Preclinical studies are supposed to provide precise, controllable, and translational models for human diseases. But the manipulations that researchers use — like injecting a precise dose of THC into a rat — may sometimes miss important points. What if smoking and injection have different effects? How might this bias results? University of Florida researchers asked just that question, studying the effects of injected vs. smoked THC in rats. Injecting low doses of THC impaired memory. But female rats’ memory were slightly improved by cannabis smoke. Male rats showed no differences when exposed to the smoke. The researchers also did an exploratory analysis of their data (which means that after they tested their hypothesis, they sifted through the data to find more trends). They found that the males who had the worst memory to begin with were aided by THC, at least using this model of memory. (The model may actually be testing the rats’ ability to focus.) Why is there a sex difference? It could be caused by a difference in two neurotransmitter systems (GABA and CB1) in males and females. Note: these results shouldn’t be interpreted to mean that smoking cannabis will improve women’s memory. We are simply highlighting an important factor in preclinical research. These results partially contradict a quick hit from last week.
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