Brainstem Raphe Research Articles

Brainstem raphe hypoechogenicity is an independent predictor of post-stroke depression.

Post-stroke depression (PSD) is a common complication after stroke and has a substantial effect on the quality of life of patients. Nevertheless, reliable individual prediction of PSD is not possible. As depressive symptoms have been associated with brainstem raphe (BR) hypoechogenicity on transcranial sonography (TCS), we aimed to explore the association of BR hypoechogenicity and the occurrence of PSD. The Prognostic Markers of Post-Stroke Depression (PROMoSD) study is a prospective, observational, single-center, investigator-initiated study that included patients with acute ischemic stroke (AIS) to investigate the presence of BR hypoechogenicity by TCS early after symptom onset. The primary outcome was the presence of PSD assessed at the three-month follow-up investigation by a blinded psychiatrist and defined according to the fifth version of the Diagnostic and Statistical Manual of Mental Disorders (DSM-V criteria). From 105 included AIS patients, 99 patients completed the study. AIS patients with a hypoechogenic BR developed a PSD at three months more frequently compared to patients with normal echogenicity (48.0% versus 4.1%, P <0.001). After adjustment for confounders (sex, mRS at follow-up, previous depressive episode), a hypoechogenic BR remained independently associated with a substantial increase in the appearance of PSD (adjusted OR: 6.371, 95%-CI: 1.181-34.362). A hypoechogenic BR is a strong and independent predictor of PSD at three months after AIS. TCS could be a routine tool to assess PSD risk in clinical practice, thereby streamlining diagnostic and therapeutic algorithms.

Transcranial Sonography Characteristics of Cerebellar Neurodegenerative Ataxias.

Cerebellar neurodegenerative ataxias are a group of disorders affecting the cerebellum and its pathways with different neurological structures. Transcranial sonography (TCS) has been used for the evaluation of brain parenchymal structures in various diseases because of its fast and safe utilization, especially in neuropsychiatric and neurodegenerative diseases. The aim of our study was to investigate TCS characteristics of patients with neurodegenerative cerebellar ataxias. In our study, we included 74 patients with cerebellar degenerative ataxia; 36.5% had autosomal dominant onset, while 33.8% had sporadic onset. Standardized ultrasonographic planes were used for the identification of brain structures of interest. The SARA, INAS, neuropsychological and psychiatric scales were used for the further clinical evaluation of our study participants. The brainstem raphe was discontinued in 33.8% of the patients. The substantia nigra (SN) hyperechogenicity was identified in 79.7%. The third and fourth ventricle enlargement had 79.7% and 45.9% of patients, respectively. A positive and statistically significant correlation was found between SN hyperechogenicity with dystonia (p < 0.01), rigidity and dyskinesia (p < 0.05). The higher SARA total score is statistically significantly correlated with the larger diameter of the III (r = 0.373; p = 0.001) and IV ventricles (r = 0.324; p = 0.005). In such patients, the echogenicity of substantia nigra has been linked to extrapyramidal signs, and raphe discontinuity to depression. Furthermore, ataxia and its clinical subtypes have positively correlated with the IV ventricle diameter, indicating brain atrophy and brain mass reduction.

Contribution of the serotonergic system to developmental brain abnormalities in autism spectrum disorder.

This review highlights a key role of the serotonergic system in brain development and in distortions of normal brain development in early stages of fetal life resulting in cascades of abnormalities, including defects of neurogenesis, neuronal migration, neuronal growth, differentiation, and arborization, as well as defective neuronal circuit formation in the cortex, subcortical structures, brainstem, and cerebellum of autistic subjects. In autism, defects in regulation of neuronal growth are the most frequent and ubiquitous developmental changes associated with impaired neuron differentiation, smaller size, distorted shape, loss of spatial orientation, and distortion of cortex organization. Common developmental defects of the brain in autism include multiregional focal dysplastic changes contributing to local neuronal circuit distortion, epileptogenic activity, and epilepsy. There is a discrepancy between more than 500 reports demonstrating the contribution of the serotonergic system to autism's behavioral anomalies, highlighted by lack of studies of autistic subjects' brainstem raphe nuclei, the center of brain serotonergic innervation, and of the contribution of the serotonergic system to the diagnostic features of autism spectrum disorder (ASD). Discovery of severe fetal brainstem auditory system neuronal deficits and other anomalies leading to a spectrum of hearing deficits contributing to a cascade of behavioral alterations, including deficits of social and verbal communication in individuals with autism, is another argument to intensify postmortem studies of the type and topography of, and the severity of developmental defects in raphe nuclei and their contribution to abnormal brain development and to the broad spectrum of functional deficits and comorbid conditions in ASD.

