Retrograde Tracing with Fluorescent Microspheres Reveals Bifurcating Projections from Central Retina to Tectum and Thalamus in Chicks

Melatonin mediates monochromatic light-induced expression of somatostatin in the hypothalamus and pituitary of chicks

Melatonin (MEL) plays an important role in regulating growth and development of organisms and the cellular metabolism. This study was conducted to explore the role of MEL in mediating monochromatic light-induced secretion of somatostatin (SST) in the hypothalamus and pituitary in chicks. Pinealectomy models of newly hatched broilers were exposed to white (WL), red (RL), green (GL), and blue (BL) lights. The results showed that SST immunoreactive neurons and fibers were distributed in the hypothalamus. SST and SST receptor 2 (SSTR2) mRNA and protein levels in the hypothalamus and pituitary were higher in chicks exposed to RL than in chicks exposed to GL and BL. However, after pinealectomy, the mRNA and protein levels of SST and SSTR2 in the hypothalamus and pituitary in the different light groups were increased, and the differences between the groups disapeared. The expression trend of SSTR5 mRNA in the pituitary was the idential to that of SSTR2 mRNA in the pituitary. In vitro, exogenous SST inhibited growth hormone (GH) secretion, and selective antogonists of SSTR2 and SSTR5 promoted GH secretion. Selective antogonists of the melatonin receptor 1b (Mel1b) and Mel1c increased the relative concentrations of SST in the adenohypophysis cells. These results indicated that monochromatic light affects the expression of SST in chick hypothalamus and pituitary. MEL, via Mel1b and Mel1c, decreased SST secretion under GL, which was associated with the inhibition of SST, SSTR2, and SSTR5 in adenohypophysis cells.

Effect of monochromatic light on the temporal expression of N-acetyltransferase in chick pineal gland

The avian pineal gland is an independent molecular oscillator that receives external light information that regulates the synthesis and secretion of melatonin. Arylalkylamine N-acetyltransferase plays an important role in the pineal gland by controlling the rhythmic production of melatonin. Previous study showed that monochromatic light influences the secretion of melatonin, which is regulated by the molecular circadian clock genes in chick pineal gland. This study was designed to investigate the effect of monochromatic light on the circadian rhythm of levels of cAanat, clock protein (CLOCK and BMAL1), cCreb, and opsins (cOpnp, Pinopsin; cOpn4-1, Melanopsin-1; cOpn4-2, Melanopsin-2) in chick pineal gland. A total of 240 post-hatching day (P) 0 broiler chickens were reared under white (WL), red (RL), green (GL), and blue light (BL) with light (L)-dark (D) cycle of 12L:12D for 14 d. The results show significant circadian rhythms in the expression of cAanat, CLOCK, BMAL1, cCreb, cOpnp, cOpn4-1, and cOpn4-2, but not for cOpnp under RL. Compared with WL, GL increased the level of cAanat mRNA, while RL decreased it. Meanwhile, CLOCK and BMAL1 proteins were expressed at high levels in GL. Furthermore, the peak of the 24 h pattern of cOpnp mRNA in GL was earlier than that of in WL, RL, and BL. These results demonstrated that monochromatic light affects the daily expression of cAanat in the chick pineal gland via the biological clock. GL activates the transcription of cAanat, while RL suppresses the transcription of cAanat. Meanwhile, GL appears to induce the peak of cOpnp mRNA in advance to affect the transmission of light. Thus, monochromatic light regulates cAanat in the chick pineal gland by affecting the levels of clock regulators via entraining the expression of pineal gland opsins.

Amygdala GABA Neurons Project To vlPAG And mPFC

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Single amygdala GABA neuron projects to both brain stem and cortex.

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Bifurcating amygdala neurons may regulate emotions and muscle tone.

The amygdala regulates multiple behaviors and emotions by projecting to multiple brain regions. However, the topographical distribution of amygdala neurons projecting to specific brain areas is still unclear. In the present study, we focus on determining whether single amygdala neurons project to the brain stem ventrolateral periaqueductal grey (vlPAG) and to the medial prefrontal cortex (mPFC). The mPFC neurons are involved in detecting emotional content while the vlPAG neurons are involved in regulating muscle tone. In VGAT-Cre mice a cre-inducible retrograde AAV tracer expressing tdTomato was microinjected into the ventrolateral periaqueductal grey matter (vlPAG), while a second retrograde AAV tracer with generic expression of GFP was delivered into the medial prefrontal cortex (mPFC). The results identified a subgroup of bifurcating GABAergic neurons in the central nucleus (CeA) and basolateral amygdala (BLA) that projects to vlPAG and mPFC. Based on these projections we suggest that amygdala GABA neurons may be involved in triggering emotionally-induced cataplexy in the sleep disorder, narcolepsy.

Effect of monochromatic light on circadian rhythmic expression of clock genes and arylalkylamine N-acetyltransferase in chick retina

Birds have more developed visual function. They not only have the ability to detect light and darkness but also have the color vision. Previous study showed that monochromatic light influenced avian physiological processes, which were controlled by clock genes. Therefore, bird's eye is a good model to studying the impact of color of light on circadian rhythms. Avian retina is one of the most important central oscillations. The study was designed to investigate the effect of color of light on the expression of clock genes and arylalkylamine N-acetyltransferase (Aanat) mRNA expression in chick retina. A total of 240 post-hatching day (P) 0 broiler chickens were exposed to blue (BL), green (GL), red (RL) and white light (WL) from a LED system under a light-dark cycle 12L:12D for 14 d. The results show that the significant daily variations existed in the gene expression of cBmal1, cBmal2, cCry1, cCry2, cPer2 and cPer3, but not for cClock under four light treatments. The genes cBmal1, cCry1, cPer2 and cPer3 presented circadian rhythmic expression under the various monochromatic lights. When compared with WL, GL elevated the expression of positive regulators of cellular clock (cBmal1, cBmal2 and cClock) and cAanat mRNA level, whereas RL increased the mRNA levels of negative regulators of cellular clock (cCry1, cCry2, cPer2 and cPer3) and decreased the cAanat mRNA expression in the retina. These results demonstrated that monochromatic light affect the periodic expression levels of the biological clock mRNA by positive and negative feedback loop interactions, GL activated the transcription of cAanat; while RL suppressed the transcription of cAanat. Thereby, color of light regulates ocular cAanat expression by affecting on expression of cellular clock regulators.

β-III-Tubulin: a reliable marker for retinal ganglion cell labeling in experimental models of glaucoma

AIM

To evaluate the reliability of β-III-Tubulin protein as a retinal ganglion cell (RGC) marker in the experimental glaucoma model.

METHODS

Glaucoma mouse models were established by injecting polystyrene microbeads into the anterior chamber of C57BL/6J mice, then their retinas were obtained 14d and 28d after the intraocular pressure (IOP) was elevated. Retinal flat mounts and sections were double-labeled by fluorogold (FG) and β-III-Tubulin antibody or single-labeled by β-III-Tubulin antibody, then RGCs were counted and compared respectively.

RESULTS

IOP of the injected eyes were elevated significantly and reached the peak at 22.8±0.7 mm Hg by day 14 after injection, then dropped to 11.3±0.7 mm Hg by day 28. RGC numbers counted by FG labeling and β-III-Tubulin antibody labeling were 64 807±4930 and 64614±5054 respectively in the control group, with no significant difference. By day 14, RGCs in the experimental group decreased significantly compared to the control group, but there was no significant difference between the FG labeling counting and the β-III-Tubulin antibody labeling counting either in the experimental group or in the control group. The result was similar by day 28, with further RGC loss.

CONCLUSION

Our result suggested that the β-III-Tubulin protein was not affected by IOP elevation and can be used as a reliable marker for RGC in experimental models of glaucoma.

Effect of suction on macular thickness and retinal nerve fiber layer thickness during LASIK used femtosecond laser and Moria M2 microkeratome

AIM

To compare the effect of suction on the macular thickness and retinal nerve fiber layer (RNFL) thickness during laser in situ keratomileusis (LASIK) used Ziemer FEMTO LDV femtosecond laser (Ziemer group) and Moria M2 automated microkeratome (Moria group) for flap creation.

METHODS

Fourier-domain optical coherence tomography (FD-OCT) was used to measure macular thickness, ganglion cell complex thickness and (RNFL) thickness of 204 eyes of 102 patients with the Ziemer femtosecond laser (102 eyes) and the Moria M2 microkeratome (102 eyes) before surgery and 30min; 1, 3d; 1wk; 1, 3mo; 1y after surgery.

RESULTS

The average foveal thickness and parafoveal retinal thickness 30min after the surgery were statistically more than that before surgery (Ziemer P<0.001, P=0.003 and Moria P=0.001, P=0.006) and the effect was less in the Ziemer group than that in the Moria group (P all<0.05). The ganglion cell complex thickness was not significantly changed in both groups (P all>0.05). The RNFL thickness was statistically less 30min after surgery in both groups (P=0.014, P<0.001), but the influence was less in Ziemer group than that in Moria group (P=0.038). However, the RNFL thickness had recovered to the preoperative level only 1d after surgery.

CONCLUSION

The suction of femtosecond laser and mechanical microkeratome led to the increase in macular central fovea thickness and the decrease in RNFL thickness values at the early stage after LASIK. The effect of suction on macular and the RNFL thicknesses in Ziemer group is smaller than that in Moria group.