BACKGROUND: Major burn injury causes aberrant responses to neuromuscular blocking agents, and an increase in fetal type nicotinic acetylcholine receptors (nAchR) has been speculated to contribute to the altered response. This study was conducted to test the hypothesis that the increases in nAchR are due to generalized systemic effects, not limited to area of burn in humans. Using the rectus abdominis muscle of the burned area and quadriceps muscle of nonburned area from the single major burn patient, the changes of nAchR subunits of alpha1, gamma and alpha7 were compared. METHODS: Twelve adults (M:F = 11:1) with total body surface area (TBSA) of 48.8 +/- 19.3% major burns, undergoing burn related elective surgery, were included at 30.8 +/- 16.4 days after the burn injury. Only those with burns in abdominal area and no burns in the lower extremity, were selected. Under general anesthesia, muscle biopsy was taken from the rectus abdominis muscle under the burned abdominal area as well as from the quadriceps muscle under the unburned thigh, at least 30 cm away from the closest burn wound margin. The nAchR changes in the muscles were assayed by western blot using subtype specific mouse antibody for alpha1, gamma and alpha7. RESULTS: The nAchR subunit quantitation (volume% compared to nonburn controls) of alpha1, gamma and alpha7 in the rectus and quadriceps by densitometry were 335.4 +/- 45.4 vs. 321.7 +/- 76.2, 298.3 +/- 234.3 vs. 290.0 +/- 202.3, 149.7 +/- 22.6 vs. 141.6 +/- 35.6, respectively, showing no significant statistical differences between burned and nonburned area (P > 0.05). However, large coefficients of variation were noted in both muscles of gamma group, which may suggest indirect evidence of proliferation of fetal type nAchR in the major burns. TBSA and days after the burn injury were poorly correlated with the amount of expression of subtypes of acetylcholine receptors tested. CONCLUSIONS: Our results confirm that systemic effects of thermal injury include an increase in nAchR at sites distant from the thermal injury, which may account for the skeletal muscle dysfunction and aberrant responses to neuromuscular relaxation. Further studies need to address the importance of burn size and its effects on quantitative and qualitative changes in receptor.