Dynamics of polysynaptic spinal reflexes during prolonged stimulation of afferent fibers

1977 ◽  
Vol 8 (6) ◽  
pp. 485-486
Author(s):  
�. I. Slivko
Keyword(s):  
Spinal Reflexes ◽  
Prolonged Stimulation ◽  
Afferent Fibers ◽  
Stimulation Of

Supraspinal inhibition of a cutaneous vascular reflex in the cat

1964 ◽  
Vol 207 (2) ◽  
pp. 303-307 ◽  
Author(s):  
B. J. Prout ◽  
J. H. Coote ◽  
C. B. B. Downman
Keyword(s):  
Carotid Sinus ◽  
Spinal Reflexes ◽  
Descending Pathways ◽  
Skin Response ◽  
Reflex Arc ◽  
Vascular Reflex ◽  
Carotid Sinus Nerve Stimulation ◽  
Sympathetic Discharge ◽  
Stimulation Of ◽  
Cerebellar Stimulation

In cats anesthetized with chloralose-urethane mixture, stimulation of an afferent nerve evoked a vasoconstrictor reflex (VCR) and a galvanic skin response (GSR) in the pads of the feet. Stimulation of the ventromedial medullary reticular substance at the level of the obex abolished the VCR and the GSR. VCR could also be reduced by occlusion during prolonged stimulation of another spinal or visceral afferent pathway. Medulla stimulation was effective without itself causing a sympathetic discharge to the paw, showing that inhibition rather than occlusion was operative. Anterior cerebellar stimulation also inhibited the VCR. Carotid sinus nerve stimulation did not abolish the VCR. It is concluded that the effective mechanism includes a bulbospinal inhibitory path projecting on a spinal vasoconstrictor reflex arc. This arrangement is similar to the descending pathways inhibiting other spinal reflexes but the VCR-inhibitory path can be activated independently of them.

T2-T5 spinothalamic neurons projecting to medial thalamus with viscerosomatic input

1985 ◽  
Vol 54 (1) ◽  
pp. 73-89 ◽  
Author(s):  
W. S. Ammons ◽  
M. N. Girardot ◽  
R. D. Foreman
Keyword(s):  
Receptive Fields ◽  
Cell Group ◽  
Spinothalamic Tract ◽  
Medial Thalamus ◽  
Dorsal Nucleus ◽  
Afferent Fibers ◽  
C Fiber ◽  
Antidromic Responses ◽  
Alpha Chloralose ◽  
Stimulation Of

Spinothalamic tract neurons projecting to medial thalamus (M-STT cells), ventral posterior lateral nucleus (VPL) of the thalamus (L-STT cells), or both thalamic regions (LM-STT cells) were studied in 19 monkeys anesthetized with alpha-chloralose. Twenty-seven M-STT cells were antidromically activated from nucleus centralis lateralis, nucleus centrum medianum, or the medial dorsal nucleus. Stimulation of VPL elicited antidromic responses from 22 cells and 13 cells were activated from both VPL and medial thalamus. Antidromic conduction velocities of M-STT cells were significantly slower than those of L-STT or LM-STT cells. M-STT cells were located in laminae I, IV, V, and VII with greater numbers found in the deepest laminae. L-STT cells were located mostly in lamina IV, whereas most LM-STT cells were found in lamina V. Twenty-four of 27 M-STT cells, all L-STT cells, and all LM-STT cells received input from both cardiopulmonary sympathetic and somatic afferent fibers. WDR cells were most common among the L-STT and LM-STT groups, whereas HT cells were the most common class in the M-STT cell group. Excitatory receptive fields of M-STT cells were large, and often bilateral. Receptive fields of L-STT cells were simple and never bilateral. Receptive fields of LM-STT cells could be similar to M-STT or L-STT cells. Thirty-three percent of the M-STT cells, 37% of the L-STT cells, and 62% of the LM-STT cells had inhibitory receptive fields. Inhibition was elicited most often by a noxious pinch of the hindlimbs. Sixteen of 23 (70%) M-STT cells received C-fiber cardiopulmonary sympathetic input in addition to A-delta-fiber input. The other 7 cells received only A-delta-fiber input. Only 45% of the L-STT cells and 38% of the LM-STT cells received both A-delta- and C-fiber inputs. The maximum number of spikes elicited by A-delta-input was related to segmental locations for L-STT cells with greatest responses in T2 and lesser responses in more caudal segments; however, no such trend was apparent for M-STT cells or for responses to C-fiber input for either group. Electrical stimulation of the left thoracic vagus nerve inhibited 7 of 18 M-STT cells, 10 of 16 L-STT cells, and 6 of 12 LM-STT cells. These results are the first description of visceral input to cells projecting to medial thalamus.(ABSTRACT TRUNCATED AT 400 WORDS)

Mormyromast electroreceptor organs and their afferent fibers in mormyrid fish. II. Intra-axonal recordings show initial stages of central processing

1990 ◽  
Vol 63 (2) ◽  
pp. 303-318 ◽  
Author(s):  
C. C. Bell
Keyword(s):  
Lateral Line ◽  
Electric Organ Discharge ◽  
Electric Organ ◽  
Direct Stimulation ◽  
Postsynaptic Potentials ◽  
Central Processing ◽  
Refractory Periods ◽  
Synaptic Potentials ◽  
Afferent Fibers ◽  
Stimulation Of

