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Jens D Mikkelsen - One of the best experts on this subject based on the ideXlab platform.
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origin of projections from the midbrain raphe nuclei to the hypothalamic Paraventricular Nucleus in the rat a combined retrograde and anterograde tracing study
1996Co-Authors: Philip J Larsen, Anders Hayschmidt, Niels Vrang, Jens D MikkelsenAbstract:Abstract A number of neuronal functions governed by the hypothalamic Paraventricular Nucleus are influenced by serotonin, and it is generally believed that the moderate density of serotonin-immunoreactive fibres and terminals within the Paraventricular Nucleus originates from the midbrain dorsal and median raphe nuclei. To further evaluate the intricate anatomy of projections from brain stem raphe nuclei of the rat, a combination of retrograde and anterograde tracing experiments were conducted to determine the medullary raphe nuclei projection to the Paraventricular Nucleus. Rhodamine-labelled latex microspheres, Cholera toxin subunit B and FluoroGold we used as retrograde tracers. Intracerebroventricular injections into the third ventricle of all retrograde tracers labelled a distinct population of neurons in the dorsal raphe situated in the subependymal stratum adjacent to the cerebral aqueduct indicating that these cells take up the tracer from the cerebrospinal fluid. Very few retrogradely labelled neurons were seen in the median raphe after i.c.v. administration of the tracers. Retrograde tracers delivered into the medial part of the Paraventricular Nucleus labelled no further cells in the midbrain dorsal and median raphe nuclei, whereas a substantial number of retrogradely labelled cells emerged in the pontine raphe magnus. However, when the retrograde tracers were delivered into the lateral part of the Paraventricular Nucleus, avoiding leakage of the tracer into the ventricle, very few labelled neurons were seen in the dorsal and median raphe, whereas the prominent labelling of raphe magnus neurons persisted. The anatomical organization of nerve fibres terminating in the area of Paraventricular Nucleus originating from midbrain raphe nuclei was studied in a series of anterograde tracing experiments using the plant lectin Phaseolus vulgaris leucoagglutinin. Injections delivered into the dorsal raphe or median raphe labelled but a few fibres in the Paraventricular Nucleus proper. A high number of fine calibered nerve fibres overlying the ependyma adjacent to the Paraventricular Nucleus was, however, seen after the injections into the subependymal rostral part of the dorsal raphe. Injections delivered into the raphe magnus gave rise to a dense plexus of terminating fibres in the parvicellular parts of the Paraventricular Nucleus and moderately innervated the posterior magnocellular part of the Paraventricular Nucleus as well as the magnocellular supraoptic Nucleus. Concomitant visualization of serotonin-immunoreactive neurons and retrograde FluoroGold-tracing from the Paraventricular Nucleus revealed that none of the serotonergic neurons of the raphe magnus projects to this Nucleus, while a few of the neurons putatively projecting to the Paraventricular Nucleus from the median raphe are serotonergic. The current observations suggest that the raphe magnus constitute by far the largest raphe input to the Paraventricular Nucleus and strongly questions the earlier held view that most raphe fibres innervating the Paraventricular Nucleus are derived from the midbrain dorsal and median raphe. However, the source of serotonergic innervation of the Paraventricular Nucleus remains elusive.
