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Excitatory amino acid receptors mediate asymmetry and lateralization in the descending cardiovascular pathways from the dorsomedial hypothalamus.

Xavier CH, Ianzer D, Lima AM, Marins FR, Pedrino GR, Vaz G, Menezes GB, Nalivaiko E, Fontes MA - PLoS ONE (2014)

Bottom Line: We recently reported that removal of GABA-ergic tone in the unilateral DMH produces: asymmetry, that is, a right- (R-) sided predominance in cardiac chronotropism, and lateralization, that is, a greater increase in ipsilateral renal sympathetic activity (RSNA).We conclude that EAA receptors contribute to the right-sided predominance in cardiac chronotropism.This interhemispheric difference that involves EAA receptors was observed in the DMH but not in the PAG.

View Article: PubMed Central - PubMed

Affiliation: Laboratório de Fisiologia e Terapêutica Cardiovascular, Departamento Ciências Fisiológicas, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil; Departamento de Fisiologia e Biofísica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.

ABSTRACT
The dorsomedial hypothalamus (DMH) and lateral/dorsolateral periaqueductal gray (PAG) are anatomically and functionally connected. Both the DMH and PAG depend on glutamatergic inputs for activation. We recently reported that removal of GABA-ergic tone in the unilateral DMH produces: asymmetry, that is, a right- (R-) sided predominance in cardiac chronotropism, and lateralization, that is, a greater increase in ipsilateral renal sympathetic activity (RSNA). In the current study, we investigated whether excitatory amino acid (EAA) receptors in the DMH-PAG pathway contribute to the functional interhemispheric difference. In urethane (1.2 to 1.4 g/kg, i.p.) anesthetized rats, we observed that: (i) nanoinjections of N-methyl D-aspartate (NMDA 100 pmol/100 nl) into the unilateral DMH produced the same right-sided predominance in the control of cardiac chronotropy, (ii) nanoinjections of NMDA into the ipsilateral DMH or PAG evoked lateralized RSNA responses, and (iii) blockade of EAA receptors in the unilateral DMH attenuated the cardiovascular responses evoked by injection of NMDA into either the R- or left- (L-) PAG. In awake rats, nanoinjection of kynurenic acid (1 nmol/100 nL) into the L-DMH or R- or L-PAG attenuated the tachycardia evoked by air stress. However, the magnitude of stress-evoked tachycardia was smallest when the EAA receptors of the R-DMH were blocked. We conclude that EAA receptors contribute to the right-sided predominance in cardiac chronotropism. This interhemispheric difference that involves EAA receptors was observed in the DMH but not in the PAG.

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Related in: MedlinePlus

Photomicrographs of rat brain slices depicting spots from animals injected with green and red retrobeads at the level of (A) the DMH and (C) the PAG, respectively.Zoom view of the (B) PAG and (D) DMH neurons that were retrogradely labeled with green and red retrobeads, respectively. DMH: dorsomedial hypothalamus; ME: median eminence; mt: mammillothalamic tract; f: fornix; VMH: ventromedial hypothalamus; III: third ventricle; l/dlPAG: lateral/dorsolateral periaqueductal gray; Aq: aqueduct.
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pone-0112412-g005: Photomicrographs of rat brain slices depicting spots from animals injected with green and red retrobeads at the level of (A) the DMH and (C) the PAG, respectively.Zoom view of the (B) PAG and (D) DMH neurons that were retrogradely labeled with green and red retrobeads, respectively. DMH: dorsomedial hypothalamus; ME: median eminence; mt: mammillothalamic tract; f: fornix; VMH: ventromedial hypothalamus; III: third ventricle; l/dlPAG: lateral/dorsolateral periaqueductal gray; Aq: aqueduct.

Mentions: Photomicrographs depicting the injection sites of retrobeads into the right DMH and left PAG and labeled neurons are shown in Figure 5A and B. In the left DMH, neurons labeled with red beads that were originally injected into the left PAG were observed. Similarly, in the right PAG, neurons labeled green with beads injected into the right DMH were observed.