Transcranial brain parenchyma sonographic findings in patients with myotonic dystrophy type 1 and 2

IntroductionMyotonic dystrophy type 1 (DM1) and 2 (DM2) are genetically determined progressive muscular disorders with multisystemic affection, including brain involvement. Transcranial sonography (TCS) is a reliable diagnostic tool for the investigation of deep brain structures. We sought to evaluate TCS findings in genetically confirmed DM1 and DM2 patients, and further correlate these results with patients’ clinical features. MethodsThis cross-sectional study included 163 patients (102 DM1, 61 DM2). Echogenicity of the brainstem raphe (BR) and substantia nigra (SN) as well as the diameter of the third ventricle (DTV) were assessed by TCS. Patients were evaluated using the Hamilton Depression Rating Scale, Fatigue Severity Scale and Daytime Sleepiness Scale. ResultsSN hyperechogenicity was observed in 40% of DM1 and 34% of DM2 patients. SN hypoechogenicity was detected in 17% of DM1 and 7% of DM2 patients. BR hypoechogenicity was found in 36% of DM1 and 47% of DM2 subjects. Enlarged DTV was noted in 19% of DM1 and 15% of DM2 patients. Older, weaker, depressive, and fatigued DM1 patients were more likely to have BR hypoechogenicity (p < 0.05). DTV correlated with age and disease duration in DM1 (p < 0.01). In DM2 patients SN hyperechogenicity correlated with fatigue. Excessive daytime sleepiness was associated with hypoechogenic BR (p < 0.05) and enlarged DVT (p < 0.01) in DM2 patients. ConclusionsTCS is an easy applicable and sensitive neuroimaging technique that could offer new information regarding several brainstem structures in DM1 and DM2. This may lead to better understanding of the pathogenesis of the brain involvement in DM with possible clinical implications.

Validation of brain parenchyma sonography as a marker of neurodegeneration in multiple sclerosis

BackgroundMultiple sclerosis (MS) is widely known to cause brain atrophy due to neurodegeneration. Neuroimaging investigations revealed a direct link between brain atrophy detected by MRI and impairment. Transcranial sonography is a safe, feasible and cost-effective imaging technique. In this study, we aimed to validate B-mode transcranial sonography (TCS) as a marker of neurodegeneration in MS. This study is the first study directed to set cut-off point for brain parenchyma measurement in Egyptian population. An observational, case–control study, conducted on 125 subjects; divided into 2 groups: first group, 71 healthy volunteers and patients’ group (54 patients) with relapsing–remitting multiple sclerosis (RRMS). All studied subjects were assessed using B-mode TCS. Transcranial sonography findings were categorized into: first, assessment of brain atrophy parameters by measuring diameter (cm) of third ventricle and both frontal horns of lateral ventricles. Then, the echogenicity of thalamus and brainstem structures (substantia nigra (SN), red nucleus) planimetric surface area (cm2) were assessed along with their abnormal echogenicity (cm2), while brainstem raphe was assessed semi-quantitatively for its echogenicity (intact or interrupted).ResultsQuantitative measures of brain atrophy: in normal control group the third ventricle diameter mean was 0.2 cm (± 0.08), right and left frontal horn diameter were 0.3 cm (± 0.13) and 0.28 cm (± 0.1), respectively, brain atrophy parameters could differentiate between MS patients and normal control group as a statistically significant (p< 0.001) larger ventricular diameter was found in MS patients. On the other hand, assessment of brain stem structures and thalamus showed no statistical significance between MS patients and normal control except in surface area of both red nuclei.ConclusionsBrain parenchymal sonography may be used as a tool in assessment of neurodegeneration in MS patients.

