Organization in the descending tracts of the dorsolateral funiculus in the cat

2006 ◽  
Vol 1117 (1) ◽  
pp. 61-68
Author(s):  
Yanmei Tie ◽  
Mesut Sahin ◽  
Nappinnai Sundararajan
Keyword(s):  
Dorsolateral Funiculus

Ascending pathways in the spinal cord involved in the activation of subnucleus reticularis dorsalis neurons in the medulla of the rat

1990 ◽  
Vol 63 (3) ◽  
pp. 424-438 ◽  
Author(s):  
Z. Bing ◽  
L. Villanueva ◽  
D. Le Bars
Keyword(s):  
Spinal Cord ◽  
Electrical Stimulation ◽  
The Body ◽  
Cervical Cord ◽  
Lateral Part ◽  
Neuronal Responses ◽  
C Fiber ◽  
Dorsal Columns ◽  
Dorsolateral Funiculus ◽  
The Right

1. Recordings were made from neurons in the left medullary subnucleus reticularis dorsalis (SRD) of anesthetized rats. Two populations of neurons were recorded: neurons with total nociceptive convergence (TNC), which gave responses to A delta- and C-fiber activation from the entire body after percutaneous electrical stimulation, and neurons with partial nociceptive convergence (PNC), which responded to identical stimuli with an A delta-peak regardless of which part of the body was stimulated and with a C-fiber peak of activation from some, mainly contralateral, parts of the body. 2. The effects of various, acute, transverse sections of the cervical (C4-C5) spinal cord on the A delta- and C-fiber-evoked responses were investigated by building poststimulus histograms (PSHs) after 50 trials of supramaximal percutaneous electrical stimulation of the extremity of either hindpaw (2-ms duration; 3 times threshold for C-fiber responses), before and 30-40 min after making the spinal lesion. 3. In the case of TNC neurons, hemisections of the left cervical cord blocked the responses elicited from the right hindpaw and slightly, but not significantly, diminished those evoked from the left hindpaw. Conversely, hemisections of the right cervical cord abolished TNC responses elicited from the left hindpaw without significantly affecting the responses elicited from the right hindpaw. 4. Lesioning the dorsal columns or the left dorsolateral funiculus was found not to affect the TNC neuronal responses elicited from either hindpaw. By contrast, lesioning the left lateral funiculus or the most lateral part of the ventrolateral funiculus, respectively, reduced and blocked the responses elicited from the right hindpaw without affecting those evoked from the left hindpaw. 5. After lesions that included the most lateral parts of the left ventral funiculus, PNC neuronal responses elicited from the right hindpaw were also abolished, whereas those elicited from the left hindpaw remained unchanged. 6. We conclude that the signals responsible for the activation of SRD neurons travel principally in the lateral parts of the ventrolateral quadrant, a region that classically has been implicated in the transmission of noxious information. Both a crossed and a double-crossed pathway are involved in this process. The postsynaptic fibers of the dorsal columns and the spinocervical and spinomesencephalic tracts do not appear to convey signals that activate SRD neurons. 7. The findings also suggest that lamina I nociceptive specific neurons, the axons of which travel within the dorsolateral funiculus, do not contribute very much to the activation of SRD neurons.

Ascending pathways mediating somatoautonomic reflexes in exercising dogs

1987 ◽  
Vol 62 (3) ◽  
pp. 1186-1191 ◽  
Author(s):  
J. W. Kozelka ◽  
G. W. Christy ◽  
R. D. Wurster
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Surgical Techniques ◽  
Arterial Occlusion ◽  
Cardiovascular Responses ◽  
Spinal Pathways ◽  
Arterial Blood ◽  
Bilateral Carotid ◽  
Dorsolateral Funiculus ◽  
Carotid Arterial

The ascending spinal pathways mediating somatocardiovascular reflexes during exercise were studied in unanesthetized dogs by placing lesions in the lumbar spinal cord. After training to run on a treadmill with hindlimbs only, 20 dogs were anesthetized and instrumented using sterile surgical techniques. To chronically record heart rate and arterial blood pressure, the aorta was cannulated via the omocervical artery. To test the intactness of descending spinal sympathetic pathways, reflex pressor responses to baroreceptor hypotension were produced by bilateral carotid arterial occlusion using pneumatic vessel occluders placed around the common carotid arteries. To generate transient ischemic exercise (120 s), a pneumatic occluder was placed around the left iliac artery. Eight to 10 days after instrumentation, blood pressure and heart rate were monitored at rest and during hindlimb running with and without simultaneous iliac arterial occlusion. The modest pressor response and tachycardia elicited by hindlimb exercise were markedly augmented by simultaneous hindlimb ischemia (i.e., iliac arterial occlusion). Lesion placement in the dorsolateral sulcus area and the dorsolateral funiculus at L2 significantly reduced the blood pressure and heart rate responses to simultaneous exercise occlusion. The cardiovascular responses to nonischemic exercise and bilateral carotid arterial occlusion were not altered by such spinal sections. It is concluded that in the dog the ascending spinal pathways mediating cardiovascular responses to ischemic exercise are located in the lateral funiculus, including the dorsolateral sulcus area and dorsolateral funiculus.

