1. A method of promoting or inhibiting neurogenesis, the method comprising the step of directly exciting neural progenitor cells in a rat with a therapeutic amount of an agent that directly acts on one or both of voltage-activated gated Ca 2+ channels or NMDA receptors, wherein when said agent is an agonist of said voltage-activated gated Ca 2+ channels or NMDA receptors neurogenesis is promoted in said neural progenitor cells, and wherein when said agent is an antagonist of said voltage-activated gated Ca 2+ channels or NMDA receptors neurogenesis is inhibited in said neural progenitor cells.