Neuroanatomical Relationship Research Articles

Osteopathische Behandlung neuropathischer Nacken- und Beckenbodenschmerzen

A 32-year-old female patient presented with persistent neck and pelvic floor pain. Despite extensive external evaluations and treatments, including medication and physiotherapy, she experienced no lasting improvement. An osteopathic examination revealed significant dysfunctional and structural findings, including talus dislocation and signs of neural irritation. After targeted osteopathic interventions, the patient reported complete and sustained symptom relief.This report discusses the osteopathic approach in the context of current literature, emphasizing the importance of a deeper understanding of musculoskeletal interactions and neuroanatomical relationships.

Metastases and Primary Brain Tumors Affecting the Fornix of the Brain.

Background The aim of this study is to evaluate the clinical and radiological findings of metastatic tumors and primary brain tumors affecting the fornix. Methods Between January 2015 and March 2023, we retrospectively evaluated 1087 patients of both sexes who underwent cranial magnetic resonance imaging (MRI) for a preliminary diagnosis of intracranial malignancy in the radiology department of our hospital. Two radiologists with six and 10 years of experience in MRI examination assessed the relationship between primary and metastatic tumors and the fornix. Results Involvement of the fornix was diagnosed in 29 of the 1087 patients (2.66%), of which fornix was affected by metastatic lesions in 14 patients (48.2%) and primary tumors in 15 patients (51.7%).The majority of metastatic lesions were from lung and breast cancers, with other tumor types including osteosarcoma, renal cell carcinoma, pancreatic adenocarcinoma, pleomorphic sarcoma, and diffuse large B-cell lymphoma. Among all primary tumors, glioblastoma was the most common primary brain tumor invading the fornix, with other diagnoses including diffuse astrocytoma, medulloblastoma, and anaplastic oligodendroglioma.Metastatic and primary brain tumors affecting the fornix were detected over a broad timeline, from the time of diagnosis up to 120 months after diagnosis. A retrospective evaluation of medical records revealed memory deficits in four patients. Conclusion The fornix can be affected by both metastatic and primary brain tumors. It is crucial to understand the relevant neuroanatomical relationships when evaluating lesions that affect the fornix.

FRI278 Kisspeptin Neuron Projections And Expression Patterns Are Unaltered In Prenatally Androgenized Female Mice Modeling PCOS

Abstract Disclosure: M. Prescott: None. Y. Watanabe: None. A. Ruddenklau: None. L. Fisher: None. C.L. Jasoni: None. R.E. Campbell: Consulting Fee; Self; Bayer, Inc. Polycystic ovary syndrome (PCOS) is associated with impaired gonadal steroid hormone feedback and a hyperactive central reproductive axis, implicating the brain in PCOS pathophysiology. Excess prenatal androgen (PNA) exposure is linked with the development of PCOS, and preclinical evidence suggests that PNA can program altered connections within the gonadotropin-releasing hormone (GnRH) neuronal network. Kisspeptin neurons are critical upstream regulators of GnRH neurons, relaying hormone feedback and potently activating GnRH secretion, but their role in PCOS remains incompletely understood. This study tested the hypothesis that prenatal androgen excess programmes altered neuroanatomical connections between kisspeptin neurons and GnRH neurons and modified neuropeptide and steroid hormone receptor expression in kisspeptin neurons. To investigate this, we labelled, imaged and assessed kisspeptin fibers, GnRH neurons, and gonadal steroid hormone receptors in adult female transgenic kisspeptin reporter mice (Kiss1(Cre-GFP)Coll; ROSA26tdTomato) exposed prenatally to di-hydrotestosterone or an oil vehicle (VEH) on gestational days 16-18 (n=7-10/group). PNA mice were acyclic and all tissue was collected in diestrus. Fixed coronal brain sections were immunofluorescently labelled for GnRH and kisspeptin reporter tdTomato and imaged on a confocal microscope to assess close fiber contacts to the soma and proximal dendrite of GnRH neurons. Neither the proportion of GnRH neurons with kisspeptin fiber contacts (VEH: 86.3±3.4%, PNA: 87.3±4.3%), nor the mean number of kisspeptin fiber close appositions per GnRH neuron (VEH: 6.1±0.6, PNA: 5.7±0.8) was different between groups. Kisspeptin neuron number and kisspeptin neuron co-expression with estrogen and progesterone receptors was evaluated in immunolabelled sections throughout the rostral periventricular nucleus of the 3rd ventricle (RP3V) and the arcuate nucleus (ARN). PNA had no significant impact on kisspeptin neuron number or the proportion of neurons with gonadal hormone co-expression in either population. Expression of neuropeptides was quantified by RT-qPCR in micro-dissected RP3V and ARN tissue from a separate cohort of adult PNA and VEH mice (n=5-8/group). PNA did not affect Kiss1, Tac2 or Pdyn expression in the ARN or Kiss1 expression in the RP3V. These data indicate that PNA does not modify anatomical connections between RP3V kisspeptin neurons and GnRH neurons, nor does it have a robust impact on steroid hormone responsiveness or neuropeptide expression of kisspeptin neurons. While the neuroanatomical relationship between ARN kisspeptin neurons and the GnRH neuron distal dendron in PNA mice remains to be determined, these data suggest that PNA-mediated neuroendocrine dysfunction is not due to programmed changes in the neuroanatomical projections or gonadal hormone sensitivity of kisspeptin neurons. Presentation: Friday, June 16, 2023

