From ScienceDaily: "It has been long known that stress plays a part not just in the graying of hair but in hair loss as well. ... Now, a team [that] was investigating how stress affects gastrointestinal function may have found a chemical compound that induces hair growth by blocking a stress-related hormone associated with hair loss - entirely by accident. ... Our findings show that a short-duration treatment with this compound causes an astounding long-term hair regrowth in chronically stressed mutant mice. This could open new venues to treat hair loss in humans through the modulation of the stress hormone receptors, particularly hair loss related to chronic stress and aging. ... the researchers had been using mice that were genetically altered to overproduce a stress hormone called corticotrophin-releasing factor, or CRF. As these mice age, they lose hair and eventually become bald on their backs, making them visually distinct from their unaltered counterparts. The [researchers] had developed the chemical compound, a peptide called astressin-B, and described its ability to block the action of CRF. ... researchers injected the astressin-B into the bald mice to observe how its CRF-blocking ability affected gastrointestinal tract function. .... About three months later, the investigators returned to these mice to conduct further gastrointestinal studies and found they couldn't distinguish them from their unaltered brethren. They had regrown hair on their previously bald backs."

Link: http://www.sciencedaily.com/releases/2011/02/110216185406.htm