We have considered two types of interactions between particles resulting in autoionization of the intermediate Rydberg collisional complex. The first type is caused by the charge exchange processes inside the ionic core of the complex and is responsible for the formation of the final associative ionization channel due to the departure of a Rydberg electron (RE) of the complex to the energy continuum. We have investigated the evolution of the orbital momentum L of RE and discovered a non-trivial time dependence of L, demonstrating a contrasting oscillatory structure in both direction orientation and its absolute value. The second type of interaction, dipole-dipole interaction, dominates in cold highly excited gaseous media and leads to Penning ionization of various pairs of Rydberg atoms. We have found the optimal quantum configurations of atomic pairs, which intensify the PI rates by several orders of magnitude, and become important suppliers of charged particles upon the evolution of Rydberg gas into cold plasma.