Serotonergic regulation of appetite and sodium appetite.

Serotonin is a neurotransmitter that is synthesized and released from the brainstem raphe nuclei to affect many brain functions. It is well known that the activity of raphe serotonergic neurons is changed in response to the changes in feeding status to regulate appetite via the serotonin receptors. Likewise, changes in volume status are known to alter the activity of raphe serotonergic neurons and drugs targeting serotonin receptors were shown to affect sodium appetite. Therefore, the central serotonin system appears to regulate ingestion of both food and salt, although neural mechanisms that induce appetite in response to hunger and sodium appetite in response to volume depletion are largely distinct from each other. In this review, we discuss our current knowledge regarding the regulation of ingestion - appetite and sodium appetite - by the central serotonin system.

Echogenicity of Brain Structures in Huntington's Disease Patients Evaluated by Transcranial Sonography - Magnetic Resonance Fusion Imaging using Virtual Navigator and Digital Image Analysis.

Transcranial sonography (TCS) magnetic resonance (MR) fusion imaging and digital image analysis are useful tools for the evaluation of various brain pathologies. This study aimed to compare the echogenicity of predefined brain structures in Huntington's disease (HD) patients and healthy controls by TCS-MR fusion imaging using Virtual Navigator and digitized image analysis. The echogenicity of the caudate nucleus (CN), substantia nigra (SN), lentiform nucleus (LN), insula, and brainstem raphe (BR) evaluated by TCS-MR fusion imaging using digitized image analysis was compared between 21 HD patients and 23 healthy controls. The cutoff values of echogenicity indices for the CN, LN, insula, and BR with optimal sensitivity and specificity were calculated using receiver operating characteristic analysis. The mean echogenicity indices for the CN (67.0±22.6 vs. 37.9±7.6, p<0.0001), LN (110.7±23.6 vs. 59.7±11.1, p<0.0001), and insula (121.7±39.1 vs. 70.8±23.0, p<0.0001) were significantly higher in HD patients than in healthy controls. In contrast, BR echogenicity (24.8±5.3 vs. 30.1±5.3, p<0.001) was lower in HD patients than in healthy controls. The area under the curve was 90.9%, 95.5%, 84.1%, and 81.8% for the CN, LN, insula, and BR, respectively. The sensitivity and specificity were 86% and 96%, respectively, for the CN and 90% and 100%, respectively, for the LN. Increased CN, LN, and insula echogenicity and decreased BR echogenicity are typical findings in HD patients. The high sensitivity and specificity of the CN and LN hyperechogenicity in TCS-MR fusion imaging make them promising diagnostic markers for HD.

Prognostic markers of post-stroke depression (PROMoSD): study protocol of a prospective single-center observational study on raphe hypoechogenicity as a predictor of post-stroke depression

Post-stroke depression (PSD) is an important and frequent non-motor complication after a stroke. As valid prediction of PSD occurrence is still not possible, the unselective use of preventive therapy in stroke patients has risen a questionable risk-to-benefit consideration. Therefore, there is a need to increase the prediction probability of PSD to identify patients at very high risk of a depressive complication who might benefit from preventive therapy. In this context, a brainstem raphe hypoechogenicity (BRH) in transcranial sonography (TCS) has previously been associated with depressive symptoms in a broad spectrum of diseases. BRH might therefore represent a valid maker of vulnerability for depressive symptoms that could be of interest in the risk assessment of PSD occurrence. In the prognostic markers of post-stroke depression (PROMoSD) study, a prospective, observational, single-center, investigator-initiated study, we aim to include 100 patients with acute ischemic stroke (AIS). Besides data on clinical characteristics and baseline psychiatric assessment, we conduct a TCS examination to identify patients with BRH. The primary outcome is the incidence of PSD threemonths after inclusion, determined by a blinded investigator according to the fifth version of the Diagnostic and Statistical Manual of Mental Disorders (DSM-V) criteria. The results of PROMoSD will answer the question of whether screening of BRH after AIS improves the prediction of PSD occurrence. A positive result of this study could have direct consequences on psychiatric support after AIS by streamlining diagnostic and therapeutic algorithms. Trial registration ClinicalTrials.gov identifier no. NCT05580198.

RT-4 WORLD'S FIRST HEMISPHERE-SHAPE BRAIN-DEDICATED PET FOR SMALL LESION DETECTION

Abstract Positron emission tomography (PET) is useful to detect malignant tumors by imaging glucose or amino acid metabolism. Whole-body PET with the detector arrangement in a large diameter is currently used for brain imaging, however, the detector arrangement in small diameter is better for brain imaging. Stereotactic radiosurgery (SRS) treats brain tumor with maintaining cognitive function. Therefore, it needs more dedicated PET to identify small lesions and their localization. Then, we developed the world's first brain-dedicated PET with detectors arranged in a hemisphere of 28 cm diameter, attaining 2.2 mm in spatial resolution. This development was performed with ATOX CO., LTD and the brain-dedicated PET has been commercialized as VrainTM. Ten normal volunteers (22 - 45 age male) underwent 18FDG-PET using a whole-body PET (Discovery MI, GE) and the brain-PET for 10-min each, which were started 30-min and 45-min after FDG injection, respectively. A phantom with 10-22 diameter hot spheres and background (radioactivity ratio, 4:1) was also acquired by both PET systems, then estimated the radioactivity ratio in case of 2-mm diameter hot sphere. As a results, the inferior colliculus, substantia nigra, red nucleus, and brain stem raphe nucleus were identified with the brain-PET. The inferior colliculus was identified with the whole-body PET, but other nuclei were not. Based on phantom study, it was estimated that radioactivity in a 2-mm diameter sphere was measured with 1.4 - 2.9 times higher contrast than whole-body PET. The substantia nigra and the red nucleus has 5.0-6.0mm in short diameter on MRI T2WI axial image. The raphe nucleus extends laterally to 2.5mm on postmortem brain specimens. We concluded that our brain-dedicated PET can identify approximately 2.5mm diameter tumor clearly and will be particularly useful in SRS.

Transcranial Sonography as a Diagnostic Tool for Depressive Disorders.

Transcranial sonography (TCS) is an available and noninvasive neuroimaging method that has been found to reduce the echogenicity of the brainstem raphe (BR) in patients with depression. Applying the criteria of the Diagnostic and Statistical Manual of Mental Disorders-IV (DSM-IV), we performed a meta-analysis of the diagnostic accuracy of TCS. A systematic search was conducted in PubMed, EMBASE, The Cochrane Library, and Web of Science. The databases were searched from inception to December 2021. The quality of the included literature was assessed using the QUADAS-2. Heterogeneity analysis was performed. A summary receiver operating characteristic (SROC) curve was generated to evaluate the diagnostic accuracy of TCS. We included 12 studies with 809 patients. The pooled sensitivity was 0.66 (95% confidence interval [CI]: 0.61-0.71), and the specificity was 0.84 (95% CI: 0.80-0.87). The combined positive likelihood ratio (LR) was 3.84 (95% CI: 2.68-5.51), the negative LR was 0.41 (95% CI: 0.29-0.57), and the diagnostic odds ratio (DOR) was 11.45 (95% CI: 5.57-23.02). The area under the curve (AUC) of the plotted SROC curve was 0.86 (95% CI: 0.83-0.89). The meta-regression and subgroup analyses found no source of heterogeneity. TCS has high potential and efficacy in diagnosing depression and may be a reasonable test to perform clinically for the assessment of depression.

Visual and Brainstem Auditory-evoked Potentials Correlate with Specific Motor and Non-motor Symptoms in Parkinson's Disease

Parkinson’s disease (PD) is a common and complex neurodegenerative disease characterized by progressive motor and non-motor symptoms. The current study investigated the dysfunction of brain hemispheres and brainstem of PD patients and its relation to motor and non-motor symptoms using brainstem auditory evoked potentials (BAEP) and pattern reversal visual evoked potentials (p-VEP). We hypothesized that some motor and non-motor symptoms of PD due to specific dysfunctions of brainstem and brain hemispheres could be related to changes in p-VEP and BAEP. Accordingly, the aim of this study was to explore the abnormalities of BAEPs and p-VEPs in patients with PD and its correlation to the motor and non-motor symptoms of PD. Seventy-six nondemented PD patients took part in the p-VEP evaluations and 66 nondemented PD patients were included in BAEP evaluation. In order to compare the p-VEP performance of PD group, we included a control group comprising 32 age-matched participants. A BAEP substudy involved 29 age-matched healthy controls. All patients underwent a comprehensive motor and non-motor neuropsychological assessment. We found significant changes in all tested parameters of p-VEPs in PD patients compared to control subjects. In addition, these lower scores in p-VEP correlate with the results of some tests for cognition related to frontal-striatal dysfunction and contralateral rigidity, but not with the results of overall motor evaluation or other non-motor symptoms studied. In BAEP, PD patients have a significant prolongation of III and V wave latencies compared to controls. In addition, when examining the possible associations of BAEP with other non-motor manifestations of the disease, such association was observed only by the apathy scale. In conclusion, the current study confirms the visual and auditory abnormalities among PD patients thatreflect brain hemispheres and brainstem pathological changes. It also correlates these abnormalities to some motor and non-motor features of the disease, providing a localizing tool for associated brain hemispheres and brainstem dysfunctions. Furthermore, abnormal visual evoked potentials are associated with motor and non-motor symptoms due to the basal ganglia dysfunction. In contrast, abnormal auditory evoked potentials are connected with apathy, which is considered to be related with brainstem raphe nuclei dysfunction.

Hypoechogenicity of brainstem raphe in long-COVID syndrome–less common but independently associated with depressive symptoms: a cross-sectional study

ObjectiveLong coronavirus disease (Long-COVID) syndrome is a hitherto poorly understood phenomenon with a broad spectrum of symptoms, including depression and anxiety. Depressive symptoms have been associated with brainstem raphe (BR) alterations in transcranial sonography (TCS) that might reflect dysfunction of the serotonergic system. The primary aim was to investigate the connection of BR alterations with depressive and anxiety symptoms in patients with Long-COVID syndrome.MethodsIn a cross-sectional study design, we included outpatients fulfilling the criteria of Long-COVID syndrome. All patients were examined by TCS in the axial plane with focus on BR signal alterations. The Hospital Anxiety and Depression Scale (HADS) was used to test for symptoms of anxiety and depression.ResultsWe included n = 70 patients with Long-COVID syndrome, of which 28.6% (n = 20) exhibited a reduced echogenicity of BR in the TCS examination. Patients with hypoechogenic BR had higher subscores for anxiety and depression compared to normoechogenic patients (HADS depression: median 8 versus 5.5, p = 0.006; HADS anxiety: median 9 versus 6.5, p = 0.006). After adjustment for reasonable confounders, only the odds ratio (OR) for relevant depressive symptoms was higher among Long-COVID patients with hypoechogenic raphe (adjusted OR 3.884, 95% CI 1.244–12.123).DiscussionHypoechogenic BR alterations are independently associated with depressive symptoms in Long-COVID patients but are not highly frequent. Future studies should investigate whether the hypoechogenicity of the BR is a direct consequence or whether it reflects a priori a higher susceptibility to depressive symptoms after COVID-19, thus enabling to identify COVID-19 patients at higher risk of developing Long-COVID depressive symptoms.

Serotonin transporter binding in major depressive disorder: impact of serotonin system anatomy.

Serotonin transporter (5-HTT) binding deficits are reported in major depressive disorder (MDD). However, most studies have not considered serotonin system anatomy when parcellating brain regions of interest (ROIs). We now investigate 5-HTT binding in MDD in two novel ways: (1) use of a 5-HTT tract-based analysis examining binding along serotonergic axons; and (2) using the Copenhagen University Hospital Neurobiology Research Unit (NRU) 5-HT Atlas, based on brain-wide binding patterns of multiple serotonin receptor types. [11C]DASB 5-HTT PET scans were obtained in 60 unmedicated participants with MDD in a current depressive episode and 31 healthy volunteers (HVs). Binding potential (BPP) was quantified with empirical Bayesian estimation in graphical analysis (EBEGA). Within the [11C]DASB tract, the MDD group showed significantly lower BPP compared with HVs (p = 0.02). This BPP diagnosis difference also significantly varied by tract location (p = 0.02), with the strongest MDD binding deficit most proximal to brainstem raphe nuclei. NRU 5-HT Atlas ROIs showed a BPP diagnosis difference that varied by region (p < 0.001). BPP was lower in MDD in 3/10 regions (p-values < 0.05). Neither [11C]DASB tract or NRU 5-HT Atlas BPP correlated with depression severity, suicidal ideation, suicide attempt history, or antidepressant medication exposure. Future studies are needed to determine the causes of this deficit in 5-HTT binding being more pronounced in proximal axon segments and in only a subset of ROIs for the pathogenesis of MDD. Such regional specificity may have implications for targeting antidepressant treatment, and may extend to other serotonin-related disorders.

Differential Serotonergic Modulation of Principal Neurons and Interneurons in the Anterior Piriform Cortex.

Originating from the brainstem raphe nuclei, serotonin is an important neuromodulator involved in a variety of physiological and pathological functions. Specific optogenetic stimulation of serotonergic neurons results in the divisive suppression of spontaneous, but not sensory evoked activity in the majority of neurons in the primary olfactory cortex and an increase in firing in a minority of neurons. To reveal the mechanisms involved in this dual serotonergic control of cortical activity we used a combination of in vitro electrophysiological recordings from identified neurons in the primary olfactory cortex, optogenetics and pharmacology and found that serotonin suppressed the activity of principal neurons, but excited local interneurons. The results have important implications in sensory information processing and other functions of the olfactory cortex and related brain areas.

Neurosonological Findings Related to Non-Motor Features of Parkinson's Disease: A Systematic Review.

Non-motor symptoms (NMS) in Parkinson’s disease (PD), including neuropsychiatric or dysautonomic complaints, fatigue, or pain, are frequent and have a high impact on the patient’s quality of life. They are often poorly recognized and inadequately treated. In the recent years, the growing awareness of NMS has favored the development of techniques that complement the clinician’s diagnosis. This review provides an overview of the most important ultrasonographic findings related to the presence of various NMS. Literature research was conducted in PubMed, Scopus, and Web of Science from inception until January 2021, retrieving 23 prospective observational studies evaluating transcranial and cervical ultrasound in depression, dementia, dysautonomic symptoms, psychosis, and restless leg syndrome. Overall, the eligible articles showed good or fair quality according to the QUADAS-2 assessment. Brainstem raphe hypoechogenicity was related to the presence of depression in PD and also in depressed patients without PD, as well as to overactive bladder. Substantia nigra hyperechogenicity was frequent in patients with visual hallucinations, and larger intracranial ventricles correlated with dementia. Evaluation of the vagus nerve showed contradictory findings. The results of this systematic review demonstrated that transcranial ultrasound can be a useful complementary tool in the evaluation of NMS in PD.

Sonographic hypoechogenicity of brainstem raphe nucleus is correlated with electroencephalographic spike frequency in patients with epilepsy

