An Intracellular Study of the Actions of Carbon Dioxide on the Spinal Monosynaptic Pathway

1973 ◽  
Vol 51 (6) ◽  
pp. 424-436 ◽  
Author(s):  
D. W. Esplin ◽  
R. Čapek ◽  
Barbara A. Esplin
Keyword(s):  
Transmitter Release ◽  
Afferent Fiber ◽  
Membrane Resistance ◽  
Postsynaptic Membrane ◽  
Release Mechanism ◽  
Afferent Fibers ◽  
Depressant Action ◽  
Intracellular Study ◽  
Primary Afferent Fibers ◽  
Antidromic Response

The actions of CO2 were studied on 48 lumbosacral motoneurones impaled with microelectrodes in spinal cats. CO2 produced a reversible depolarization in some cells tested and a reversible hyper-polarization in other cells tested. Both increases and decreases in membrane resistance were produced by CO2, and these were significantly correlated with hyperpolarizations and depolarizations of the membrane, respectively. The after-hyperpolarization following an antidromic response was always reduced by CO2, irrespective of the CO2-induced change in membrane potential. The firing threshold of the motoneurone in response to injected depolarizing currents was increased by CO2. Statistical analysis of excitatory postsynaptic potentials produced by activity in a single afferent fiber revealed that the principal depressant action of CO2 on this pathway is to block intraspinal branches of the primary afferent fibers. Neither the transmitter release mechanism nor the sensitivity of the postsynaptic membrane to the released transmitter was significantly affected.

High susceptibility to hypoxia of afferent synaptic transmission in the goldfish sacculus

1987 ◽  
Vol 58 (5) ◽  
pp. 1066-1079 ◽  
Author(s):  
T. Suzue ◽  
G. B. Wu ◽  
T. Furukawa
Keyword(s):  
Synaptic Transmission ◽  
Hair Cells ◽  
Afferent Fiber ◽  
Marked Change ◽  
Threshold Current ◽  
Postsynaptic Membrane ◽  
Afferent Fibers ◽  
Presynaptic Mechanisms ◽  
Binomial Parameter ◽  
Set Up

1. The effect of hypoxia on synaptic transmission between hair cells and afferent fibers was examined in the sacculus of goldfish. For this, we recorded potentials, intracellularly, from large afferent fibers. Anoxia was introduced by perfusing the gill with water deprived of oxygen or by halting the water flow to the gill. 2. The ear of the goldfish is most sensitive to hypoxia. Sound-evoked afferent activities were profoundly depressed within several minutes after the introduction of hypoxia. 3. The depressed afferent activity was attributed to a reduction in the amplitude of sound-evoked excitatory postsynaptic potentials (EPSPs) generated at afferent fiber terminals, since no significant change was detected in the resting and action potentials of afferent fibers or in intensity of the threshold current required to set up an action potential. Also, there was no marked change in the electrical activity of hair cells, determined by the finding that the amplitude of intramacularly recorded microphonic potentials and that of the coupling potentials was not altered. 4. A statistical analysis of the amplitude of sound-evoked EPSPs revealed that the binomial parameter n decreased during hypoxia, in parallel with a reduction in the amplitude of EPSPs, while the binomial parameter p either remained unaltered or was augmented. No change was found in the quantal size, thereby indicating that the sensitivity of the postsynaptic membrane remained unchanged. These results indicate that presynaptic mechanisms within hair cells, especially those playing a role in transmitter release or in replenishment of the latter, are suppressed during hypoxia.

