[PRESYNAPTIC SEROTONERGIC MODULATION OF SPONTANEOUS AND MINIATURE SYNAPTIC ACTIVITY IN THE FROG LUMBAR MOTONEURONS].

In this study we investigated the effect of 5-HT on the spontaneous and miniature synaptic activity in lumbar motoneurons from isolated frog spinal cord using intracellular recording. 5-HT increased the frequency of the spontaneous and miniature postsynaptic potentials (mPSPs). The effect of 5-HT on different subpopulations of mPSPs was multidirectional: it increased the frequency of glutamatergic excitatoty mPSP by 18 % and decreased the frequency of glycinergic inhibitory mPSP by 28 %, but had no effect on the frequency of GABAergic inhibitory mPSP.

[THE INHIBITORY EFFECT OF GLYCINE AND GABA ON MONOSYNAPTIC EPSPs IN THE FROG SPTNAL MOTONFUCTYNMR].

In this research we have studied the inhibitory effect of glycine and GABA on the monosynaptic EPSPs induced by microstimulation of presynaptic fibers close to the frog lumbar motoneurones. Monosynaptic EPSPs had two components mediated by AMPA/KA (78%) and NMDA (22%) receptors. Both inhibitory mediators considerably decreased EPSP's decay time by 33.

[Inhibitory regulation of glutamate receptors in the frog motoneuron].

The interaction of exogenously applied excitatory (glutamate and their agonists NMDA, AMPA, kainate) and inhibitory (glycine and GABA) amino acid effects was studied intracellularly in the motoneurones of the isolated frog spinal cord. During simultaneous glycine or GABA bath applications GLU-, AMPA-, KA- and NMDA-evoked responses were, respectively, decreased up to 45.8 +/- 2.

[The contribution of glycine and GABA(A) receptors to generation of the inhibitory postsynaptic potentials in the frog spinal cord motoneurones].

The contribution of glycine and GABA(A) receptors to generation of the inhibitory postsynaptic potentials (IPSPs) evoked by microstimulation of the inhibitory fibers was studied intracellularly in the motoneurones of the isolated frog spinal cord. IPSPs were isolated by bloking EPSPs with kynurenate or CNQX and AP-5. The reversion under the small depolarising current (1-10) nA was used for the identification of IPSPs.

Differences in the activation of inhibitory motoneuron receptors in the frog Rana ridibunda by GABA and glycine and their interaction.

Intracellular recording of potentials was used in isolated spinal cord segments from the frog Rana ridibunda to compare the inhibitory effects of GABA and glycine on the motoneuron membrane. At equal concentrations, the response (a change in membrane potential) to application of glycine was 1.5-2 times greater than the response to GABA in terms of amplitude, and EC(50) values were 0.

[Differences in activation of the motoneurone inhibitory receptors in a frog Rana ridibunda by GABA and glycine and their interaction].

The membrane potential responses evoked by GABA and glycine bath applications were studied intracellularly in the motoneurons of the isolated frog spinal cord. The amplitude of glycine-evoked responses was 1.5-2.

Three types of inhibitory miniature potentials in frog spinal cord motoneurons: possible GABA and glycine cotransmission.

Miniature inhibitory postsynaptic potentials (mIPSP) of motoneurons in isolated frog spinal cord were recorded in conditions of blockade of the conduction of nerve spikes and ionotropic glutamate receptors (TTX, 1 microM, CNQX, 25 microM, D-AP5, 50 microM). Three types of mIPSP were identified: those with fast and slow time characteristics and mIPSP with two-component decays. Two-component mIPSP accounted for 8.

[Three types of miniature inhibitory potentiaes in the frog spinal cord motoneurons: the possibility of GABA and glycine co-release].

Miniature inhibitory postsynaptic potentials (mlPSPs) were recorded from motoneurons of the frog isolated spinal cord after blocking action potentials and ionotropic glutamate receptors (TTX 1 mcm: CNQX 25 mcm, D-AP5 50 mcm). Three types of mlPSPs were selected by their time characteristics) fast, slow and mlPSPs with two decay time constants. We classified 8.

[The effect of excitatory amino acid antagonists on postsynaptic potentials in the motoneurons of the frog Rana ridibunda].

The effects of excitatory amino acids on postsynaptic potentials (PSP) generated by activation of three synaptic inputs in isolated frog Rana ridibunda spinal cord motoneurons were investigated. PSP evoked by dorsal root (DR) and reticular formation (RF) stimulation were blocked by kynurenate (0.5-1 mM) and CNQX (1 mkM).

[The potentiation of postsynaptic potentials under the influence of glutamate and agonists in the motoneurons of the frog Rana ridibunda].

Effects of glutamate and agonists (aspartate, NMDA, quisqualate, AMPA, kainate) on dorsal root and reticulomotoneuronal excitatory postsynaptic potentials (EPSPs), as well as on spontaneous postsynaptic potentials (PSP), were studied in the motoneurons of isolated frog spinal cord. Depolarizing responses were evoked by glutamate or agonists bath application. Amplitude of the response decreased in conditions of TTX-block or replacement of Ca2+ by Mn2+, Mg2+ or Co2+ in perfusing solution.

[The heterogeneity of the excitatory synaptic inputs in the spinal motor neurons of the frog Rana ridibunda].

The synaptic responses induced in motoneurones by the stimulations of the dorsal root (DR), single afferent fibres and reticular formation (RF) were intracellularly recorded in the isolated frog spinal cord. It was shown that argiopine (the selective blocker of glutamate receptors of non-NMDA type) in concentrations ranging from 3.10(-7) to 1.

[Properties of the response of frog motoneurons to glutamate application].

The reversal potential (E) of the glutamate response produced by iontophoretically applied glutamate and that of the EPSP's recorded from three synaptic inputs produced by reticular formation (RF), dorsal roots (DS), and microstimulation of presynaptic terminals (PT) at the point of glutamate application were compared at the same motoneuron of the isolated frog spinal cord using current-chop technique. Following Cs injection the glutamate response and EPSP's were reversed. Different points of glutamate application were tested.

[Reversal potential of the EPSP of frog motoneurons].

The current-chop technique has shown that I-V characteristic of the membrane are nonlinear in lumbar motoneurons of isolated perfused frog spinal cord. Input resistance of the membrane decreased with depolarization when constant current was applied during 0.1-1.

[Amplitude of miniature potentials of motor neurons in the frog Rana ridibunda].

Miniature synaptic potentials have been recorded from motoneurones of the isolated spinal cord of the frog Rana ridibunda. In normal Ringer's solution, their frequency varied from 5 to 50/sec, whereas their amplitude reached 2-5 mV. Only 50-300 microV (rarely 0.

[Properties of the excitatory postsynaptic currents in the cat motor neurons].

Monosynaptic supraspinal and la excitatory postsynaptic current (e. p. s.