Neurons in the hypothalamic paraventricular nucleus send collaterals to the spinal cord and to the rostral ventrolateral medulla in the rat

Shafton, Anthony D; Ryan, Andrew; Badoer, Emilio

doi:10.1016/s0006-8993(98)00587-3

Cited by 240 publications

(198 citation statements)

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“…14,15 Moreover, these responses were found to be highly reproducible in control experiments, when bicuculline microinjections were made into the PVN before and after injections of losartan, L-158,809, or muscimol into the contralateral RVLM, which is not part of the descending pathway from the PVN to the spinal sympathetic outflow. 12 Thus, the fact that the pressor and sympathoexcitatory response to microinjections of bicuculline were consistently reduced only after microinjection of losartan, L-158,809, or muscimol into the ipsilateral RVLM indicates that this reduction was specifically due to an action of these compounds on the synaptic transmission of signals to RVLM neurons originating from the PVN.…”

Section: Discussionmentioning

confidence: 96%

“…12 As a control, the effect on the PVN-evoked response of blockade of AT 1 receptors in the RVLM on the contralateral side was also tested. In addition, we also tested the effect on the PVN-evoked response of inhibition of neurons (by microinjection of the GABA A receptor agonist muscimol) in either the ipsilateral or contralateral RVLM.…”

Section: Responses Evoked From the Pvnmentioning

confidence: 99%

“…It has been shown, however, that both the PVN and the lateral parabrachial nucleus in the pons contain neurons that are immunoreactive for Ang II. 20 The PVN projects directly to the RVLM, 12 whereas the lateral parabrachial nucleus projects to the RVLM 21 but also receives afferent inputs from the PVN. 19 Thus, activation of the PVN could lead to the release of Ang II from the terminals of axons originating from Ang IIcontaining cell bodies in the PVN itself or in the lateral parabrachial nucleus (or other relay nucleus).…”

Section: Tagawa and Dampney Function Of At 1 Receptors On Rvlm Pressomentioning

confidence: 99%

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AT ₁ Receptors Mediate Excitatory Inputs to Rostral Ventrolateral Medulla Pressor Neurons From Hypothalamus

1999

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Abstract-Angiotensin II type 1 (AT 1 ) receptors are located on pressor neurons in the rostral ventrolateral medulla, and their activation results in an increase in arterial pressure. However, the normal role of these AT 1 receptors in cardiovascular regulation is unknown. In this study, we tested the hypothesis that these receptors mediate synaptic excitation of rostral ventrolateral medullary pressor neurons in response to activation of the hypothalamic paraventricular nucleus. In anesthetized rats, microinjections of the ␥-aminobutyric acid receptor antagonist bicuculline were made into the paraventricular nucleus; this injection causes activation of the nucleus as a consequence of disinhibition. The pressor and sympathoexcitatory responses evoked by paraventricular nucleus activation were significantly reduced (by Ϸ40% to 50%) after microinjection of the specific AT 1 receptor antagonists losartan or L-158,809 into the rostral ventrolateral medulla on the ipsilateral, but not contralateral, side. These responses were reduced to a similar degree after microinjections of the neuroinhibitory compound muscimol into the ipsilateral, but not contralateral, rostral ventrolateral medulla. However, bilateral microinjections of the glutamate receptor antagonist kynurenic acid into the rostral ventrolateral medulla had no effect on the responses evoked from the paraventricular nucleus. Conversely, bilateral microinjections of kynurenic acid into the rostral ventrolateral medulla virtually abolished the somatosympathoexcitatory reflex, whereas bilateral microinjections of losartan or L-158,809 had no effect on this reflex. The results indicate that excitatory synaptic inputs to pressor neurons in the rostral ventrolateral medulla arising from activation of the paraventricular nucleus are mediated predominantly by AT 1 receptors. (Hypertension. 1999;34:1301-1307.)Key Words: angiotensin II Ⅲ blood pressure Ⅲ brain Ⅲ receptors, glutamate Ⅲ bicuculline Ⅲ blood vessels I t is well established that the rostral part of the ventrolateral medulla (RVLM) contains a group of spinally projecting sympathoexcitatory neurons that play a crucial role in the tonic and phasic regulation of sympathetic vasomotor activity and arterial blood pressure (for reviews see References 1 and 2). These neurons are a site of convergence of central pathways subserving many cardiovascular reflexes as well as responses evoked from higher brain regions. 1,2 Numerous studies have demonstrated that glutamate and ␥-aminobutyric acid (GABA) receptors play a major role in the synaptic regulation of RVLM sympathoexcitatory neurons. 1,2 There is also evidence, however, indicating that angiotensin (Ang) receptors may also play a role in the synaptic regulation of these neurons. First, studies using in vitro autoradiography have shown that there is a high density of Ang receptors in the RVLM of several mammalian species, including humans (for review see Reference 3). These receptors are predominantly Ang II type 1 (AT 1 ) receptors, and their location corresponds...