Morphology of functional long-ranging primary afferent projections in the cat spinal cord

1995 ◽  
Vol 74 (6) ◽  
pp. 2336-2348 ◽  
Author(s):  
H. R. Koerber ◽  
K. Mirnics
Keyword(s):  
Spinal Cord ◽  
Sagittal Plane ◽  
Sensory Information ◽  
Afferent Fiber ◽  
Primary Afferent ◽  
Afferent Projections ◽  
Current Pulses ◽  
Afferent Fibers ◽  
Dorsal Columns ◽  
Primary Afferent Fibers

1. A beta-cutaneous primary afferent fibers were impaled in the dorsal columns of alpha-chloralose-anesthetized cats. Penetrations were made with the use of electrodes filled with 2 or 5% N-(2-aminoethyl) biotinamide hydrochloride (Neurobiotin, NB) in 0.1 or 1 M KCl. After determining its adequate stimulus, each fiber was activated by current pulses (18 Hz) injected via the microelectrode. The resulting cord dorsum potential (CDP) was recorded at four locations. NB was then injected into the fiber with the use of positive current pulses (11-22 nA) and a 75% duty cycle. 2. After allowing 2-8 h for diffusion, animals were perfused with saline (37 degrees C) followed by 4% paraformaldehyde (4 degrees C). Frozen 50-microns sections were cut in either the transverse or sagittal plane, processed on slides with the use of standard avidin-biotin protocols, and visualized by the nickel-enhanced diaminobenzidine (DAB) reaction. 3. A total of 15 A beta-cutaneous afferents innervating both rapidly (RA) and slowly adapting (SA) receptors were adequately stained and their central projections recovered. For selected fibers the rostrocaudal and laminar bouton distributions were determined and compared with the distribution of monosynaptic CDP amplitudes recorded at the four surface locations. 4. The rostrocaudal extent of a single A beta-afferent fiber bouton distribution visualized with NB ranged from 8 to 17.5 mm (14.4 +/- 2.4 mm, mean +/- SD), or two to three times greater than that previously shown with the use of horseradish peroxidase (HRP). 5. The strong correlation between the rostrocaudal distribution of boutons and monosynaptic CDP amplitudes, and the improved agreement between modeled and observed CDP amplitudes over that seen previously with the use of HRP (mean percent error, HRP = 23 +/- 2.9%; NB = 9 +/- 2.3%), suggest that boutons along the entire length of the visualized distribution contribute to the recorded potentials. 6. Taken together, these findings suggest that inputs from a given point on the skin can directly influence sensory information processing over a much greater rostrocaudal extent than predicted by dorsal horn somatotopic maps. These findings are discussed in terms of their implications for spinal cord plasticity.

Electrical Properties of Fibres from Stridulatory and Flight Muscles of a Tettigoniid

1982 ◽  
Vol 99 (1) ◽  
pp. 109-125
Author(s):  
ROBERT K. JOSEPHSON ◽  
DARRELL R. STOKES
Keyword(s):  
Electrical Properties ◽  
Transmitter Release ◽  
Longitudinal Muscle ◽  
Membrane Resistance ◽  
Neural Stimulation ◽  
Release Mechanism ◽  
Voltage Response ◽  
Voltage Dependent ◽  
Flight Muscles ◽  
Passive Electrical Properties

1. The mesothoracic dorsal longitudinal muscle (DLM) of the katydid Neoconocephalus robustus is used in stridulation and flight; the metathoracic DLM is used in flight only. The DLM's in the two segments have radically different maximum operating frequencies, 200 Hz for the mesothoracic muscle during stridulation and 20 Hz for the metathoracic muscle during flight. 2. Cable analysis was used to determine the passive electrical properties of mesothoracic and metathoracic DLM fibres. Fibres in the two segments are of similar diameter and have similar sarcoplasmic resistivity. The apparent membrane resistance is lower, the apparent membrane capacitance higher, and the time constant shorter in mesothoracic fibres than in the metathoracic homologues. 3. The depolarization evoked by neural stimulation in both mesothoracic and metathoracic fibres is principally an excitatory junctional potential (e.j.p.) with little or no contribution from voltage-dependent, inward current channels. At short interstimulus intervals the second e.j.p. of a pair is reduced in amplitude relative to the first e.j.p. The period of e.j.p. depression is shorter in mesothoracic than in metathoracic fibres. It is suggested that the faster recovery of e.j.p.'s in mesothoracic fibres is due to more rapid recovery of the transmitter release mechanism in their motorneurones. 4. In mesothoracic but not metathoracic fibres the voltage response to large depolarizing currents is usually oscillatory, and the recovery of e.j.p. amplitude as a function of time in paired shock experiments is sometimes oscillatory. The oscillation frequency is 250–300 Hz (35 °C) which is higher than the natural operating frequency of the muscle.

