Coupling between serotoninergic and noradrenergic neurones and gamma-motoneurones in the cat.
Noradrenaline is known to suppress transmission from group II muscle afferents when locally applied to gamma-motoneurones, and serotonin (5-HT) facilitates the transmission. The purpose of this investigation was to search for evidence of monoaminergic innervation of gamma-motoneurones. Eight gamma-motoneurones were labelled with rhodamine-dextran, and 50 micrometer thick sagittal sections of the spinal cord containing them were exposed to antibodies against dopamine beta-hydroxylase (DBH) and 5-HT. All the cells were directly and/or indirectly excited by muscle group II afferents from the muscle they innervated and/or other muscles. Appositions between monoaminergic fibres and the labelled somata and dendrites were located with three-colour confocal laser scanning microscopy by examining series of optical sections at 1 or 0.5 micrometer intervals. DBH and 5-HT varicosities formed appositions with the somata and dendrites of all the gamma-motoneurones. The mean packing densities for 5-HT (1.12 +/- 0.11 appositions per 100 micrometer(2) for somata and 0.91 +/- 0.07 per 100 micrometer(2) for dendrites) were similar to the densities of contacts reported for alpha-motoneurones. Monoaminergic varicosities in apposition to dendrites greatly outnumbered those on the somata. The density of DBH appositions was consistently lower - corresponding means were 53% and 62% of those for 5-HT on the somata and dendrites, respectively. It is concluded from an analysis of the distribution and density of varicosities in apposition to the gamma-motoneurones compared with the density in the immediate surround of the dendrites that there is indeed both a serotoninergic and noradrenergic innervation of gamma-motoneurones.
Gladden
M H
MH
Institute of Biomedical and Life Sciences, Glasgow University, Glasgow G12 8QQ, UK. m.h.gladden@udcf.gla.ac.uk
Maxwell
D J
DJ
Sahal
A
A
Jankowska
E
E
D000818:Animals; D002415:Cats; D002450:Cell Communication / Q000502:physiology; D003712:Dendrites / Q000502:physiology; D003911:Dextrans; D004299:Dopamine beta-Hydroxylase / Q000378:metabolism; D006614:Hindlimb / Q000294:innervation; D007091:Image Processing, Computer-Assisted; D018613:Microscopy, Confocal; D009047:Motor Neurons, Gamma / Q000502:physiology* / Q000648:ultrastructure; D009412:Nerve Fibers / Q000502:physiology; D009474:Neurons / Q000502:physiology* / Q000648:ultrastructure; D009638:Norepinephrine / Q000502:physiology*; D012235:Rhodamines; D012701:Serotonin / Q000502:physiology*; D013116:Spinal Cord / Q000166:cytology
D003911:Dextrans; D012235:Rhodamines; C051311:rhodamine dextran; D012701:Serotonin; D004299:Dopamine beta-Hydroxylase; D009638:Norepinephrine