Monosynaptic connections between primary afferents and giant neurons in the turtle spinal dorsal horn

TY - JOUR

T1 - Monosynaptic connections between primary afferents and giant neurons in the turtle spinal dorsal horn

AU - Fernández, A

AU - Radmilovich, M

AU - Russo, R E

AU - Hounsgaard, J

AU - Trujillo-Cenóz, O

PY - 1996/3/1

Y1 - 1996/3/1

N2 - This paper reports the occurrence of monosynaptic connections between dorsal root afferents and a distinct cell type-the giant neuron-deep in the dorsal horn of the turtle spinal cord. Light microscope studies combining Nissl stain and transganglionic HRP-labeling of the primary afferents have revealed the occurrence of axosomatic and axodendritic contacts between labeled boutons and giant neurons. The synaptic nature of these contacts has been confirmed by use of electron microscope procedures involving the partial three-dimensional reconstruction of identified giant neurons. Intracellular recording in spinal cord slices provided functional evidence indicating the monosynaptic connections between dorsal root afferents and giant neurons. The recorded neurons were morphologically identified by means of biocytin injection and with avidin conjugates. Electrical stimulation of the ipsilateral dorsal roots evoked synaptic responses with short, fixed latencies (1.6-5.6 ms), which remained unchanged at high frequencies (10 Hz). Excitatory polysynaptic potentials were also observed. By means of pharmacological procedures the short-latency response was dissected in two components: one insensitive to tetrodotoxin, the other abolished by the drug. The toxin-resistant component was presumed to be sustained by small-diameter C fibers. The synaptic response was mainly mediated by the glutamate-AMPA receptor subtype; however, a small component mediated by NMDA receptor was also present.

AB - This paper reports the occurrence of monosynaptic connections between dorsal root afferents and a distinct cell type-the giant neuron-deep in the dorsal horn of the turtle spinal cord. Light microscope studies combining Nissl stain and transganglionic HRP-labeling of the primary afferents have revealed the occurrence of axosomatic and axodendritic contacts between labeled boutons and giant neurons. The synaptic nature of these contacts has been confirmed by use of electron microscope procedures involving the partial three-dimensional reconstruction of identified giant neurons. Intracellular recording in spinal cord slices provided functional evidence indicating the monosynaptic connections between dorsal root afferents and giant neurons. The recorded neurons were morphologically identified by means of biocytin injection and with avidin conjugates. Electrical stimulation of the ipsilateral dorsal roots evoked synaptic responses with short, fixed latencies (1.6-5.6 ms), which remained unchanged at high frequencies (10 Hz). Excitatory polysynaptic potentials were also observed. By means of pharmacological procedures the short-latency response was dissected in two components: one insensitive to tetrodotoxin, the other abolished by the drug. The toxin-resistant component was presumed to be sustained by small-diameter C fibers. The synaptic response was mainly mediated by the glutamate-AMPA receptor subtype; however, a small component mediated by NMDA receptor was also present.

KW - 6-Cyano-7-nitroquinoxaline-2,3-dione

KW - Afferent Pathways

KW - Animals

KW - Cell Size

KW - Evoked Potentials

KW - Excitatory Amino Acid Antagonists

KW - Horseradish Peroxidase

KW - Microscopy, Electron

KW - Neurons, Afferent

KW - Nissl Bodies

KW - Receptors, N-Methyl-D-Aspartate

KW - Spinal Cord

KW - Spinal Nerve Roots

KW - Tetrodotoxin

KW - Turtles

M3 - Journal article

C2 - 8801115

SN - 0014-4819

VL - 108

SP - 347

EP - 356

JO - Experimental Brain Research

JF - Experimental Brain Research

IS - 3

ER -