What substance can act as a retrograde messenger to suppress release of GABA to contribute to LTP? 00:29 Biology Chapter 8 What substance can act as a retrograde messenger to suppress release of GABA to contribute to LTP? A. acetylcholine B. endocannabinoid C. carbon monoxide D. norepinephrines Answer: endocannabinoid Learn More : Share this Share on FacebookTweet on TwitterPlus on Google+