Role of the glutamatergic system of ventrolateral periaqueductal gray (vlPAG) in the cardiovascular responses in normal and hemorrhagic conditions in rats

Document Type : Original Article


1 Department of Physiology, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran

2 Applied Biomedical Research Center, Mashhad University of Medical Sciences, Mashhad, Iran

3 Division of Neurocognitive Sciences, Psychiatry and Behavioral Sciences Research Center, Mashhad University of Medical Sciences, Mashhad, Iran


Objective(s): Periaqueductal gray (PAG) is a mesencephalic area divided into four columns including ventrolateral periaqueductal gray (vlPAG). vlPAG plays a role in cardiovascular regulation during normal and hemorrhagic (Hem) conditions. Due to presence of glutamate in this area, we evaluated the effect of glutamatergic receptors of this area on cardiovascular activity in normotensive and hypovolemic Hem rats.
Materials and Methods: Animals were divided into twelve groups: saline (vehicle), Glutamate, GYK52466 (non-NMDA receptor antagonist), and MK801 (NMDA receptor antagonist) with and without Glu microinjected into vlPAG in normal and Hem conditions. Following the femoral artery cannulating and microinjecting, changes (Δ) of heart rate (HR), systolic blood pressure (SBP), and mean arterial pressure (MAP) were recorded via a PowerLab unit.
Results: In normotensive conditions, microinjection of Glu increased ΔMAP, ΔSBP, and ΔHR (p <0.001). MK-801 and GYKI-52466 nonsignificant reduced cardiovascular responses than vehicle while their changes were significant compared with glutamate (p <0.001). Co-injection of GYKI- 52466 with Glu did not significantly reduce ΔSBP and ΔMAP induced by Glu (P>0.05) but co-injection of MK-801 with Glu significantly attenuate these effects(p <0.01). In Hem, Glu increased ΔSBP, ΔMAP, and ΔHR (p <0.05). GYKI-52466 alone did not change cardiovascular responses but MK-801 decreased ΔSBP than Hem (p <0.01). Co-injection of GYKI-52466 with Glu had significant(p <0.05) but MK-801 with Glu had no significant effect compared with Hem (P>0.05).
Conclusion: The glutamatergic system of vlPAG increases cardiovascular values that are mostly mediated through the NMDA receptor. Since vlPAG is well known as an inhibitory region, it seems that glutamate does not have a noteworthy cardiovascular role in vlPAG during Hem and normal conditions.


1. Lagatta DC, Ferreira‐Junior NC, Deolindo M, Corrêa FM, Resstel LB. Ventrolateral periaqueductal grey matter neurotransmission modulates cardiac baroreflex activity. Eur J Neuro Sci 2016;44:2877-2884.
2. Dampney R. Emotion and the cardiovascular system: postulated role of inputs from the medial prefrontal cortex to the dorsolateral periaqueductal gray. Front Neurosci 2018;12:343-351.
3. Wright KM, Jhou TC, Pimpinelli D, McDannald MA. Cue-inhibited ventrolateral periaqueductal gray neurons signal fear output and threat probability in male rats. Elife 2019;8:50054.
4. Hao S, Yang H, Wang X, He Y, Xu H, Wu X, et al. The lateral hypothalamic and BNST GABAergic projections to the anterior ventrolateral periaqueductal gray regulate feeding. Cell Rep 2019;28:616-624.
5. Kroeger D, Bandaru SS, Madara JC, Vetrivelan R. Ventrolateral periaqueductal gray mediates rapid eye movement sleep regulation by melanin-concentrating hormone neurons. Neuroscience 2019;406:314-324.
6. Sun Y, Wang J, Liang S-H, Ge J, Lu Y-C, Li J-N, et al. Involvement of the ventrolateral periaqueductal gray matter-central medial thalamic nucleus-basolateral amygdala pathway in neuropathic pain regulation of rats. Front Neuroanat 2020;14:32-46.
7. Tjen-A-Looi SC, Li P, Longhurst JC. Midbrain vlPAG inhibits rVLM cardiovascular sympathoexcitatory responses during electroacupuncture. Am J Physiol Heart Circ 2006;290:2543-2553.
