Inhibition of nociceptive neurons in the nucleus ventralis posterolateralis following conditioning stimulation of either the nucleus raphe magnus or the periaqueductal gray of the cat

1990 ◽  
Vol 11 ◽  
pp. S125
Author(s):  
Philip J. Pamplin ◽  
Arneil T. Chua ◽  
Toshikatsu Yokota
Keyword(s):  
Periaqueductal Gray ◽  
Conditioning Stimulation ◽  
Nucleus Raphe Magnus ◽  
Nociceptive Neurons ◽  
Raphe Magnus ◽  
Stimulation Of

Parabrachial area and nucleus raphe magnus-induced modulation of nociceptive and nonnociceptive trigeminal subnucleus caudalis neurons activated by cutaneous or deep inputs

1994 ◽  
Vol 71 (6) ◽  
pp. 2430-2445 ◽  
Author(s):  
C. Y. Chiang ◽  
J. W. Hu ◽  
B. J. Sessle
Keyword(s):  
Spontaneous Activity ◽  
Inhibitory Effects ◽  
Conditioning Stimulation ◽  
Nucleus Raphe Magnus ◽  
Nociceptive Neurons ◽  
Nociceptive Responses ◽  
Significant Difference ◽  
Raphe Magnus ◽  
Trigeminal Subnucleus Caudalis ◽  
Stimulation Of

1. The aim of this study was to test whether parabrachial area (PBA) stimulation exerts inhibitory influences on the spontaneous activity and responses evoked by skin and deep afferent inputs in trigeminal subnucleus caudalis (Vc) neurons, and to compare these effects with those of nucleus raphe magnus (NRM) stimulation. A total of 92 nonnociceptive and nociceptive Vc neurons was recorded in urethan/alpha-chloralose-anesthetized rats. Each neuron was functionally classified as low-threshold mechanoceptive (LTM), wide dynamic range (WDR), nociceptive-specific (NS), nociceptive convergent with both skin and deep inputs (S+D), or deep nociceptive (D); the LTM neurons could be subdivided as rapidly adapting (RA) or slowly adapting (SA). Conditioning stimulation was applied to histologically verified sites in PBA and NRM. 2. The spontaneous or evoked activity of all classes of neurons could be inhibited by PBA as well as by NRM stimulation, but generally the incidence and magnitude of inhibition were lower for the LTM neurons. Occasionally, facilitation of neuronal activity was also produced by PBA and NRM stimulation. 3. The spontaneous activity of 11 LTM neurons (6 RA, 5 SA), 13 nociceptive neurons (6 WDR, 7 NS), and 5 D neurons was tested with stimulation of PBA or NRM or both. LTM spontaneous activity was more significantly inhibited by NRM stimulation than by PBA stimulation, whereas both NRM and PBA stimulation had similar and significant inhibitory effects on NS, WDR, and D neurons. 4. The evoked nonnociceptive responses of 28 LTM neurons (16 RA, 12 SA) and of 6 WDR neurons were also tested with stimulation of PBA or NRM or both. The magnitudes of inhibition of the responses produced by PBA conditioning stimulation were statistically significantly less than those induced by NRM conditioning stimulation. 5. The cutaneous and deep nociceptive responses of cutaneous nociceptive neurons (9 NS, 19 WDR) and seven D neurons, respectively, were also tested with PBA and NRM stimulation. There was a significant difference in potency between PBA- and NRM-induced inhibition, but no difference in the magnitude of inhibitory effects among NS, WDR, and D neurons. For both PBA and NRM conditioning stimulation, graded increases in intensities of stimulation produced linear increases in inhibitory effects on nociceptive responses; an increase in stimulation frequency from 5 to 400 Hz also produced increases in inhibition of the nociceptive responses. 6. In five S+D nociceptive convergent neurons, the responses elicited by deep inputs were more powerfully inhibited by PBA stimulation than those elicited by cutaneous inputs.(ABSTRACT TRUNCATED AT 400 WORDS)

Spinal pathways mediating tonic or stimulation-produced descending inhibition from the periaqueductal gray or nucleus raphe magnus are separate in the cat

1987 ◽  
Vol 58 (2) ◽  
pp. 327-341 ◽  
Author(s):  
J. Sandkuhler ◽  
Q. G. Fu ◽  
M. Zimmermann
Keyword(s):  
Electrical Stimulation ◽  
Dorsal Horn ◽  
Periaqueductal Gray ◽  
Descending Inhibition ◽  
Relative Significance ◽  
Nucleus Raphe Magnus ◽  
Nociceptive Neurons ◽  
Spinal Pathways ◽  
C Fibers ◽  
Raphe Magnus

