The relationship between descending serotonin projections and ascending projections in the nucleus raphe magnus: a double labeling study

1986 ◽  
Vol 70 (3) ◽  
pp. 348-353 ◽  
Author(s):  
Robert M. Bowker
Keyword(s):  
Double Labeling ◽  
Nucleus Raphe Magnus ◽  
Raphe Magnus ◽  
The Relationship

scholarly journals Effects of Transcranial Ultrasound Stimulation on Trigeminal Blink Reflex Excitability

2021 ◽  
Vol 11 (5) ◽  
pp. 645
Author(s):  
Andrea Guerra ◽  
Edoardo Vicenzini ◽  
Ettore Cioffi ◽  
Donato Colella ◽  
Antonio Cannavacciuolo ◽  
...  
Keyword(s):  
Substantia Nigra ◽  
Superior Colliculus ◽  
Blink Reflex ◽  
Transcranial Ultrasound ◽  
Recovery Cycle ◽  
Brain Areas ◽  
Nucleus Raphe Magnus ◽  
Ultrasound Stimulation ◽  
Raphe Magnus ◽  
Interstimulus Intervals

Recent evidence indicates that transcranial ultrasound stimulation (TUS) modulates sensorimotor cortex excitability. However, no study has assessed possible TUS effects on the excitability of deeper brain areas, such as the brainstem. In this study, we investigated whether TUS delivered on the substantia nigra, superior colliculus, and nucleus raphe magnus modulates the excitability of trigeminal blink reflex, a reliable neurophysiological technique to assess brainstem functions in humans. The recovery cycle of the trigeminal blink reflex (interstimulus intervals of 250 and 500 ms) was tested before (T0), and 3 (T1) and 30 min (T2) after TUS. The effects of substantia nigra-TUS, superior colliculus-TUS, nucleus raphe magnus-TUS and sham-TUS were assessed in separate and randomized sessions. In the superior colliculus-TUS session, the conditioned R2 area increased at T1 compared with T0, while T2 and T0 values did not differ. Results were independent of the interstimulus intervals tested and were not related to trigeminal blink reflex baseline (T0) excitability. Conversely, the conditioned R2 area was comparable at T0, T1, and T2 in the nucleus raphe magnus-TUS and substantia nigra-TUS sessions. Our findings demonstrate that the excitability of brainstem circuits, as evaluated by testing the recovery cycle of the trigeminal blink reflex, can be increased by TUS. This result may reflect the modulation of inhibitory interneurons within the superior colliculus.

Inhibition of primate spinothalamic tract neurons by stimulation in the region of the nucleus raphe magnus

1976 ◽  
Vol 114 (2) ◽  
pp. 328-333 ◽  
Author(s):  
J.E. Beall ◽  
R.F. Martin ◽  
A.E. Applebaum ◽  
W.D. Willis
Keyword(s):  
Spinothalamic Tract ◽  
Nucleus Raphe Magnus ◽  
Raphe Magnus

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.

Descending inhibitory influences from periaqueductal gray, nucleus raphe magnus, and adjacent reticular formation. II. Effects on medullary dorsal horn nociceptive and nonnociceptive neurons

1983 ◽  
Vol 49 (4) ◽  
pp. 948-960 ◽  
Author(s):  
J. O. Dostrovsky ◽  
Y. Shah ◽  
B. G. Gray
Keyword(s):  
Dorsal Horn ◽  
Dynamic Range ◽  
Periaqueductal Gray ◽  
Nucleus Raphe Magnus ◽  
Nucleus Reticularis ◽  
Medullary Dorsal Horn ◽  
Significant Difference ◽  
Raphe Magnus ◽  
Somatosensory Responses ◽  
Wdr Neurons

1. This study examined the inhibitory effects elicited by brain stem stimulation on the somatosensory responses of trigeminal medullary dorsal horn (subnucleus caudalis of the spinal trigeminal nucleus) neurons. Single-unit extracellular recordings were obtained in chloralose-anesthetized cats. Neurons were classified as wide dynamic range (WDR), nociceptive specific (NS), or low-threshold mechanoreceptive (LTM). Conditioning stimuli were delivered to the periaqueductal gray (PAG), nucleus cuneiformis (CU), nucleus raphe magnus (NRM), nucleus reticularis gigantocellularis (NGC), and nucleus reticularis magnocellularis (NMC). 2. Over 97% of the neurons tested could be inhibited by stimulation in all regions except PAG. Stimulation in the PAG inhibited 91% of the neurons tested. There was no statistically significant difference in the incidence of inhibition of WDR and NS nociceptive (noci) neurons and the LTM nonnociceptive (nonnoci) neurons. 3. Mean stimulation intensities necessary to produce inhibition were determined for each neuron from each stimulation site. The current thresholds necessary to inhibit the responses of noci neurons were found to be significantly lower, on the average, than those of nonnoci neurons at stimulation sites in the PAG, CU, and NGC. 4. Inhibition of the responses of WDR neurons required a lower mean current than for NS neurons but was statistically significant only for PAG and NGC. Thresholds for inhibiting the responses of NS neurons were similar to those for inhibiting the responses of LTM neurons for all regions except CU, where LTM thresholds were markedly but not significantly higher. 5. Stimulation thresholds were found to be lowest in NMC, while in NGC, NRM, and CU they were all similar and slightly higher. Stimulation in the PAG required the highest currents to produce inhibition. 6. These results indicate that stimulation in NRM and PAG not only inhibits the responses of noci neurons but also those of nonnoci neurons. Furthermore, stimulation in reticular regions adjacent to NRM and PAG is frequently even more effective in inhibiting the responses of both noci and nonnoci neurons. In addition, WDR neurons are more effectively inhibited than NS or LTM neurons. These results are compared with those obtained using similar methods in cat lumbar dorsal horn.

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