Somatodendritic morphology of on‐ and off‐cells in the rostral ventromedial medulla

Mason, Peggy; Floeter, Mary Kay

doi:10.1002/cne.903010104

Cited by 30 publications

(25 citation statements)

References 63 publications

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“…An example of an intracellularly labeled ON cell imaged with the confocal microscope is shown in Figure 2. The neurons varied in the size and complexity of their dendritic arbors, and were similar to previously published descriptions (Mason et al, 1990;Potrebic and Mason, 1993). No qualitative differences between ON and OFF cells in any somatodendritic feature were observed, but within the ON cell group, dorsally situated cells tended to have a large cell surface area compared to those that were ventrally situated.…”

Section: Physiology and Intracellular Labelingsupporting

confidence: 83%

“…Methods for intracellular recording and labeling in rats were similar to those previously described (Mason et al, 1989(Mason et al, , 1990, and will be briefly detailed here. Glass micropipettes were filled with a solution of 2% Neurobiotin (Vector Laboratories, Burlingame, California) in 0.1 M Tris buffer (pH 7.4) and 0.15 M KCl.…”

Section: Intracellular Recording and Labelingmentioning

confidence: 99%

“…Noxious pinch was applied by toothed forceps at a pressure that was judged painful by the experimenters. Feedback-controlled noxious thermal stimuli were applied to the tail Mason et al, 1990). Identified RVM neurons were labeled with Neurobiotin by injecting constant depolarizing current (1.2-3.0 nA) for two to twenty minutes.…”

Section: Intracellular Recording and Labelingmentioning

confidence: 99%

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Noradrenergic input to nociceptive modulatory neurons in the rat rostral ventromedial medulla

Meng

Budra²,

Skinner³

et al. 1997

J. Comp. Neurol.

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Within the rostral ventromedial medulla (RVM), there are two classes of putative pain modulation neurons: ON cells and OFF cells, which respectively burst or pause prior to withdrawal reflexes elicited by noxious stimulation. Alpha-adrenergic agonists injected into the RVM produce changes in the latency of spinal nocifensive reflexes and, when iontophoretically applied, alter the firing of RVM ON but not OFF cells. To provide further information about the contribution of norepinephrine to RVM neuron function, we analyzed the distribution of tyrosine hydroxylase immunoreactive (TH-ir) appositions upon RVM ON and OFF cells. In the lightly anesthetized rat, seven ON and five OFF cells were identified by changes in their discharge rate in relation to nociceptive withdrawal reflexes and were labeled by intracellular injection of neurobiotin. Sections containing labeled cells were visualized by using avidin conjugated to a Texas Red fluorophore. Tissue with labeled cells was subsequently processed for TH-ir by using a Bodipy fluorophore conjugated secondary antibody. The distribution of the Bodipy-labeled fibers and terminals upon the Texas Red-labeled neurons was mapped using a confocal laser-scanning microscope. All the labeled neurons exhibited close TH-ir appositions. Appositions were of two types: swellings and fibers. Although the numbers and density of appositions varied among the cells, there were no consistent differences that correlated with physiological properties. Thus the overall density of appositions for ON cells (29.0 +/- 22.2 x 10(4) microns2) did not differ significantly from that for OFF cells (25.4 +/- 22.2 x 10(4) microns2). Tyrosine hydroxylase immunoreactive (TH-ir) appositions upon ON and OFF cells varied with their location along the dorso-ventral axis with more ventral neurons having a greater density of TH-ir swelling-type appositions. In a separate study, TH-ir and dopamine-beta-hydroxylase-like immunoreactivity (DBH-ir) were mapped in the same sections by using confocal microscopy. Nearly 97% of the TH-ir profiles co-localized with DBH-ir. These observations provide evidence that both ON and OFF cells in the RVM are targeted by noradrenergic inputs.