Excitatory amino acid receptors mediate asymmetry and lateralization in the descending cardiovascular pathways from the dorsomedial hypothalamus.

Xavier CH, Ianzer D, Lima AM, Marins FR, Pedrino GR, Vaz G, Menezes GB, Nalivaiko E, Fontes MA - PLoS ONE (2014)

Photomicrographs of rat brain slices depicting spots from animals injected with green and red retrobeads at the level of (A) the DMH and (C) the PAG, respectively.Zoom view of the (B) PAG and (D) DMH neurons that were retrogradely labeled with green and red retrobeads, respectively. DMH: dorsomedial hypothalamus; ME: median eminence; mt: mammillothalamic tract; f: fornix; VMH: ventromedial hypothalamus; III: third ventricle; l/dlPAG: lateral/dorsolateral periaqueductal gray; Aq: aqueduct.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4232378&req=5

pone-0112412-g005: Photomicrographs of rat brain slices depicting spots from animals injected with green and red retrobeads at the level of (A) the DMH and (C) the PAG, respectively.Zoom view of the (B) PAG and (D) DMH neurons that were retrogradely labeled with green and red retrobeads, respectively. DMH: dorsomedial hypothalamus; ME: median eminence; mt: mammillothalamic tract; f: fornix; VMH: ventromedial hypothalamus; III: third ventricle; l/dlPAG: lateral/dorsolateral periaqueductal gray; Aq: aqueduct.
Mentions: Photomicrographs depicting the injection sites of retrobeads into the right DMH and left PAG and labeled neurons are shown in Figure 5A and B. In the left DMH, neurons labeled with red beads that were originally injected into the left PAG were observed. Similarly, in the right PAG, neurons labeled green with beads injected into the right DMH were observed.

Bottom Line: We recently reported that removal of GABA-ergic tone in the unilateral DMH produces: asymmetry, that is, a right- (R-) sided predominance in cardiac chronotropism, and lateralization, that is, a greater increase in ipsilateral renal sympathetic activity (RSNA).We conclude that EAA receptors contribute to the right-sided predominance in cardiac chronotropism.This interhemispheric difference that involves EAA receptors was observed in the DMH but not in the PAG.

View Article: PubMed Central - PubMed

Affiliation: Laboratório de Fisiologia e Terapêutica Cardiovascular, Departamento Ciências Fisiológicas, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil; Departamento de Fisiologia e Biofísica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.

ABSTRACT
The dorsomedial hypothalamus (DMH) and lateral/dorsolateral periaqueductal gray (PAG) are anatomically and functionally connected. Both the DMH and PAG depend on glutamatergic inputs for activation. We recently reported that removal of GABA-ergic tone in the unilateral DMH produces: asymmetry, that is, a right- (R-) sided predominance in cardiac chronotropism, and lateralization, that is, a greater increase in ipsilateral renal sympathetic activity (RSNA). In the current study, we investigated whether excitatory amino acid (EAA) receptors in the DMH-PAG pathway contribute to the functional interhemispheric difference. In urethane (1.2 to 1.4 g/kg, i.p.) anesthetized rats, we observed that: (i) nanoinjections of N-methyl D-aspartate (NMDA 100 pmol/100 nl) into the unilateral DMH produced the same right-sided predominance in the control of cardiac chronotropy, (ii) nanoinjections of NMDA into the ipsilateral DMH or PAG evoked lateralized RSNA responses, and (iii) blockade of EAA receptors in the unilateral DMH attenuated the cardiovascular responses evoked by injection of NMDA into either the R- or left- (L-) PAG. In awake rats, nanoinjection of kynurenic acid (1 nmol/100 nL) into the L-DMH or R- or L-PAG attenuated the tachycardia evoked by air stress. However, the magnitude of stress-evoked tachycardia was smallest when the EAA receptors of the R-DMH were blocked. We conclude that EAA receptors contribute to the right-sided predominance in cardiac chronotropism. This interhemispheric difference that involves EAA receptors was observed in the DMH but not in the PAG.

Show MeSH
Related in: MedlinePlus