TY - JOUR

T1 - Zinc co-localizes with GABA and glycine in synapses in the lamprey spinal cord

AU - Birinyi, András

AU - Parker, David

AU - Antal, Miklós

AU - Shupliakov, Oleg

PY - 2001/4/30

Y1 - 2001/4/30

N2 - The presence of zinc in synaptic terminals in the lamprey spinal cord was examined utilizing a modification of the Timm's sulfide silver method and with the fluorescent marker 6-methoxy-8-quinolyl-p-toluenesulfonamide (TSQ). Axons labeled with a Timm's staining method were predominantly located in the lateral region of the dorsal column. This correlated with a maximum of TSQ fluorescence in this region of the spinal cord. Single labeled terminals accumulating Timm reaction product were also found throughout the gray matter and fiber tracts. At the ultrastructural level, zinc was located in a population of synaptic terminals that co-localized γ-aminobutyric acid (GABA) and glycine. Possible effects of Zn 2+ on neuronal activity were examined. In spinobulbar interneurons, which receive GABAergic input in the dorsal column, zinc potentiated responses to GABA application, but it did not affect responses to GABA in motoneurons. Responses in motoneurons to pressure application of glycine were also not affected by Zn 2+ . Zinc, however, potentiated monosynaptic glycinergic inhibitory postsynaptic potentials (IPSPs) evoked in motoneurons by inhibitory locomotor network interneurons and increased frequency, but not amplitude of spontaneous miniature IPSPs recorded in the presence of tetrodotoxin (TTX), suggesting presynaptic effects. Glutamate responses and the amplitude of monosynaptic excitatory postsynaptic potentials (EPSPs) in motoneurons were reduced by zinc. These effects appeared to be mediated largely postsynaptically through an effect on the N-methyl-D-aspartate (NMDA) component of the glutamatergic input. Our results thus show that free zinc is present in inhibitory synaptic terminals in the lamprey spinal cord, and that it may function as a modulator of inhibitory synaptic transmission.

AB - The presence of zinc in synaptic terminals in the lamprey spinal cord was examined utilizing a modification of the Timm's sulfide silver method and with the fluorescent marker 6-methoxy-8-quinolyl-p-toluenesulfonamide (TSQ). Axons labeled with a Timm's staining method were predominantly located in the lateral region of the dorsal column. This correlated with a maximum of TSQ fluorescence in this region of the spinal cord. Single labeled terminals accumulating Timm reaction product were also found throughout the gray matter and fiber tracts. At the ultrastructural level, zinc was located in a population of synaptic terminals that co-localized γ-aminobutyric acid (GABA) and glycine. Possible effects of Zn 2+ on neuronal activity were examined. In spinobulbar interneurons, which receive GABAergic input in the dorsal column, zinc potentiated responses to GABA application, but it did not affect responses to GABA in motoneurons. Responses in motoneurons to pressure application of glycine were also not affected by Zn 2+ . Zinc, however, potentiated monosynaptic glycinergic inhibitory postsynaptic potentials (IPSPs) evoked in motoneurons by inhibitory locomotor network interneurons and increased frequency, but not amplitude of spontaneous miniature IPSPs recorded in the presence of tetrodotoxin (TTX), suggesting presynaptic effects. Glutamate responses and the amplitude of monosynaptic excitatory postsynaptic potentials (EPSPs) in motoneurons were reduced by zinc. These effects appeared to be mediated largely postsynaptically through an effect on the N-methyl-D-aspartate (NMDA) component of the glutamatergic input. Our results thus show that free zinc is present in inhibitory synaptic terminals in the lamprey spinal cord, and that it may function as a modulator of inhibitory synaptic transmission.

KW - Inhibition

KW - Locomotor network

KW - Synaptic modulation

UR - http://www.scopus.com/inward/record.url?scp=0035972116&partnerID=8YFLogxK

U2 - 10.1002/cne.1136

DO - 10.1002/cne.1136

M3 - Article

C2 - 11283960

AN - SCOPUS:0035972116

VL - 433

SP - 208

EP - 221

JO - Journal of Comparative Neurology

JF - Journal of Comparative Neurology

SN - 0021-9967

IS - 2

ER -