Preventive injection for Cluster Headache, typically using subcutaneous or intramuscular administration of medications like sumatriptan or dihydroergotamine, acts on serotonin receptors (5-HT1B/1D) to constrict cranial blood vessels and inhibit neurogenic inflammation. These agents effectively reduce the frequency, severity, and duration of cluster headache attacks by modulating neurovascular pathways and interrupting the trigeminal-vascular pain cascade.