A 44-year-old female with generalized anxiety disorder and a history of alcohol use disorder in sustained remission for 2 years presents with persistent anxiety symptoms despite an adequate trial of buspirone 30 mg daily. She reports constant muscle tension, restlessness, and difficulty sleeping due to racing thoughts. She expresses strong reluctance to take benzodiazepines given her substance use history. The PMHNP considers gabapentin as an off-label adjunct. Which of the following best describes gabapentin's mechanism and its relevance to this clinical scenario?