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origin of projections from the midbrain raphe nuclei to the hypothalamic Paraventricular Nucleus in the rat a combined retrograde and anterograde tracing study
1996Co-Authors: Philip J Larsen, Anders Hayschmidt, Niels Vrang, Jens D MikkelsenAbstract:A number of neuronal functions governed by the hypothalamic Paraventricular Nucleus are influenced by serotonin, and it is generally believed that the moderate density of serotonin-immunoreactive fibres and terminals within the Paraventricular Nucleus originates from the midbrain dorsal and median raphe nuclei. To further evaluate the intricate anatomy of projections from brain stem raphe nuclei of the rat, a combination of retrograde and anterograde tracing experiments were conducted to determine the medullary raphe nuclei projection to the Paraventricular Nucleus. Rhodamine-labelled latex microspheres, Cholera toxin subunit B and FluoroGold we used as retrograde tracers. Intracerebroventricular injections into the third ventricle of all retrograde tracers labelled a distinct population of neurons in the dorsal raphe situated in the subependymal stratum adjacent to the cerebral aqueduct indicating that these cells take up the tracer from the cerebrospinal fluid. Very few retrogradely labelled neurons were seen in the median raphe after i.c.v. administration of the tracers. Retrograde tracers delivered into the medial part of the Paraventricular Nucleus labelled no further cells in the midbrain dorsal and median raphe nuclei, whereas a substantial number of retrogradely labelled cells emerged in the pontine raphe magnus. However, when the retrograde tracers were delivered into the lateral part of the Paraventricular Nucleus, avoiding leakage of the tracer into the ventricle, very few labelled neurons were seen in the dorsal and median raphe, whereas the prominent labelling of raphe magnus neurons persisted. The anatomical organization of nerve fibres terminating in the area of the Paraventricular Nucleus originating from midbrain raphe nuclei was studied in a series of anterograde tracing experiments using the plant lectin Phaseolus vulgaris leucoagglutinin. Injections delivered into the dorsal raphe or median raphe labelled but a few fibres in the Paraventricular Nucleus proper. A high number of fine calibered nerve fibres overlying the ependyma adjacent to the Paraventricular Nucleus was, however, seen after the injections into the subependymal rostral part of the dorsal raphe. Injections delivered into the raphe magnus gave rise to a dense plexus of terminating fibres in the parvicellular parts of the Paraventricular Nucleus and moderately innervated the posterior magnocellular part of the Paraventricular Nucleus as well as the magnocellular supraoptic Nucleus. Concomitant visualization of serotonin-immunoreactive neurons and retrograde FluoroGold-tracing from the Paraventricular Nucleus revealed that none of the serotonergic neurons of the raphe magnus projects to this Nucleus, while a few of the neurons putatively projecting to the Paraventricular Nucleus from the median raphe are serotonergic. The current observations suggest that the raphe magnus constitute by far the largest raphe input to the Paraventricular Nucleus and strongly questions the earlier held view that most raphe fibres innervating the Paraventricular Nucleus are derived from the midbrain dorsal and median raphe. However, the source of serotonergic innervation of the Paraventricular Nucleus remains elusive.
Philip J Larsen - One of the best experts on this subject based on the ideXlab platform.
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origin of projections from the midbrain raphe nuclei to the hypothalamic Paraventricular Nucleus in the rat a combined retrograde and anterograde tracing study
1996Co-Authors: Philip J Larsen, Anders Hayschmidt, Niels Vrang, Jens D MikkelsenAbstract:Abstract A number of neuronal functions governed by the hypothalamic Paraventricular Nucleus are influenced by serotonin, and it is generally believed that the moderate density of serotonin-immunoreactive fibres and terminals within the Paraventricular Nucleus originates from the midbrain dorsal and median raphe nuclei. To further evaluate the intricate anatomy of projections from brain stem raphe nuclei of the rat, a combination of retrograde and anterograde tracing experiments were conducted to determine the medullary raphe nuclei projection to the Paraventricular Nucleus. Rhodamine-labelled latex microspheres, Cholera toxin subunit B and FluoroGold we used as retrograde tracers. Intracerebroventricular injections into the third ventricle of all retrograde tracers labelled a distinct population of neurons in the dorsal raphe situated in the subependymal stratum adjacent to the cerebral aqueduct indicating that these cells take up the tracer from the cerebrospinal fluid. Very few retrogradely labelled neurons were seen in the median raphe after i.c.v. administration of the tracers. Retrograde tracers delivered into the medial part of the Paraventricular Nucleus labelled no further cells in the midbrain dorsal and median raphe nuclei, whereas a substantial number of retrogradely labelled cells emerged in the pontine raphe magnus. However, when the retrograde tracers were delivered into the lateral part of the Paraventricular Nucleus, avoiding leakage of the tracer into the ventricle, very few labelled neurons were seen in the dorsal and median raphe, whereas the prominent labelling of raphe magnus neurons persisted. The anatomical organization of nerve fibres terminating in the area of Paraventricular Nucleus originating from midbrain raphe nuclei was studied in a series of anterograde tracing experiments using the plant lectin Phaseolus vulgaris leucoagglutinin. Injections delivered into the dorsal raphe or median raphe labelled but a few fibres in the Paraventricular Nucleus proper. A high number of fine calibered nerve fibres overlying the ependyma adjacent to the Paraventricular Nucleus was, however, seen after the injections into the subependymal rostral part of the dorsal raphe. Injections delivered into the raphe magnus gave rise to a dense plexus of terminating fibres in the parvicellular parts of the Paraventricular Nucleus and moderately innervated the posterior magnocellular part of the Paraventricular Nucleus as well as the magnocellular supraoptic Nucleus. Concomitant visualization of serotonin-immunoreactive neurons and retrograde FluoroGold-tracing from the Paraventricular Nucleus revealed that none of the serotonergic neurons of the raphe magnus projects to this Nucleus, while a few of the neurons putatively projecting to the Paraventricular Nucleus from the median raphe are serotonergic. The current observations suggest that the raphe magnus constitute by far the largest raphe input to the Paraventricular Nucleus and strongly questions the earlier held view that most raphe fibres innervating the Paraventricular Nucleus are derived from the midbrain dorsal and median raphe. However, the source of serotonergic innervation of the Paraventricular Nucleus remains elusive.
