulation consisting of high-frequency (100 Hz) bursts delivered at 10 Hz frequency induced the highest rate of Arc transcription. Concurrently, the amplitudes of nuclear calcium transients also reached their peak with 10 Hz burst stimulation, indicating a correlation between calcium concentration and transcription. However, our dual-color single-cell imaging revealed that there were no significant differences in calcium amplitudes between Arc-positive and Arc-negative neurons upon 10 Hz burst stimulation, suggesting the involvement of other factors in the induction of Arc transcription. Our live-cell RNA imaging provides a deeper insight into the complex regulation of transcription by activity patterns and calcium signaling pathways.

Caspase-12 is Expressed in Purkinje Neurons and Prevents Psychiatric-Like Behavior in Mice.

Caspase-12 is a caspase family member for which functions in regulating cell death and inflammation have previously been suggested. In this study, we used caspase-12 lacZ reporter mice to elucidate the expression pattern of caspase-12 in order to obtain an idea about its possible in vivo function. Strikingly, these reporter mice showed that caspase-12 is expressed explicitly in Purkinje neurons of the cerebellum. As this observation suggested a function for caspase-12 in Purkinje neurons, we analyzed the brain and behavior of caspase-12 deficient mice in detail. Extensive histological analyses showed that caspase-12 was not crucial for establishing cerebellum structure or for maintaining Purkinje cell numbers. We then performed behavioral tests to investigate whether caspase-12 deficiency affects memory, motor, and psychiatric functions in mice. Interestingly, while the absence of caspase-12 did not affect memory and motor function, caspase-12 deficient mice showed depression and hyperactivity tendencies, together resembling manic behavior. Next, suggesting a possible molecular mechanistic explanation, we showed that caspase-12 deficient cerebella harbored diminished signaling through the brain-derived neurotrophic factor/tyrosine kinase receptor B/cyclic-AMP response binding protein axis, as well as strongly enhanced expression of the neuronal activity marker c-Fos. Thus, our study establishes caspase-12 expression in mouse Purkinje neurons and opens novel avenues of research to investigate the role of caspase-12 in regulating psychiatric behavior.

Pregnancy-induced oxidative stress and inflammation are not associated with impaired maternal neuronal activity or memory function.

Pregnancy is associated with neural and behavioral plasticity, systemic inflammation, and oxidative stress, yet the impact of inflammation and oxidative stress on maternal neural and behavioral plasticity during pregnancy is unclear. We hypothesized that healthy pregnancy transiently reduces learning and memory and these deficits are associated with pregnancy-induced elevations in inflammation and oxidative stress. Cognitive performance was tested with novel object recognition (recollective memory), Morris water maze (spatial memory), and open field (anxiety-like) behavior tasks in female Sprague-Dawley rats of varying reproductive states [nonpregnant (nulliparous), pregnant (near term), and 1-2 mo after pregnancy (primiparous); n = 7 or 8/group]. Plasma and CA1 proinflammatory cytokines were measured with a MILLIPLEX magnetic bead assay. Plasma oxidative stress was measured via advanced oxidation protein products (AOPP) assay. CA1 markers of oxidative stress, neuronal activity, and apoptosis were quantified via Western blot analysis. Our results demonstrate that CA1 oxidative stress-associated markers were elevated in pregnant compared with nulliparous rats (P ≤ 0.017) but there were equivalent levels in pregnant and primiparous rats. In contrast, reproductive state did not impact CA1 inflammatory cytokines, neuronal activity, or apoptosis. Likewise, there was no effect of reproductive state on recollective or spatial memory. Even so, spatial learning was impaired (P ≤ 0.007) whereas anxiety-like behavior (P ≤ 0.034) was reduced in primiparous rats. Overall, our data suggest that maternal hippocampal CA1 is protected from systemic inflammation but vulnerable to peripartum oxidative stress. Peripartum oxidative stress elevations, such as in pregnancy complications, may contribute to peripartum neural and behavioral plasticity.NEW & NOTEWORTHY Healthy pregnancy is associated with elevated maternal systemic and brain oxidative stress. During postpregnancy, brain oxidative stress remains elevated whereas systemic oxidative stress is resolved. This sustained maternal brain oxidative stress is associated with learning impairments and decreased anxiety-like behavior during the postpregnancy period.