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Section: Discussionmentioning

confidence: 96%

Section: Responses Evoked From the Pvnmentioning

confidence: 99%

Section: Tagawa and Dampney Function Of At 1 Receptors On Rvlm Pressomentioning

confidence: 99%

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AT ₁ Receptors Mediate Excitatory Inputs to Rostral Ventrolateral Medulla Pressor Neurons From Hypothalamus

1999

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“…Because anatomical studies have shown that 15-20% of RVLM-projecting PVN neurons have branched axons that also target the IML (Pyner and Coote 2000;Shafton et al 1998;Stocker et al 2006), one would expect that a reasonably large sample of cells antidromically activated from the spinal cord would include at least some neurons with branched axons that also innervate the RVLM. This being the case, one would expect that some group I or group II neurons from our previous study should have had properties nearly identical to those of PVN-RVLM/IML neurons in the present study.…”

Section: Pvn-rvlm and Pvn-rvlm/iml Neurons And Support Of Sympatheticmentioning

confidence: 99%

“…One group monosynaptically targets the spinal intermediolateral cell column (IML; PVN-IML), the location of sympathetic preganglionic neurons (Saper et al 1976;Swanson and Sawchenko 1980). Another group innervates presympathetic neurons in the rostral ventrolateral medulla (RVLM; PVN-RVLM) (Pyner and Coote 2000;Shafton et al 1998;Stocker et al 2006;Swanson and Sawchenko 1980). A third and more recently identified group has branched axons that innervate both the RVLM and IML (PVN-RVLM/IML) (Pyner and Coote 2000;Shafton et al 1998;Stocker et al 2004a).…”

Section: Introductionmentioning

confidence: 99%

In Vivo Discharge Properties of Hypothalamic Paraventricular Nucleus Neurons With Axonal Projections to the Rostral Ventrolateral Medulla

Chen

Toney

2010

Journal of Neurophysiology

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Chen Q-H, Toney GM. In vivo discharge properties of hypothalamic paraventricular nucleus neurons with axonal projections to the rostral ventrolateral medulla. J Neurophysiol 103: 4 -15, 2010. First published November 4, 2009 doi:10.1152/jn.00094.2009. The hypothalamic paraventricular nucleus (PVN) and rostral ventrolateral medulla (RVLM) are key components of a neural network that generates and regulates sympathetic nerve activity (SNA). Although each region has been extensively studied, little is presently known about the in vivo discharge properties of individual PVN neurons that directly innervate the RVLM. Here extracellular recording was performed in anesthetized rats, and antidromic stimulation was used to identify single PVN neurons with axonal projections to the RVLM (n ϭ 94). Neurons were divided into two groups that had either unbranched axons terminating in the RVLM (i.e., PVN-RVLM neurons, n ϭ 65) or collateralized axons targeting both the RVLM and spinal cord [i.e., PVN-RVLM/ intermediolateral cell column (IML) neurons, n ϭ 29]. Many PVN-RVLM (32/65, 49%) and PVN-RVLM/IML (17/29, 59%) neurons were spontaneously active. The average firing frequency was not different across groups. Spike-triggered averaging revealed that spontaneous discharge of most neurons was temporally correlated with renal SNA (PVN-RVLM: 12/21, 57%; PVN-RVLM/IML: 6/9, 67%). Time histograms triggered by the electrocardiogram (ECG) R-wave indicated that discharge of most cells was also cardiac rhythmic (PVN-RVLM: 25/32, 78%; PVN-RVLM/IML: 10/17, 59%). Raising and lowering arterial blood pressure to increase and decrease arterial baroreceptor input caused a corresponding decrease and increase in firing frequency among cells of both groups (PVN-RVLM: 9/13, 69%; PVN-RVLM/IML: 4/4, 100%). These results indicate that PVN-RVLM and PVN-RVLM/IML neurons are both capable of contributing to basal sympathetic activity and its baroreflex modulation.

