While intracerebroventricular pharmacological manipulation of Tac1 receptor signaling does not affect locomotion in tests of anxiety and depression67, injection of substance P—a product of the Tac1 gene—into brainstem regions69 or the mesolimbic system70 induces bouts of locomotion, although the endogenous sources of tachykinins are so far elusive. The gene discussed is TAC1; the disease is Anxiety.