The hyperalgesic effects induced by the injection of angiotensin II into the caudal ventrolateral medulla are mediated by the pontine A5 noradrenergic cell group. 2010

José Marques-Lopes, and Dora Pinho, and António Albino-Teixeira, and Isaura Tavares
Instituto de Farmacologia & Terapêutica, Faculdade de Medicina do Porto, Universidade do Porto, Porto, Portugal.

The caudal ventrolateral medulla (CVLM) is a key component of the supraspinal pain modulatory system. Pain modulation from the CVLM is partially relayed by spinally projecting noradrenergic neurons of the pontine A(5) cell group, which leave collateral fibres at the CVLM. The injection of angiotensin II (Ang II) into the CVLM was recently shown to induce hyperalgesia mediated by angiotensin type 1 (AT(1)) receptors, expressed by CVLM neurons that do not project to the spinal cord. The present study evaluates the effects of lesioning the noradrenergic pontine A(5) cell group by the retrograde transport of the selective toxin anti-dopamine beta-hydroxylase-saporin (anti-DBH-SAP) from the CVLM in pain behavioural responses elicited by Ang II injection into the CVLM. The injection of anti-DBH-SAP induced neurodegeneration, identified by the marker Fluoro-Jade B, restricted to the A(5) noradrenergic cell group. These results were confirmed by the decrease in the number of noradrenergic neurons only in the A(5) group. Pain behavioural evaluation using the formalin test showed that Ang II injection into the CVLM induced hyperalgesia, which was partially prevented by lesion of the A(5) noradrenergic cell group with anti-DBH-SAP. Immunostaining of AT(1) receptors in CVLM neurons retrogradely labelled from the A(5) noradrenergic cell group showed that CVLM neurons that project to the A(5) express AT(1) receptors, indicating that Ang II can modulate directly the CVLM-A(5) connection. The results show that Ang II-induced hyperalgesia elicited from the CVLM is mediated by an indirect pathway relayed at the pontine noradrenergic A(5) group.

