[Homosynaptic depression--a model of the habituation phenomenon]

A high functional stability of the cat spinal cord motoneurons was shown in conditions of long-term orto- and antidromic activation with frequency corresponding to their natural rhythmicity. The depression of reflex discharges was shown to be related not to any postsynaptic depression or presynaptic inhibition but to a drop of probability of the transmitter release from the primary afferents' terminals. Analysis of signs of the habituation phenomenon revealed their similarity to the homosynaptic depression phenomenon and, consequently, their submittance to the same principles of experimental analysis and consideration.