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 8.7% of all selected responses, fast mIPSP for 64.5%, and slow mIPSP for 26.8%. Blockade of GABA(A) receptors with bicuculline (20 microM) led to decreases in the numbers of slow and two-component mIPSP and an increase in the number of mIPSP with fast kinetics. Strychnine (1 microM), a blocker of glycine receptors, led to a reduction in the number of fast receptors and an increase in the number of slow potentials. These data suggest that frog spinal cord motoneurons have three types of inhibitory mIPSP, mediated by GABA, glycine, and simultaneous release of these two transmitters from the same presynaptic terminals.
Polina
Yu A
YA
Karelia State Pedagogical University, Petrozavodsk, Russia.
Amakhin
D V
DV
Kozhanov
V M
VM
Kurchavyi
G G
GG
Veselkin
N P
NP
D000818:Animals; D001001:Anura; D001640:Bicuculline / Q000494:pharmacology; D004347:Drug Interactions; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018756:GABA Antagonists / Q000494:pharmacology; D005998:Glycine / Q000378:metabolism*; D018684:Glycine Agents / Q000494:pharmacology; D066298:In Vitro Techniques; D053444:Inhibitory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D009046:Motor Neurons / Q000145:classification* / Q000187:drug effects / Q000502:physiology*; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D013116:Spinal Cord / Q000166:cytology*; D013331:Strychnine / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D018691:Excitatory Amino Acid Antagonists; D018756:GABA Antagonists; D018684:Glycine Agents; D005680:gamma-Aminobutyric Acid; D013331:Strychnine; D005998:Glycine; D001640:Bicuculline