Involvement of supralemniscal nucleus (B9) 5-HT neuronal system in nociceptive processing: a fiber photometry study

Abstract

Nociception is important perception that has harmful influence on daily life of humans. As to main pain management system, some descending pathways are called descending antinociceptive systems (DAS). As main pathways of DAS, it is well known that dorsal raphe (B6/B7)-rostral ventromedial medulla (B3)-spinal dorsal horn includes serotonergic system. However, possible role of supralemniscal (B9) serotonin (5-HT) cell group in pain management is still open question. In this study, we measured activities of B9 5-HT neuronal cell bodies and B9 5-HT neuron-derived axons located in the locus coeruleus (LC) and ventral tegmental area (VTA), which are also main players of pain management, using fiber photometry system. We introduced the G-CaMP6 in B9 5-HT neurons using transgenic mice carrying a tetracycline-controlled transactivator transgene (tTA) under the control of a tryptophan hydroxylase-2 (TPH2) promoter and site-specific injection of adeno associated virus (AAV-TetO(3G)-G-CaMP6). After confirmation of specific expression of G-CaMP6 in the target population, G-CaMP6 fluorescence intensity in B9 group and LC/VTA groups was measured in awake mice exposed to acute tail pinch and heat stimuli. G-CaMP6 fluorescence intensity rapidly increased by both stimuli in all groups, but not significantly reacted by nonnociceptive control stimuli. The present results clearly indicate that acute nociceptive stimuli cause a rapid increase in the activities of B9-LC/B9-VTA 5-HTergic pathways, suggesting that B9 5-HT neurons play important roles in nociceptive processing.

Involvement of A5/A7 noradrenergic neurons and B2 serotonergic neurons in nociceptive processing: a fiber photometry study

“…We usedtransgenic mice carryingtTA under the control of a DBHorTPH2 promoter (DBH-tTA mice or TPH2-tTA mice, respectively) [22,23,24] (Fig. 1a);10-14-week-old male mice were usedin this experiment.…”

“…Asaforementioned, a few studies have reported that A5/A7 NA neurons are implicated in the regulation of pain management, but to the best of our knowledge, only few studies have assessed how the activities of A5/A7 NA neurons are affected by nociceptive stimuli. A ber photometry system adopting acalcium (Ca 2+ ) imaging system is an advanced tool for evaluating nociceptive signaling, as demonstrated in a recent paper focused onB9 5-HT neurons [23], A10 (ventral tegmental area, VTA)dopamine (DA) neurons [24], and A13 DA neurons [25]. Therefore, we deemed it meaningfulto assessthe activities of A5/A7 NA neurons and B2 5-HT neurons in response to acute nociceptive stimuli.…”

Involvement of A13 dopaminergic neurons located in the zona incerta in nociceptive processing: a fiber photometry study

“…1a). Fourteen to eighteenweek-old male mice were maintained in the laboratory under standard conditions as recently described [7]. In this study, AAV-CAG-FLEX-G-CaMP6-WPRE (serotype DJ; 1 μl/injection, 3 × 10 copies/ml) and AAV-CAG-FLEX-mCherry-WPRE (serotype DJ; 1 μl/ injection, 5 × 10 12 copies/ml) were unilaterally injected into the A13 site (from bregma − 1.94 mm, lateral + 1.06 mm, and ventral − 4.20 mm from the surface of the brain) ( Fig.…”

“…In this study, the primary antibody used was antityrosine hydroxylase raised in rabbit (AB152, EMD Millipore., Temecula, CA, USA), which was diluted at 1:500 in phosphate-buffered saline (PBS), and the secondary antibody used was CF647 donkey anti-rabbit (20,047, Biotium, Inc., Fremont, CA, USA), which was diluted at 1:200 in PBS. We adopted a fiber photometry system and the same two acute nociceptive stimuli and two noninvasive stimuli as in our previous report [7]. In short, the blue/yellow excitation light (470 nm/590 nm) was produced by a high-power LED driver.…”

“…To make recordings, a silica fiber was placed just above the A13 site (from bregma − 1.94 mm, lateral + 1.06 mm, and ventral − 4.20 mm from the surface of the brain). Neuronal activity characteristic indices and data analyses were performed as in our previous study [7]. Values are expressed as the mean ± standard error of the mean (S.E.M).…”