A Crafty Approach for Learning the Topographical Anatomy of the Cranial Nerves

Certain neuroanatomical relationships can be complex for students to visualise and understand. This article describes creation of a simple and cheap model to help students more easily learn the relationships of the cranial nerves to each other and to the different regions of the central nervous system (forebrain and brainstem).

Neuroanatomical distribution of the enkephalinergic and tachykininergic systems in the alpaca brainstem: an immunohistochemical study.

A recent study has shown a close neuroanatomical relationship between the enkephalinergic (methionine-enkephalin) and tachykininergic (substance P) systems in the alpaca diencephalon. In this study, our aim is to show this relationship in the alpaca brainstem. Using an immunohistochemical technique, the distribution of immunoreactive (Ir) fibers and cell bodies containing substance P (SP) or methionine-enkephalin (MET) has been studied in the alpaca brainstem. Five adult males were used; brain tissue was fixed and processed by standard methods. SP- and MET-Ir fibers showed a widespread and similar distribution in the mesencephalon, pons and medulla oblongata. The co-localization of fibers containing SP or MET was found in most of the nuclei/tracts of the alpaca brainstem. This close neuroanatomical relationship suggests multiple physiological interactions between both neuropeptides. The distribution of the cell bodies containing SP was very restricted (cell bodies were only observed in a few nuclei located in the mesencephalon and medulla oblongata), whereas MET-Ir perikarya showed a moderately widespread distribution in the mesencephalon, pons and medulla oblongata. This study increases the knowledge on the neuroanatomical distribution/relationship of the tachykininergic (SP) and enkephalinergic (MET) systems in the alpaca central nervous system.

3D Printing for Complex Cranial Surgery Education: Technical Overview and Preliminary Validation Study

Background 3D printing-also known as additive manufacturing-has a wide range of applications. Reproduction of low-cost, high-fidelity, disease- or patient-specific models presents a key developmental area in simulation and education research for complex cranial surgery. Methods Using cadaveric dissections as source materials, skull base models were created, printed, and tested for educational value in teaching complex cranial approaches. In this pilot study, assessments were made on the value of 3D printed models demonstrating the retrosigmoid and posterior petrosectomy approaches. Models were assessed and tested in a small cohort of neurosurgery resident subjects ( n = 3) using a series of 10 radiographic and 2 printed case examples, with efficacy determined via agreement survey and approach selection accuracy. Results All subjects indicated agreement or strong agreement for all study endpoints that 3D printed models provided significant improvements in understanding of neuroanatomic relationships and principles of approach selection, as compared to 2D dissections or patient cross-sectional imaging alone. Models were not superior to in-person hands-on teaching. Mean approach selection accuracy was 90% (±13%) for 10 imaging-based cases, or 92% (±7%) overall. Trainees strongly agreed that approach decision-making was enhanced by adjunctive use of 3D models for both radiographic and printed cases. Conclusion 3D printed models incorporating skull base approaches and/or pathologies provide a compelling addition to the complex cranial education armamentarium. Based on our preliminary analysis, 3D printed models offer substantial potential for pedagogical value as dissection guides, adjuncts to preoperative study and case preparation, or tools for approach selection training and evaluation.