Negative allosteric modulation of CB1 cannabinoid receptor signaling suppresses opioid-mediated tolerance and withdrawal without blocking opioid antinociception

The direct blockade of CB1 cannabinoid receptors produces therapeutic effects as well as adverse side-effects that limit their clinical potential. CB1 negative allosteric modulators (NAMs) represent an indirect approach to decrease the affinity and/or efficacy of orthosteric cannabinoid ligands or endocannabinoids at CB1. We recently reported that GAT358, a CB1-NAM, blocked opioid-induced mesocorticolimbic dopamine release and reward via a CB1-allosteric mechanism of action. Whether a CB1-NAM dampens opioid-mediated therapeutic effects such as analgesia or alters other unwanted opioid side-effects remain unknown. Here, we characterized the effects of GAT358 on nociceptive behaviors in the presence and absence of morphine in male rats. We examined the impact of GAT358 on formalin-evoked pain behavior and Fos protein expression, a marker of neuronal activation, in the lumbar spinal cord. We also assessed the impact of GAT358 on morphine-induced slowing of colonic transit, tolerance, and withdrawal behaviors in male mice. GAT358 attenuated morphine antinociceptive tolerance without blocking acute antinociception and reduced morphine-induced slowing of colonic motility without impacting fecal boli production. GAT358 also produced antinociception in the presence and absence of morphine in the formalin model of inflammatory nociception and reduced the number of formalin-evoked Fos protein-like immunoreactive cells in the lumbar spinal cord. Finally, GAT358 mitigated the somatic signs of naloxone-precipitated, but not spontaneous, opioid withdrawal following chronic morphine dosing. Our results support the therapeutic potential of CB1-NAMs as novel drug candidates aimed at preserving opioid-mediated analgesia while preventing their unwanted side-effects. Our studies also uncover previously unrecognized antinociceptive properties associated with an arrestin-biased CB1-NAM.

Effects of time of the day at sampling on CSF and plasma levels of Alzheimer’ disease biomarkers

BackgroundStudies suggest that cerebrospinal fluid (CSF) levels of amyloid-β (Aβ)42 and Aβ40 present a circadian rhythm. However sustained sampling of large volumes of CSF with indwelling intrathecal catheters used in most of these studies might have affected CSF dynamics and thereby confounded the observed fluctuations in the biomarker levels.MethodsWe included 38 individuals with either normal (N = 20) or abnormal (N = 18) CSF Aβ42/Aβ40 levels at baseline. CSF and plasma were collected at two visits separated by an average of 53 days with lumbar punctures and venipunctures performed either in the morning or evening. At the first visit, sample collection was performed in the morning for 17 participants and the order was reversed for the remaining 21 participants. CSF and plasma samples were analyzed for Alzheimer’ disease (AD) biomarkers, including Aβ42, Aβ40, GFAP, NfL p-tau181, p-tau217, p-tau231 and t-tau. CSF samples were also tested using mass spectrometry for 22 synaptic and endo-lysosomal proteins.ResultsCSF Aβ42 (mean difference [MD], 0.21 ng/mL; p = 0.038), CSF Aβ40 (MD, 1.85 ng/mL; p < 0.001), plasma Aβ42 (MD, 1.65 pg/mL; p = 0.002) and plasma Aβ40 (MD, 0.01 ng/mL, p = 0.002) were increased by 4.2-17.0% in evening compared with morning samples. Further, CSF levels of 14 synaptic and endo-lysosomal proteins, including neurogranin and neuronal pentraxin-1, were increased by 4.5-13.3% in the evening samples (MDrange, 0.02-0.56 fmol/µl; p < 0.042). However, no significant differences were found between morning and evening levels for the Aβ42/Aβ40 ratio, different p-tau variants, GFAP and NfL. There were no significant interaction between sampling time and Aβ status for any of the biomarkers, except that CSF t-tau was increased (by 5.74%) in the evening samples compared to the morning samples in Aβ-positive (MD, 16.46 ng/ml; p = 0.009) but not Aβ-negative participants (MD, 1.89 ng/ml; p = 0.47). There were no significant interactions between sampling time and order in which samples were obtained.DiscussionOur findings provide evidence for diurnal fluctuations in Aβ peptide levels, both in CSF and plasma, while CSF and plasma p-tau, GFAP and NfL were unaffected. Importantly, Aβ42/Aβ40 ratio remained unaltered, suggesting that it is more suitable for implementation in clinical workup than individual Aβ peptides. Additionally, we show that CSF levels of many synaptic and endo-lysosomal proteins presented a diurnal rhythm, implying a build-up of neuronal activity markers during the day. These results will guide the development of unified sample collection procedures to avoid effects of diurnal variation for future implementation of AD biomarkers in clinical practice and drug trials.

