Effects of tetanic stimulation on monosynaptic and dorsal root reflexes in kittens

1991 ◽  
Vol 69 (10) ◽  
pp. 1428-1435
Author(s):  
Parveen Bawa
Keyword(s):  
Spinal Cord ◽  
Dorsal Root ◽  
Monosynaptic Reflex ◽  
Cutaneous Afferents ◽  
Tetanic Stimulation ◽  
Dorsal Root Reflex ◽  
Peripheral Afferents ◽  
Post Tetanic Potentiation ◽  
Tetanic Depression ◽  
Stimulation Of

The effects of tetanic stimulation of peripheral afferents were examined on monosynaptic reflexes and dorsal root reflexes in kittens of various ages. Concomitantly recorded monosynaptic and dorsal root reflexes resulting from the stimulation of muscle nerves showed similar post-tetanic changes, namely, predominantly post-tetanic depression in neonates and post-tetanic potentiation in older kittens or adults. However, the changes in post-tetanic responses expressed as a percentage of control in dorsal root reflexes were much smaller than those in monosynaptic reflexes. When dorsal root reflexes originating from muscle and cutaneous afferents were compared, dorsal root reflexes from the latter behaved quite differently. For all ages, post-tetanic effects on dorsal root reflexes arising from cutaneous afferents were either insignificant or very small. The possible mechanisms underlying differences in post-tetanic effects from muscle and cutaneous afferents in adults and neonates are discussed.Key words: cat, kitten, development, dorsal root reflex, monosynaptic reflex, spinal cord, post-tetanic potentiation.

scholarly journals Neonatal Mice Spinal Cord Interneurons Sending Axons in Dorsal Roots

2020 ◽  
Author(s):  
Laura Paulina Osuna-Carrasco ◽  
Sergio Horacio Duenas-Jimenez ◽  
Carmen Toro-Castillo ◽  
Braniff De la Torre ◽  
Irene Aguilar-Garcia ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Action Potentials ◽  
Dorsal Root ◽  
Staining Technique ◽  
Spinal Cord Dorsal Horn ◽  
Monosynaptic Reflex ◽  
Primary Afferent Depolarization ◽  
Dorsal Roots ◽  
Dorsal Root Reflex

Abstract Background: Spinal cord interneurons send their axons in the dorsal root. Their antidromic fire could modulate peripheral receptors. Thus, it could control pain, other sensorial modality, or muscle spindle activity. In this study, we assessed a staining technique to analyze whether interneurons send axons in the neonate mouse’s dorsal roots. We conducted experiments in 10 Swiss-Webster mice, which ranged in age from 2 to 13 postnatal days. We dissected the spinal cord and studied it in vitro. Results: We observed interneurons in the spinal cord dorsal horn sending axons through dorsal roots. A mix of fluorochromes applied in dorsal roots marked these interneurons. They have a different morphology than motoneurons. Primary afferent depolarization in afferent terminals produces antidromic action potentials (dorsal root reflex; DRR). These reflexes appeared by stimulation of adjacent dorsal roots. We found that in the presence of bicuculline, DRR recorded in the L4 dorsal root evoked by L5 dorsal root stimulation was reduced. Simultaneously, the monosynaptic reflex (MR) in the L5 ventral root was not affected; nevertheless, a long-lasting after discharge appeared. The addition of 2-amino-5 phosphonovalric acid (AP5), an antagonist of NMDA receptors, abolished the MR without changing the after discharge. Action potentials persisted in dorsal roots even in low Ca2+ concentration. Conclusions: Thus, firing interneurons could send their axons by dorsal roots. Antidromic potentials may be characteristics of the neonatal mouse, probably disappearing in adulthood.

scholarly journals POST-TETANIC POTENTIATION OF POLYSYNAPTIC REFLEXES OF THE SPINAL CORD

