Hypertensive rats subjected to peripheral neuropathy develop lower mechanical allodynia than their normotensive nontrols
Dora
Pinho1, 2*,
Marta
R.
Couto1, 2,
Daniela
Patinha1, 2,
Jose
Marques-Lopes1, 2,
Isaura
Tavares2, 3 and
Antonio
Albino-Teixeira1, 2
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1
Universidade do Porto, Instituto de Farmacologia e Terapeutica, Faculdade de Medicina, Portugal
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2
Universidade do Porto, IBMC-Instituto de Biologia Celular e Molecular, Portugal
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3
Universidade do Porto, Instituto de Histologia e Embriologia, Faculdade de Medicina, Portugal
Attenuation of the responses to acute pain has been described in clinical and experimental hypertension. Although some researchers describe an inversion of this hypertension-associated hypoalgesia in chronic pain conditions, a lower prevalence of chronic pain in human hypertension has been reported and our most recent work describes lower hyperalgesia in a model of chronic inflammatory pain, in several models of hypertension. Considering the high prevalence of neuropathic pain and the difference in the mechanisms underlying inflammatory and neuropathic pain, we decided to investigate the interactions between cardiovascular and pain control systems in angiotensin II (AngII)-hypertensive rats subjected to spared nerve injury (SNI) peripheral neuropathy.
Osmotic minipumps (Alzet 2004) were subcutaneously implanted on Wistar rats, for continuous infusion of saline (n=5) or AngII (n=5). Ten days later (day 0), all animals were subjected to the SNI procedure, comprising ligation and axotomy of the tibial and common peroneal terminal branches of the sciatic nerve, leaving the sural branch intact. Both surgical procedures were performed under ketamine plus medetomidine anaesthesia. BP was monitored by non-invasive tail-cuff measurement. The development of mechanical allodynia was evaluated by testing the lateral plantar surface of the paw with von Frey monofilaments. Animals were tested on days 0, 3, 14 and 21. Statistical analysis was performed with ANOVA for repeated measures, followed by Student-Newman-Keuls post-hoc test.
AngII-hypertensive animals, unlike saline-controls, showed an increase in mean BP upon development of SNI neuropathy (AngII, day0: 142±3 vs day21: 171±10 mmHg, P<0.05; Sal, day0: 110±5 vs day21: 126±4 mmHg, P>0.10). Von Frey thresholds (VFT) decreased in all rats already at day 3 of SNI, and continued to decrease until day 14, stabilizing thereafter until the end of the study. Hypertensive animals, however, exhibited higher VFT values than their normotensive controls, as evidenced on days 14 and 21 (day14, AngII: 2.35±0.16 vs Saline: 1.71±0.06, P<0.01; day21, AngII: 2.36±0.21 vs Saline: 1.89±0.07, P<0.05).
During SNI peripheral neuropathy, AngII-hypertensive rats developed lower mechanical allodynia than their normotensive controls, supporting the hypothesis that the hypertension-associated hypoalgesia described in acute pain paradigms also occurs in chronic neuropathic pain.
Conference:
11th Meeting of the Portuguese Society for Neuroscience, Braga, Portugal, 4 Jun - 6 Jun, 2009.
Presentation Type:
Poster Presentation
Topic:
Abstracts
Citation:
Pinho
D,
Couto
MR,
Patinha
D,
Marques-Lopes
J,
Tavares
I and
Albino-Teixeira
A
(2009). Hypertensive rats subjected to peripheral neuropathy develop lower mechanical allodynia than their normotensive nontrols.
Front. Neurosci.
Conference Abstract:
11th Meeting of the Portuguese Society for Neuroscience.
doi: 10.3389/conf.neuro.01.2009.11.125
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Received:
11 Aug 2009;
Published Online:
11 Aug 2009.
*
Correspondence:
Dora Pinho, Universidade do Porto, Instituto de Farmacologia e Terapeutica, Faculdade de Medicina, Porto, Portugal, dpinho@med.up.pt