Endovascular deep brain stimulation: Investigating the relationship between vascular structures and deep brain stimulation targets

BackgroundEndovascular delivery of current using ‘stentrodes’ – electrode bearing stents – constitutes a potential alternative to conventional deep brain stimulation (DBS). The precise neuroanatomical relationships between DBS targets and the vascular system, however, are poorly characterized to date. ObjectiveTo establish the relationships between cerebrovascular system and DBS targets and investigate the feasibility of endovascular stimulation as an alternative to DBS. MethodsNeuroanatomical targets as employed during deep brain stimulation (anterior limb of the internal capsule, dentatorubrothalamic tract, fornix, globus pallidus pars interna, medial forebrain bundle, nucleus accumbens, pedunculopontine nucleus, subcallosal cingulate cortex, subthalamic nucleus, and ventral intermediate nucleus) were superimposed onto probabilistic vascular atlases obtained from 42 healthy individuals. Euclidian distances between targets and associated vessels were measured. To determine the electrical currents necessary to encapsulate the predefined neurosurgical targets and identify potentially side-effect inducing substrates, a preliminary volume of tissue activated (VTA) analysis was performed. ResultsSix out of ten DBS targets were deemed suitable for endovascular stimulation: medial forebrain bundle (vascular site: P1 segment of posterior cerebral artery), nucleus accumbens (vascular site: A1 segment of anterior cerebral artery), dentatorubrothalamic tract (vascular site: s2 segment of superior cerebellar artery), fornix (vascular site: internal cerebral vein), pedunculopontine nucleus (vascular site: lateral mesencephalic vein), and subcallosal cingulate cortex (vascular site: A2 segment of anterior cerebral artery). While VTAs effectively encapsulated mfb and NA at current thresholds of 3.5 V and 4.5 V respectively, incremental amplitude increases were required to effectively cover fornix, PPN and SCC target (mean voltage: 8.2 ± 4.8 V, range: 3.0–17.0 V). The side-effect profile associated with endovascular stimulation seems to be comparable to conventional lead implantation. Tailoring of targets towards vascular sites, however, may allow to reduce adverse effects, while maintaining the efficacy of neural entrainment within the target tissue. ConclusionsWhile several challenges remain at present, endovascular stimulation of select DBS targets seems feasible offering novel and exciting opportunities in the neuromodulation armamentarium.

Neuroanatomical relationship between Jingbi and the brachial plexus.

This study examined the stratified anatomy of the traditional acupuncture point Jingbi and the neuroanatomical relationship between Jingbi and the brachial plexus, and investigated neural pathways that could be affected by acupuncture stimulation at Jingbi. Twelve dissected specimens were used to study the pathway of an acupuncture needle inserted at Jingbi. The stratified anatomy and the neuroanatomical relationship between Jingbi and the brachial plexus were studied. Our samples were grouped by gender and cause of death for comparative analysis. All needles (n = 24, on both sides of a total of 12 cadavers) punctured the anterior scalene muscle medial to the brachial plexus and external jugular vein, lateral to the phrenic nerve and internal jugular vein, and superior to the clavicle and subclavian artery/vein. The depth of needle insertion at Jingbi on the right side of male samples was 28.0 (interquartile range (IQR), 22.5-30.8) mm, which was approximately 8 mm deeper than for female subjects (p < 0.05). The needle was 3.0 (IQR, 2.0-5.0) mm and 7.0 (IQR, 5.5-8.0) mm medial to the brachial plexus on the left and right sides, respectively. Deep needle insertion at Jingbi can puncture the anterior scalene muscle. The mechanism of action of acupuncture stimulation at Jingbi might be related to its close relationship with the brachial plexus. Significant differences in needling depth were observed when our samples were grouped by gender. More studies are needed.

A close neuroanatomical relationship between the enkephalinergic (methionine-enkephalin) and tachykininergic (substance P) systems in the alpaca diencephalon.

In the alpaca diencephalon, the distribution of immunoreactive cell bodies and fibers containing methionine-enkephalin (MET) or substance P (SP) has been studied. The immunohistochemical study was performed by standard method on the diencephalon of four male alpacas that lived at sea level. Nerve fibers containing MET or SP were widely distributed in the thalamus and hypothalamus. METand SP-immunoreactive fibers showed a similar distribution in the whole diencephalon. Immunoreactive cell bodies containing MET or SP were only observed in the hypothalamus. The distribution of MET-immunoreactive cell bodies was more widespread than that observed for cell bodies containing SP. A close neuroanatomical relationship between the tachykininergic (SP) and enkephalinergic (MET) systems was observed in the whole diencephalon suggestive of the existence of multiple physiological interactions between both systems.