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Decussations of the descending paraventricular pathways to the brainstem and spinal cord autonomic centers

et al. 1999

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Decussations of descending fibers of the hypothalamic paraventricular nucleus (PVN) were investigated by using Phaseolus vulgaris‐leucoagglutinin (PHA‐L) in intact and brainstem‐operated rats. Fibers descend ipsilaterally along the brainstem and spinal cord and decussate at four levels: 1) Supramamillary decussations (SM). PVN fibers reach this area through the lateral hypothalamus and along the third ventricle in the dorsal hypothalamus. In the posterior hypothalamus some fibers crossover in the SM and terminate in the supramamillary region bilaterally. 2) Pontine tegmentum. PVN fibers run in the lateral part of the tegmentum arching to the basis of the pons. Some fibers crossover under the fourth ventricle. The locus ceruleus and the Barrington‘s nucleus receive bilateral innervation with ipsilateral dominance. 3) Commissural part of the nucleus of the solitary tract (NTS). The major crossover of PVN fibers is found here. The decussated fibers form a dense network here, and loop rostralward to innervate the entire NTS. A midsagittal knife‐cut through the NTS eliminated paraventricular‐fibers on the contralateral side. Synaptic contacts between PHA‐L‐labeled boutons and tyrozine hydroxilase‐positive neurons were verified in the NTS. The caudal ventrolateral medulla also receives bilateral innervation. 4) Lamina X of the thoracic spinal cord. Paraventricular fibers enter the lateral funiculus ipsilaterally and innervate the intermediolateral cell column (IML). Some fibers cross the midline ventral and dorsal to the central canal running to the contralateral IML, at the level of the decussation. Our results demonstrated that paraventricular projections form a continuous descending pathway on their side of origin, and provide crossover fibers which may terminate segmentally without forming long tracts after crossover. J. Comp. Neurol. 414:255–266, 1999. © 1999 Wiley‐Liss, Inc.

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Neurons in the hypothalamic paraventricular nucleus send collaterals to the spinal cord and to the rostral ventrolateral medulla in the rat

Cited by 240 publications

References 5 publications

AT ₁ Receptors Mediate Excitatory Inputs to Rostral Ventrolateral Medulla Pressor Neurons From Hypothalamus

AT ₁ Receptors Mediate Excitatory Inputs to Rostral Ventrolateral Medulla Pressor Neurons From Hypothalamus

In Vivo Discharge Properties of Hypothalamic Paraventricular Nucleus Neurons With Axonal Projections to the Rostral Ventrolateral Medulla

Decussations of the descending paraventricular pathways to the brainstem and spinal cord autonomic centers

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Neurons in the hypothalamic paraventricular nucleus send collaterals to the spinal cord and to the rostral ventrolateral medulla in the rat

Cited by 240 publications

References 5 publications

AT 1 Receptors Mediate Excitatory Inputs to Rostral Ventrolateral Medulla Pressor Neurons From Hypothalamus

AT 1 Receptors Mediate Excitatory Inputs to Rostral Ventrolateral Medulla Pressor Neurons From Hypothalamus

In Vivo Discharge Properties of Hypothalamic Paraventricular Nucleus Neurons With Axonal Projections to the Rostral Ventrolateral Medulla

Decussations of the descending paraventricular pathways to the brainstem and spinal cord autonomic centers

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AT ₁ Receptors Mediate Excitatory Inputs to Rostral Ventrolateral Medulla Pressor Neurons From Hypothalamus

AT ₁ Receptors Mediate Excitatory Inputs to Rostral Ventrolateral Medulla Pressor Neurons From Hypothalamus