Rabbit Anti-Human Tyrosine Hydroxylase (a.a. 10-59) Polyclonal antibody

The role of endothelium in the electrical-field stimulation (EFS)-induced contractions of Chelonoidis carbonaria aorta was investigated. Contractions were evaluated in the presence and absence of L-NAME (100 mu M), tetrodotoxin (1 mu M), phentolamine (10 and 100 mu M), phenoxybenzamine (1 and 10 mu M), prazosin (100 mu M), idazoxan (100 mu M), atropine (10 mu M), D-tubocurarine (10 mu M) or indomethacin (10 mu M). EFS-induced contraction was also carried out in endothelium-denuded rings. EFS-induced contraction was investigated by the sandwich assay. Concentration curves to endothelin-1 (0.1-100 nM) and U46619 (0.001-100 mu M) were also constructed to calculate both Emax and EC50. EFS at 16 Hz contracted Chelonoidis aorta, which was almost abolished by the endothelium removal. The addition of L-NAME increased the EFS response (2.0 +/- 0.4 and 8.3 +/- 1.9 mN). In L-NAME treated aortic rings, tetrodotoxin did not change the EFS-response (5.1 +/- 1.8 and 4.9 +/- 1.7 mN). Indomethacin, atropine and d-tubucurarine also did not affect the EFS-response. Phentolamine at 10 mu M did not change the EFS-induced contraction; however, at 100 mu M, reduced it (3.9 +/- 1 and 1.9 +/- 0.3 mN). Prazosin and idazoxan did not change EFS-induced contractions. Phenoxybenzamine at 1 reduced by 76% (9.6 +/- 3.4 and 2.3 +/- 0.8 mN) and at 10 mu M by 90% the EFS response. Immunohistochemistry identified tyrosine hydroxylase in the endothelium and brain, whereas S100 protein was found only in brain. In conclusion, endothelium modulates EFS-induced contractions in Chelonoidis aortic rings and this modulation may be due to endothelium-derived catecholamines, possibly dopamine.

Neuropathy is major source of chronic pain that can be caused by mechanically or chemically induced nerve injury. Intraplantar formalin injection produces local necrosis over a two-week period and has been used to model neuropathy in rats. To determine whether neuropathy alters dopamine (DA) receptor responsiveness in mesolimbic brain regions, we examined dopamine D-1-like and D-2-like receptor (D1/2R) signaling and expression in male rats 14 days after bilateral intraplantar formalin injections into both rear paws. D2R-mediated G-protein activation and expression of the D2R long, but not short, isoform were reduced in nucleus accumbens (NAc) core, but not in NAc shell, caudate-putamen or ventral tegmental area of formalin- compared to saline-treated rats. In addition, D1R-stimulated adenylyl cyclase activity was also reduced in NAc core, but not in NAc shell or prefrontal cortex, of formalin-treated rats, whereas D1R expression was unaffected. Other proteins involved in dopamine neurotransmission, including dopamine uptake transporter and tyrosine hydroxylase, were unaffected by formalin treatment. In behavioral tests, the potency of a D2R agonist to suppress intracranial self-stimulation (ICSS) was decreased in formalin-treated rats, whereas D1R agonist effects were not altered. The combination of reduced D2R expression and signaling in NAc core with reduced suppression of ICSS responding by a D2R agonist suggest a reduction in D-2 autoreceptor function. Altogether, these results indicate that intraplantar formalin produces attenuation of highly specific DA receptor signaling processes in NAc core of male rats and suggest the development of a neuropathy-induced allostatic state in both pre- and post-synaptic DA receptor function.