Why humans and animals love stroking

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)

Matches

MORE TOP STORIES TODAY

Bangalore lose nerve, lose game

Bangalore lose nerve, lose game

IPL 7, GAME 11—Vinay's over, Lynn's catch turns last-over finish in KKR's favour. More »

Boycotting IPL will not save cricket

Boycotting IPL will not save cricket

Boycotting the IPL as a means of protest against the grime in the game may not yield the desired results. More »

Jadeja spins out Rajasthan in close chase

Jadeja spins out Rajasthan in close chase

IPL 7, GAME 10—Chennai beat Rajasthan by 7 runs after last-over scare. More »

Gambhir a knock away from striking form - KKR coach

Gambhir a knock away from striking form - KKR coach

Gautam made an eight-ball duck in the opening game against Mumbai and in the second game against Delhi, he lasted only half those balls. More »

Rivals say Srini group delaying BCCI special general meeting

Rivals say Srini group delaying BCCI special general meeting

The group opposed to Srinivasan alleged that since BCCI secretary Sanjay Patel belongs to the president’s group, he was intentionally delaying the SGM… More »

April 24: A legend is born

As Sachin Tendulkar turns 41 - here's a look at some offbeat moments from the Master Blaster's innings. More »

Cleaning up the game starts with fans

Cleaning up the game starts with fans

... because, as recent events reveal, the BCCI has little intention of doing it. More »

SL in 'difficult place' after Farbrace exit

SL in 'difficult place' after Farbrace exit

Sri Lanka depart for assignments in Ireland and England in two weeks, and Sanath Jayasuriya suggested Marvan Atapattu would be interim head coach for those… More »

Chandimal axed as T20 captain

Chandimal axed as T20 captain

Sri Lanka's cricket selectors on Wednesday sacked Dinesh Chandimal as Twenty20 captain and replaced him with Lasith Malinga, while Angelo Mathews was… More »

Vithanage, Priyanjan get T20 call-ups

Vithanage, Priyanjan get T20 call-ups

Herath has been rested, while the team will be without the veteran pair of Mahela Jayawardene and Kumar Sangakkara, who retired from T20 internationals… More »

'BCCI should have picked panel with care'

'BCCI should have picked panel with care'

Dalmiya said that it was the first time that the BCCI had been faced with a situation where the apex court had hauled up the Board and it should have acted… More »

Farbrace is England's assistant coach

Farbrace is England's assistant coach

The ECB continued the restructuring of the England coaching set-up on Wednesday by announcing the appointment of Paul Farbrace as assistant coach. More »

SC asks Mudgal committee to continue

SC asks Mudgal committee to continue

Mukul Mudgal has communicated to the court his willingness to take up the investigation and has been asked to specify the terms and modalities on April… More »

Sri Lanka players resolve pay dispute

Sri Lanka players resolve pay dispute

The pay dispute between Sri Lanka Cricket and its 13 contracted players ended on Wednesday when the latter agreed to accept 10 percent of the participation… More »

Hope to be fit for next game - Pietersen

Hope to be fit for next game - Pietersen

With two heavy defeats at the hands of Bangalore and Chennai, Daredevils currently languish near the bottom of the table. More »

'SC decision could hurt BCCI's status'

'SC decision could hurt BCCI's status'

The Supreme Court prefers that the Justice Mudgal panel further investigate the IPL corruption scandal. More »

Mudgal panel drops bombshell in court

Mudgal panel drops bombshell in court

The Mukul Mudgal probe committee dropped a bombshell in the Supreme Court on Tuesday by making a sensational claim that it was forced to stop audio recording… More »

Perfect Punjab trounce Hyderabad

Perfect Punjab trounce Hyderabad

IPL7, GAME 9—Maxwell (95, 43b), Balaji (4-13) set up 72-run win. More »

Have the ECB played an unfair game?

Have the ECB played an unfair game?

Money talks, but it is in light of this ICC shakeup that the ECB's act of soliciting of another team's coach deteriorates from free-market aggression to… More »

Farbrace quits for England post

Farbrace quits for England post

He will assist Peter Moores who was unveiled as the new England coach on Saturday. More »

Moin appointed to manage Pakistan team

Moin appointed to manage Pakistan team

Pakistan on Monday reappointed Moin Khan as chief selector and manager of the national team, a week after fellow former captain Rashid Latif turned down… More »

Chennai smash Delhi for first win

Chennai smash Delhi for first win

IPL7, MATCH 8—Raina-led middle order, superlative catching give CSK a 93-run win. More »

'BCCI reputation lowest in 80 years'

'BCCI reputation lowest in 80 years'

The former BCCI president says he was "disillusioned" by the happenings at the emergent working committee meeting on Sunday. More »

Injured Bravo to miss rest of IPL

Injured Bravo to miss rest of IPL

Dwayne Bravo is set to be sidelined for at least four weeks due to a shoulder problem. Bravo sustained the injury when attempting a catch on the boundary… More »