BackgroundBrainstem raphe nucleus (BRN) hypoechogenicity in transcranial sonography (TCS) has been demonstrated in patients with major depression, possibly representing a sonographic manifestation of serotonergic dysfunction in depression. Most patients with epilepsy with comorbid depression exhibit hypoechogenic BRN in TCS. However, the role of BRN in the pathogenesis of epilepsy is unclear. This study aimed to evaluate the correlation of BRN echogenicity with epilepsy itself, and the echogenicity of other midbrain structures and the size of lateral ventricle (LV) will also be evaluated in patients with epilepsy. MethodsThirty-six patients with epilepsy without depression and 37 healthy controls were recruited. Sonographic echogenicity of BRN, caudate nucleus (CN), lentiform nucleus (LN), substantia nigra (SN), and the width of frontal horns of the lateral ventricles (LV) and the third ventricle (TV) were evaluated with TCS. The frequency of interictal epileptiform discharges (IEDs) was assessed with ambulatory electroencephalogram (AEEG). ResultsHypoechogenicity of BRN was depicted in 36.1% of patients with epilepsy and 18.9% of controls, showing no significant difference. Patients with epilepsy with BRN hypoechogenicity had higher epileptic discharge index (EDI) than those with normal BRN echogenecity. Especially, higher EDI in patients with BRN hypoechogenicity was observed during the sleep period but not during awake period. The width of TV was significantly larger in patients with epilepsy than that in controls. We did not find any difference between patients with epilepsy and controls in the echogenicity of CN, LN, and SN, as well as in the width of frontal horn of LV. ConclusionsHypoechogenic BRN is correlated with a high frequency of epileptic discharges in electroencephalogram (EEG), especially during sleep period but not during awake period, indicating that BRN alterations may play a potential role in the pathogenesis of epilepsy in association with sleep cycle.

Neurochemically and Hodologically Distinct Ascending VGLUT3 versus Serotonin Subsystems Comprise the r2-Pet1Median Raphe

Brainstem median raphe (MR) neurons expressing the serotonergic regulator gene Pet1 send collateralized projections to forebrain regions to modulate affective, memory-related, and circadian behaviors. Some Pet1 neurons express a surprisingly incomplete battery of serotonin pathway genes, with somata lacking transcripts for tryptophan hydroxylase 2 (Tph2) encoding the rate-limiting enzyme for serotonin (5-hydroxytryptamine, 5-HT) synthesis, but abundant for vesicular glutamate transporter 3 (Vglut3) encoding a synaptic-vesicle associated glutamate transporter. Genetic fate maps show these non-classical, putatively glutamatergic Pet1 neurons in the MR arise embryonically from the same progenitor cell compartment - hindbrain rhombomere 2 (r2) - as serotonergic TPH2+ MR Pet1 neurons. Well established is the distribution of efferents en masse from r2-derived, Pet1-neurons; unknown is the relationship between these efferent targets and the specific constituent source-neuron subgroups identified as r2-Pet1Tph2 -high versus r2-Pet1Vglut3 -high Using male and female mice, we found r2-Pet1 axonal boutons segregated anatomically largely by serotonin+ versus VGLUT3+ identity. The former present in the suprachiasmatic nucleus, paraventricular nucleus of the thalamus, and olfactory bulb; the latter are found in the hippocampus, cortex, and septum. Thus r2-Pet1Tph2- high and r2-Pet1Vglut3- high neurons likely regulate distinct brain regions and behaviors. Some r2-Pet1 boutons encased interneuron somata, forming specialized presynaptic "baskets" of VGLUT3+ or VGLUT3+/5-HT+ identity; this suggests that some r2-Pet1Vglut3- high neurons may regulate local networks, perhaps with differential kinetics via glutamate versus serotonin signaling. Fibers from other Pet1 neurons (non-r2-derived) were observed in many of these same baskets, suggesting multifaceted regulation. Collectively, these findings inform brain organization and new circuit nodes for therapeutic considerations.Significance statementOur findings match axonal bouton neurochemical identity with distant cell bodies in the brainstem raphe. The results are significant because they suggest that disparate neuronal subsystems derive from Pet1+ precursor cells of the embryonic progenitor compartment rhombomere 2 (r2). Of these r2-Pet1 neuronal subsystems, one appears largely serotonergic, as expected given expression of the serotonergic regulator PET1, and projects to the olfactory bulb, thalamus, and suprachiasmatic nucleus. Another expresses VGLUT3, suggesting principally glutamate transmission, and projects to the hippocampus, septum, and cortex. Some r2-Pet1 boutons-those that are VGLUT3+ or VGLUT3+/5-HT+ co-positive-comprise "baskets" encasing interneurons, suggesting they control local networks perhaps with differential kinetics via glutamate versus serotonin signaling. Results inform brain organization and circuit nodes for therapeutic consideration.

