P or Not P

Dr. Nirao Shah

Stanford researchers have found the specific cells in the brains of male mice that activate sexual desire. They were able to manipulate desire through the application of a protein called "Substance P."

[Nirao] Shah and his team found buried in mice brains, a bit above the roof of the mouth, tiny neural connections that are tasked with processing information from the outside world.

They tell a male mouse whether another mouse is female, and feeling flirty.

If so, this good news is relayed to an adjacent set of brain cells, located on the same circuit. Then a small protein, called Substance P, issues a call to action — like a Marvin Gaye groove.

The team focused on a set of genetically distinct neurons in the amygdala that do something special: They secrete a small and slow-acting peptide dubbed Substance P.

Then the scientists watched a different set of neurons in the preoptic hypothalamus that had receptors for this Substance P. Those two groups of neurons work together, like lock and key.

When Substance P binds to these receptors, it gradually sensitizes the neurons so they become increasingly active...

Normally, male mice are slow to warm up, taking 10 to 15 minutes before mounting. Afterwards, they take a five-day break before regaining interest.

But when the researchers directly infused Substance P into mice brains, the animals turned into love junkies.

Rather than waiting to mate, the mice were ready instantaneously. They even fell in love with lab equipment, mounting plastic tubes adorned with the tail end of a toy mouse bought on Amazon.

They could also become prim, proper and prudish. When researchers silenced the neurons and switched off the circuit, dialing down production of Substance P, the mice lost desire.

We're years away from determining if there's a similar mechanism in the brains of human males and whether the human version of Substance P can be administered (or turned off) safely. If that can be achieved, the control of man's biggest sex organ, the brain, is around the corner.