TY - JOUR
T1 - Calcium imaging of motoneuron activity in the en-bloc spinal cord preparation of the neonatal rat
AU - Lev-Tov, A.
AU - O'Donovan, M. J.
PY - 1995
Y1 - 1995
N2 - 1. This paper describes the use of calcium imaging to monitor patterns of activity in neonatal rat motoneurons retrogradely labeled with the calcium- sensitive dye, calcium green-dextran. 2. Pressure ejection of calcium green- dextran into ventral roots and into the surgically peeled ventrolateral funiculi (VLF) at the lumbar cord labeled spinal motoneurons and interneurons. The back labeled motoneurons often formed two to three discrete clusters of cells. 3. Fluorescent changes (10-20%) could be detected in labeled motoneurons after a single antidromic stimulus of the segmental ventral root. These changes progressively increased in amplitude during stimulus trains (1-5 s) at frequencies from 5 to 50 Hz, presumably reflecting a frequency-dependent increase in free intracellular calcium. 4. Stimulation of the ipsilateral VLF at the caudal lumbar level (L6), elicited frequency- dependent, synaptically induced motoneuronal discharge. Frequency-dependent fluorescent changes could be detected in calcium green-labeled motoneurons during the VLF-induced synaptic activation. 5. The spatial spread of synaptic activity among calcium green labeled clusters of motoneurons could be resolved after dorsal root stimulation. Low-intensity stimulation of the roots produced fluorescence changes restricted to the lateral clusters of motoneurons. With increasing stimulation intensity the fluorescence change increased in the lateral cells and could spread into the medial motoneuronal group. After a single supramaximal stimulus a similar pattern was observed with activity beginning laterally and spreading medially. 6. Substantial changes in fluorescence of calcium green-labeled motoneurons were also observed during motoneuron bursting induced by bath application of the glycine receptor antagonist strychnine or the potassium channel blocker 4- aminopyridine (4-AP). 7. Our results show that membrane-impermeant fluorescent calcium indicators can be used as a tool to study the activity of specific populations of spinal neurons during execution of motor functions in the developing mammalian spinal cord. They also suggest that lateral clusters of motoneurons in the developing spinal cord of the rat are more recruitable or excitable than more medial clusters. Further understanding of these findings requires identification of these clusters.
AB - 1. This paper describes the use of calcium imaging to monitor patterns of activity in neonatal rat motoneurons retrogradely labeled with the calcium- sensitive dye, calcium green-dextran. 2. Pressure ejection of calcium green- dextran into ventral roots and into the surgically peeled ventrolateral funiculi (VLF) at the lumbar cord labeled spinal motoneurons and interneurons. The back labeled motoneurons often formed two to three discrete clusters of cells. 3. Fluorescent changes (10-20%) could be detected in labeled motoneurons after a single antidromic stimulus of the segmental ventral root. These changes progressively increased in amplitude during stimulus trains (1-5 s) at frequencies from 5 to 50 Hz, presumably reflecting a frequency-dependent increase in free intracellular calcium. 4. Stimulation of the ipsilateral VLF at the caudal lumbar level (L6), elicited frequency- dependent, synaptically induced motoneuronal discharge. Frequency-dependent fluorescent changes could be detected in calcium green-labeled motoneurons during the VLF-induced synaptic activation. 5. The spatial spread of synaptic activity among calcium green labeled clusters of motoneurons could be resolved after dorsal root stimulation. Low-intensity stimulation of the roots produced fluorescence changes restricted to the lateral clusters of motoneurons. With increasing stimulation intensity the fluorescence change increased in the lateral cells and could spread into the medial motoneuronal group. After a single supramaximal stimulus a similar pattern was observed with activity beginning laterally and spreading medially. 6. Substantial changes in fluorescence of calcium green-labeled motoneurons were also observed during motoneuron bursting induced by bath application of the glycine receptor antagonist strychnine or the potassium channel blocker 4- aminopyridine (4-AP). 7. Our results show that membrane-impermeant fluorescent calcium indicators can be used as a tool to study the activity of specific populations of spinal neurons during execution of motor functions in the developing mammalian spinal cord. They also suggest that lateral clusters of motoneurons in the developing spinal cord of the rat are more recruitable or excitable than more medial clusters. Further understanding of these findings requires identification of these clusters.
UR - http://www.scopus.com/inward/record.url?scp=0029046705&partnerID=8YFLogxK
U2 - 10.1152/jn.1995.74.3.1324
DO - 10.1152/jn.1995.74.3.1324
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C2 - 7500153
AN - SCOPUS:0029046705
SN - 0022-3077
VL - 74
SP - 1324
EP - 1334
JO - Journal of Neurophysiology
JF - Journal of Neurophysiology
IS - 3
ER -