Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:In previous studies, we reported that dilatation of pial arterioles in response to agonists that stimulate the synthesis/release of nitric oxide is profoundly impaired during acute exposure to high concentrations of alcohol and during chronic (2–3 mo) alcohol consumption (22, 23).
Category: