The effect of inhibitory amino acids on the synaptic activity of spinal motoneurones in the lamprey Lampetra fluviatilis

Batueva, IV.; Suderevskaya, EI.; Veselkin, NP.; Pierre, J.; Reperant, J.

Zhurnal Evolyutsionnoi Biokhimii I Fiziologii 282: 170-190


Accession: 021916092

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The effects of glycine, gamma-aminobutyric acid and taurine on the motoneuron monosynaptic potentials evoked by stimulation of dorsal roots, spinal tracts and single Muller (reticulospinal) axons were investigated on the isolated lamprey spinal cord preparation. All amino acids investigated increased the membrane potential and depressed the synaptic activity. Judging by the low effective concentration and complete blocking of synaptic responses, the most probable candidate for inhibitory transmitter on motoneurons is glycine. The concentration of GABA-ergic cells and fibers in the dorsal part of the spinal cord indicates a possibility of GABA utilization for modulation of excitation in afferent pathways, for presynaptic inhibition, in particular. However, GABA can also depress the motor cell activity, probably, by acting on the glycine postsynaptic receptors. Taurine, like GABA, can modulate the neuronal activity, or, like glycine, can act as a potent depressant. The comparative aspects of investigated amino acid action on the lower vertebrate spinal neurons as well as the possible role of inhibitory interneurons in the motor pattern generation are discussed.