1. Physiologically and morphologically identified primary afferent fibers from mormyromast electroreceptor organs were recorded intracellularly. The fiber recordings were made from the nerve root of the posterior lateral line nerve, where the fibers enter the brain, and from the electrosensory lateral line lobe (ELL), near the central terminals of the fibers. 2. The intracellular recordings reveal a variety of potentials, synaptic and nonsynaptic, in addition to the large orthodromic action potentials from the periphery. The goal of the present study was to describe and interpret these various potentials in mormyromast afferent fibers as a first step in understanding the processing of electrosensory information in ELL. 3. Three types of synaptic potentials were recorded inside mormyromast afferent fibers: 1) electric organ corollary discharge (EOCD) excitatory postsynaptic potentials (EPSPs), driven by the motor command that elicits the electric organ discharge (EOD); 2) EPSPs evoked by electrosensory stimulation of electroreceptors in the skin near the electroreceptor from which the recorded fiber originates or by direct stimulation of an electrosensory nerve; and 3) inhibitory postsynaptic potentials (IPSPs) evoked by electrosensory stimulation of more distant electroreceptors. These synaptic potentials can be attributed to synaptic input to postsynaptic cells in ELL that is observed inside the afferent fibers because of electrical synapses between the fibers and the postsynaptic cells. 4. The peripherally evoked EPSPs could frequently be shown to be unitary. The unitary EPSPs were identical to the orthodromic spikes in originating from a single electroreceptor, in threshold, and in latency shift with increasing stimulus intensity. These similarities suggest that the unitary EPSPs are electrotonic EPSPs caused by impulses in other mormyromast afferent fibers that terminate on some of the same postsynaptic cells as the recorded fiber. The peripherally evoked IPSPs had a longer latency than the EPSPs or orthodromic spikes, requiring the presence of an inhibitory interneuron. 5. The peripherally evoked EPSPs, both unitary and nonunitary, show absolute refractory periods of 3-8 ms, followed by relative refractory periods of approximately 8 ms, when tested with two identical stimuli to a nerve. These refractory periods are interpreted as because of refractoriness in the fine preterminal branches of the axonal arbor. 6. A depolarizing afterpotential is commonly associated with the orthodromic spike and probably results from the successful propagation of the spike into the entire terminal arbor. The depolarizing afterpotential has a refractory period that is similar to that of the peripherally evoked EPSPs and that is also interpreted as refractoriness in the fine preterminal branches.(ABSTRACT TRUNCATED AT 400 WORDS)

Capsaicin-activated bronchial- and alveolar-initiated pathways regulating tracheal ciliary beat frequency

1994 ◽  
Vol 77 (3) ◽  
pp. 1239-1245 ◽  
Author(s):  
M. Eljamal ◽  
L. B. Wong ◽  
D. B. Yeates
Keyword(s):  
Low Dose ◽  
Beat Frequency ◽  
Ciliary Beat Frequency ◽  
Neural Stimulation ◽  
Short Exposure ◽  
Tracheal Lumen ◽  
Prolonged Stimulation ◽  
Prior Administration ◽  
Stimulation Of ◽  
Ciliary Beat

We questioned whether the prolonged stimulation of ciliary beat frequency (CBF) to a short exposure of low-dose capsaicin (Wong et al. J. Appl. Physiol. 68: 257–2580, 1990) could be due to the activation of indirect pathways involving neural reflexes initiated independently in the bronchi and alveoli. Tracheal CBF (CBFtr) was measured temporally in anesthetized groups of 10 dogs by means of heterodyne-mode correlation analysis laser light scattering. To elucidate the site of the afferent neural stimulation and the efferent mediators affecting the ciliated epithelium, capsaicin (3 nM) aerosol was delivered for 4 min, either predominantly to the bronchi or to the alveolar regions, with use of pulsed aerosol techniques. This resulted in 13 pg of bronchial (85%) and 10 pg of alveolar (96%) capsaicin deposited, which caused marked stimulation of CBFtr with maxima at 7 and 35 min, respectively. Prior administration of aerosolized indomethacin to the bronchi or aerosolized cromolyn to the alveoli inhibited the bronchial and alveolar responses, respectively. Prior administration of aerosolized hexamethonium to the tracheal lumen blocked the stimulatory CBFtr responses from both capsaicin challenges. Ipratropium or propranolol aerosols delivered to the tracheal lumen also inhibited these responses. It is proposed that these pathways comprise one set of sensitive mechanisms to ensure a prolonged stimulation of CBF to effect the removal of secretions and the irritant from the lungs.

Depressor responses to stimulation of sympathetic afferents in monkeys and dogs

1981 ◽  
Vol 240 (1) ◽  
pp. R23-R28 ◽  
Author(s):  
D. R. Kostreva ◽  
F. A. Hopp ◽  
J. P. Kampine
Keyword(s):  
Fiber Type ◽  
Depressor Response ◽  
Stellate Ganglia ◽  
Afferent Fibers ◽  
Pressor Responses ◽  
Conduction Velocities ◽  
C Fiber ◽  
Cervical Vagotomy ◽  
Left And Right ◽  
Stimulation Of

In dogs and monkeys anesthetized with pentobarbital sodium, stimulation of the cut central ends of the stellate cardiac nerve, the left and right anterior ansae subclavia, and the stellate ganglia resulted in a depressor response when stimulating fibers with conduction velocities in the range of 2.5-10 m/s. These afferents are in the A delta-fiber-type range. Pressor responses could be elicited by stimulating afferent fibers with conduction velocities in the range of 0.5-3.0 m/s. These fibers are in the C-fiber-type range. Stimulation of the abdominal sympathetic afferents always resulted in a depressor response regardless of the conduction velocities of the fibers. No changes in heart rate were observed. Bilateral cervical vagotomy did not alter the pressor or depressor responses.

Sign in / Sign up

Export Citation Format

Share Document