A new study from the NC State College of Veterinary Medicine is the first to pinpoint the intricate pathway mechanisms of itch in dogs, information vital to developing targeted treatments for common and chronic canine skin disorders.
The research describes the expression of itch-signaling somatostatin and other major itch-associated neuropeptides and receptors in canine neurons. It details the inflammatory molecule interleukin-31, serotonin and histamine as activators of the neurons. The exact itch-associated neurotransmitters, neuropeptides and respective receptors in canines have not been previously reported.
For the study, researchers isolated canine dorsal root ganglia, a group of cell bodies with sensory neurons that lie between vertebrae and send information to the spinal cord. Then researchers determined the messenger RNA levels of neuropeptides and neuropeptide receptors in canine DRGs and spinal cords.
In humans and animals, sensory nerves reacting to an array of inflammatory motivators lead to the sensation to itch. That sensation is transmitted from the spinal cord to the brain. The outlined canine itch expression mirrors much of the same molecular mechanisms of itch previously observed in mice.
Dermatological issues account for almost 20% of all dog veterinary visits, with 30% those cases related to pruritus, or itching, according to a recent study. Canine atopic dermatitis, which leads to everything from excessive itching and licking to flaky skin and hair loss, is a common allergic reaction seen across dog breeds.
“Canine atopic dermatitis is a huge problem but our understanding of how itch sensation is detected and transmitted in these companion animals is sparse,” said Santosh Mishra, an assistant professor in the CVM’s Department of Molecular Biomedical Sciences. “Here we provide direct evidence of physiological expression and function of itch-associated receptors and neurotransmitters in dogs, which will provide a realistic approach in the development of potential therapeutics by targeting neurons.
Canine atopic dermatitis is a complex condition and not completely understood, said Mishra. Different therapies for itch are available, including medication, but can be costly and may include side effects. Often, long-term treatment for canine dermatitis requires trial and error.
Characterizing neuronal pathways of itch in dogs now provides a solid foundation for finding ways to treat atopic dermatitis and other forms of pruritus.
“This is the beginning,” said Mishra. “We still need to know a lot about the molecular components associated with these conditions and if similar pathways exist in other diseases. Then eventually treating the dogs using these identified pathways in the future will be very satisfying.”
Mishra’s lab at the CVM investigates the underlying mechanisms of chronic itch and the itch-responsive neurons of the spinal cord. Last month, he was the lead author of a study outlining the role inflammation-induced overexpression of calcium channel genes may play in pain hypersensitivity.
~Jordan Bartel/NC State Veterinary Medicine