1. The spinal pathways for tonic and stimulation-produced descending inhibition of spinal nociceptive neurons were investigated in anesthetized paralyzed cats. Reversible circumscribed blocks were produced at various depths in the lateral funiculi (LF) at L1-L2 using the microinjection of the local anesthetic lidocaine. The total amount of tonic descending inhibition in the absence of LF blocks was evaluated by monitoring the spinal neuronal activity during reversible spinalization by cold block and compared with the activity of the same neuron during LF blocks. Stimulation-induced descending inhibition of neuronal responses to noxious skin heating was produced by bipolar focal electrical stimulation in the periaqueductal gray (PAG) or nucleus raphe magnus (NRM) and compared with the inhibition of the same neurons during LF blocks. The relative significance of ipsi- and contralateral pathways in the dorsal, medial, or ventral aspects of the lateral funiculi for these types of descending inhibition are quantitatively described. 2. All 35 lumbar spinal dorsal horn neurons studied responded to noxious and innocuous mechanical and noxious thermal stimuli applied within the receptive fields on the glabrous skin of the hindlimb. Responses to noxious skin stimuli (50 degrees C, 10 s at 3-min intervals) were constant over time and served as a parameter to evaluate tonic and stimulation-produced descending inhibition. All neurons also responded to electrical stimulation of hindlimb cutaneous nerves supramaximal for the activation of A-beta-, delta-, and C-fibers. Neurons were located in laminae I-VI of the dorsal horn at L5-L7 levels. LF blocks were produced by the microinjection of 1 microliter lidocaine at each of one to six sites in the ipsilateral and/or contralateral LF 500, 1,500, and/or 2,500 microns below cord surface. 3. LF blocks ipsilateral to the recording sites in the cord significantly reduced tonic inhibition, with blocks in the dorsal part of the LF [i.e., the dorsolateral funiculus (DLF)] being equally effective to complete LF blocks. Stimulation-produced inhibition from PAG or NRM was, however, not significantly affected by ipsilateral LF blocks. 4. Contralateral LF blocks significantly reduced stimulation-produced descending inhibition and failed to affect tonic descending inhibition. Ventral LF blocks attenuated inhibition from the PAG but not from NRM, whereas DLF blocks were more effective on inhibition from the NRM. 5. Bilateral LF blocks significantly reduced tonic as well as stimulation-produced descending inhibition.(ABSTRACT TRUNCATED AT 400 WORDS)

The effects of focal stimulation in nucleus raphe magnus and periaqueductal gray on intracellularly recorded neurons in spinal laminae I and II

1986 ◽  
Vol 56 (3) ◽  
pp. 555-571 ◽  
Author(s):  
A. R. Light ◽  
E. J. Casale ◽  
D. M. Menetrey
Keyword(s):  
Brain Stem ◽  
Periaqueductal Gray ◽  
The Other ◽  
Descending Pathways ◽  
Nucleus Raphe Magnus ◽  
Raphe Magnus ◽  
Low Threshold ◽  
Conductance Increase ◽  
Small Conductance ◽  
Postsynaptic Mechanism

Single neurons in spinal laminae I and II of cats were recorded intracellularly while stimulating in nucleus raphe magnus (NRM) and periaqueductal gray (PAG) with monopolar tungsten microelectrodes. Brain stem stimulation inhibited about one-half of the nociceptive-specific neurons, whereas the other half was unaffected. Brain stem stimulation inhibited about one-half of the multireceptive neurons, but the other half was excited and then inhibited. Brain stem stimulation inhibited about one-third of the low-threshold neurons, one-half was excited then inhibited, and one-fifth showed no effect. In all classes of neurons, the inhibition was produced by an inhibitory postsynaptic potential (IPSP) that began with a latency of approximately 25 ms and lasted approximately 400 ms following a single stimulus. The IPSP occurred with a small conductance increase and was reversed by hyperpolarizing currents applied to the cell. These data indicate that NRM and PAG modulated laminae I and II neurons via a postsynaptic mechanism. The conduction velocity of this descending pathway was calculated to range from 6.1 to 66.6 m/s with an average of 13.8 m/s. These data also indicate heterogeneity in the pathway, since some neurons were inhibited, whereas other neurons were excited then inhibited by descending stimulation. Finally, these data indicate specificity in these descending pathways since nearly one-half of neurons that had low-threshold inputs were excited by brain stem stimulation, whereas nearly all nociceptive-specific neurons were either inhibited or unaffected.

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