[Frequency potentiation in newborn rabbit hippocampus]

Ontogenetic development of the frequency potentiation in the entorhinal afferent input of the hippocampus was studied on unanesthetized rabbits 1--15 days after birth. In the fields CA1 and CA3 of the new-born rabbits rhythmical electrical stimulation (1--20 Hz) of the perforant path led to a 20--100% increase in the amplitude of local potentials as compared to the control value and to an increase in the probability of the mass discharge response from 0--0.5 (in control) to 0.8--1.0 (during tetanization). In 1--3-day-old rabbits the potentiation was especially pronounced at frequencies of 4--6 Hz. The frequency optimum of 4--15 Hz appeared on the fifth day after birth. The frequency potentiation of the mass discharge was observed on the 8th--10th day of life. The results show that the frequency potentiation in the cortical afferent connections of the hippocampus can be recorded already in new-born rabbits and achieved the mature pattern at the beginning of the second week of the postnatal life.