Cholecystokinin in the central nervous system of the sea lamprey Petromyzon marinus: precursor identification and neuroanatomical relationships with other neuronal signalling systems.

Cholecystokinin (CCK) is a neuropeptide that modulates processes such as digestion, satiety, and anxiety. CCK-type peptides have been characterized in jawed vertebrates and invertebrates, but little is known about CCK-type signalling in the most ancient group of vertebrates, the agnathans. Here, we have cloned and sequenced a cDNA encoding a sea lamprey (Petromyzon marinus L.) CCK-type precursor (PmCCK), which contains a CCK-type octapeptide sequence (PmCCK-8) that is highly similar to gnathostome CCKs. Using mRNA in situ hybridization, the distribution of PmCCK-expressing neurons was mapped in the CNS of P. marinus. This revealed PmCCK-expressing neurons in the hypothalamus, posterior tubercle, prethalamus, nucleus of the medial longitudinal fasciculus, midbrain tegmentum, isthmus, rhombencephalic reticular formation, and the putative nucleus of the solitary tract. Some PmCCK-expressing neuronal populations were only observed in adults, revealing important differences with larvae. We generated an antiserum to PmCCK-8 to enable immunohistochemical analysis of CCK expression, which revealed that GABA or glutamate, but not serotonin, tyrosine hydroxylase or neuropeptide Y, is co-expressed in some PmCCK-8-immunoreactive (ir) neurons. Importantly, this is the first demonstration of co-localization of GABA and CCK in neurons of a non-mammalian vertebrate. We also characterized extensive cholecystokinergic fibre systems of the CNS, including innervation of habenular subnuclei. A conspicuous PmCCK-8-ir tract ascending in the lateral rhombencephalon selectively innervates a glutamatergic population in the dorsal isthmic grey. Interestingly, this tract is reminiscent of the secondary gustatory/visceral tract of teleosts. In conclusion, this study provides important new information on the evolution of the cholecystokinergic system in vertebrates.

Neuroanatomical relationship between the cholinergic and tachykininergic systems in the adult human brainstem: An immunohistochemical study

The cholinergic system plays an important role in brain homeostasis and interacts with the neuropeptidergic systems, and the functional relationships between both systems are well known. However, in the brainstem the possible physiological interactions between neurokinins and acetylcholine are unknown, although both substances have been detected in the same brainstem nuclei and have been implicated in similar functions controlled from brainstem regions such as some cranial motor nuclei. The aim of this work is to determine whether these possible physiological interactions might have a neuroanatomical basis by means of the double immunohistochemical detection of neurokinins (NK) and the enzyme choline acetyl-transferase (ChAT) in the human brainstem. No double-labelled structures were detected, although both NK and ChAT were observed in cell bodies and fibers of the same brainstem nuclei. The distribution of immunoreactive fibers is widespread, and NK and ChAT were observed in several motor cranial nerves as well as in the substantia nigra. The results obtained in the present work provide a neuroanatomical basis for possible physiological interactions between NK and ChAT that may be carried out by volume-transmission mechanisms. These interactions might participate in motor regulation or in limbic pathways as well as influence on other neurotransmitter systems such as the dopaminergic system.

How words and space collide: Lexical and sublexical reading are reliant on separable reflexive and voluntary attention regions in hybrid tasks

Reading ability requires the coordination of many cognitive processes to be effective, including spatial attention. Recent functional magnetic resonance imaging (fMRI) evidence from Ekstrand et al. (2019) suggests that lexical reading is more associated with reflexive attentional orienting regions, whereas sublexical reading is more associated with voluntary attentional orienting regions. The current research sought to further examine the neuroanatomical relationship between reading and attention using a novel experimental design in fMRI. Participants performed four hybrid attentional orienting and reading-aloud tasks, where a reflexive or voluntary spatial cue preceded a lexical or sublexical target. Results indicated that lexical reading resulted in greater activation in the right temporoparietal junction, a reflexive orienting region. Sublexical reading resulted in greater activation in the left inferior frontal gyrus, left fusiform and inferior temporal gyrus, and right superior parietal lobule and intraparietal sulcus (voluntary orienting regions). Further, we found an interaction between reading and attention in the middle occipital gyrus. This study provides the most direct evidence to date that lexical and sublexical reading recruit differential attentional orienting regions during single-word reading in skilled readers. Implications for models of reading and attention, as well as for strategic remediation of their dysfunction, are discussed.

