[Synaptic responses of medulla oblongata neurons to stimulation of the "locomotor area" in the turtle].

Responses of medullary neurons to microstimulation of medullary locomotor region by current up to 30 micro A were recorded intracellularly in decerebrated turtles. Resting potential of these neurons varied from 22 to 42 mV. Depolarizing PSPs (EPSPs) were evoked in 43 neurons, hyperpolarizing ones (IPSPs) in 12 neurons, and both types of PSPs were observed in 36 neurons. Discharges of synaptic origin were observed in 29 neurons, including 11 which generated action potentials without any visible PSP. Latencies of PSPs were usually in the range from 2 to 8 ms. The delay from the beginning of EPSP to the onset of action potential was 1-3 ms when the firing index was high, but fluctuated significantly and increased under weaker stimulation. Unitary EPSPs in 15 neurons and IPSPs in 3 neurons were recorded. Their amplitudes were 0.6-0.8 mV, that was 2-12 times less than thresholds depolarization (1-7 mV). The data obtained as well as results of extracellular recordings from medullary neurons in turtles and cats are employed for discussion on possible mechanism of locomotor activity propagation in the lower brain stem.