Have you ever been caught in the crossfire of a wet dog shivering violently and spraying water droplets from its fur? Well, they can’t help it. Scientists have discovered the underlying mechanism by which dogs and many other hairy mammals shake water from their fur, through a fascinating investigation into the genetics that causes this involuntary behavior.
Neurobiology researchers at Harvard Medical School’s Howard Hughes Medical Institute have identified a complex but fairly efficient sensory mechanism that causes “wet dog tremors,” allowing your pet to pay for your bath by soaking you too. He proved that he was not trying to make him do anything.
“Wet dog shaking is an evolutionarily conserved behavior observed in mammals that serves to remove water and other irritants from the hairy skin of the back and neck,” the researchers wrote in a preprint of their paper. “This skin area is largely incapable of grooming or licking on its own.” . “We found that the C-LTMR detects the lightest forces acting on hairy skin, such as water, the movement of insects or parasites, and other stimuli that distract vellus hair, and detects the lightest forces acting on hairy skin, such as water, the movement of insects or parasites, and other stimuli that distract the vellus hair. We propose that this triggers an evolved locomotor behavior to remove the
Scientists tested the animals through a series of complex experiments, applying a number of stimuli, including oil and air blows, to areas of the animals’ backs and necks that are difficult to groom. They tracked the onset of the vibrations on high-speed video and recorded their onset time, frequency, and duration.
Because neurobiology focuses on identifying the mechanisms in the brain that cause behavior, rather than simply observing it, the research team used optogenetics, genetic manipulation to suppress specific pathways, and We employed in vivo calcium imaging to identify active neurons. They then bred mice without C-LTMR neurons and observed a significant reduction in “wet dog trembling” behavior in response to mechanical stimuli such as oil and water.
C-LTMRs (C-fiber low-threshold mechanoreceptors) are sensory neurons that activate in response to mild mechanical stimulation of mammalian fur and hairy skin. It was known that they were activated by stimuli involving touch, but it was not clear whether they were the key to causing this almost comical whole-body tremor in the animals.
Through their work, the research team has determined how stimulation opens the Piezo2 mechanosensory ion channel, controls C-LTMR, connects with spinal parabrachial (SPB) neurons, and along specific pathways that control this neuron. We identified what causes excitatory postsynaptic currents (EPSCs). Motor response mechanism.
The researchers also found that they could stimulate neurons with light (optogenetics) to trigger a shivering response without physically stimulating the fur, and that activation of the C-LTMR alone could initiate a shivering response. showed.
“The discovery that C-LTMR contributes to stimulus-induced tremors in wet dogs raises questions about how these enigmatic mechanosensory neurons engage central circuits to mediate somatosensory behavior. “This provided us with an opportunity to ask whether this is the case,” the research team pointed out. “We found that C-LTMRs are indeed synaptically coupled to SPNs, as optogenetic activation of C-LTMR terminals evoked excitatory postsynaptic currents (EPSCs) in both SPN populations.”
“Taken together, these findings demonstrate the contribution of the C-LTMR-spinal parabrachial pathway in mechanically induced wet dog tremors,” the researchers added in their paper.
Why water drips from the ceiling after Fido takes a bath may be more than we want to know, but it’s an interesting insight into how complex sensory communication and responsive behavior are. And until very recently, technology limitations have kept this kind of discovery at the hypothetical stage.
So next time your dog gives you a spray, remember that they are not trying to embarrass you. It’s all just in the dog’s genes.
The study was published in the journal Science.
Source: Howard Hughes Medical Institute (via Phys.org)
