[The effect of creatine phosphate on reflex transmission in the normal spinal cord and under hypoxic conditions]. / Vliianie kreatinfosfata na reflektornuiu peredachu v spinnom mozge v norme i v usloviiakh gipoksii.

The effect of phosphocreatine on reflex transmission in the spinal cord was studied in rats in vivo and in vitro. Low concentrations (10(-8)-10(-6) M) of phosphocreatine facilitated while high concentrations (10(-4)-10(-3) M) inhibited the amplitude of mono- and polysynaptic reflexes. It was found that phosphocreatine decreases the inhibiting action of hypoxia on test responses and accelerates restoration of the reflex transmission in the spinal cord.

[Effect of dopamine on the background and evoked activity of interneurons from isolated spinal cord segments of newborn rats]. / Vliianie dopamina na fonovuiu i vyzvanniui aktivnost' interneironov izolirovannogo segmenta spinnogo mozga krysiat.

The effects of dopamine on the background and dorsal root stimulation-evoked activity of spinal interneurons and on the field potentials in the dorsal horn were studied in the isolated superfused spinal cord of 11-18 days old rats. It was established that application of dopamine in concentration 1.10(-6)-1.10(-3) mol/l caused exciting and depressing effects on the background and evoked activity of spinal cord cells. The postsynaptic wave of field potentials was depressed by dopamine. In some interneurons the effects of dopamine disappeared in the solution with 0.01 mmol/l Ca2+ and 1.5-2 mmol/l Mn2+ (trans-synaptic effects). In other cells exciting or inhibiting effects of dopamine were preserved in the medium blocking synaptic transmission, that evidenced for direct depolarization and hyperpolarization of the interneuron membrane. The effects of dopamine were reversible and dose-dependent. These results suggest that dopamine may have influence on the transmission of excitation in the spinal cord on the interneurons level. It is supposed to be possible that different types of interneurons responses are the result of the existence of two types of dopamine receptors in the spinal cord.

[Depolarizing action of dopamine on the motor neurons of an isolated segment of the spinal cord in rat pups]. / Depoliarizuiushchee deistvie dofamina na motoneirony izolirovannogo segmenta spinnogo mozga krysiat.

The dopamine effect on the ventral root potential was studied in the experiment with the isolated superfused spinal cord of 13-18-day old rats. It was established that application of dopamine in concentration of 1.10(-6)-1.10(-2) mol/l caused the reversible dose-dependent depolarization in the motoneurons. Depolarization was retained in the calcium-free solution with magnesium or manganese ions. An increase of the motoneurons frequency discharges was observed simultaneously with the slow ventral root depolarization. The segmental reflex response evoked by dorsal root stimulation was depressed against the background of depolarization.

[Depolarizing action of dopamine on the endings of the primary afferent fibers of an isolated segment of the spinal cord in rat pups]. / Depoliarizuiushchee deistvie dofamina na terminali pervichnykh afferentnykh volokon izolirovannogo segmenta spinnogo mozga krysiat.

The effect of dopamine on the dorsal root potential was studied in the isolated superfused spinal cord of 12-18-day old rats. It was established that application of dopamine in concentration of 1.10(-9)-1.10(-3) mol/l caused the reversible dose-dependent depolarization in the dorsal root. The depolarization was retained in the calcium-free solution with magnesium or manganese ions. Its maximal amplitude reached 1.5 mV. Haloperidol, a dopamine antagonist, decreased depolarization evoked by dopamine. The possibility of dopaminergic brainstem-spinal pathways participation in the control of the sensory information transmission at the spinal cord entrance is discussed.

[Inhibitory action of dopamine on excitatory transmission in the isolated spinal cord of the rat]. / Ugnetaiushchee deistvie dofamina na peredachu vozbuzhdeniia v izolirovannom spinnom mozge krys.

The effect of dopamine on the ventral root potential evoked by single supramaximal dorsal root stimulation was studied in the experiment in the isolated superfused spinal cord of 10-16 days old rats. It was discovered that application of dopamine caused the reversible dose-dependent inhibition of the mono- and polysynaptic ventral root reflex responses. The minimal effective concentration was 1 X 10(-8) mol/l. Dopamine applied in concentrations of 1 X 10(-4) mol/l and 1 X 10(-3) mol/l decreased the amplitude of the monosynaptic ventral root potential by 20% and 87% as against the control, respectively. Under the same conditions the amplitude of the polysynaptic ventral root potential decreased by 18% and 87% as against the control, respectively. The obtained results demonstrate that the dopaminergic brainstem-spinal pathways take part in the control of the transmission in the segmentary reflex arc.