Meningiomas Originated at the Falcotentorial Region: Analysis of Topographic and Diagnostic Features Guiding an Optimal Surgical Planning

Meningiomas arising at the pineal region are a rare entity and still represent a great neurosurgical challenge given their deep location and critical neuroanatomic relationships. The optimal surgical approach to treat these lesions is still under debate. Our objective is to review the topographic and diagnostic features of these lesions, which can help to guide an optimal surgical outcome. We present 2 clinical cases of falcotentorial meningiomas successfully treated at our institution (2016-2017) with different surgical approaches. A literature review is performed, and a description of the classification, anatomic relationships, clinical features, diagnosis, and different surgical options and outcomes of these lesions is presented. The first patient was treated via a supracerebellar infratentorial approach, and the second patient was treated via a parieto-occipital interhemispheric approach. In both tumors, a gross total resection was achieved with no permanent neurologic deficits. In the literature review, gross total resection rates range from 33% to 100%, with no differences regarding the type of meningioma or the surgical approach performed. Permanent neurologic morbidity varies from 0% to 50%, and mortality rates range from 0% to 23%. The distortion and displacement of the vein of Galen and straight sinus represent the most important feature in the decision of optimal surgical approach. Pineal region meningiomas represent very infrequent, challenging lesions, and their description in the literature is scarce. The systematic topographic classification of these tumors and evaluation of the neuroanatomic structures involved are crucial to guide a safe and optimal surgical approach and achieve satisfactory outcomes.

Common Recruitment of Angular Gyrus in Episodic Autobiographical Memory and Bodily Self-Consciousness.

Parietal cortex and adjacent parts of the temporal cortex have recently been associated with bodily self-consciousness (BSC). Similarly, growing evidence suggests that the lateral parietal cortex is crucial for the subjective aspects of episodic autobiographical memory (EAM), which is based on the conscious experience of reliving past events. However, the neuroanatomical relationship between both fundamental aspects remains currently unexplored. Moreover, despite the wealth of neuroimaging data on EAM, only few neuroimaging studies have examined BSC and even fewer examined those aspects of BSC that are most closely related to EAM. Here, we investigated whether regions in the inferior parietal lobule (IPL) that have been involved in spatial aspects of BSC (self-location and first-person perspective), as described by Ionta et al. (2011) are also active in studies investigating autobiographical memory. To examine this relation, we thus compared the regions indicated in the study by Ionta et al. (2011) based on data in healthy participants and neurological patients, with the results from a meta-analytical study we performed based on functional neuroimaging studies on EAM and semantic autobiographical memory (SAM). We report an anatomical overlap bilaterally in the angular gyrus (AG), but not in other parietal or temporal lobe structures between BSC and EAM. Moreover, there was no overlap between BSC and SAM. These preliminary data suggest that the bilateral AG may be a key structure for the conscious re-experiencing of past life episodes (EAM) and the conscious on-line experience of being located and experiencing the world in first-person (BSC).

Distribution of somatostatin-28 (1-12), calcitonin gene-related peptide, and substance P in the squirrel monkey brainstem: an immunocytochemical study.

Using an immunocytochemical technique, we have studied the distribution of fibers and cell bodies containing somatostatin-28 (1-12) [SOM-28 (1-12)], calcitonin gene-related peptide (CGRP), and substanceP (SP) in the brainstem of Saimiri sciureus. The distribution of the peptidergic cell bodies was very restricted: perikarya containing SOM-28 (1-12) were only observed in the substantia grisea centralis, while no immunoreactive cell bodies containing CGRP or SP were visualized. Fibers containing SOM-28 (1-12), CGRP, or SP were widely distributed in the brainstem: immunoreactive fibers containing SOM-28 (1-12) showed the most widespread distribution and were the most abundant. The distribution of SOM-28 (1-12)-, CGRP- or SP-immunoreactive fibers was very similar. Colocalization of immunoreactive fibers containing SOM-28 (1-12), CGRP or SP was observed in many brainstem nuclei. A neuroanatomical relationship between CGRP- and SP-immunoreactive fibers was observed, although this relationship was less marked for SOM-28 (1-12) and SP and lower still for SOM-28 (1-12) and CGRP. The widespread distribution of the peptidergic fibers suggests that the studied neuropeptides are involved in many physiological actions.