Evidence for prodromal changes in neuronal excitability and neuroinflammation in the hippocampus in young alpha-synuclein (A30P) transgenic mice.

Neuronal hyperexcitability and neuroinflammation are thought to occur at early stages in a range of neurodegenerative diseases. Neuroinflammation, notably activation of microglia, has been identified as a potential prodromal marker of dementia with Lewy bodies (DLB). Using a transgenic mouse model of DLB that over-expresses human mutant (A30P) alpha-synuclein (hα-syn) we have investigated whether early neuroinflammation is evident in the hippocampus in young pre-symptomatic animals. Previous studies have shown early hyperexcitability in the hippocampal CA3 region in male A30P mice at 2-4 months of age, therefore, in the current study we have immunostained this region for markers of neuronal activity (c-Fos), reactive astrocytes (glial fibrillary acidic protein, GFAP), microglia (ionizing calcium binding adapter protein 1, Iba-1) and reactive microglia (inducible nitric oxide synthase, iNOS). We found an interesting biphasic change in the expression of c-Fos in A30P mice with high expression at 1 month, consistent with early onset of hyperexcitability, but lower expression from 2-4 months in male A30P mice compared to wild-type (WT) controls, possibly indicating chronic hyperexcitability. Neuroinflammation was indicated by significant increases in the % area of GFAP and the number of Iba-1+ cells that expressed iNOS immunoreactivity in the CA3 region in 2-4 months A30P male mice compared to WT controls. A similar increase in % area of GFAP was observed in female A30P mice, however, the Iba-1 count was not different between female WT and A30P mice. In WT mice aged 2-4 months only 4.6% of Iba-1+ cells co-expressed iNOS. In contrast, in age matched A30P mice 87% of cells co-expressed Iba-1 and iNOS. Although there was no difference in GFAP immunoreactivity at 1 month, Iba-1/iNOS co-expression was also increased in a cohort of 1 month old A30P mice. Abnormal hα-syn expression in A30P mice caused early changes in network excitability, as indicated by c-Fos expression, and neuroinflammation which might contribute to disease progression.

The odor of a nontoxic tetrodotoxin analog, 5,6,11-trideoxytetrodotoxin, is detected by specific olfactory sensory neurons of the green spotted puffers.

