A WSU neuroscience undergraduate is looking into how the psychoactive component of cannabis affects different types of pain, as more people turn to cannabis for medicinal pain relief.

Abby Pondelick, a junior in the College of Veterinary Medicine, is currently conducting research to determine how delta-9-tetrahydrocannabinol, the active ingredient in cannabis commonly called THC, affects pain in rats.

Pondelick’s research specifically investigates the difference between affective and sensory pain. Affective pain refers to how bothersome or distressing that pain may be, Pondelick said, while sensory pain refers to the intensity, location and type of pain.

The focus of Pondelick’s research, she said, is to find out if THC reduces affective pain. She is also looking into how doses of THC impact affective and sensory pain differently. Her last research question asks if there are sex differences in THC’s effects.

Pondelick said opioids, such as morphine, are commonly used drugs to treat pain. Higher doses are used until the patient is nearly or completely pain-free, Pondelick said.

“Completely blocking pain might not be ideal since pain can help us avoid damages to ourselves,” Pondelick said. “In addition, the higher doses used, the greater risk of developing tolerance and addiction.”

Pondelick conducted research over a four-day period with a three-compartment apparatus using Sprague-Dawley rats between 60 and 100 days old. She used a method called “pain-induced conditioned place aversion,” a common procedure in studies of rodents that models the emotional aspect of pain. Rats tend to avoid a place where they previously experienced pain.

“This is like if you were to get hurt in a car accident, you may avoid the area where the accident occurred,” Pondelick said, “even if just unconsciously because of the negative experience you had there.”

The apparatus contained chambers with different wall colors and floor types. The rats were first injected with THC and then injected with either saline or a solution to induce pain. Next, the rats were restricted to either the “black wall/grid floor” or “white wall/bar floor” side for 45 minutes.

Pondelick said affective pain was measured by observing if the rats returned to the part of the chamber where they were injected. A rat avoiding the part of the chamber where it received the injection could indicate “place aversion,” meaning it experienced affective pain. To measure sensory pain, Pondelick counted how many times the rats licked the injection site on their paws.

Although Pondelick’s study is ongoing, so far THC appears to be reducing the emotional aspect of pain without reducing the sensory aspect. Unexpectedly, she said, rats injected on the “white wall/bar floor” side were significantly more likely to avoid that side. However, Pondelick said, rats from both sides licked their paws about the same, indicating no significant difference in sensory pain between the two groups.

According to Pondelick’s research poster, no significant sex differences were found on any measure, suggesting affective pain may not be sex-dependent.

Pondelick still has approximately 40 percent of data left to collect. She conducted her research with the help of her adviser Rebecca Craft, a professor in the psychology department.

This research is important, Pondelick said, because more people are using cannabis medicinally for pain relief.

“This could provide a new way to treat pain that doesn’t completely eliminate all pain, yet makes it manageable,” she said.