Anyone who has obeyed nature by transmitting a piece of gossip experiences the explosive relief that accompanies the satisfying of a primary need.
This is an interesting thought ... coming from an atheist. He is saying that people "obey nature" when they gossip. There is this urge in the soul of unsanctified people, those that have not yielded this area of their lives to be conformed into the image of the Son, to transmit information, gossipy information. The urge is so powerful, that when they release the information, Levi says there is an "explosive relief." It's this explosive relief that makes gossip so powerful to the speaker, so addictive.