Effects of Asphyxia and Repetitive Stimulation on Intramedullary Afferent Fibers

1957 ◽  
Vol 191 (2) ◽  
pp. 225-232 ◽  
Author(s):  
Adele E. U. Edisen
Keyword(s):  
Afferent Fiber ◽  
Repetitive Stimulation ◽  
High Frequency Stimulation ◽  
High Frequencies ◽  
Afferent Fibers ◽  
Focal Potential ◽  
Antidromic Responses ◽  
Frequency Stimulation ◽  
Antidromic Response ◽  
Pulse Stimulation

Effects of asphyxia and of repetitive stimulation on intramedullary projections of the afferent fibers were studied in spinal cords of cats anesthetized with Nembutal. The spinal cord focal potential, elicited by dorsal root stimulation and recorded from the cord, and the antidromically conducted response of afferent fibers produced by intraspinal needle electrode stimulation and recorded from the dorsal roots, were used as indices of afferent fiber activity. The focal potential and the antidromic response from terminal presynaptic fibers disappeared with 5–6 minutes of asphyxiation. Antidromic responses from preterminal regions were less susceptible to asphyxial block. Asphyxia impaired the ability of both types of responses to follow high frequencies of stimulation. The focal potential and the antidromic responses were observed to follow similar orders of high frequency stimulation. Double pulse stimulation of intramedullary fibers demonstrated a longer refractory period of terminal regions with progressive decrease of refractoriness in more dorsally located regions. A gradient of sensitivity to asphyxia and a postresponse recovery gradient exist along the intramedullary fibers.

scholarly journals Sustained Morphine Exposure Induces a Spinal Dynorphin-Dependent Enhancement of Excitatory Transmitter Release from Primary Afferent Fibers

2002 ◽  
Vol 22 (15) ◽  
pp. 6747-6755 ◽  
Author(s):  
Luis R. Gardell ◽  
Ruizhong Wang ◽  
Shannon E. Burgess ◽  
Michael H. Ossipov ◽  
Todd W. Vanderah ◽  
...  
Keyword(s):  
Transmitter Release ◽  
Primary Afferent ◽  
Afferent Fibers ◽  
Primary Afferent Fibers ◽  
Excitatory Transmitter

scholarly journals Opioid Actions in Primary-Afferent Fibers—Involvement in Analgesia and Anesthesia

2011 ◽  
Vol 4 (2) ◽  
pp. 343-365 ◽  
Author(s):  
Eiichi Kumamoto ◽  
Kotaro Mizuta ◽  
Tsugumi Fujita
Keyword(s):  
Primary Afferent ◽  
Afferent Fibers ◽  
Primary Afferent Fibers

scholarly journals Functional Interactions between Tumor and Peripheral Nerve: Changes in Excitability and Morphology of Primary Afferent Fibers in a Murine Model of Cancer Pain

2001 ◽  
Vol 21 (23) ◽  
pp. 9367-9376 ◽  
Author(s):  
David M. Cain ◽  
Paul W. Wacnik ◽  
Michelle Turner ◽  
Gwen Wendelschafer-Crabb ◽  
William R. Kennedy ◽  
...  
Keyword(s):  
Peripheral Nerve ◽  
Cancer Pain ◽  
Murine Model ◽  
Primary Afferent ◽  
Functional Interactions ◽  
Afferent Fibers ◽  
Primary Afferent Fibers
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