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origin of projections from the midbrain raphe nuclei to the hypothalamic Paraventricular Nucleus in the rat a combined retrograde and anterograde tracing study
1996Co-Authors: Philip J Larsen, Anders Hayschmidt, Niels Vrang, Jens D MikkelsenAbstract:A number of neuronal functions governed by the hypothalamic Paraventricular Nucleus are influenced by serotonin, and it is generally believed that the moderate density of serotonin-immunoreactive fibres and terminals within the Paraventricular Nucleus originates from the midbrain dorsal and median raphe nuclei. To further evaluate the intricate anatomy of projections from brain stem raphe nuclei of the rat, a combination of retrograde and anterograde tracing experiments were conducted to determine the medullary raphe nuclei projection to the Paraventricular Nucleus. Rhodamine-labelled latex microspheres, Cholera toxin subunit B and FluoroGold we used as retrograde tracers. Intracerebroventricular injections into the third ventricle of all retrograde tracers labelled a distinct population of neurons in the dorsal raphe situated in the subependymal stratum adjacent to the cerebral aqueduct indicating that these cells take up the tracer from the cerebrospinal fluid. Very few retrogradely labelled neurons were seen in the median raphe after i.c.v. administration of the tracers. Retrograde tracers delivered into the medial part of the Paraventricular Nucleus labelled no further cells in the midbrain dorsal and median raphe nuclei, whereas a substantial number of retrogradely labelled cells emerged in the pontine raphe magnus. However, when the retrograde tracers were delivered into the lateral part of the Paraventricular Nucleus, avoiding leakage of the tracer into the ventricle, very few labelled neurons were seen in the dorsal and median raphe, whereas the prominent labelling of raphe magnus neurons persisted. The anatomical organization of nerve fibres terminating in the area of the Paraventricular Nucleus originating from midbrain raphe nuclei was studied in a series of anterograde tracing experiments using the plant lectin Phaseolus vulgaris leucoagglutinin. Injections delivered into the dorsal raphe or median raphe labelled but a few fibres in the Paraventricular Nucleus proper. A high number of fine calibered nerve fibres overlying the ependyma adjacent to the Paraventricular Nucleus was, however, seen after the injections into the subependymal rostral part of the dorsal raphe. Injections delivered into the raphe magnus gave rise to a dense plexus of terminating fibres in the parvicellular parts of the Paraventricular Nucleus and moderately innervated the posterior magnocellular part of the Paraventricular Nucleus as well as the magnocellular supraoptic Nucleus. Concomitant visualization of serotonin-immunoreactive neurons and retrograde FluoroGold-tracing from the Paraventricular Nucleus revealed that none of the serotonergic neurons of the raphe magnus projects to this Nucleus, while a few of the neurons putatively projecting to the Paraventricular Nucleus from the median raphe are serotonergic. The current observations suggest that the raphe magnus constitute by far the largest raphe input to the Paraventricular Nucleus and strongly questions the earlier held view that most raphe fibres innervating the Paraventricular Nucleus are derived from the midbrain dorsal and median raphe. However, the source of serotonergic innervation of the Paraventricular Nucleus remains elusive.