1955 ◽  
Vol 39 (2) ◽  
pp. 197-206 ◽  
Author(s):  
Victor J. Wilson
Keyword(s):  
Spinal Cord ◽  
Time Course ◽  
Monosynaptic Reflex ◽  
Primary Afferent ◽  
Reflex Pathways ◽  
Post Tetanic Potentiation ◽  
Reflex Discharge ◽  
Polysynaptic Reflexes ◽  
Afferent Terminals ◽  
Stimulation Of

The phenomenon of post-tetanic potentiation has been studied in the cat spinal cord with particular reference to polysynaptic responses. Following tetanization of dorsal roots, these reflexes show an increased response, as measured in terms of their voltage-time area, with a predominant change in the earlier reflex pathways. Both of these changes in the reflex discharge have a time course of 15 to 25 seconds. Post-tetanic potentiation is also observed in response to stimulation of a dorsal rootlet following tetanization of another rootlet in the same or in a neighboring segment. This effect can be explained by post-tetanic changes in the terminals of secondary, and possibly higher order, internuncial cells, essentially similar to those changes in the primary afferent terminals which give rise to potentiation of the monosynaptic reflex.

scholarly journals Early postnatal development of GABAergic presynaptic inhibition of Ia proprioceptive afferent connections in mouse spinal cord

2013 ◽  
Vol 109 (8) ◽  
pp. 2118-2128 ◽  
Author(s):  
Patrick M. Sonner ◽  
David R. Ladle
Keyword(s):  
Spinal Cord ◽  
Postnatal Development ◽  
Presynaptic Inhibition ◽  
Dorsal Root ◽  
Reciprocal Inhibition ◽  
Afferent Feedback ◽  
Early Postnatal Development ◽  
Ia Afferent ◽  
Ia Afferents ◽  
Stimulation Of

Sensory feedback is critical for normal locomotion and adaptation to external perturbations during movement. Feedback provided by group Ia afferents influences motor output both directly through monosynaptic connections and indirectly through spinal interneuronal circuits. For example, the circuit responsible for reciprocal inhibition, which acts to prevent co-contraction of antagonist flexor and extensor muscles, is driven by Ia afferent feedback. Additionally, circuits mediating presynaptic inhibition can limit Ia afferent synaptic transmission onto central neuronal targets in a task-specific manner. These circuits can also be activated by stimulation of proprioceptive afferents. Rodent locomotion rapidly matures during postnatal development; therefore, we assayed the functional status of reciprocal and presynaptic inhibitory circuits of mice at birth and compared responses with observations made after 1 wk of postnatal development. Using extracellular physiological techniques from isolated and hemisected spinal cord preparations, we demonstrate that Ia afferent-evoked reciprocal inhibition is as effective at blocking antagonist motor neuron activation at birth as at 1 wk postnatally. In contrast, at birth conditioning stimulation of muscle nerve afferents failed to evoke presynaptic inhibition sufficient to block functional transmission at synapses between Ia afferents and motor neurons, even though dorsal root potentials could be evoked by stimulating the neighboring dorsal root. Presynaptic inhibition at this synapse was readily observed, however, at the end of the first postnatal week. These results indicate Ia afferent feedback from the periphery to central spinal circuits is only weakly gated at birth, which may provide enhanced sensitivity to peripheral feedback during early postnatal experiences.

scholarly journals Cutaneous stimulation evokes long-lasting excitation of spinal interneurons in the turtle

1990 ◽  
Vol 64 (4) ◽  
pp. 1134-1148 ◽  
Author(s):  
S. N. Currie ◽  
P. S. Stein
Keyword(s):  
Spinal Cord ◽  
Receptive Field ◽  
Action Potential ◽  
Receptive Fields ◽  
Neural Mechanisms ◽  
Cutaneous Afferents ◽  
Cutaneous Stimulation ◽  
Single Action ◽  
Single Action Potential ◽  
Stimulation Of