Red Nucleus Stimulation Inhibits Within the Inferior Olive

1998 ◽  
Vol 80 (6) ◽  
pp. 3127-3136 ◽  
Author(s):  
K. M. Horn ◽  
T. M. Hamm ◽  
A. R. Gibson
Keyword(s):  
Inferior Olive ◽  
Red Nucleus ◽  
Salient Feature ◽  
Cutaneous Stimulation ◽  
Motor Pathways ◽  
Peripheral Stimulation ◽  
Dorsal Columns ◽  
Dorsolateral Funiculus ◽  
Somatosensory Responses ◽  
Stimulation Of

Horn, K. M., T. M. Hamm, and A. R. Gibson. Red nucleus stimulation inhibits within the inferior olive. J. Neurophysiol. 80: 3127–3136, 1998. In the anesthetized cat, electrical stimulation of the magnocellular red nucleus (RNm) inhibits responses of rostral dorsal accessory olive (rDAO) neurons to cutaneous stimulation. We tested the hypothesis that RNm-mediated inhibition occurs within the inferior olive by using stimulation of the ventral funiculus (VF) of the spinal cord in place of cutaneous stimulation of the hindlimb. Fibers in the VF terminate on hindlimb rDAO neurons, so inhibition of this input would have to occur within the olive. rDAO responses elicited by VF stimulation were inhibited by prior stimulation of the RNm, indicating that inhibition occurs within the olive. In contrast, evoked potentials recorded from the VF or dorsal columns following hindlimb stimulation were not affected by prior stimulation of RNm, indicating that stimulation of the RNm does not inhibit olivary afferents at spinal levels. RNm stimulation that inhibited rDAO responses had little effect on evoked somatosensory responses in thalamus, indicating that inhibition generated by activity in RNm may be specific to rDAO. To test limb specificity of RNm-mediated inhibition, conditioning stimulation was applied to the dorsolateral funiculus at thoracic levels, which selectively activates RNm neurons projecting to the lumbar cord. Stimulation at thoracic levels inhibited evoked responses from hindlimb but not forelimb regions of rDAO, suggesting that inhibitory effects of RNm activity are limb specific. Several studies have reported that olivary neurons have reduced sensitivity to peripheral stimulation during movement; it is likely that RNm-mediated inhibition occurring within the olive contributes to this reduction of sensitivity. Inhibition of rDAO responses by descending motor pathways appears to be a salient feature of olivary function.

Involvement of the dorsolateral funiculus in the descending spinal projections responsible for diffuse noxious inhibitory controls in the rat

1986 ◽  
Vol 56 (4) ◽  
pp. 1185-1195 ◽  
Author(s):  
L. Villanueva ◽  
D. Chitour ◽  
D. Le Bars
Keyword(s):  
Receptive Fields ◽  
Conditioning Stimulus ◽  
Mechanical Stimuli ◽  
Diffuse Noxious Inhibitory Controls ◽  
Strong Reduction ◽  
Inhibitory Processes ◽  
C Fiber ◽  
Dorsolateral Funiculus ◽  
Electrical Stimuli ◽  
Descending Projections

Recordings were made from convergent neurons in the lumbar dorsal horn of the spinal cord of the rat. These neurons were activated by both innocuous and noxious mechanical stimuli applied to their excitatory receptive fields located on the extremity of the hindpaw. Transcutaneous application of suprathreshold 2-ms square-wave electrical stimuli to the center of the excitatory field, resulted in responses to C-fiber activation being observed. This type of response was inhibited by applying a noxious thermal conditioning stimulus on the muzzle. The immersion of the muzzle in a 52 degrees C waterbath resulted in a strong reduction of the response during the application of the noxious conditioning stimulus and this was followed by long lasting poststimulus effects. Such inhibitory processes have been termed diffuse noxious inhibitory controls (DNIC). The effects on these inhibitions of lesions including the dorsolateral funiculus (DLF) were investigated in acute experiments: tests were performed before and at least 30 min after the DLF lesion. A lesion including the DLF ipsilateral to the neuron under study completely abolished the inhibitory processes triggered from the muzzle. Concomitantly, a facilitation of C-fiber responses was observed. Nevertheless, DNIC was still impaired even using a juxtathreshold current to elicit a weak C-fiber response. To ascertain further the main, if not entire, participation of the ipsilateral DLF in the descending projections responsible for the heterotopic inhibitory processes, the effects of a lesion of the contralateral DLF were investigated. Neither the inhibitory processes nor the unconditioned C-fiber responses were altered by this procedure. Again, a second lesion including the ipsilateral DLF induced a blockade of DNIC. It is concluded that the descending projections involved in the triggering of DNIC are mainly, if not entirely, confined to the DLF ipsilateral to the neuron under study. The contralateral DLF did not appear to play a role in these processes.

Interaction of descending spinal sympathetic pathways and afferent nerves

1978 ◽  
Vol 234 (3) ◽  
pp. H223-H229
Author(s):  
S. M. Barman ◽  
R. D. Wurster
Keyword(s):  
Nerve Fibers ◽  
Nerve Activity ◽  
Afferent Nerves ◽  
Afferent Nerve Fibers ◽  
Somatosympathetic Reflex ◽  
Reflex Activation ◽  
Dorsolateral Funiculus ◽  
Ventrolateral Funiculus ◽  
Stimulation Of ◽  
Excitatory Pathway

With the use of computer-aided techniques, the interaction of descending spinal sympathetic pathways and afferent nerve fibers (cervical dorsal roots and tibial nerve) in regulation of thoracic (T2) preganglionic nerve activity was investigated in anesthetized, vagotomized, and paralyzed cats. High-frequency activation of a sympathoinhibitory pathway (ventrolateral funiculus) depressed the evoked discharges in the T2 preganglionic nerve elicited by stimulation of a sympathoexcitatory pathway (dorsolateral funiculus) and the spinal component of the somatosympathetic reflex. Submaximal evoked responses were also inhibited through baroreceptor reflex activation (blood pressure elevations up to 225 mmHg). Facilitation of the spinal component of the somatosympathetic reflex occurred during stimulation of the excitatory pathway. Carotid occlusion (baroreceptor inactivation) facilitated the submaximal evoked discharges from stimulation of the descending excitatory pathway. These data support the contention that sympathetic nerve activity can be modified by the integration of excitatory and inhibitory impulses at the spinal level.

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