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substance p inhibits the release of anterior pituitary adrenocorticotrophin via a central mechanism involving corticotrophin releasing factor containing neurons in the hypothalamic Paraventricular Nucleus
1993Co-Authors: Philip J Larsen, David S Jessop, Hemant Patel, Stafford L Lightman, Hardial S ChowdreyAbstract:Chronic osmotic stimulation influences the hypothalamo-adenohypophysial axis by inhibiting the synthesis of hypothalamic corticotrophin-releasing factor (CRF-41) and subsequently the secretion of basal and adrenalectomy-elevated adrenocorticotrophin from the adenohypophysis. In the present study, we used a substance P antagonist to test the hypothesis that this inhibition is mediated centrally by substance P or other tachykinins. In control rats and rats given 2% saline to drink for 12 days, intracerebroventricular administration of a substance P antagonist elevated plasma adrenocorticotrophin and corticosterone levels. Using quantitative in situ hybridization histochemistry, it was also demonstrated that CRF mRNA increased in the medial parvocellular division of the Paraventricular Nucleus of saline-treated as well as control rats 6 h after intracerebroventricular administration of the antagonist, while vasopressin mRNA in the medial parvocellular division of the Paraventricular Nucleus was increased in the control animals only. These results provide evidence that central endogenous substance P has an inhibitory influence over the synthesis and release of CRF-41 both under normal conditions and during a chronic osmotic stimulus.
Jaideep S Bains - One of the best experts on this subject based on the ideXlab platform.
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Paraventricular Nucleus crh neurons encode stress controllability and regulate defensive behavior selection
2020Co-Authors: Nuria Daviu, Tamas Fuzesi, David Rosenegger, Neilen P Rasiah, Tonilee Sterley, Govind Peringod, Jaideep S BainsAbstract:In humans and rodents, the perception of control during stressful events has lasting behavioral consequences. These consequences are apparent even in situations that are distinct from the stress context, but how the brain links prior stressful experience to subsequent behaviors remains poorly understood. By assessing innate defensive behavior in a looming-shadow task, we show that the initiation of an escape response is preceded by an increase in the activity of corticotropin-releasing hormone (CRH) neurons in the Paraventricular Nucleus (PVN) of the hypothalamus (CRHPVN neurons). This anticipatory increase is sensitive to stressful stimuli that have high or low levels of outcome control. Specifically, experimental stress with high outcome control increases CRHPVN neuron anticipatory activity, which increases escape behavior in an unrelated context. By contrast, stress with no outcome control prevents the emergence of this anticipatory activity and decreases subsequent escape behavior. These observations indicate that CRHPVN neurons encode stress controllability and contribute to shifts between active and passive innate defensive strategies. Prior stressful experience affects subsequent behavior even in different situations. Daviu et al. demonstrate that CRHPVN neurons encode stress controllability and contribute to shifts between active and passive innate defensive strategies.
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Paraventricular Nucleus crh neurons encode stress controllability and regulate defensive behavior selection
2020Co-Authors: Nuria Daviu, Tamas Fuzesi, David Rosenegger, Neilen P Rasiah, Tonilee Sterley, Govind Peringod, Jaideep S BainsAbstract:In humans and rodents, the perception of control during stressful events has lasting behavioral consequences. These consequences are apparent even in situations that are distinct from the stress context, but how the brain links prior stressful experience to subsequent behaviors remains poorly understood. By assessing innate defensive behavior in a looming-shadow task, we show that the initiation of an escape response is preceded by an increase in the activity of corticotropin-releasing hormone (CRH) neurons in the Paraventricular Nucleus (PVN) of the hypothalamus (CRHPVN neurons). This anticipatory increase is sensitive to stressful stimuli that have high or low levels of outcome control. Specifically, experimental stress with high outcome control increases CRHPVN neuron anticipatory activity, which increases escape behavior in an unrelated context. By contrast, stress with no outcome control prevents the emergence of this anticipatory activity and decreases subsequent escape behavior. These observations indicate that CRHPVN neurons encode stress controllability and contribute to shifts between active and passive innate defensive strategies.
