Exendin-4 promotes retinal ganglion cell survival and function by inhibiting calcium channels in experimental diabetes

Progressive damage of retinal ganglion cells (RGCs) is observed in early diabetic retinopathy. Intracellular Ca2+ overload mediated by Ca2+ influx through voltage-gated Ca2+ channels (VGCCs) is involved in neurodegeneration, whereas glucagon-like peptide-1 (GLP-1) provides neuroprotection. However, whether GLP-1 plays a neuroprotective role in diabetic retinas by modulating VGCCs remains unknown. We found that eye drops of exendin-4, a long-acting GLP-1 receptor (GLP-1R) agonist, prevented the increase of L-type Ca2+ current (ILCa) densities of RGCs induced by 4-week hyperglycemia and promoted RGC survival by suppressing L-type VGCC (L-VGCC) activity in streptozotocin-induced diabetic rats. Moreover, exendin-4-induced suppression of ILCa in RGCs may be mediated by a GLP-1R/Gs/cAMP-PKA/ryanodine/Ca2+/calmodulin/calcineurin/PP1 signaling pathway. Furthermore, exendin-4 functionally improved the light-evoked spiking ability of diabetic RGCs. These results suggest that GLP-1R activation enhances cAMP to PP1 signaling and that PP1 inactivates L-VGCCs by dephosphorylating them, thereby reducing Ca2+ influx, which could protect RGCs against excitotoxic Ca2+ overload.

[Analysis of disease composition and primary surgical procedures in pediatric secondary glaucoma inpatients: a single-center study]

Objective: To analyze the disease composition and primary surgical procedures in pediatric inpatients with secondary glaucoma. Methods: A retrospective case series study was conducted. Clinical data of children aged≤16 years with secondary glaucoma who were admitted to the Zhongshan Ophthalmic Center, Sun Yat-sen University, between January 1, 2017, and December 31, 2021, were included. The patients were classified according to the Childhood Glaucoma Research Network (CGRN) classification system, and their diagnoses, underlying factors, gender, age of onset, affected eye(s), age and type of initial surgery, and ophthalmic examination data were analyzed. Statistical analysis was performed using Kruskal-Wallis rank sum test and χ2 test. Results: A total of 540 patients (744 eyes) were included in this study, comprising 319 males (59.1%) and 221 females (40.9%). Unilateral disease was observed in 336 cases (62.2%), while bilateral involvement was present in 204 cases (37.8%). The age of onset was 4.0 (0.0, 9.0) years, and the median age of the first anti-glaucoma surgery was 5.0 (0.7, 10.0) years. Among them, there were 195 cases (36.1%) of secondary glaucoma associated with non-acquired ocular anomalies (SCG-O), with a median age of onset of 0.0 (0.0, 4.0) years, and 97 of these cases (49.7%) were male. secondary glaucoma associated with non-acquired systemic disease or syndrome (SCG-S) were observed in 68 cases (12.6%), with a median age of glaucoma onset of 0.1 (0.0, 4.0) years, and 47 of these cases (69.1%) were male. Secondary glaucoma associated with acquired conditions (SCG-A) accounted for 192 cases (35.6%), with a median age of onset of 9.0 (5.0, 13.0) years, and 125 of these cases (65.1%) were male. There were 85 cases (15.7%) of secondary glaucoma following cataract surgery (SCG-C), with a median age of onset of 3.0 (0.8, 7.0) years, and 50 of these cases (58.8%) were male. Male patients were predominant in SCG-S and SCG-A, with 47 cases (69.1%) and 125 cases (65.1%), respectively (χ2=9.94, 17.52; P=0.002,<0.001). Except for SCG-O, all other types of pediatric secondary glaucoma predominantly affected only one eye: SCG-S in 52 cases (76.5%), SCG-A in 128 cases (66.7%), and SCG-C in 54 cases (63.5%) (χ2=19.06, 21.33, 6.22; all P<0.05). The highest proportion of SCG-O was attributed to congenital ectropion uveae (46 cases, 23.6%). Sturge-Weber syndrome was the most common SCG-S (45 cases, 66.3%), while SCG-A mostly resulted from trauma (59 cases, 30.8%) and corticosteroid use (56 cases, 29.2%). Trabeculectomy (211 eyes, 30.8%) and glaucoma drainage device implantation (197 eyes, 28.7%) were the most frequently performed primary surgical procedures. Conclusions: SCG-O and SCG-A were found to be common types of pediatric secondary glaucoma. The age of onset and the choice of primary anti-glaucoma surgical procedures varied among different types of pediatric secondary glaucoma. However, overall, trabeculectomy and glaucoma drainage device implantation were the primary surgical procedures predominantly employed.