Toxic puffers accumulate tetrodotoxin (TTX), a well-known neurotoxin, by feeding on TTX-bearing organisms and using it to defend themselves from predators. Our previous studies have demonstrated that toxic puffers are attracted to 5,6,11-trideoxytetrodotoxin (TDT), a nontoxic TTX analog that is simultaneously accumulated with TTX in toxic puffers and their prey. In addition, activity labeling using immunohistochemistry targeting neuronal activity marker suggests that TDT activates crypt olfactory sensory neurons (OSN) of the green spotted puffer. However, it remains to be determined whether individual crypt OSNs can physiologically respond to TDT. By employing electroporation to express GCaMP6s in OSNs, we successfully identified a distinct group of oval OSNs that exhibited a specific calcium response when exposed to TDT in green spotted puffers. These oval OSNs showed no response to amino acids (AAs), which serve as food odor cues for teleosts. Furthermore, oval morphology and surface positioning of TDT-sensitive OSNs in the olfactory epithelium closely resemble that of crypt OSNs. These findings further substantiate that TDT is specifically detected by crypt OSNs in green spotted puffer. The TDT odor may act as a chemoattractant for finding conspecific toxic puffers and for feeding TTX-bearing organisms for effective toxification.

Prevalence and Magnitude of Olfactory Dysfunction in Allergic Rhinitis.

Although allergic rhinitis (AR) can negatively impact the ability to smell, the degree to which this occurs is not clear and prevalence estimates vary among studies. This study had 4 main objectives: (1) To estimate the prevalence and the degree of olfactory dysfunction in AR patients; (2) To compare olfactory perception between AR patients with different persistence and severity of symptoms and determine if olfactory testing may aid in differentiating among Allergic Rhinitis and its Impact on Asthma (ARIA) groups; (3) To determine whether allergic reactions to different allergens differentially impact olfactory function, and (4) Verify possible changes in the olfactory epithelium (OE) caused by AR. One hundred thirty-three patients with AR and one hundred controls were tested. The main outcome was the score in University of Pennsylvania Smell Identification Test (UPSIT®). The OE was examined using immunofluorescence markers for neuronal activity, apoptosis, oxidative stress, signal transduction, eosinophils, and epithelial thickness. Prevalence of olfactory dysfunction in the AR patients was higher (AR: 42.9% vs controls: 9%, P < .001). No difference was found either between intermittent and persistent disease cases (P = .58) or between cases with mild and those with moderate/severe symptomatology (P = .33). Lower olfactory capacity was not associated with the reaction to more (P = .48) or diverse types of allergens (Ps > .05). Although not significant, patients with AR had a greater amount of eosinophilia and a lower amount of cAMP (cyclic adenosine monophosphate) in the OE. The study highlights a higher prevalence of olfactory dysfunction in AR patients compared to controls, but olfactory testing may not effectively differentiate AR severity or allergen sensitivities. Although trends suggest potential pathophysiological changes in the OE of AR patients, further research is needed to validate these findings.

Mating-induced release of oxytocin in the mouse lateral septum: Implications for social fear extinction

In mammals, some physiological conditions are associated with the high brain oxytocin (OXT) system activity. These include lactation in females and mating in males and females, both of which have been linked to reduced stress responsiveness and anxiolysis. Also, in a murine model of social fear conditioning (SFC), enhanced brain OXT signaling in lactating mice, specifically in the lateral septum (LS), was reported to underlie reduced social fear expression. Here, we studied the effects of mating in male mice on anxiety-related behaviour, social (and cued) fear expression and its extinction, and the activity of OXT neurons reflected by cFos expression and OXT release in the LS and amygdala. We further focused on the involvement of brain OXT in the mating-induced facilitation of social fear extinction. We could confirm the anxiolytic effect of mating in male mice irrespective of the occurrence of ejaculation. Further, we found that only successful mating resulting in ejaculation (Ej+) facilitated social fear extinction, whereas mating without ejaculation (Ej-) did not. In contrast, mating did not affect cues fear expression. Using the cellular activity markers cFos and pErk, we further identified the ventral LS (vLS) as a potential region participating in the effect of ejaculation on social fear extinction. In support, microdialysis experiments revealed a rise in OXT release within the LS, but not the amygdala, during mating. Finally, infusion of an OXT receptor antagonist into the LS before mating or into the lateral ventricle (icv) after mating demonstrated a significant role of brain OXT receptor-mediated signaling in the mating-induced facilitation of social fear extinction.

