Systems neuroscienceAngiotensin II type 2 receptors facilitate reinnervation of phenol-lesioned vascular calcitonin gene-related peptide–containing nerves in rat mesenteric arteries
Section snippets
Experimental animals
Eight-week-old Wistar rats (purchased from Shimizu Experimental Animals, Shizuoka, Japan) were used in this study. The animals were given food and water ad libitum. They were housed in the Animal Research Center of Okayama University at a controlled ambient temperature of 22 °C with 50±10% relative humidity and with a 12-h light/dark cycle (lights on at 8:00 AM). This study was carried out in accordance with the Guidelines for Animal Experiments at Okayama University Advanced Science Research
Changes in SBP after phenol treatment
Fig. 1 shows the tail-cuff SBP in the six groups for 7 days after topical phenol or vehicle (sham) treatment. The Ang II group (Ph+Ang II) showed significantly increased blood pressure from 4 days after Ang II administration compared with the saline control group (Ph+Saline). Losartan administration (Ang II+Los and Ang II+Los+PD) completely inhibited the increase of blood pressure induced by Ang II.
Changes in innervation of CGRP-LI nerve fibers in mesenteric arteries following topical phenol treatment with or without administration of each drug
Fig. 2 and Fig. 3 show typical images of innervation of CGRP-LI nerves and changes in the density
Discussion
The present study is the first to demonstrate that activation of AT2 receptors facilitates reinnervation of perivascular CGRP-LI nerves, but not NPY-LI nerves, in the rat mesenteric artery, that was lesioned by topical application of phenol. Our recent report showed evidence that topical treatment with phenol around the rat superior mesenteric artery induced a marked reduction of innervation of perivascular NPY- and CGRP-containing nerves in the distal small artery (Hobara et al., 2006).
Conclusion
In conclusion, the present study suggests that AT2 receptors play an important role in the process of regeneration of CGRPergic nerves, which innervate mesenteric resistance arteries of the rat. We have reported that CGRPergic nerve innervation in SHR decreases with age and that long-term administration of AT1 receptor antagonist in SHR prevents the age-related decreases in function and distribution of CGRPergic nerves (Kawasaki et al 1990b, Hobara et al 2005). Therefore, we hypothesize that
References (31)
- et al.
Vascular expression of angiotensin type 2 receptor in the adult rat: influence of angiotensin II infusion
J Hypertens
(2001) - et al.
Angiotensin II mediates catecholamine and neuropeptide Y secretion in human adrenal chromaffin cells through the AT1 receptor
Regul Peptides
(2003) - et al.
Evidence for differential localization of noradrenaline and neuropeptide Y in neuronal storage vesicles isolated form rat vas deferens
J Neurosci
(1985) - et al.
The angiotensin AT2 receptor down-regulates neurofilament M in PC12W cells
Neurosci Lett
(1997) - et al.
Sciatic nerve transection evokes lasting up-regulation of angiotensin AT2 and AT1 receptor mRNA in adult rat dorsal root ganglia and sciatic nerves
Brain Res Mol Brain Res
(1998) - et al.
International union of pharmacologyXXIII. The angiotensin II receptors
Pharmacol Rev
(2000) - et al.
Long-term inhibition of angiotensin prevents reduction of periarterial innervation of calcitonin gene-related peptide (CGRP) containing nerves in spontaneously hypertensive rats
Hypertens Res
(2005) - et al.
Innervation and functional changes in mesenteric perivascular calcitonin gene-related peptide- and neuropeptide Y-containing nerves following topical phenol treatment
Neuroscience
(2006) - et al.
Angiotensin type 2 receptor dephosphorylates Bcl-2 by activating mitogen-activated protein kinase phosphatase-1 and induces apoptosis
J Biol Chem
(1997) - et al.
Modulation of angiotensin II type 2 receptor mRNA in rat hypothalamus and brainstem neuronal cultures by growth factors
Brain Res Mol Brain Res
(1997)