Short-term acute bright light exposure induces a prolonged anxiogenic effect in mice via a retinal ipRGC-CeA circuit

Light modulates mood through various retina-brain pathways. We showed that mice treated with short-term acute bright light exposure displayed anxiety-related phenotypes in a prolonged manner even after the termination of the exposure. Such a postexposure anxiogenic effect depended upon melanopsin-based intrinsically photosensitive retinal ganglion cell (ipRGC) activities rather than rod/cone photoreceptor inputs. Chemogenetic manipulation of specific central nuclei demonstrated that the ipRGC-central amygdala (CeA) visual circuit played a key role in this effect. The corticosterone system was likely to be involved in this effect, as evidenced by enhanced expression of the glucocorticoid receptor (GR) protein in the CeA and the bed nucleus of the stria terminalis and by the absence of this effect in animals treated with the GR antagonist. Together, our findings reveal a non-image forming visual circuit specifically designed for "the delayed" extinction of anxiety against potential threats, thus conferring a survival advantage.

Altered Retinal Dopamine Levels in a Melatonin-proficient Mouse Model of Form-deprivation Myopia

Reduced levels of retinal dopamine, a key regulator of eye development, are associated with experimental myopia in various species, but are not seen in the myopic eyes of C57BL/6 mice, which are deficient in melatonin, a neurohormone having extensive interactions with dopamine. Here, we examined the relationship between form-deprivation myopia (FDM) and retinal dopamine levels in melatonin-proficient CBA/CaJ mice. We found that these mice exhibited a myopic refractive shift in form-deprived eyes, which was accompanied by altered retinal dopamine levels. When melatonin receptors were pharmacologically blocked, FDM could still be induced, but its magnitude was reduced, and retinal dopamine levels were no longer altered in FDM animals, indicating that melatonin-related changes in retinal dopamine levels contribute to FDM. Thus, FDM is mediated by both dopamine level-independent and melatonin-related dopamine level-dependent mechanisms in CBA/CaJ mice. The previously reported unaltered retinal dopamine levels in myopic C57BL/6 mice may be attributed to melatonin deficiency.

The role of ipRGCs in ocular growth and myopia development

The increasing global prevalence of myopia calls for elaboration of the pathogenesis of this disease. Here, we show that selective ablation and activation of intrinsically photosensitive retinal ganglion cells (ipRGCs) in developing mice induced myopic and hyperopic refractive shifts by modulating the corneal radius of curvature (CRC) and axial length (AL) in an opposite way. Melanopsin- and rod/cone-driven signals of ipRGCs were found to influence refractive development by affecting the AL and CRC, respectively. The role of ipRGCs in myopia progression is evidenced by attenuated form-deprivation myopia magnitudes in ipRGC-ablated and melanopsin-deficient animals and by enhanced melanopsin expression/photoresponses in form-deprived eyes. Cell subtype-specific ablation showed that M1 subtype cells, and probably M2/M3 subtype cells, are involved in ocular development. Thus, ipRGCs contribute substantially to mouse eye growth and myopia development, which may inspire novel strategies for myopia intervention.

Signaling Mechanism for Modulation by GLP-1 and Exendin-4 of GABA Receptors on Rat Retinal Ganglion Cells

