scholarly journals Recurrent excitation between motoneurones propagates across segments and is purely glutamatergic

2017 ◽  
Author(s):  
G.S. Bhumbra ◽  
M. Beato
Keyword(s):  
Glutamate Receptors ◽  
Synaptic Input ◽  
Renshaw Cells ◽  
Motor Tasks ◽  
Spinal Segment ◽  
Recurrent Excitation ◽  
Final Output ◽  
Slow Type ◽  
Adjacent Segments ◽  
Spinal Motoneurones

AbstractSpinal motoneurones constitute the final output for the execution of motor tasks. In addition to innervating muscles, motoneurones project excitatory collateral connections to Renshaw cells and other motoneurones, but the latter have received little attention. We show that motoneurones receive strong synaptic input from other motoneurones throughout development and into maturity with fast type motoneurones systematically receiving greater recurrent excitation than slow type motoneurones. Optical recordings show that activation of motoneurones in one spinal segment can propagate to adjacent segments even in the presence of intact recurrent inhibition. Quite remarkably, while it is known that transmission at the neuromuscular junction is purely cholinergic and Renshaw cells are excited through both acetylcholine and glutamate receptors, here we show that neurotransmission between motoneurones is purely glutamatergic indicating that synaptic transmission systems are differentiated at different post-synaptic targets of motoneurones.

scholarly journals Endogenous GABA and Glutamate Finely Tune the Bursting of Olfactory Bulb External Tufted Cells

2007 ◽  
Vol 98 (2) ◽  
pp. 1052-1056 ◽  
Author(s):  
Abdallah Hayar ◽  
Matthew Ennis
Keyword(s):  
Olfactory Bulb ◽  
Glutamate Receptors ◽  
Synaptic Input ◽  
Aminobutyric Acid ◽  
Ionotropic Glutamate Receptors ◽  
Endogenous Gaba ◽  
Shunting Effect ◽  
Tufted Cells ◽  
Olfactory Bulb Slices ◽  
Spike Bursts

In rat olfactory bulb slices, external tufted (ET) cells spontaneously generate spike bursts. Although ET cell bursting is intrinsically generated, its strength and precise timing may be regulated by synaptic input. We tested this hypothesis by analyzing whether the burst properties are modulated by activation of ionotropic γ-aminobutyric acid (GABA) and glutamate receptors. Blocking GABAA receptors increased—whereas blocking ionotropic glutamate receptors decreased—the number of spikes/burst without changing the interburst frequency. The GABAA agonist (isoguvacine, 10 μM) completely inhibited bursting or reduced the number of spikes/burst, suggesting a shunting effect. These findings indicate that the properties of ET cell spontaneous bursting are differentially controlled by GABAergic and glutamatergic fast synaptic transmission. We suggest that ET cell excitatory and inhibitory inputs may be encoded as a change in the pattern of spike bursting in ET cells, which together with mitral/tufted cells constitute the output circuit of the olfactory bulb.

scholarly journals Variable amplification of synaptic input to cat spinal motoneurones by dendritic persistent inward current

2003 ◽  
Vol 552 (3) ◽  
pp. 945-952 ◽  
Author(s):  
H. Hultborn ◽  
M. Enríquez Denton ◽  
J. Wienecke ◽  
J. B. Nielsen
Keyword(s):  
Synaptic Input ◽  
Inward Current ◽  
Persistent Inward Current ◽  
Spinal Motoneurones

Developmental Reorganization of the Output of a GABAergic Interneuronal Circuit

2007 ◽  
Vol 97 (4) ◽  
pp. 2769-2779 ◽  
Author(s):  
Huaying Xu ◽  
Arthur Clement ◽  
Terrence Michael Wright ◽  
Peter Wenner
Keyword(s):  
Spinal Cord ◽  
Chick Embryo ◽  
Synaptic Input ◽  
Ventral Root ◽  
Network Activity ◽  
Inhibitory Interneurons ◽  
Optical Studies ◽  
Adjacent Segments ◽  
Whole Cell Recordings ◽  
Stimulation Of

Locally projecting inhibitory interneurons play a crucial role in the patterning and timing of network activity. However, because of their relative inaccessibility, little is known about their development or incorporation into circuits. In this report we demonstrate that the GABAergic R-interneuron circuit undergoes a reorganization in the chick embryo spinal cord between embryonic days 8 and 15 (E8 and E15). R-interneurons receive synaptic input from and project back to motoneurons. By stimulating motoneurons projecting in one ventral root and recording the disynaptic response from motoneurons in adjacent segments, we show that the output of the R-interneuron circuit is reorganized during development. After stimulation of the LS2 ventral root, disynaptic responses observed in whole cell recordings became more common and stronger for LS3 motoneurons and less common for the more distant LS4 motoneurons from E8 to E10. Optical studies demonstrated that R-interneurons activated by LS2 stimulation were restricted to the LS2 segment and had a small glutamatergic component at both E8 and E10, but that more R-interneurons were activated within the segment by E10. The recruitment of more LS2 R-interneurons at E10 is likely to contribute to stronger projections to LS3 motoneurons, but the fact that fewer LS4 motoneurons receive this input is more consistent with a functional refinement of the more distant projection of the GABAergic R-interneuron. Interestingly, this pattern of reorganization was not observed throughout the rostrocaudal extent of the cord, introducing the possibility that refinement could serve to remove connections between functionally unrelated interneurons and motoneurons.

scholarly journals Spinal segments communicating resting sympathetic activity to postganglionic nerves of the stellate ganglion

1998 ◽  
Vol 275 (2) ◽  
pp. R400-R409 ◽  
Author(s):  
Bernat Kocsis ◽  
Katalin Gyimesi-Pelczer
Keyword(s):  
Spinal Cord ◽  
Sympathetic Activity ◽  
Stellate Ganglion ◽  
Rhythmic Activity ◽  
Spinal Segment ◽  
Preganglionic Neurons ◽  
Spinal Segments ◽  
Sympathetic Reflexes ◽  
Adjacent Segments ◽  
Vertebral Nerve

It has been shown earlier using sympathetic reflexes and anatomic techniques that preganglionic neurons controlling different effectors occupy wide and overlapping ranges of adjacent segments in the spinal cord (cardiac: T1–T7, vertebral: T2–T8). Because, however, the majority of preganglionic neurons are silent at resting states, the present study was designed to estimate the segmental map of subsets of these neurons including only those active at rest using simultaneous recordings from the inferior cardiac and vertebral nerves, under chloralose-urethan or urethan anesthesia. In 22 cats, thoracic white rami T1–T8 were cut in a sequential manner. Three-minute-long data segments were recorded between sectionings and analyzed in the frequency domain using the fast Fourier transform. We found that cardiac and vertebral active maps involved segments T3–T5 and T4–T8, respectively. In individual experiments, however, most of the power of rhythmic activity originated from only one or two segments and the dominant segments for the two nerves never overlapped. Moreover, the separation between dominant segments generating cardiac and vertebral nerve discharges was wider and the distribution of tonically active preganglionic neurons projecting to each nerve was narrower under urethan than chloralose-urethan anesthesia. We conclude that the proportion of active to quiescent preganglionic neurons regulating cardiac and vertebral nerve discharges varies from spinal segment to segment and that active neurons projecting to these nerves are nonoverlapping.

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