Neuroanatomical Relationship of Neuronal Nitric Oxide Synthase to Gonadotropin-Releasing Hormone and Kisspeptin Neurons in Adult Female Sheep and Primates

Background: Neuronal intermediates that communicate estrogen and progesterone feedback to gonadotropin-releasing hormone (GnRH) neurons are essential for modulating reproductive cyclicity. Individually, kisspeptin and nitric oxide (NO) influence GnRH secretion. However, it is possible these 2 neuronal intermediates interact with one another to affect reproductive cyclicity. Methods: We investigated the neuroanatomical relationship of one isoform of the enzyme that synthesizes NO, neuronal NO synthase (nNOS), to kisspeptin and GnRH in adult female rhesus monkeys and sheep using dual-label immunofluorescence. Additionally, we evaluated if the phase of the reproductive cycle would affect these relationships. Results: Overall, no effect of the stage of cycle was observed for any variable in this study. In the arcuate nucleus (ARC) of sheep, 98.8 ± 3.5% of kisspeptin neurons colocalized with nNOS, and kisspeptin close-contacts were observed onto nNOS neurons. In contrast to ewes, no colocalization was observed between kisspeptin and nNOS in the infundibular ARC of primates, but kisspeptin fibers were apposed to nNOS neurons. In the preoptic area of ewes, 15.0 ± 4.2% of GnRH neurons colocalized with nNOS. In primates, 38.8 ± 10.1% of GnRH neurons in the mediobasal hypothalamus colocalized with nNOS, and GnRH close-contacts were observed onto nNOS neurons in both sheep and primates. Conclusion: Although species differences were observed, this work establishes a neuroanatomical framework between nNOS and kisspeptin and nNOS and GnRH in adult female nonhuman primates and sheep.

Anatomical Correlates of Uncontrollable Laughter With Unilateral Subthalamic Deep Brain Stimulation in Parkinson’s Disease

Subthalamic nucleus deep brain stimulation (STN-DBS) is a well-established treatment for the management of motor complications in Parkinson's disease. Uncontrollable laughter has been reported as a rare side effect of STN stimulation. The precise mechanism responsible for this unique phenomenon remains unclear. We examined in detail the DBS electrode position and stimulation parameters in two patients with uncontrollable laughter during programming after STN-DBS surgery and illustrated the anatomical correlates of the acute mood changes with STN stimulation. Unilateral STN-DBS induced uncontrollable laughter with activation of the most ventral contacts in both patients. However, the location of the electrodes responsible for this adverse effect differed between the patients. In the first patient, the DBS lead was placed more inferiorly and medially within the STN. In the second patient, the DBS lead was implanted more anteriorly and inferiorly than initially planned at the level of the substantia nigra reticulata (SNr). Unilateral STN-DBS can induce acute uncontrollable laughter with activation of electrodes located more anterior, medial, and inferior in relationship with the standard stereotactic STN target. We suggest that simulation of ventral and medial STN, surrounding limbic structures or the SNr, is the most plausible anatomical substrate responsible for this acute mood and behavioral change. Our findings provide insight into the complex functional neuroanatomical relationship of the STN and adjacent structures important for mood and behavior. DBS programming with more dorsal and lateral contacts within the STN should be entertained to minimize the emotional side effects.

Neuroanatomical connections between kisspeptin neurones and somatostatin neurones in female and male rat hypothalamus: a possible involvement of SSTR1 in kisspeptin release.