8. Barbosa RM, Speretta GF, Dias DPM, Ruchaya PJ, Li H, Menani JV, et al. Increased expression of macrophage migration inhibitory factor in the nucleus of the solitary tract attenuates renovascular hypertension in rats. Am J Hypertens 2017;30:435-443.
9. Vagg DJ, Bandler R, Keay KA. Hypovolemic shock: critical involvement of a projection from the ventrolateral periaqueductal gray to the caudal midline medulla. Neuroscience 2008;152:1099-1109.
10.    Shafei MN, Nasimi A, Alaei H, Pourshanazari AA. The role of non-NMDA receptor of glutamate in cuneiform nucleus on cardiovascular response in anaesthetized rats. Pharmacology Online 2009;1:454-461.
11.    Deolindo M, Pelosi GG, Tavares RF, Corrêa FMA. The ventrolateral periaqueductal gray is involved in the cardiovascular response evoked by l-glutamate microinjection into the lateral hypothalamus of anesthetized rats. Neurosci Lett 2008;430:124-129.
12.    Takahashi M, Hayashi Y, Tanaka J. Glutamatergic modulation of noradrenaline release in the rat median preoptic area. Brain Res Bull 2017;130:36-41.
13.    Yamaguchi Ki, Yamada T. Involvement of anteroventral third ventricular AMPA/kainate receptors in both hyperosmotic and hypovolemic AVP secretion in conscious rats. Brain Res Bull 2006;71:183-192.
14.    Samineni VK, Grajales-Reyes JG, Copits BA, O’Brien DE, Trigg SL, Gomez AM, et al. Divergent modulation of nociception by glutamatergic and GABAergic neuronal subpopulations in the periaqueductal gray. eNeuro 2017;4:1-24.
15.    Pajolla GP, de Aguiar Corrêa FM. Cardiovascular responses to the injection of L-glutamate in the lateral hypothalamus of unanesthetized or anesthetized rats. Auton Neurosci 2004;116:19-29.
16.    Yang Y, Lu F, Zhuang L, Yang S, Kong Y, Tan W, et al. Combined preconditioning with hypoxia and GYKI-52466 protects rats from cerebral ischemic injury by HIF-1α/eNOS pathway. Am J Transl Res. 2017;9:5308-5319.
17.    Okada M, Fukuyama K, Nakano T, Ueda Y. Pharmacological discrimination of effects of MK801 on thalamocortical, mesothalamic, and mesocortical transmissions. Biomolecules. 2019;9:746-765.
18.    Mohebbati R, Hosseini M, Khazaei M, Khajavirad A, Shafei MN. Involvement of the 5-HT1A receptor of the cuneiform nucleus in the regulation of cardiovascular responses during normal and hemorrhagic conditions. Iran J Basic Med Sci 2020;23:858-864.
19.    Paxinos G, Watson C. The rat brain in stereotaxic coordinates: compact sixth edition. New York: Academic Press; 2009; 143-149.
20.    Shafei MN, Nasimi A. Effect of glutamate stimulation of the cuneiform nucleus on cardiovascular regulation in anesthetized rats: Role of the pontine Kolliker–Fuse nucleus. Brain Res 2011;1385:135-143.
21.    Martin DS, Haywood JR. Sympathetic nervous system activation by glutamate injections into the paraventricular nucleus. Brain Res 1992;577:261-267.
22.    Geambasu A, Krukoff TL. Adrenomedullin acts in the lateral parabrachial nucleus to increase arterial blood pressure through mechanisms mediated by glutamate and nitric oxide. Am J Physiol Regu. 2008;295:38-44.
23.    Donevan SD, Rogawski MA. GYKI 52466, a 2, 3-benzodiazepine, is a highly selective, noncompetitive antagonist of AMPA/kainate receptor responses. Neuron 1993;10:51-59.
24.    Ahlgren J, Porter K, Hayward LF. Hemodynamic responses and c-Fos changes associated with hypotensive hemorrhage: standardizing a protocol for severe hemorrhage in conscious rats. Am J Physiol Regul 2007;292:1862-1871.