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Section: Physiology and Intracellular Labelingsupporting

confidence: 83%

Section: Intracellular Recording and Labelingmentioning

confidence: 99%

Section: Intracellular Recording and Labelingmentioning

confidence: 99%

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Noradrenergic input to nociceptive modulatory neurons in the rat rostral ventromedial medulla

Meng

Budra²,

Skinner³

et al. 1997

J. Comp. Neurol.

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“…Methods for physiological recording in rats have been described (Mason et al, 1990) and will be restated only briefly. Glass micropipettes (resistance of 30-80 MB) were filled with a solution of 2% neurobiotin (Vector Laboratories, Burlingame, CA) in 0.1 M Tris buffer (pH 7.4) and 0.15 M KCl.…”

Section: Methodsmentioning

confidence: 99%

“…5-HT-IR cells were concentrated near the t noxious pinch to the nose. C, There is no change in the activity of this nonserotonergic neutral cell (see tions of these neuronal cell classes (Mason et al, 1990). Neurons had multipolar or fusiform somas, and the dendrites of welllabeled cells extended mediolaterally across RVM.…”

Section: -Ht Immunoreactivitymentioning

confidence: 99%

Serotonin immunoreactivity is contained in one physiological cell class in the rat rostral ventromedial medulla

1994

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Neurons in the rostral ventromedial medulla (RVM) are the major source of serotonergic projections to the dorsal horn. A large body of evidence implicates RVM serotonergic neurons in the modulation of spinal nociceptive transmission. Three physiological classes of RVM neurons, on, off, and neutral cells, are postulated to have different nociceptive modulatory effects on spinal nocifensor reflexes. This study was undertaken to determine which RVM cell class(es) contains 5- HT. In anesthetized rats, RVM neurons were identified by their responses to noxious cutaneous stimuli, intracellularly labeled, and processed for 5-HT immunocytochemistry. Labeled neurons were examined with epifluorescence and imaged using a confocal laser microscope. A total of 25 RVM neurons were intracellularly labeled. No off (n = 9) or on (n = 8) cells were serotonergic. Half of the neutral cells (4 of 8) demonstrated 5-HT immunoreactivity. These results call for a reevaluation of the mechanisms of RVM modulatory influence on spinal cord nociceptive transmission. The finding that some neutral cells are serotonergic strongly suggests that serotonergic neutral cells are involved in the modulation of spinal nociceptive transmission. Additionally, inhibition of spinal nociceptive transmission by off cells is unlikely to involve 5-HT release. Finally, since opioid administration does not alter the firing of RVM neutral cells, the results of the present study indicate that serotonergic RVM neurons do not directly mediate the effects of supraspinal opioids in the rat.

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GABA-immunoreactive boutons contact identified OFF and ON cells in the nucleus raphe magnus

et al. 1997

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The pontomedullary raphe magnus (RM) contains two physiologically defined types of neurons that participate in the opioid-induced modulation of dorsal horn nociceptive messages: OFF cells, which decrease, and ON cells, which increase their discharge rates when reflex behavior is evoked by noxious pinch or heat. Because both types of neuron have inhibitory inputs and because there is evidence that gamma-aminobutyric acid (GABA) inhibitory mechanisms within RM contribute to the antinociceptive action of opioids, we have sought anatomical evidence for a direct GABAergic input to OFF and ON cells. In this study, cells of each type located in the RM were electrophysiologically defined and intracellularly filled with horseradish peroxidase or Neurobiotin. One cell of each type was labeled in the cat, and 2-3 cells of each type were labeled in the rat. Thin sections were labeled by a postembedding immunogold procedure by using an antibody directed against glutaraldehyde-conjugated GABA. GABA-immunoreactive (GABA-ir) boutons contained small, round, clear vesicles and made symmetrical synapses with identified dendrites. GABA-ir boutons were apposed to soma and to proximal and distal dendrites of both cell types in both species. These findings demonstrate direct GABAergic input to identified OFF and ON cells in the RM. J. Comp. Neurol. 378:196-204, 1997.

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Somatodendritic morphology of on‐ and off‐cells in the rostral ventromedial medulla

Cited by 30 publications

References 63 publications

Noradrenergic input to nociceptive modulatory neurons in the rat rostral ventromedial medulla

Noradrenergic input to nociceptive modulatory neurons in the rat rostral ventromedial medulla

Serotonin immunoreactivity is contained in one physiological cell class in the rat rostral ventromedial medulla

GABA-immunoreactive boutons contact identified OFF and ON cells in the nucleus raphe magnus

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