Intraperitoneal administration of arginine vasotocin (AVT) induces anorexigenic and anxiogenic actions via the brain V1a receptor-signaling pathway in the tiger puffer, Takifugu rubripes

Arginine vasotocin (AVT) is produced mainly in the hypothalamus and as a neurohypophyseal hormone peripherally regulates water-mineral balance in sub-mammals. In addition, AVT-containing neurons innervate several areas of the brain, and AVT also acts centrally as both an anorexigenic and anxiogenic factor in goldfish. However, it is unclear whether these central effects operate in fish in general. In the present study, therefore, we investigated AVT-like immunoreactivity in the brain of the tiger puffer, a cultured fish with a high market value in Japan and also a representative marine teleost species, focusing particularly on whether AVT affects food intake and psychomotor activity. AVT-like immunoreactivity was distributed higher in the ventral region of the telencephalon, the hypothalamus and midbrain. Intraperitoneal (IP) administration of AVT at 100 pmol g−1 body weight (BW) increased the immunoreactivity of phosphorylated ribosomal proteinS6 (RPS6), a neuronal activation marker, in the telencephalon and diencephalon, decreased food consumption and enhanced thigmotaxis. AVT-induced anorexigenic and anxiogenic actions were blocked by IP co-injection of a V1a receptor (V1aR) antagonist, Manning compound (MC) at 300 pmol g−1 BW. These results suggest that AVT acts as an anorexigenic and anxiogenic factor via the V1aR-signaling pathway in the tiger puffer brain.

SARS-CoV-2 Decreases Neuronal Activity in Brainstem Respiratory Centers in C57BI6/J Mice

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), also called COVID-19, targets the respiratory system, leading to symptoms such as cough, fever, and diffculty breathing. As the mechanisms behind SARS-CoV-2 infections continues to be studied, understanding of how this virus targets specific tissues becomes more apparent. Angiotensin-converting enzyme-2 (ACE2), the target of SARS-CoV infections and a functional receptor for SARS-CoV-2 invasions, is highly expressed in many tissues throughout the body, including the lungs, kidneys, and brain. Notably, our group previously reported that neurons are the main cells within the brain expressing ACE2. Accordingly, we hypothesized that neuronal infection of brainstem respiratory centers by SARS-CoV-2 could contribute to respiratory symptoms associated with COVID-19, specifically respiratory failure. C57BI6/J mice were mock infected or received SARS-CoV-2 (7.5x103 or 1.5x104) intranasally in a BSL-3 facility (University of Texas in Galveston) and were euthanized by CO2 hypoxia after 5 days post infection. The heads were harvested and immersed in formalin for 3 days before being transferred to LSU Health-NO for processing. Brains were carefully dissected out and preserved in optimal cutting temperature (OCT) before sectioning on a cryostat. Sections (30 μm) containing the retrotrapezoid nucleus (RTN) were selected as its neurons are part of the pontomedullary regions that generate the respiratory rhythm and pattern. Immunohistochemistry for c-Fos, a marker of neuronal activity, was used to assess neuronal activity in the RTN. Sections were incubated overnight with a primary monoclonal antibody (rabbit anti c-Fos, 1:1000) followed with a secondary goat antirabbit fluorescent IgG (GFP, 1:200, 1h) antibody. Sections were then mounted to slides in the dark to preserve the fluorescence and observed under the microscope. Images of neurons present in the RTN were captured and neurons were then hand counted and averaged. Neuronal activity in the RTN was decreased with the dose of SARS-CoV-2 used to infect cells in the brain. The greater the dose of SARS-CoV-2, the lower the number of c-Fos-positive neurons was detected in the RTN. Mock brains had the greatest number of neurons and brains infected with 1.5x104 SARS-CoV-2 had the lowest number of neurons in the RTN. This was demonstrated by counting neurons at 3 different intervals and taking the average. We conclude that SARS-CoV-2 targets neurons in respiratory centers, possibly contributing to impaired respiratory function in infected patients. NIH/NHLBI HL163814. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.