Sunday, April 26, 2015

Yes-ciception inhibits nociception in the spinal cord

At last. 

Finally a paper has come along that provides a bit of solid evidence for gate control theory of pain. It only took 50 years (..for petesake!), so I guess we shouldn't get all downcast over how hard it is to get physiotherapy to change course. (I just hope this doesn't turn into some huge TENS revival..)

But I digress..  
I'm thrilled. My confirmation bias bells are all going pingpingping
Why? because this supports manual intervention/human primate social grooming. 

1. Here is Mo Costandi's piece on the topic (the word "pain" should be replaced by the word "nociception", as usual..) :

2. Here is a link to the actual paper. 

Foster, E., et al. (2015). Targeted Ablation, Silencing, and Activation Establish Glycinergic Dorsal Horn Neurons as Key Components of a Spinal Gate for Pain and Itch. Neuron, 85: 1289-1304 [PDF].
Here is the abstract: 
SUMMARY The gate control theory of pain proposes that inhibitory neurons of the spinal dorsal horn exert critical control over the relay of nociceptive signals to higher brain areas. Here we investigated how the glycinergic subpopulation of these neurons contributes to modality-specific pain and itch processing. We generated a GlyT2::Cre transgenic mouse line suitable for virus-mediated retrograde tracing studies and for spatially precise ablation, silencing, and activation of glycinergic neurons. We found that these neurons receive sensory input mainly from myelinated primary sensory neurons and that their local toxin-mediated ablation or silencing induces localized mechanical, heat, and cold hyperalgesia; spontaneous flinching behavior; and excessive licking and biting directed toward the corresponding skin territory. Conversely, local pharmacogenetic activation of the same neurons alleviated neuropathic hyperalgesia and chloroquine- and histamine-induced itch. These results establish glycinergic neurons of the spinal dorsal horn as key elements of an inhibitory pain and itch control circuit.
My bold.

3. Here is a link to the original gate control theory of pain paper. 
Melzack, P. & Wall, P. D. (1965). Pain Mechanisms: A New Theory.Science150: 971-979 [PDF].

MORE:  Here is a link to a great great set of very short and wonderful videos of David Krakauer discussing intelligence, genius, whether or not stupidity is the opposite of intelligence (spoiler alert - it's not..) and all sorts of things. It's great. I can't recommend it highly enough. 

"...what genius does is it just changes the rules of the game. It doesn’t just make it better, or easier, or more efficient. And one of the very interesting characteristics of genius, as opposed to intelligence, is it looks a little crazy. Because an intelligent solution is almost always—and I gave some examples of stupidity—clear to most people that that is a better way of doing things. Yes, that is a better way of doing things. But when you change the rules, you make a lot of people uncomfortable, and it looks a little crazy. So in some sense, my diagnostic, my litmus test for genius as opposed to extreme intelligence is it made everything simpler, but the people, when they first saw it thought it was lunatic; because formally, it’s changing the basis set. It’s just changing the nature of the representation of the problem so completely that you get the kind of vertigo of unfamiliarity. So that for me would be genius."

My bold. There is no way to classify Melzack and Wall's work other than they are genius and so was/is their work. They pushed back the boundaries of pain research. They changed the rules. There was pushback - bitter pushback. Even nowadays Melzack remarks on what a surprise that pushback was, in some ways, and shakes his head. 
I bet he feels vindicated, a bit at least, by this new paper.

MORE:  I just today spotted a video of Martin Hey, head of the WCPT pain network, presenting an overview of pain physiotherapy in the UK. It's about 40 minutes long, was filmed in Seville in October last year and a Pain and Physiotherapy conference, and uploaded to Youtube in December 2014. 
It's very good. 
Hey describes most aspects of the mess PT is in, without actually calling it such..

Martin Hey of WCPT's Pain Network

YET MORE (courtesy of Fred Wellens):   

Shechter RBaruch KSchwartz MRolls A.;  Touch gives new life: mechanosensation modulates spinal cord adult neurogenesisMol Psychiatry. 2011 Mar;16(3):342-52


"The ability to respond to a wide range of novel touch sensations and to habituate upon repeated exposures is fundamental for effective sensation. In this study we identified adult spinal cord neurogenesis as a potential novel player in the mechanism of tactile sensation. We demonstrate that a single exposure to a novel mechanosensory stimulus induced immediate proliferation of progenitor cells in the spinal dorsal horn, whereas repeated exposures to the same stimulus induced neuronal differentiation and survival. Most of the newly formed neurons differentiated toward a GABAergic fate. This touch-induced neurogenesis reflected the novelty of the stimuli, its diversity, as well as stimulus duration. Introducing adult neurogenesis as a potential mechanism of response to a novel stimulus and for habituation to repeated sensory exposures opens up potential new directions in treating hypersensitivity, pain and other mechanosensory disorders."


No comments: