#opsin

FIGURE 16.21 The chemistry of colour detection in the eye following absorption of a particular wavelength of light by rhodopsin.

Look inside the eyes of a jumping spider, a human, or any other animal, and you’ll find light-detecting cells called photoreceptors.  These cells might vary dramatically from one species to another, but they share a universal feature:  They contain proteins called opsins.  Every animal that sees does so with opsins, which work by tightly embracing a partner molecule called a chromophore, usually derived from vitamin A.  The chromophore can absorb the energy from a single photon of light.  When it does, it instantly snaps into a different shape, and its contortions force its opsin partner to reshape itself, too.  The opsin’s transformation then sets off a chemical chain reaction that ends with an electrical signal traveling down a neuron.  This is how light is sensed.  Think of the chromophore as a car key and the opsin as an ignition switch.  The two fit together, light turns the key, and the engine of vision whirs into life.

Skin keeps time independent of the brain 

A study has now found that a type of opsin known as neuropsin is expressed in the hair follicles of mice and synchronize the skin’s circadian clock to the light-dark cycle, independent of the eyes or brain.

Some fishes in the deep, dark sea may see their world in more than just shades of gray.

A survey of 101 fish species reveals that four from the deep sea had a surprising number of genes for light-sensitive eye proteins called rod opsins, researchers report in the May 10 Science. Depending on how the animals use those light catchers, the discovery might challenge the widespread idea that deep-sea fishes don’t see color, says coauthor Zuzana Musilová, an evolutionary biologist at Charles University in Prague.

To see, many fishes, humans and most other vertebrates rely on two types of light-detecting cells in the eye known as rods and cones. Cone cells use two or more kinds of opsins and need decent amounts of light to work. Rods generally use only one opsin called RH1, which works in dim light. That variety in opsins in cones, but not in rods, lets vertebrates see a range of colors in well-lit conditions but be color-blind in the near dark.

In the new study, Musilová and Fabio Cortesi of the University of Queensland in Brisbane, Australia sailed on research ships equipped to reach into the ocean depths for fish. The deep-sea specimens came from the “twilight” zone 200 to 1,000 meters below the surface, where sunlight becomes only a subtle lessening of darkness. The most colorful things to look at would be bioluminescent spots on animals’ bodies.

The four deep-sea fishes with the special eyes came from three different lineages that had independently evolved genes for more than one kind of RH1 rod opsin, Musilová, Cortesi and their colleagues report. A glacier lantern fish (Benthosema glaciale) had genes for five different forms of RH1, and a tube-eye (Stylephorus chordatus) had six. Two kinds of spinyfin had even more, 18 genes for the longwing spinyfin (Diretmoides pauciradiatus) and a stunning 38 for the silver spinyfin (Diretmus argenteus).

Finding even two rod opsins would have been notable, but the silver spinyfin’s tally is “astounding,” says evolutionary biologist Megan Porter at the University of Hawaii at Manoa, who was not involved in the new research. But she and others warn against jumping to conclusions about how fishes use all this variety, because there are no tests with fish behavior.

Considering where these fishes live, such tests may not even be possible, Musilová says. When brought to the surface, “most of them simply die due to the pressures changes,” she says. “Even getting them to the surface alive doesn’t guarantee they would behave the same way they do in the depths.”

The fish that the researchers caught let them check which opsin genes were actually turned on in the animals’ retinas. That work confirmed that the silver spinyfin actually uses at least 14 of its 38 RH1 genes to make proteins.

The researchers also put the silver spinyfin’s various RHI genes into bacteria, which manufactured fish opsins. Tests of those opsins’ function showed they have the potential to capture both very faint daylight and a wide range of blue and green light from living bioluminescent creatures, the scientists found.

Overall, the authors are rightly “cautious” in not claiming that deep-sea fish can see color, says Almut Kelber of Lund University in Sweden, who has studied low-light color vision in frogs.

The new fish results, for example, don’t say whether different RHI opsins cluster in individual rod cells or are scattered, with different rod cells carrying different opsins. To differentiate colors, the rod opsins would need to be in different cells. But if the proteins clump in each rod, then the fish probably just have enhanced sensitivity to light and could pick out fainter objects in shades of black and white.

“It’s a] strong demonstration that opsin-dependent photoreceptors in deep brain areas affect behaviors,” 

A optogenetics method that may be used to treat chronic pain

When your finger prick from a thorn, an immediate sensory response happened. Neurons at the injury site send an electrical signal to the central nervous system along the nerve fiber in that moment. Then your brain reminds you to keep away from the thorns and the feelings of pain subsides. However, some chronic and debilitating pain, causing by some health conditions, may derive from organs deep inside the body and may affect the body function. A long course of medicine to treat the discomfort could have undesirable side effects, such as drug dependency.

Patients with interstitial cystitis/bladder pain syndrome (IC/BPS) suffer from chronic pain that severely affects quality of life. Those affected experience abdominal discomfort that increases as their bladder fills, which in turn causes excessive urinary urgency and frequency. A research reported the first use of optogenetics to reduce bladder pain. The results in mice suggest that selective optogenetic silencing of nociceptive bladder afferents may represent a potential future therapeutic strategy for the treatment of bladder pain.

Researchers performed the tests with mice bred with light-sensitive opsin proteins expressed in pain-sensing neurons. They also implanted some mice with small, flexible, light-emitting diode (LED) devices that are wirelessly controlled. By flipping the on-switch of the LED, they activated the opsin, which silenced the neuronal signal, resulting in pain relief for the animals. In the present study, the researchers tested whether a similar optogenetic system could be used to control neurons deep inside the body, with mice affected by bladder pain.

Robert W. Gereau IV, one of authors of this article, whose team studies the cellular and molecular mechanisms of chronic pain and collaborates with clinicians whose patients are affected by the disorder. One prevailing hypotheses of Urologists is that this problem is largely a dysfunction of the nervous system. This optogenetic approach could be a drug-free way to do a local nerve block coming from the bladder.

The team of Professor John A. Rogers designed the implanted LED devices used in the study. The miniaturized, wirelessly powered implantable devices are flexible and stretchable, so they do not impede the animals’ movement, enabling stable operation in the animal, without any measurable adverse effects over many months.

Researchers performed three tests in mice. In the first, they recorded electronic signals of abdominal-muscle response during a procedure to fill the bladder, including normal mice and mice bred with the light-sensitive opsin gene. When LED light from a fiber-optic cable illuminated the bladder, the electronic signal measurements showed that genetically modified mice received pain relief during light exposure. The second time, they performed a test to measure referred pain, in which the pain is felt at a location different from the original site of the stimulus. In this case, the pain from the bladder is felt in the abdomen wall. In this test, animals with the opsin protein received total reversal of referred pain. Then they continue to determine whether mice with bladder pain would respond to pain relief from the activation of a wireless LED implant. Mice is placed in a v-shaped maze, where they can move freely, and their movements are recorded. Results find that they like to hide in the corners of these things.

Another set of mice experiencing bladder pain are tested. Those without a light-sensitive opsin protein found a random corner to huddle. But those with the light-sensitive opsin protein and an implanted LED preferred the end of the maze at which researchers wirelessly activated the LED. It is the first time to demonstrate that an animal has ongoing pain that they are able to relieve on a moment-by-moment basis.

Significant challenges in gene therapy would need to be overcome if the approach is applied to human chronic pain eventually, but the hardware could be ready very soon. Implantable stimulators are already used to treat neurologic conditions, and scientists are trying to come up with safe, non-addictive ways to treat pain. It is imagined that patients could use a smart-phone app to adjust activation of implanted LEDs to regulate their chronic pain.