Glucagon-like peptide-1 (GLP-1) is expressed in retinal neurons, but its role in the retina is largely unknown. Here, we demonstrated that GLP-1 or the GLP-1 receptor (GLP-1R; a G protein-coupled receptor) agonist exendin-4 suppressed γ-aminobutyric acid receptor (GABAR)-mediated currents through GLP-1Rs in isolated rat retinal ganglion cells (GCs). Pre-incubation with the stimulatory G protein (G_s) inhibitor NF 449 abolished the exendin-4 effect. The exendin-4-induced suppression was mimicked by perfusion with 8-Br-cAMP (a cAMP analog), but was eliminated by the protein kinase A (PKA) inhibitor Rp-cAMP/KT-5720. The exendin-4 effect was accompanied by an increase in [Ca²⁺]_i of GCs through the IP₃-sensitive pathway and was blocked in Ca²⁺-free solution. Furthermore, when the activity of calmodulin (CaM) and CaM-dependent protein kinase II (CaMKII) was inhibited, the exendin-4 effect was eliminated. Consistent with this, exendin-4 suppressed GABAR-mediated light-evoked inhibitory postsynaptic currents in GCs in rat retinal slices. These results suggest that exendin-4-induced suppression may be mediated by a distinct G_s/cAMP-PKA/IP₃/Ca²⁺/CaM/CaMKII signaling pathway, following the activation of GLP-1Rs.

Cell-Subtype-Specific Remodeling of Intrinsically Photosensitive Retinal Ganglion Cells in Streptozotocin-Induced Diabetic Mice

Recent evidence suggests that melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs), a neuronal class regulating nonimage forming (NIF) vision and generally thought to be injury resistant, are dysfunctional in certain neurodegenerative diseases. Although disrupted NIF visual functions have been reported in patients and animals with diabetes, it remains controversial whether ipRGCs exhibit remodeling during diabetes and if so, whether such remodeling is variable among ipRGC subtypes. Here, we demonstrate that survival, soma-dendritic profiles, and melanopsin-based functional activity of M1 ipRGCs were unaltered in streptozotocin-induced 3-month diabetic mice. Such resistance remained at 6 months after streptozotocin administration. In contrast, M2/M3 ipRGCs underwent significant remodeling in diabetic mice, manifested by enlarged somata and increased dendritic branching complexity. Consistent with the unaltered melanopsin levels, the sensitivity of melanopsin-based activity was unchanged in surviving M2 cells, but their response gain displayed a compensatory enhancement. Meanwhile, the pupillary light reflex, a NIF visual function controlled by M2 cells, was found to be impaired in diabetic animals. The resistance of M1 cells might be attributed to the adjacency of their dendrites to capillaries, which makes them less disturbed by the impaired retinal blood supply at the early stage of diabetes.

Spontaneous Depolarization-Induced Action Potentials of ON-Starburst Amacrine Cells during Cholinergic and Glutamatergic Retinal Waves

Correlated spontaneous activity in the developing retina (termed “retinal waves”) plays an instructive role in refining neural circuits of the visual system. Depolarizing (ON) and hyperpolarizing (OFF) starburst amacrine cells (SACs) initiate and propagate cholinergic retinal waves. Where cholinergic retinal waves stop, SACs are thought to be driven by glutamatergic retinal waves initiated by ON-bipolar cells. However, the properties and function of cholinergic and glutamatergic waves in ON- and OFF-SACs still remain poorly understood. In the present work, we performed whole-cell patch-clamp recordings and Ca²⁺ imaging from genetically labeled ON- and OFF-SACs in mouse flat-mount retinas. We found that both SAC subtypes exhibited spontaneous rhythmic depolarization during cholinergic and glutamatergic waves. Interestingly, ON-SACs had wave-induced action potentials (APs) in an age-dependent manner, but OFF-SACs did not. Simultaneous Ca²⁺ imaging and patch-clamp recordings demonstrated that, during a cholinergic wave, APs of an ON-SAC appeared to promote the dendritic release of acetylcholine onto neighboring ON- and OFF-SACs, which enhances their Ca²⁺ transients. These results advance the understanding of the cellular mechanisms underlying correlated spontaneous activity in the developing retina.

