Spatial integration of local transmitter responses in motoneurones of the turtle spinal cord in vitro

TY - JOUR

T1 - Spatial integration of local transmitter responses in motoneurones of the turtle spinal cord in vitro

AU - Skydsgaard, Morten Arnika

AU - Hounsgaard, J

PY - 1994

Y1 - 1994

N2 - 1. Integration of responses to local activation of transmitter receptors in the dendrites of motoneurones was investigated in a slice preparation of the turtle spinal cord. Membrane-active substances were applied from up to three independent iontophoresis electrodes during intracellular recording from the cell body. 2. Responses to glutamate could be evoked from dendrites closer than 20 microns from the tip of the glutamate electrode. The effects of other substances were more widespread. 3. In normal medium the configuration of a glutamate response was affected by time-dependent anomalous rectification. In the presence of muscarine the sum of glutamate responses from two different dendrites recruited a voltage-sensitive plateau potential. 4. The response to glutamate from one dendrite could be attenuated by local application of gamma-aminobutyric acid (GABA) without effects on soma conductance or glutamate responses from other dendrites. 5. The response to glutamate from one dendrite could be selectively enhanced by local application of tetraethylammonium (TEA) or N-methyl-D-aspartate (NMDA) without effects on soma conductance or glutamate responses from other dendrites. 6. NMDA could convert a tonic glutamate response from one dendrite into a phasic response without affecting the configuration of glutamate responses from other dendrites. 7. The effects of TEA and NMDA were facilitated by depolarization and reduced by hyperpolarization. 8. We conclude that the cable structure of motoneurones and the distribution of synapses and voltage-sensitive ion channels provide relative autonomy to non-linear synaptic processing and modulation in confined dendritic regions.

AB - 1. Integration of responses to local activation of transmitter receptors in the dendrites of motoneurones was investigated in a slice preparation of the turtle spinal cord. Membrane-active substances were applied from up to three independent iontophoresis electrodes during intracellular recording from the cell body. 2. Responses to glutamate could be evoked from dendrites closer than 20 microns from the tip of the glutamate electrode. The effects of other substances were more widespread. 3. In normal medium the configuration of a glutamate response was affected by time-dependent anomalous rectification. In the presence of muscarine the sum of glutamate responses from two different dendrites recruited a voltage-sensitive plateau potential. 4. The response to glutamate from one dendrite could be attenuated by local application of gamma-aminobutyric acid (GABA) without effects on soma conductance or glutamate responses from other dendrites. 5. The response to glutamate from one dendrite could be selectively enhanced by local application of tetraethylammonium (TEA) or N-methyl-D-aspartate (NMDA) without effects on soma conductance or glutamate responses from other dendrites. 6. NMDA could convert a tonic glutamate response from one dendrite into a phasic response without affecting the configuration of glutamate responses from other dendrites. 7. The effects of TEA and NMDA were facilitated by depolarization and reduced by hyperpolarization. 8. We conclude that the cable structure of motoneurones and the distribution of synapses and voltage-sensitive ion channels provide relative autonomy to non-linear synaptic processing and modulation in confined dendritic regions.

KW - Animals

KW - Dendrites

KW - Glutamic Acid

KW - Ionophores

KW - Motor Neurons

KW - N-Methylaspartate

KW - Quisqualic Acid

KW - Spinal Cord

KW - Synapses

KW - Synaptic Transmission

KW - Tetraethylammonium

KW - Tetraethylammonium Compounds

KW - Turtles

KW - gamma-Aminobutyric Acid

U2 - 10.1113/jphysiol.1994.sp020291

DO - 10.1113/jphysiol.1994.sp020291

M3 - Journal article

C2 - 7799223

SN - 0022-3751

VL - 479

SP - 233

EP - 246

JO - The Journal of Physiology

JF - The Journal of Physiology

IS - 2

ER -