A drug that can alleviate the exaggerated startle responses seen in hyperekplexia - or “startle disease” - in a mouse model of the condition is discussed in a paper published online in Nature Neuroscience. These findings suggest potential therapeutic avenues for individuals with hyperekplexia.
People with hyperekplexia exhibit exaggerated startle responses to unexpected auditory or tactile stimuli, such as hands clapping or taps on shoulder. Previous studies have found that this disease can be caused by mutations in the brain receptor for the neurotransmitter glycine. Existing treatments for hyperekplexia increase the function of a different neurotransmitter, GABA, which like glycine is an inhibitory neurotransmitter and reduces activity in neurons.
Taking a different path, Li Zhang and colleagues focused specifically on drugs that affect glycine receptors. They showed that one drug, TH-CBD, could increase the function of mutated glycine receptors in neurons, and indeed could ameliorate acoustic and tactile startle responses in hyperekplexia model mice. TH-CBD is a chemically modified form of cannabidiol, a prevalent constituent of cannabis plants, which is non-psychoactive, making it a more viable therapeutic option.
While the effects of drugs like TH-CBD will have to be tested further, this work highlights the potential of therapies for hyperekplexia that target glycine receptors directly.