Source: https://www.nibib.nih.gov/news-events/newsroom/turning-light-switch-treat-chronic-pain

Article: Optogenetic silencing of nociceptive primary afferents reduces evoked and ongoing bladder pain.

New Post has been published on http://www.bioadvisers.com/optogenetics-method-may-used-treat-chronic-pain/

A optogenetics method that may be used to treat chronic pain

When your finger prick from a thorn, an immediate sensory response happened. Neurons at the injury site send an electrical signal to the central nervous system along the nerve fiber in that moment. Then your brain reminds you to keep away from the thorns and the feelings of pain subsides. However, some chronic and debilitating pain, causing by some health conditions, may derive from organs deep inside the body and may affect the body function. A long course of medicine to treat the discomfort could have undesirable side effects, such as drug dependency.

Patients with interstitial cystitis/bladder pain syndrome (IC/BPS) suffer from chronic pain that severely affects quality of life. Those affected experience abdominal discomfort that increases as their bladder fills, which in turn causes excessive urinary urgency and frequency. A research reported the first use of optogenetics to reduce bladder pain. The results in mice suggest that selective optogenetic silencing of nociceptive bladder afferents may represent a potential future therapeutic strategy for the treatment of bladder pain.

Researchers performed the tests with mice bred with light-sensitive opsin proteins expressed in pain-sensing neurons. They also implanted some mice with small, flexible, light-emitting diode (LED) devices that are wirelessly controlled. By flipping the on-switch of the LED, they activated the opsin, which silenced the neuronal signal, resulting in pain relief for the animals. In the present study, the researchers tested whether a similar optogenetic system could be used to control neurons deep inside the body, with mice affected by bladder pain.

Robert W. Gereau IV, one of authors of this article, whose team studies the cellular and molecular mechanisms of chronic pain and collaborates with clinicians whose patients are affected by the disorder. One prevailing hypotheses of Urologists is that this problem is largely a dysfunction of the nervous system. This optogenetic approach could be a drug-free way to do a local nerve block coming from the bladder.

The team of Professor John A. Rogers designed the implanted LED devices used in the study. The miniaturized, wirelessly powered implantable devices are flexible and stretchable, so they do not impede the animals’ movement, enabling stable operation in the animal, without any measurable adverse effects over many months.

Researchers performed three tests in mice. In the first, they recorded electronic signals of abdominal-muscle response during a procedure to fill the bladder, including normal mice and mice bred with the light-sensitive opsin gene. When LED light from a fiber-optic cable illuminated the bladder, the electronic signal measurements showed that genetically modified mice received pain relief during light exposure. The second time, they performed a test to measure referred pain, in which the pain is felt at a location different from the original site of the stimulus. In this case, the pain from the bladder is felt in the abdomen wall. In this test, animals with the opsin protein received total reversal of referred pain. Then they continue to determine whether mice with bladder pain would respond to pain relief from the activation of a wireless LED implant. Mice is placed in a v-shaped maze, where they can move freely, and their movements are recorded. Results find that they like to hide in the corners of these things.

Another set of mice experiencing bladder pain are tested. Those without a light-sensitive opsin protein found a random corner to huddle. But those with the light-sensitive opsin protein and an implanted LED preferred the end of the maze at which researchers wirelessly activated the LED. It is the first time to demonstrate that an animal has ongoing pain that they are able to relieve on a moment-by-moment basis.

Significant challenges in gene therapy would need to be overcome if the approach is applied to human chronic pain eventually, but the hardware could be ready very soon. Implantable stimulators are already used to treat neurologic conditions, and scientists are trying to come up with safe, non-addictive ways to treat pain. It is imagined that patients could use a smart-phone app to adjust activation of implanted LEDs to regulate their chronic pain.

Source: https://www.nibib.nih.gov/news-events/newsroom/turning-light-switch-treat-chronic-pain

Article: Optogenetic silencing of nociceptive primary afferents reduces evoked and ongoing bladder pain.