Excitatory amino acid projections to the nucleus of the solitary tract in the rat: a retrograde transport study utilizing d-[3H]aspartate and [3H]GABA

1994 ◽  
Vol 50 (1) ◽  
pp. 109-122 ◽  
Author(s):  
P.M. Beart ◽  
R.J. Summers ◽  
J.A. Stephenson ◽  
M.J. Christie
Keyword(s):  
Amino Acid ◽  
Excitatory Amino Acid ◽  
Retrograde Transport ◽  
Solitary Tract ◽  
Transport Study

Cholinergic systems in the nucleus of the solitary tract of rats

1999 ◽  
Vol 276 (4) ◽  
pp. R1141-R1148 ◽  
Author(s):  
Miwako Shihara ◽  
Nobuaki Hori ◽  
Yoshitaka Hirooka ◽  
Kenichi Eshima ◽  
Norio Akaike ◽  
...  
Keyword(s):  
Amino Acid ◽  
Excitatory Amino Acid ◽  
Baroreceptor Reflex ◽  
Synaptic Activation ◽  
Muscarinic Antagonists ◽  
Intracellular Recordings ◽  
Solitary Tract ◽  
Functional Correlation ◽  
Physiological Properties ◽  
Receptor Profile

The pharmacological and physiological properties of excitatory amino acid and ACh systems in the nucleus of the solitary tract (NTS) were studied in slices of rat brain stem by extracellular and intracellular recordings from neurons activated by solitary tract (ST) stimulation. These neurons were characterized as having several long dendrites with multiple varicosities. Synaptic activation of the medial NTS (mNTS) neurons by ST stimulation was mediated by non- N-methyl-d-aspartate (NMDA) glutamate (Glu) receptors, because the excitation was blocked by 6-cyano-7-nitro-quinoxaline-2,3-dione but not by NMDA, nicotinic, or muscarinic antagonists. Identified mNTS neurons were excited by iontophoresis of both Glu and ACh. The most sensitive region of the cell was on the dendrites ∼100 μm from the cell body for both putative neurotransmitters. Nicotinic and/or muscarinic excitatory ACh responses were detected on the mNTS neurons. Our observations suggest that both types of ACh receptors may contribute to the attenuation of the baroreceptor reflex, but the functional correlation of this receptor profile remains to be determined.

ATP potently modulates anion channel-mediated excitatory amino acid release from cultured astrocytes

2002 ◽  
Vol 283 (2) ◽  
pp. C569-C578 ◽  
Author(s):  
Alexander A. Mongin ◽  
Harold K. Kimelberg
Keyword(s):  
Amino Acid ◽  
Excitatory Amino Acid ◽  
Atp Release ◽  
Anion Channel ◽  
P2y Receptors ◽  
Cell Swelling ◽  
Channel Blockers ◽  
Medium Osmolarity ◽  
Subsequent Activation

Volume-dependent ATP release and subsequent activation of purinergic P2Y receptors have been implicated as an autocrine mechanism triggering activation of volume-regulated anion channels (VRACs) in hepatoma cells. In the brain ATP is released by both neurons and astrocytes and participates in intercellular communication. We explored whether ATP triggers or modulates the release of excitatory amino acid (EAAs) via VRACs in astrocytes in primary culture. Under basal conditions exogenous ATP (10 μM) activated a small EAA release in 70–80% of the cultures tested. In both moderately (5% reduction of medium osmolarity) and substantially (35% reduction of medium osmolarity) swollen astrocytes, exogenous ATP greatly potentiated EAA release. The effects of ATP were mimicked by P2Y agonists and eliminated by P2Y antagonists or the ATP scavenger apyrase. In contrast, the same pharmacological maneuvers did not inhibit volume-dependent EAA release in the absence of exogenous ATP, ruling out a requirement of autocrine ATP release for VRAC activation. The ATP effect in nonswollen and moderately swollen cells was eliminated by a 5–10% increase in medium osmolarity or by anion channel blockers but was insensitive to tetanus toxin pretreatment, further supporting VRAC involvement. Our data suggest that in astrocytes ATP does not trigger EAA release itself but acts synergistically with cell swelling. Moderate cell swelling and ATP may serve as two cooperative signals in bidirectional neuron-astrocyte communication in vivo.

scholarly journals Commissural Interneurons in Rhythm Generation and Intersegmental Coupling in the Lamprey Spinal Cord

1999 ◽  
Vol 81 (5) ◽  
pp. 2037-2045 ◽  
Author(s):  
James T. Buchanan
Keyword(s):  
Spinal Cord ◽  
Amino Acid ◽  
Excitatory Amino Acid ◽  
Rhythmic Activity ◽  
Ventral Root ◽  
Rhythm Generation ◽  
Spinal Segment ◽  
Spinal Segments ◽  
Autocorrelation Method

Commissural interneurons in rhythm generation and intersegmental coupling in the lamprey spinal cord. To test the necessity of spinal commissural interneurons in the generation of the swim rhythm in lamprey, longitudinal midline cuts of the isolated spinal cord preparation were made. Fictive swimming was then induced by bath perfusion with an excitatory amino acid while recording ventral root activity. When the spinal cord preparation was cut completely along the midline into two lateral hemicords, the rhythmic activity of fictive swimming was lost, usually replaced with continuous ventral root spiking. The loss of the fictive swim rhythm was not due to nonspecific damage produced by the cut because rhythmic activity was present in split regions of spinal cord when the split region was still attached to intact cord. The quality of this persistent rhythmic activity, quantified with an autocorrelation method, declined with the distance of the split spinal segment from the remaining intact spinal cord. The deterioration of the rhythm was characterized by a lengthening of burst durations and a shortening of the interburst silent phases. This pattern of deterioration suggests a loss of rhythmic inhibitory inputs. The same pattern of rhythm deterioration was seen in preparations with the rostral end of the spinal cord cut compared with those with the caudal end cut. The results of this study indicate that commissural interneurons are necessary for the generation of the swimming rhythm in the lamprey spinal cord, and the characteristic loss of the silent interburst phases of the swimming rhythm is consistent with a loss of inhibitory commissural interneurons. The results also suggest that both descending and ascending commissural interneurons are important in the generation of the swimming rhythm. The swim rhythm that persists in the split cord while still attached to an intact portion of spinal cord is thus imposed by interneurons projecting from the intact region of cord into the split region. These projections are functionally short because rhythmic activity was lost within approximately five spinal segments from the intact region of spinal cord.

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