[Endogenous regulators of long-term potentiation and depression in slices of the olfactory cortex in rats].

Two fractions of the perfusate collected during tetanic stimulation of the rat lateral olfactory tract, were studied. The > 50 kDa fractions induced a long-term depression of focal potentials, whereas the < 50 fractions mainly induced an activation. The findings suggest a release of a number of neurohumoral substances by the donor cells during tetanisation, the substances being polypeptides, most probably, modulating the synaptic plasticity.