Glycine- and GABA-immunoreactive nerve terminals apposed to alpha-motoneurons during postnatal development in kittens: a quantitative study using the disector.
The distribution of gamma-aminobutyric acid (GABA) and/or glycine-immunoreactive (IR) terminal-like structures apposed to somatic and dendritic membrane of lumbar alpha-motoneurons in column 2 was examined in 1- and 3-week-old kittens and in the adult cat. This quantitative study was carried out using a postembedding technique on semithin sections and a stereological method, the disector. Analysis of immunoreactive terminals showed that the percentages of GABA-IR and glycine-IR terminals (these populations include terminals containing both GABA and glycine) apposed to somatic and proximal dendritic compartments of alpha-motoneurons are almost the same in kittens, while in the adult glycinergic innervation becomes predominant. This change results from: (1) the decrease in numbers of GABA-IR terminals contacting the somatic compartment between 3 weeks and adult stage, while the numbers of glycine-IR terminals show no significant changes after birth and the numbers of terminals containing both neurotransmitters (GABA-IR+glycine-IR) present transient changes and (2) the postnatal increase in the dendritic compartment, in numbers of GABA-IR, glycine-IR and GABA-IR+glycine-IR terminals; the increase being larger for glycine-IR terminals. Furthermore, using a postembedding immunogold technique, observations by electron microscopy showed that GABA-IR P boutons apposed to M boutons can already be identified at 1 week after birth.
Simon
M
M
URA CNRS 1448, Laboratoire de Physiologie et Biologie de la Motricité, Université René Descartes, 45 rue des Saints-Pères, F-75 270 Paris Cedex 06, France. magda.simon@ic.ac.uk
Horcholle-Bossavit
G
G
D000367:Age Factors; D000818:Animals; D002415:Cats; D002452:Cell Count / Q000295:instrumentation / Q000379:methods; D003712:Dendrites / Q000737:chemistry* / Q000502:physiology; D005998:Glycine / Q000032:analysis*; D019044:Image Cytometry / Q000295:instrumentation / Q000379:methods; D008867:Microtomy; D009046:Motor Neurons / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation; D017729:Presynaptic Terminals / Q000737:chemistry*; D013116:Spinal Cord / Q000166:cytology / Q000254:growth & development*; D009435:Synaptic Transmission / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000032:analysis*
D005680:gamma-Aminobutyric Acid; D005998:Glycine