Quantitative analysis and postsynaptic targets of GABA-immunoreactive boutons within the rat trigeminal motor nucleus.
We have used the post-embedding immunogold labelling method using antibodies to gamma-aminobutyric acid (GABA) to obtain quantitative data on the distribution, frequency, postsynaptic targets and ultrastructural characteristics of GABA-immunoreactive (GABA-IR) boutons in the trigeminal motor nucleus of rats. We have also combined this method with horseradish peroxidase tracing to obtain specific evidence for termination of some GABA-IR boutons onto identified jaw-elevator motoneurones. Twenty-eight percent of all synapses in the motor nucleus involved GABA-IR boutons. Seventy-three percent of the GABA-IR boutons formed axo-dendritic synapses, 13% axo-somatic synapses and 14% axo-axonic synapses. Ninety-three percent of GABA-IR boutons formed symmetrical synapses. Overall, 58% of all boutons contained only flattened vesicles, while 26% contained round vesicles and 16% a mixture of vesicle types. Measurements of bouton cross sectional area, apposition length, and active zone length were obtained from serial reconstructions of 15 GABA-IR boutons and 30 unlabelled boutons. In each case mean values for GABA-IR boutons were significantly smaller than those for nonlabelled boutons.
Saha
S
S
Department of Physiology, University of Leeds, U.K.
Appenteng
K
K
Batten
T F
TF
D000818:Animals; D005071:Evoked Potentials / Q000502:physiology; D006735:Horseradish Peroxidase; D007150:Immunohistochemistry; D008854:Microscopy, Electron; D009046:Motor Neurons / Q000737:chemistry*; D051381:Rats; D013569:Synapses / Q000737:chemistry*; D014278:Trigeminal Nuclei / Q000737:chemistry*; D005680:gamma-Aminobutyric Acid / Q000032:analysis*
D005680:gamma-Aminobutyric Acid; D006735:Horseradish Peroxidase