Is oxytocin the “trust” signal in humans?

Paul Zak’s experiments showing the involvement of oxytocin in the trust involved in money transfers between people opened up a new field of study called neuroeconomics. In 1759 the philosopher Adam Smith wrote that social and economic interactions between people are driven by what he called “fellow feeling.” Now, 250 years later, the oxytocin studies validate this and have put it into the language of cell signaling. What other things besides economic generosity release oxytocin? Zak and others have shown that many pleasant activities, even massage and hugs, release oxytocin and induce positive behaviors as a result. Oxytocin is released during sexual activity in humans, and the release results in bonding behaviors just as it does in voles. Of course, oxytocin is now available for purchase. An ad proclaims “We 100% guarantee that Oxytocin Spray will enrich your social life or your money back.”

Future directions

In this chapter you have seen how a natural substance such as caffeine acts on receptors to alter cell function. As signal transduction pathways have been described for important processes such as the regulation of cell division, it has become possible to perturb intermediate steps in the pathway between signal and cell effects. In the signaling that stimulates cells to reproduce, two important steps are the focus of intense interest. One is at the cell membrane and involves the ras GTPase that converts GTP bound to ras to GDP that can be inactive in cancer cells (see Figure 7.9). Drugs that target this GTPase make it more active, so there is less active ras in the cell and the signal transduction pathway for cell division does not get under way. Another area of intense interest is an intermediate step in the phospholipase C pathway (see Figure 7.14) that involves the protein kinase mTOR. Several drugs that target mTOR inactivate it, resulting in less cell division in tumor cells and cells involved in inflammation.