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repeated stress impairs endocannabinoid signaling in the Paraventricular Nucleus of the hypothalamus
2010Co-Authors: Jaclyn I Wamsteeker, Brent J Kuzmiski, Jaideep S BainsAbstract:Endocannabinoids (eCBs) are ubiquitous retrograde signaling molecules in the nervous system that are recruited in response to robust neuronal activity or the activation of postsynaptic G-protein-coupled receptors. Physiologically, eCBs have been implicated as important mediators of the stress axis and they may contribute to the rapid feedback inhibition of the hypothalamic–pituitary–adrenal axis (HPA) by circulating corticosteroids (CORTs). Understanding the relationship between stress and eCBs, however, is complicated by observations that eCB signaling is itself sensitive to stress. The mechanisms that link stress to changes in synaptic eCB signaling and the impact of these changes on CORT-mediated negative feedback have not been resolved. Here, we show that repetitive immobilization stress, in juvenile male rats, causes a functional downregulation of CB1 receptors in the Paraventricular Nucleus of the hypothalamus (PVN). This loss of CB1 receptor signaling, which requires the activation of genomic glucocorticoid receptors, impairs both activity and receptor-dependent eCB signaling at GABA and glutamate synapses on parvocellular neuroendocrine cells in PVN. Our results provide a plausible mechanism for how stress can lead to alterations in CORT-mediated negative feedback and may contribute to the development of plasticity of HPA responses.
Alastair V Ferguson - One of the best experts on this subject based on the ideXlab platform.
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depolarizing actions of hydrogen sulfide on hypothalamic Paraventricular Nucleus neurons
2013Co-Authors: Sahara C Khademullah, Alastair V FergusonAbstract:Hydrogen sulfide (H2S) is a novel neurotransmitter that has been shown to influence cardiovascular functions as well and corticotrophin hormone (CRH) secretion. Since the Paraventricular Nucleus of the hypothalamus (PVN) is a central relay center for autonomic and endocrine functions, we sought to investigate the effects of H2S on the neuronal population of the PVN. Whole cell current clamp recordings were acquired from the PVN neurons and sodium hydrosulfide hydrate (NaHS) was bath applied at various concentrations (0.1, 1, 10, and 50 mM). NaHS (1, 10, and 50 mM) elicited a concentration-response relationship from the majority of recorded neurons, with almost exclusively depolarizing effects following administration. Cells responded and recovered from NaHS administration quickly and the effects were repeatable. Input differences from baseline and during the NaHS-induced depolarization uncovered a biphasic response, implicating both a potassium and non-selective cation conductance. The results from the neuronal population of the PVN shed light on the possible physiological role that H2S has in autonomic and endocrine function.
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angiotensinergic regulation of autonomic and neuroendocrine outputs critical roles for the subfornical organ and Paraventricular Nucleus
2009Co-Authors: Alastair V FergusonAbstract:Considerable recent work has focused on identifying the mechanisms through which circulating angiotensin II acts in the central nervous system (CNS) to control a variety of different autonomic and neuroendocrine effectors. The following review will focus on work identifying the subfornical organ (SFO), and its efferent projections to the Paraventricular Nucleus of the hypothalamus (PVN), as a critical component of the CNS circuitry activated by circulating angiotensin II. It will also summarize the current knowledge describing cellular mechanisms through which this peptide controls the excitability of both SFO and PVN neurons.
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the Paraventricular Nucleus of the hypothalamus a potential target for integrative treatment of autonomic dysfunction
2008Co-Authors: Alastair V Ferguson, Kevin J Latchford, Willis K SamsonAbstract:Background: The Paraventricular Nucleus of the hypothalamus (PVN) has emerged as one of the most important autonomic control centers in the brain, with neurons playing essential roles in controlling stress, metabolism, growth, reproduction, immune and other more traditional autonomic functions (gastrointestinal, renal and cardiovascular). Objectives: Traditionally the PVN was viewed as a Nucleus in which afferent inputs from other regions were faithfully translated into changes in single specific outputs, whether neuroendocrine or autonomic. Here we present data which suggest that the PVN plays significant and essential roles in integrating multiple sources of afferent input and sculpting an integrated autonomic output by concurrently modifying the excitability of multiple output pathways. In addition, we highlight recent work that suggests that dysfunction of such intranuclear integrative circuitry contributes to the pathology of conditions such as hypertension and congestive heart failure. Conclusions: ...
