Severe Burn Injury Alters Expression of Adrenergic Receptor Transcripts in a Rodent Model.

BACKGROUND: Norepinephrine is commonly used during acute burn resuscitation to maintain adequate perfusion pressure. However, its effects, together with the burn-induced catecholamine surge, on arterial α1-adrenergic receptors (α1-AR) remain unclear. This study examined whether burn injury and continuous norepinephrine infusion alter arterial α1-AR subtype expression at the transcriptional and protein levels. METHODS: Sprague-Dawley rats were randomized to full-thickness scald burn involving 25% total body surface area with continuous intravenous norepinephrine or sodium chloride (NaCl) infusion, sham injury with norepinephrine infusion, or untreated controls. Mean arterial pressure (MAP) was measured at baseline and before euthanasia (six or 24 h). Aorta, carotid, and renal arteries were collected for analysis of α1-AR subtypes (Adra1a, Adra1b, and Adra1d) using quantitative PCR (qPCR) and immunohistochemistry (IHC). RESULTS: Norepinephrine efficiently increased MAP in sham animals. In burned animals with norepinephrine, MAP increased at six hours (+10.6 mmHg) but fell below baseline at 24 h (-6.4 mmHg). Burned animals given NaCl had persistently lower MAP than those given norepinephrine, at six hours (-19.1 mmHg) and 24 h (-21.1 mmHg). qPCR demonstrated significant downregulation of Adra1b in the renal artery across all groups compared to control (7.8-16.4-fold, p < 0.001). Overall, changes in protein expression across different vascular beds and receptor subtypes were inconsistent. CONCLUSIONS: Norepinephrine increased MAP in both sham and burned animals, confirming the drug's efficacy. Burn injury and sustained norepinephrine exposure were associated with early, vessel-specific alterations in α1-AR mRNA expression. The absence of consistent protein-level changes within 24 h suggests a delay in receptor expression on protein level.