Brain corticotropin releasing hormone and stress reactivity

The hypothalamic-pituitary-adrenocortical axis is one of the main components of stress adaptation. Corticotropin-releasing hormone (CRH) coming from the nucleus paraventricularis hypothalami (PVN) is the canonical central regulator of the axis. This CRH acts on the CRH-R1 receptors of the pituitary, and, through adrenocorticotropin, stimulates glucocorticoid release from the adrenal cortex. However, it may be synthetized in other parts of the brain as well, and may act both on CRH-R1 and CRH-R2 receptors. These areas form the central CRH network. Many of them are also stress reactive and participate in physical and psychological stress response. The central nucleus of the amygdala and bed nucleus of stria terminalis are two areas best known for their role in emotions, while hippocampus is mostly involved in glucocorticoid feedback as well as memory formation, all heavily connected to stress adaptation. Among others, the brainstem raphe nuclei get dense CRHergic innervation that, through CRH-R1 receptors, may influence the serotoninergic tone of the brain. Both stress and serotonin are strongly implicated in depression, therefore, it is not surprising that CRH-R1 antagonists were developed as therapeutic tools that extensively act on the brain CRH system. Our review suggests a general role of brain CRH network in stress adaptation which is not restricted to PVN.

Echogenicity Changes in Brainstem Raphe Detected by Transcranial Parenchymal Sonography and Clinical Characteristics in Parkinson's Disease

Background: Decreased brainstem raphe (BR) echogenicity detected by transcranial parenchymal sonography (TCS) is associated with depression in psychiatric and neurologic diseases. However, previous studies focusing on the relationship between motor and non-motor symptoms and echogenicity changes in BR in patients with PD yielded controversial results.Objectives: To investigate the relationship between echogenicity changes in BR detected by TCS and motor and a series of non-motor symptoms in patients with PD.Methods: Consecutive PD patients were recruited from the Second Affiliated Hospital of Soochow University. Demographic information and Motor and non-motor symptoms for all subjects were collected. TCS was used to detect the echogenicity changes in BR in PD patients.Results: One hundred and thirty-five consecutive patients with PD were enrolled in the study. The BR abnormal rate was significantly higher in PD patients with anxiety (p = 0.003) or depression (p = 0.022) than patients without. Spearman correlation analyses showed that Hamilton Rating Scale for Depression(HRSD) (r = 0.274, p = 0.002) and Parkinson's Disease Questionnaire 39-item(PDQ-39) (r = 0.208, p = 0.034) scores were positively correlated with abnormal BR echogenicity. Multivariate logistic regression analyses showed that HRSD and HAMA scores were associated with BR hypoechogenicity, the corresponding odds ratios (confidence intervals) were 1.07 (95% CI, 1.01–1.13) and 1.10(1.01–1.18), respectively. However, the PDQ-39 score was not associated with BR hypoechogenicity.Conclusion: The abnormal reduction in BR echogenicity detected by TCS is associated with depression and anxiety, but not motor symptoms in PD patients.

A single-cell transcriptomic and anatomic atlas of mouse dorsal raphe Pet1 neurons.

Among the brainstem raphe nuclei, the dorsal raphe nucleus (DR) contains the greatest number of Pet1-lineage neurons, a predominantly serotonergic group distributed throughout DR subdomains. These neurons collectively regulate diverse physiology and behavior and are often therapeutically targeted to treat affective disorders. Characterizing Pet1 neuron molecular heterogeneity and relating it to anatomy is vital for understanding DR functional organization, with potential to inform therapeutic separability. Here we use high-throughput and DR subdomain-targeted single-cell transcriptomics and intersectional genetic tools to map molecular and anatomical diversity of DR-Pet1 neurons. We describe up to fourteen neuron subtypes, many showing biased cell body distributions across the DR. We further show that P2ry1-Pet1 DR neurons - the most molecularly distinct subtype - possess unique efferent projections and electrophysiological properties. These data complement and extend previous DR characterizations, combining intersectional genetics with multiple transcriptomic modalities to achieve fine-scale molecular and anatomic identification of Pet1 neuron subtypes.