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nesfatin 1 influences the excitability of Paraventricular Nucleus neurones
2007Co-Authors: Christopher J Price, Willis K Samson, Ted D Hoyda, Alastair V FergusonAbstract:Nesfatin-1 is a newly-discovered satiety peptide found in several nuclei of the hypothalamus, including the Paraventricular Nucleus. To begin to understand the physiological mechanisms underlying these satiety-inducing actions, we examined the effects of nesfatin-1 on the excitability of neurones in the Paraventricular Nucleus. Whole-cell current-clamp recordings from rat Paraventricular Nucleus neurones showed nesfatin-1 to have either hyperpolarising or depolarising effects on the majority of neurones tested. Both types of response were observed in neurones irrespective of classification based on electrophysiological fingerprint (magnocellular, neuroendocrine or pre-autonomic) or molecular phenotype (vasopressin, oxytocin, corticotrophin-releasing hormone, thyrotrophin-releasing hormone or vesicular glutamate transporter), determined using single cell reverse transcription-poylmerase chain reaction. Consequently, we provide the first evidence that this peptide, which is produced in the Paraventricular Nucleus, has effects on the membrane potential of a large proportion of different subpopulations of neurones located in this Nucleus, and therefore identify nesfatin-1 as a potentially important regulator of Paraventricular Nucleus output.
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orexin actions in hypothalamic Paraventricular Nucleus physiological consequences and cellular correlates
2002Co-Authors: Willis K Samson, Meghan M Taylor, Matthew J Follwell, Alastair V FergusonAbstract:Abstract Orexinergic neurons originating in the perifornical, lateral hypothalamus project to numerous brain sites including neuroendocrine centers known to be important in the physiologic response to stress. Those projections suggest an action of endogenous orexin on adrenocorticotropin (ACTH) release, either by neuromodulatory effects in the Paraventricular Nucleus (PVN), or by neuroendocrine actions in the pituitary gland following release into the median eminence. We sought to determine if exogenously applied orexin A might act in the brain to alter ACTH release and to determine if a site of action in the hypothalamic Paraventricular Nucleus could be identified. Cerebroventricular administration of orexin A in conscious male rats resulted in a dose-related elevation in circulating ACTH levels. At 30 min post-infusion, ACTH levels were elevated 2.5-fold by the low dose of orexin A (0.3 nmol), 5.7-fold by the middle dose tested (1.0 nmol), and 7.5-fold by the highest dose tested (3.0 nmol). Pretreatment with a CRH-antagonist (i.v.) blocked the ability of i.c.v. administered orexin A to activate the hypothalamo-pituitary-adrenal (HPA) axis. Bath application of orexin A in hypothalamic slice preparations resulted in depolarizations (8.0±0.6 mV), accompanied by increases in spike frequency in identified magno- and parvocellular neurons in the PVN. Our data suggest a potential role for endogenous orexin in the hypothalamic regulation of stress hormone secretion.
Niels Vrang - One of the best experts on this subject based on the ideXlab platform.
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origin of projections from the midbrain raphe nuclei to the hypothalamic Paraventricular Nucleus in the rat a combined retrograde and anterograde tracing study
1996Co-Authors: Philip J Larsen, Anders Hayschmidt, Niels Vrang, Jens D MikkelsenAbstract:Abstract A number of neuronal functions governed by the hypothalamic Paraventricular Nucleus are influenced by serotonin, and it is generally believed that the moderate density of serotonin-immunoreactive fibres and terminals within the Paraventricular Nucleus originates from the midbrain dorsal and median raphe nuclei. To further evaluate the intricate anatomy of projections from brain stem raphe nuclei of the rat, a combination of retrograde and anterograde tracing experiments were conducted to determine the medullary raphe nuclei projection to the Paraventricular Nucleus. Rhodamine-labelled latex microspheres, Cholera toxin subunit B and FluoroGold we used as retrograde tracers. Intracerebroventricular injections into the third ventricle of all retrograde tracers labelled a distinct population of neurons in the dorsal raphe situated in the subependymal stratum adjacent to the cerebral aqueduct indicating that these cells take up the tracer from the cerebrospinal fluid. Very few retrogradely labelled neurons were seen in the median raphe after i.c.v. administration of the tracers. Retrograde tracers delivered into the medial part of the Paraventricular Nucleus labelled no further cells in the midbrain dorsal and median raphe nuclei, whereas a substantial number of retrogradely labelled cells emerged in the pontine raphe magnus. However, when the retrograde tracers were delivered into the lateral part of the Paraventricular Nucleus, avoiding leakage of the tracer into the ventricle, very few labelled neurons were seen in the dorsal and median raphe, whereas the prominent labelling of raphe magnus neurons persisted. The anatomical organization of nerve fibres terminating in the area of Paraventricular Nucleus originating from midbrain raphe nuclei was studied in a series of anterograde tracing experiments using the plant lectin Phaseolus vulgaris leucoagglutinin. Injections delivered into the dorsal raphe or median raphe labelled but a few fibres in the Paraventricular Nucleus proper. A high number of fine calibered nerve fibres overlying the ependyma adjacent to the Paraventricular Nucleus was, however, seen after the injections into the subependymal rostral part of the dorsal raphe. Injections delivered into the raphe magnus gave rise to a dense plexus of terminating fibres in the parvicellular parts of the Paraventricular Nucleus and moderately innervated the posterior magnocellular part of the Paraventricular Nucleus as well as the magnocellular supraoptic Nucleus. Concomitant visualization of serotonin-immunoreactive neurons and retrograde FluoroGold-tracing from the Paraventricular Nucleus revealed that none of the serotonergic neurons of the raphe magnus projects to this Nucleus, while a few of the neurons putatively projecting to the Paraventricular Nucleus from the median raphe are serotonergic. The current observations suggest that the raphe magnus constitute by far the largest raphe input to the Paraventricular Nucleus and strongly questions the earlier held view that most raphe fibres innervating the Paraventricular Nucleus are derived from the midbrain dorsal and median raphe. However, the source of serotonergic innervation of the Paraventricular Nucleus remains elusive.