25.    Shafei MN, Nasimi A, Alaei H, Pourshanazari AA, Hosseini M. Role of cuneiform nucleus in regulation of sympathetic vasomotor tone in rats. Pathophysiology 2012;19:151-155.
26.    Lagatta DC, Ferreira-Junior NC, Deolindo M, Corrêa FM, Resstel LB. Ventrolateral periaqueductal grey matter neurotransmission modulates cardiac baroreflex activity. Eur J Neurosci 2016;44:2877-2884.
27.    Deolindo MV, Pelosi GG, Busnardo C, Resstel LB, Corrêa FM. Cardiovascular effects of acetylcholine microinjection into the ventrolateral and dorsal periaqueductal gray of rats. Brain Res 2011;1371:74-81.
28.    Depaulis A, Bandler R. The midbrain periaqueductal gray matter: Functional, anatomical, and neurochemical organization. Springer Science & Business Media; 2012:45-54.
29.    Riedel G, Platt B, Micheau J. Glutamate receptor function in learning and memory. Behav. Brain Res 2003;140:1-47.
30.    Altevogt BM, Davis M, Pankevich DE. Glutamate-Related biomarkers in drug development for disorders of the nervous system: Workshop summary: National Academies Press; 2011:1-4.
31.    Nakanishi S, Nakajima Y, Masu M, Ueda Y, Nakahara K, Watanabe D, et al. Glutamate receptors: Brain function and signal transduction. Brain Res Rev 1998;26:230-235.
32.    Bereiter DA. Microinjections of glutamate within trigeminal subnucleus interpolaris alters adrenal and autonomic function in the cat. Brain Res 1993;622:155-162.
33.    Len W-B, Chan SH, Chan JY. Parabrachial nucleus induces suppression of baroreflex bradycardia by the release of glutamate in the rostral ventrolateral medulla of the rat. J Biomed Sci 2000;7:401-411.
34.    Guyenet PG. The sympathetic control of blood pressure. Nat Rev Neurosci 2006;7:335-346.
35.    Zoccal DB, Furuya WI, Bassi M, Colombari DS, Colombari E. The nucleus of the solitary tract and the coordination of respiratory and sympathetic activities. Front Physiol 2014;5:238-250.
36.    Sweazey RD. Distribution of aspartate and glutamate in the nucleus of the solitary tract of the lamb. Exp Brain Res 1995;105:241-253.
37.    Nasimi A, Shafei M, Alaei H. Glutamate injection into the cuneiform nucleus in rat, produces correlated single unit activities in the Kolliker-Fuse nucleus and cardiovascular responses. Neuroscience 2012;223:439-446.
38.    Tu Y-C, Yang Y-C, Kuo C-C. Modulation of NMDA channel gating by Ca 2+ and Cd 2+ binding to the external pore mouth. Sci Rep 2016;6:37029-37045.
39.    Taylor NE, Pei J, Zhang J, Vlasov KY, Davis T, Taylor E, et al. The role of glutamatergic and dopaminergic neurons in the periaqueductal gray/Dorsal raphe: separating analgesia and anxiety. Eneuro 2019;6:1-14.
40.    Henderson L, Keay K, Bandler R. The ventrolateral periaqueductal gray projects to caudal brainstem depressor regions: a functional-anatomical and physiological study. Neuroscience 1998;82:201-221.
41.    Dean C. Sympathoinhibition from ventrolateral periaqueductal gray mediated by the caudal midline medulla. Am J Physiol Regul Integr Comp Physiol 2005;289:1477-1481.
42.    Dean C. Hemorrhagic sympathoinhibition mediated through the periaqueductal gray in the rat. Neurosci Lett 2004;354:79-83.
43.    Zhu H, Xiang H-C, Li H-P, Lin L-X, Hu X-F, Zhang H, et al. Inhibition of GABAergic neurons and excitation of glutamatergic neurons in the ventrolateral periaqueductal gray participate in electroacupuncture analgesia mediated by cannabinoid receptor. Front Neurol 2019;13:484-498.
