Role of glutamate in locomotor rhythm generating neuronal circuitry.
Central pattern generators (CPGs) are defined as neuronal circuits capable of producing a rhythmic and coordinated output without the influence of sensory input. The locomotor and respiratory neuronal circuits are two of the better-characterized CPGs, although much work remains to fully understand how these networks operate. Glutamatergic neurons are involved in most neuronal circuits of the nervous system and considerable efforts have been made to study glutamate receptors in nervous system signaling using a variety of approaches. Because of the complexity of glutamate-mediated signaling and the variety of receptors triggered by glutamate, it has been difficult to pinpoint the role of glutamatergic neurons in neuronal circuits. In addition, glutamate is an amino acid used by every cell, which has hampered identification of glutamatergic neurons. Glutamatergic excitatory neurotransmission is dependent on the release from glutamate-filled presynaptic vesicles loaded by three members of the solute carrier family, Slc17a6-8, which function as vesicular glutamate transporters (VGLUTs). Recent data describe that Vglut2 (Slc17a6) null mutant mice die immediately after birth due to a complete loss of the stable autonomous respiratory rhythm generated by the pre-Bötzinger complex. Surprisingly, we found that basal rhythmic locomotor activity is not affected in Vglut2 null mutant embryos. With this perspective, we discuss data regarding presence of VGLUT1, VGLUT2 and VGLUT3 positive neuronal populations in the spinal cord.
Gezelius
Henrik
H
Department of Neuroscience, Unit of Developmental Genetics, Uppsala University, Box 587, 751 23 Uppsala, Sweden.
Wallén-Mackenzie
Asa
A
Enjin
Anders
A
Lagerström
Malin
M
Kullander
Klas
K
D000818:Animals; D001522:Behavior, Animal; D018698:Glutamic Acid / Q000494:pharmacology / Q000502:physiology*; D017403:In Situ Hybridization / Q000379:methods; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009043:Motor Activity / Q000502:physiology*; D009046:Motor Neurons / Q000187:drug effects / Q000502:physiology*; D010507:Periodicity; D012125:Respiratory Center / Q000166:cytology*; D015656:Respiratory Mechanics / Q000235:genetics / Q000502:physiology*; D013116:Spinal Cord / Q000166:cytology / Q000502:physiology; D050599:Vesicular Glutamate Transport Protein 2 / Q000172:deficiency
C493477:Slc17a6 protein, mouse; D050599:Vesicular Glutamate Transport Protein 2; D018698:Glutamic Acid