Somatostatin (SST) a neuropeptide involved in the central modulation of several physiological functions, is co-distributed in the same hypothalamic areas as kisspeptin (KP), the most potent secretagogue of the gonadotropin-releasing hormone (GnRH) secretion known to date. As SST infused intracerebroventricularly (icv) evoked a potent inhibition of GnRH release, we explored neuroanatomical relationships between KP and SST populations in male and female rats. For that, intact males and ovariectomised oestradiol-replaced females were killed and their brains processed in order to simultaneously detect KP, SST and synapsin, a marker for synapses. We observed numerous appositions of KP on SST neurones both in female and male arcuate nucleus (ARC) and ventromedial hypothalamus. A large association between SST terminals and KP neurones at the level of the pre-optic area (POA) was also observed in female rats and in a more limited frame in males. Finally, most KP neurones from the ARC showed SST appositions in both sexes. To determine whether SST could affect KP cell activity, we assessed whether SST receptors (SSTR) were present on KP neurones in the ARC. We also looked for the presence of SSTR1 and SSTR2A in the brain of male rats. Brains were processed through a sequential double immunocytochemistry in order to detect KP and SSTR1 or KP and SSTR2A. We observed overlapping distributions of immunoreactive neurones for SSTR1 and KP and counted approximately one third of KP neurones with SSTR1. In contrast, neurones labelled for SSTR2A or KP were often juxtaposed in the ARC and the occurrence of double-labelled neurones was sporadic (<5%). These results suggest that SST action on KP neurones would pass mainly through SSTR1 at the level of the ARC. This article is protected by copyright. All rights reserved.

Kisspeptin, gonadotrophin-releasing hormone and oestrogen receptor α colocalise with neuronal nitric oxide synthase neurones in prepubertal female sheep.

Puberty is a process that integrates multiple inputs ultimately resulting in an increase in gonadotrophin-releasing hormone (GnRH) secretion. Although kisspeptin neurones play an integral role in GnRH secretion and puberty onset, other systems are also likely important. One potential component is nitric oxide (NO), a gaseous neurotransmitter synthesised by nitric oxide synthase (NOS). The present study aimed to neuroanatomically characterise neuronal NOS (nNOS) in prepubertal female sheep and determine whether oestradiol exerts effects on this system. Luteinising hormone secretion was reduced by oestradiol treatment in prepubertal ovariectomised ewes. Neurones immunoreactive for nNOS were identified in several areas, with the greatest number present in the ventrolateral portion of the ventromedial hypothalamus, followed by the ventromedial hypothalamus, preoptic area (POA) and arcuate nucleus (ARC). Next, we determined whether nNOS neurones contained oestrogen receptor (ER)α and could potentially communicate oestradiol (E2 ) feedback to GnRH neurones. Neuronal NOS neurones contained ERα with the percentage of coexpression (12%-40%) depending upon the area analysed. We next investigated whether a neuroanatomical relationship existed between nNOS and kisspeptin or nNOS and GnRH neurones. A high percentage of kisspeptin neurones in the POA (79%) and ARC (98%) colocalised with nNOS. Kisspeptin close contacts were also associated with nNOS neurones. A greater number of close contacts were observed in the ARC than the POA. A high percentage of POA GnRH neurones (79%) also expressed nNOS, although no GnRH close contacts were observed onto nNOS neurones. Neither the numbers of nNOS neurones in the POA or hypothalamus, nor the percentage of nNOS coexpression with GnRH, kisspeptin or ERα were influenced by oestradiol. These experiments reveal that a neuroanatomical relationship exists between both nNOS and kisspeptin and nNOS and GnRH in prepubertal ewes. Therefore, nNOS may act both directly and indirectly to influence GnRH secretion in prepubertal sheep.

A Technical Guide for Fiber Tract Dissection of the Internal Capsule.

Dissection of white fibers is important in identifying detailed neuroanatomical relationships. With tractrography it is possible to transport and apply this knowledge in a practical way to treat many diseases involving the white matter. The Klingler method, subsequently disseminated by Türe with slight modifications was used. We review some historical aspects of white fibers and provide a guide for dissection of the internal capsule. The removal of gray matter allowed us to obtain a view of the white matter. We removed all U-shaped fibers to expose the insular cortex. The cortex of the insular lobe was removed, which exposed the extreme capsule. The removal of the claustrum exposed the external capsule, which covers the lentiform nucleus, specifically the putamen. During dissection, removing some fibers of the external capsule produced windows in which the putamen could be medially visualized. Since the internal capsule lies medial to the lentiform nucleus, it was necessary to remove the nucleus in order to expose the internal capsule. We identified five regions of the internal capsule: the anterior limb, genu, posterior limb, and sublenticular and retrolenticular parts. Finally, we determined that the fibers of the corona radiata condense into the internal capsule at the level of the superior border of the lentiform nucleus. Knowledge gained with the cadaveric fiber dissection technique can be applied in microsurgical practice and can be used to evaluate the surgical treatment for different tumors and vascular malformations.