44.    Guyenet PG, Stornetta RL, Holloway BB, Souza GM, Abbott SB. Rostral ventrolateral medulla and hypertension. Hypertension 2018;72:559-566.
45.    Berthoud H-R, Patterson LM, Sutton GM, Morrison C, Zheng H. Orexin inputs to caudal raphe neurons involved in thermal, cardiovascular, and gastrointestinal regulation. Histochem Cell Biol 2005;123:147-156.
46.    Wiklund L, Behzadi G, Kalén P, Headley PM, Nicolopoulos LS, Parsons CG, et al. Autoradiographic and electrophysiological evidence for excitatory amino acid transmission in the periaqueductal gray projection to nucleus raphe magnus in the rat. Neurosci Lett 1988;93:158-163.
47.    Wang W, Lovick T. The inhibitory effect of the ventrolateral periaqueductal grey matter on neurones in the rostral ventrolateral medulla involves a relay in the medullary raphe nuclei. Exp. Brain Res 1993;94:295-300.
48.    Mokhtar M, Singh P. Neuroanatomy, periaqueductal gray. StatPearls [Internet]: StatPearls Publishing; 2020;1-8.
49.    Talman W. Glutamatergic transmission in the nucleus tractus solitarii: from server to peripherals in the cardiovascular information superhighway. Braz J Med Biol Res 1997;30:1-7.
50.    Busnardo C, Crestani C, Fassini A, Resstel L, Corrêa F. NMDA and non-NMDA glutamate receptors in the paraventricular nucleus of the hypothalamus modulate different stages of hemorrhage-evoked cardiovascular responses in rats. Neuroscience 2016;320:149-159.
51.    Dávalos A, Shuaib A, Wahlgren NG. Neurotransmitters and pathophysiology of stroke: Evidence for the release of glutamate and other transmitters/mediators in animals and humans. J Stroke Cerebrovasc Dis 2000;9:2-8.
52.    Yamaguchi Ki, Watanabe K. Anteroventral third ventricular N-methyl-D-aspartate receptors, but not metabotropic glutamate receptors are involved in hemorrhagic AVP secretion. Brain Res Bull 2005;66:59-69.
53.    Takemoto Y. Amino acids that centrally influence blood pressure and regional blood flow in conscious rats. J Amino Acids 2012;2012:1-14.
54.    Cavun S, Resch GE, Evec AD, Rapacon-Baker MM, Millington WR. Blockade of delta opioid receptors in the ventrolateral periaqueductal gray region inhibits the fall in arterial pressure evoked by hemorrhage. J Pharmacol Exp Ther 2001;297:612-619.
55.    Kung L-H, Glasgow J, Ruszaj A, Gray T, Scrogin KE. Serotonin neurons of the caudal raphe nuclei contribute to sympathetic recovery following hypotensive hemorrhage. Am J Physiol Regul Integr Comp Physiol 2010;298:939-953.
56.    Dean C, Bago M. Renal sympathoinhibition mediated by 5-HT1Areceptors in the RVLM during severe hemorrhage in rats. Am J Physiol Regul Integr Comp Physiol 2002;282:122-130.
57.    Floyd NS, Keay KA, Arias CM, Sawchenko PE, Bandler R. Projections from the ventrolateral periaqueductal gray to endocrine regulatory subdivisions of the paraventricular nucleus of the hypothalamus in the rat. Neurosci Lett 1996;220:105-108.
58.    Yang Z, Coote J. Paraventricular nucleus influence on renal sympathetic activity in vasopressin gene‐deleted rats. Exp Physiol 2007;92:109-117.
59.    Li C-S, Smith DV. Glutamate Receptor Antagonists block gustatory afferent input to the nucleus of the solitary tract. J Neurophysiol 1997;77:1514-1525.
60.    Ohta H, Talman WT. Both NMDA and non-NMDA receptors in the NTS participate in the baroreceptor reflex in rats. Am J Physiol Regul Integr Comp Physiol 1994;267:1065-1070.