Why humans and animals love stroking

   Jan 31, 12:12 pm

London, January 31 (ANI): Biologists at the California Institute of Technology (Caltech) have identified in mice a specific class of skin sensory neurons that reacts to an apparently pleasurable stimulus.

More specifically, the team, led by David J. Anderson, Seymour Benzer Professor of Biology at Caltech, was able to pinpoint individual neurons that were activated by massage-like stroking of the skin.

"We've known a lot about the neurons that detect things that make us hurt or feel pain, but we've known much less about the identity of the neurons that make us feel good when they are stimulated," said Anderson, who is also an investigator with the Howard Hughes Medical Institute.

The researchers had to develop new methods and technologies to get their results. First, Sophia Vrontou, a postdoctoral fellow in Anderson's lab and the lead author of the study, developed a line of genetically modified mice that had tags, or molecular markers, on the neurons that the team wanted to study. Then she placed a molecule in this specific population of neurons that fluoresced, or lit up, when the neurons were activated.

"The next step was to figure out a way of recording those flashes of light in those neurons in an intact mouse while stroking and poking its body," said Anderson.

"We took advantage of the fact that these sensory neurons are bipolar in the sense that they send one branch into the skin that detects stimuli, and another branch into the spinal cord to relay the message detected in the skin to the brain," he added.

The team obtained the needed data by placing the mouse under a special microscope with very high magnification and recording the level of fluorescent light in the fibers of neurons in the spinal cord as the animal was stroked, poked, tickled, and pinched. Through a painstaking process of applying stimuli to one tiny area of the animal's body at a time, they were able to confirm that certain neurons lit up only when stroked.

A different class of neurons, by contrast, was activated by poking or pinching the skin, but not by stroking.

"Massage-like stroking is a stimulus that, if were we to experience it, would feel good to us, but as scientists we can't just assume that because something feels good to us, it has to also feel good to an animal," says Anderson.

"So we then had to design an experiment to show that artificially activating just these neurons-without actually stroking the mouse-felt good to the mouse," he explained.

The researchers did this by creating a box that contained left, right, and center rooms connected by little doors. The left and right rooms were different enough that a mouse could distinguish them through smell, sight, and touch. In the left room, the mouse received an injection of a drug that selectively activated the neurons shown to detect massage-like stroking .

In the room on the right, the mouse received a control injection of saline. After a few sessions in each outer room, the animal was placed in the center, with the doors open to see which room it preferred. It clearly favored the room where the massage-sensitive neurons were activated.

According to Anderson, this was the first time anyone has used this type of conditioned place-preference experiment to show that activating a specific population of neurons in the skin can actually make an animal experience a pleasurable or rewarding state-in effect, to "feel good."

The team's results are outlined in the January 31 issue of the journal Nature. (ANI)

Why sick people always pitied more than those unemployed May 27, 1:58 pm
Washington D.C, May 27 (ANI): A new study has revealed why everyone wants to help the sick, but not the unemployed.
Full Story
Altering perception of food can extend healthspan May 27, 12:45 pm
Washington D.C, May 27 (ANI): It is well documented that calorie restriction (CR) has extended lifespan on countless species and now, a team of researchers are claiming that altering the perception of food can also give the same result.
Full Story
Presidential candidates' 'charismatic' speaking strategies May 26, 1:13 pm
Washington D.C, May 26 (ANI): A new study has shed some light on the charismatic speaking strategies of the presidential candidates.
Full Story
Probable connection between primordial black holes, dark matter? May 25, 4:31 pm
Washington D.C., May 25 (ANI): The nature of dark matter still poses to be one of biggest mysteries in astrophysics. While one view suggests that dark matter is composed of material universe, another proposes that it is made up of black holes formed during the first second of our universe's existence.
Full Story
Comments