UI MeSH Term Description Entries
D008297 Male Males
D008526 Medulla Oblongata The lower portion of the BRAIN STEM. It is inferior to the PONS and anterior to the CEREBELLUM. Medulla oblongata serves as a relay station between the brain and the spinal cord, and contains centers for regulating respiratory, vasomotor, cardiac, and reflex activities. Accessory Cuneate Nucleus,Ambiguous Nucleus,Arcuate Nucleus of the Medulla,Arcuate Nucleus-1,External Cuneate Nucleus,Lateral Cuneate Nucleus,Nucleus Ambiguus,Ambiguus, Nucleus,Arcuate Nucleus 1,Arcuate Nucleus-1s,Cuneate Nucleus, Accessory,Cuneate Nucleus, External,Cuneate Nucleus, Lateral,Medulla Oblongatas,Nucleus, Accessory Cuneate,Nucleus, Ambiguous,Nucleus, External Cuneate,Nucleus, Lateral Cuneate
D009434 Neural Pathways Neural tracts connecting one part of the nervous system with another. Neural Interconnections,Interconnection, Neural,Interconnections, Neural,Neural Interconnection,Neural Pathway,Pathway, Neural,Pathways, Neural
D009474 Neurons The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM. Nerve Cells,Cell, Nerve,Cells, Nerve,Nerve Cell,Neuron
D009638 Norepinephrine Precursor of epinephrine that is secreted by the ADRENAL MEDULLA and is a widespread central and autonomic neurotransmitter. Norepinephrine is the principal transmitter of most postganglionic sympathetic fibers, and of the diffuse projection system in the brain that arises from the LOCUS CERULEUS. It is also found in plants and is used pharmacologically as a sympathomimetic. Levarterenol,Levonorepinephrine,Noradrenaline,Arterenol,Levonor,Levophed,Levophed Bitartrate,Noradrenaline Bitartrate,Noradrénaline tartrate renaudin,Norepinephrin d-Tartrate (1:1),Norepinephrine Bitartrate,Norepinephrine Hydrochloride,Norepinephrine Hydrochloride, (+)-Isomer,Norepinephrine Hydrochloride, (+,-)-Isomer,Norepinephrine d-Tartrate (1:1),Norepinephrine l-Tartrate (1:1),Norepinephrine l-Tartrate (1:1), (+,-)-Isomer,Norepinephrine l-Tartrate (1:1), Monohydrate,Norepinephrine l-Tartrate (1:1), Monohydrate, (+)-Isomer,Norepinephrine l-Tartrate (1:2),Norepinephrine l-Tartrate, (+)-Isomer,Norepinephrine, (+)-Isomer,Norepinephrine, (+,-)-Isomer
D010146 Pain An unpleasant sensation induced by noxious stimuli which are detected by NERVE ENDINGS of NOCICEPTIVE NEURONS. Suffering, Physical,Ache,Pain, Burning,Pain, Crushing,Pain, Migratory,Pain, Radiating,Pain, Splitting,Aches,Burning Pain,Burning Pains,Crushing Pain,Crushing Pains,Migratory Pain,Migratory Pains,Pains, Burning,Pains, Crushing,Pains, Migratory,Pains, Radiating,Pains, Splitting,Physical Suffering,Physical Sufferings,Radiating Pain,Radiating Pains,Splitting Pain,Splitting Pains,Sufferings, Physical
D011149 Pons The front part of the hindbrain (RHOMBENCEPHALON) that lies between the MEDULLA and the midbrain (MESENCEPHALON) ventral to the cerebellum. It is composed of two parts, the dorsal and the ventral. The pons serves as a relay station for neural pathways between the CEREBELLUM to the CEREBRUM. Pons Varolii,Ponte,Pons Varolius,Pontes,Varolii, Pons,Varolius, Pons
D002491 Central Nervous System Agents A class of drugs producing both physiological and psychological effects through a variety of mechanisms. They can be divided into "specific" agents, e.g., affecting an identifiable molecular mechanism unique to target cells bearing receptors for that agent, and "nonspecific" agents, those producing effects on different target cells and acting by diverse molecular mechanisms. Those with nonspecific mechanisms are generally further classed according to whether they produce behavioral depression or stimulation. Those with specific mechanisms are classed by locus of action or specific therapeutic use. (From Gilman AG, et al., Goodman and Gilman's The Pharmacological Basis of Therapeutics, 8th ed, p252) Central Nervous System Drugs
D006930 Hyperalgesia An increased sensation of pain or discomfort produced by minimally noxious stimuli due to damage to soft tissue containing NOCICEPTORS or injury to a peripheral nerve. Hyperalgesia, Tactile,Hyperalgesia, Thermal,Hyperalgia,Hyperalgia, Mechanical,Hyperalgia, Primary,Hyperalgia, Secondary,Allodynia,Allodynia, Mechanical,Allodynia, Tactile,Allodynia, Thermal,Hyperalgesia, Mechanical,Hyperalgesia, Primary,Hyperalgesia, Secondary,Hyperalgesic Sensations,Mechanical Allodynia,Mechanical Hyperalgesia,Tactile Allodynia,Thermal Allodynia,Allodynias,Hyperalgesias,Hyperalgesias, Thermal,Hyperalgesic Sensation,Mechanical Hyperalgia,Mechanical Hyperalgias,Primary Hyperalgia,Primary Hyperalgias,Secondary Hyperalgia,Secondary Hyperalgias,Sensation, Hyperalgesic,Sensations, Hyperalgesic,Thermal Hyperalgesia
D000804 Angiotensin II An octapeptide that is a potent but labile vasoconstrictor. It is produced from angiotensin I after the removal of two amino acids at the C-terminal by ANGIOTENSIN CONVERTING ENZYME. The amino acid in position 5 varies in different species. To block VASOCONSTRICTION and HYPERTENSION effect of angiotensin II, patients are often treated with ACE INHIBITORS or with ANGIOTENSIN II TYPE 1 RECEPTOR BLOCKERS. Angiotensin II, Ile(5)-,Angiotensin II, Val(5)-,5-L-Isoleucine Angiotensin II,ANG-(1-8)Octapeptide,Angiotensin II, Isoleucine(5)-,Angiotensin II, Valine(5)-,Angiotensin-(1-8) Octapeptide,Isoleucine(5)-Angiotensin,Isoleucyl(5)-Angiotensin II,Valyl(5)-Angiotensin II,5 L Isoleucine Angiotensin II,Angiotensin II, 5-L-Isoleucine

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