1. We demonstrated multisecond increases in the excitability of the rostral-scratch reflex in the turtle by electrically stimulating the shell at sites within the rostral-scratch receptive field. To examine the cellular mechanisms for these multisecond increases in scratch excitability, we recorded from single cutaneous afferents and sensory interneurons that responded to stimulation of the shell within the rostral-scratch receptive field. A single segment of the midbody spinal cord (D4, the 4th postcervical segment) was isolated in situ by transecting the spinal cord at the segment's anterior and posterior borders. The isolated segment was left attached to its peripheral nerve that innervates part of the rostral-scratch receptive field. A microsuction electrode (4-5 microns ID) was used to record extracellularly from the descending axons of cutaneous afferents and interneurons in the spinal white matter at the posterior end of the D4 segment. 2. The turtle shell is innervated by slowly and rapidly adapting cutaneous afferents. All cutaneous afferents responded to a single electrical stimulus to the shell with a single action potential. Maintained mechanical stimulation applied to the receptive field of some slowly adapting afferents produced several seconds of afterdischarge at stimulus offset. We refer to the cutaneous afferent afterdischarge caused by mechanical stimulation of the shell as "peripheral afterdischarge." 3. Within the D4 spinal segment there were some interneurons that responded to a brief mechanical stimulus within their receptive fields on the shell with short afterdischarge and others that responded with long afterdischarge. Short-afterdischarge interneurons responded to a single electrical pulse to a site in their receptive fields either with a brief train of action potentials or with a single action potential. Long-afterdischarge interneurons responded to a single electrical shell stimulus with up to 30 s of afterdischarge. Long-afterdischarge interneurons also exhibited strong temporal summation in response to a pair of electrical shell stimuli delivered up to several seconds apart. Because all cutaneous afferents responded to an electrical shell stimulus with a single action potential, we conclude that electrically evoked afterdischarge in interneurons was produced by neural mechanisms in the spinal cord; we refer to this type of afterdischarge as "central afterdischarge." 4. These results demonstrate that neural mechanisms for long-lasting excitability changes in response to cutaneous stimulation reside in a single segment of the spinal cord. Cutaneous interneurons with long afterdischarge may serve as cellular loci for multise

Modulation of monosynaptic excitation in the neonatal rat spinal cord

1993 ◽  
Vol 70 (3) ◽  
pp. 1151-1158 ◽  
Author(s):  
M. Pinco ◽  
A. Lev-Tov
Keyword(s):  
Spinal Cord ◽  
Dorsal Root ◽  
Neonatal Rat ◽  
Bathing Solution ◽  
Duration Stimulus ◽  
Low Calcium ◽  
Dorsal Root Afferents ◽  
Stimulation Of ◽  
Monosynaptic Excitation

1. The effects of high-frequency (5-50 Hz) stimulation of dorsal root afferents on monosynaptic excitation of alpha motoneurons was studied in the in vitro spinal cord preparation of the neonatal rat, using sharp-electrode intracellular recordings. 2. Double pulse stimulation of dorsal root afferents induced severe depression of testing excitatory postsynaptic potentials (EPSPs) at each of the tested interstimulus intervals (15 ms-5 s). After perfusion of the preparation with low-calcium, high-magnesium Krebs saline, the amplitude of the conditioning EPSPs was markedly decreased and the testing EPSPs exhibited substantial facilitation that was maximal at the 20-ms interval and that was accompanied by depression at intervals > or = 60-100 ms. 3. Short-duration stimulus trains applied to dorsal root afferents normally induced tetanic depression of the intracellularly recorded monosynaptic EPSPs. Switching the bathing solution to low-calcium, high-magnesium saline decreased the control EPSP and induced facilitation and then tetanic potentiation (TP) of the EPSPs within the applied train. The magnitude of potentiation (% potentiation) of these EPSPs depended on the interpulse interval of the short stimulus train and on the degree of attenuation of the unpotentiated control EPSP after the solution was changed from normal- to low-calcium Krebs solution. 4. Long-duration stimulus trains applied to dorsal root afferents at 5-10 Hz induced marked depression of monosynaptic EPSPs during the train. The depression was alleviated after cessation of the tetanic stimulation and was followed in some cases by slight posttetanic potentiation.(ABSTRACT TRUNCATED AT 250 WORDS)

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