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origin of projections from the midbrain raphe nuclei to the hypothalamic Paraventricular Nucleus in the rat a combined retrograde and anterograde tracing study
1996Co-Authors: Philip J Larsen, Anders Hayschmidt, Niels Vrang, Jens D MikkelsenAbstract:A number of neuronal functions governed by the hypothalamic Paraventricular Nucleus are influenced by serotonin, and it is generally believed that the moderate density of serotonin-immunoreactive fibres and terminals within the Paraventricular Nucleus originates from the midbrain dorsal and median raphe nuclei. To further evaluate the intricate anatomy of projections from brain stem raphe nuclei of the rat, a combination of retrograde and anterograde tracing experiments were conducted to determine the medullary raphe nuclei projection to the Paraventricular Nucleus. Rhodamine-labelled latex microspheres, Cholera toxin subunit B and FluoroGold we used as retrograde tracers. Intracerebroventricular injections into the third ventricle of all retrograde tracers labelled a distinct population of neurons in the dorsal raphe situated in the subependymal stratum adjacent to the cerebral aqueduct indicating that these cells take up the tracer from the cerebrospinal fluid. Very few retrogradely labelled neurons were seen in the median raphe after i.c.v. administration of the tracers. Retrograde tracers delivered into the medial part of the Paraventricular Nucleus labelled no further cells in the midbrain dorsal and median raphe nuclei, whereas a substantial number of retrogradely labelled cells emerged in the pontine raphe magnus. However, when the retrograde tracers were delivered into the lateral part of the Paraventricular Nucleus, avoiding leakage of the tracer into the ventricle, very few labelled neurons were seen in the dorsal and median raphe, whereas the prominent labelling of raphe magnus neurons persisted. The anatomical organization of nerve fibres terminating in the area of the Paraventricular Nucleus originating from midbrain raphe nuclei was studied in a series of anterograde tracing experiments using the plant lectin Phaseolus vulgaris leucoagglutinin. Injections delivered into the dorsal raphe or median raphe labelled but a few fibres in the Paraventricular Nucleus proper. A high number of fine calibered nerve fibres overlying the ependyma adjacent to the Paraventricular Nucleus was, however, seen after the injections into the subependymal rostral part of the dorsal raphe. Injections delivered into the raphe magnus gave rise to a dense plexus of terminating fibres in the parvicellular parts of the Paraventricular Nucleus and moderately innervated the posterior magnocellular part of the Paraventricular Nucleus as well as the magnocellular supraoptic Nucleus. Concomitant visualization of serotonin-immunoreactive neurons and retrograde FluoroGold-tracing from the Paraventricular Nucleus revealed that none of the serotonergic neurons of the raphe magnus projects to this Nucleus, while a few of the neurons putatively projecting to the Paraventricular Nucleus from the median raphe are serotonergic. The current observations suggest that the raphe magnus constitute by far the largest raphe input to the Paraventricular Nucleus and strongly questions the earlier held view that most raphe fibres innervating the Paraventricular Nucleus are derived from the midbrain dorsal and median raphe. However, the source of serotonergic innervation of the Paraventricular Nucleus remains elusive.
