We have previously investigated the dynamics of probabilistic neural nets with chemical markers and Gaussian distribution of connectivities of the constituent neurons. These investigations have shown that the change from a Poisson to a Gaussian distribution may cause a net to change class. We have now generalized these studies by considering the intrinsic noise of the systems, caused by the spontaneous release of synaptic transmitter substance. A simple mathematical model is developed, the dynamics of which is compared with the Poisson model.