Aerobic exercise delays retinal ganglion cell death after optic nerve injury

Aerobic exercise has been shown to play a crucial role in preventing neurological diseases and improving cognitive function. In the present study, we investigated the effect of treadmill training on retinal ganglion cells (RGCs) following optic nerve transection in adult rats. We exercised the rats on a treadmill for 5 d/week (30 min/d at a rate of 9 m/min) or placed control rats on static treadmills. After 3 weeks of exercise, the left optic nerve of each rat was transected. After the surgery, the rat was exercised for another week. The percentages of surviving RGCs in the axotomized eyes of inactive rats were 67% and 39% at 5 and 7 days postaxotomy, respectively. However, exercised rats had significant more RGCs at 5 (74% survival) and 7 days (48% survival) after axotomy. Moreover, retinal brain-derived neurotrophic factor (BDNF) protein levels were significantly upregulated in response to exercise compared with those in the axotomized eyes of inactive rats. Blocking BNDF signaling during exercise by intraperitoneal injections of ANA-12, a BDNF tropomyosin receptor kinase (TrkB) receptor antagonist, reduced the number of RGCs in exercised rats to the level of RGCs in the inactive rats, effectively abolishing the protection of RGCs afforded by exercise. The results suggest that treadmill training effectively rescues RGCs from neurodegeneration following optic nerve transection by upregulating the expression of BDNF.

nGnG Amacrine Cells and Brn3b-negative M1 ipRGCs are Specifically Labeled in the ChAT-ChR2-EYFP Mouse

Purpose

Experimental access to specific cell subtypes is essential for deciphering the complexity of retinal networks. Here, we characterized the selective labeling, caused by ectopic transgene expression, of two atypical retinal neurons in the ChAT-Channelrhodopsin-2 (ChR2)-EYFP mouse.

Methods

Retinal sections and flat-mounts were prepared for double-staining immunohistochemistry with antibodies against EYFP and various neuronal markers. Sagittal/coronal brain slices were made to visualize EYFP signals in central nuclei. Whole-cell recordings were conducted to test the functionality of ChR2.

Results

Two populations of EYFP-positive retinal cells were observed. The inner nuclear layer (INL)-located one (type I cell) distributed regularly throughout the entire retina, whereas the ganglion cell layer (GCL)-residing one (type II cell) was restricted ventrally. None of them was cholinergic, as evidenced by the complete absence of ChAT immunoreactivity. Type I cells were immunolabeled by the amacrine marker syntaxin. However, the vast majority of them were neither positive to GABA/GAD65, nor to GlyT1/glycine, suggesting that they were non-GABAergic non-glycinergic amacrine cells (nGnG ACs), which was confirmed by double-labeling with the nGnG AC marker PPP1R17. Type II cells were immunopositive to melanopsin, but not to Brn3a or Brn3b. They possessed dendrites stratifying in the outermost inner plexiform layer (IPL) and axons projecting to the suprachiasmatic nucleus (SCN) rather than the olivary pretectal nucleus (OPN), suggesting that they belonged to a Brn3b-negative subset of M1-type intrinsically photosensitive retinal ganglion cells (ipRGCs). Glutamatergic transmission-independent photocurrents were elicited in EYFP-positive cells, indicating the functional expression of ChR2.

Conclusions

The ChAT-ChR2-EYFP retina exhibits ectopic, but functional, transgene expression in nGnG ACs and SCN-innervating M1 ipRGCs, thus providing an ideal tool to achieve efficient labeling and optogenetic manipulation of these cells.

Optic nerve crush modulates refractive development of the C57BL/6 mouse by changing multiple ocular dimensions

Higher visual centers could modulate visually-guided ocular growth, in addition to local mechanisms intrinsic to the eye. There is evidence that such central modulations could be species (even subspecies)-dependent. While the mouse has recently become an important experimental animal in myopia studies, it remains unclear whether and how visual centers modulate refractive development in mice, an issue that was examined in the present study. We found that optic nerve crush (ONC), performed at P18, could modify normal refractive development in the C57BL/6 mouse raised in normal visual environment. Unexpectedly, sham surgery caused a steeper cornea, leading to a modest myopic refractive shift, but did not induce significant changes in ocular axis length. ONC caused corneal flattening and re-calibrated the refractive set-point in a bidirectional manner, causing significant myopic (<-3 D, 54.5%) or hyperopic (>+3 D, 18.2%) shifts in refractive error in most (totally 72.7%) animals, both due to changes in ocular axial length. ONC did not change the density of dopaminergic amacrine cells, but increased retinal levels of dopamine and DOPAC. We conclude that higher visual centers are likely to play a role in fine-tuning of ocular growth, thus modifying refractive development in the C57BL/6 mouse. The changes in refractive error induced by ONC are accounted for by alternations in multiple ocular dimensions, including corneal curvature and axial length.

Morphological alterations of intrinsically photosensitive retinal ganglion cells after ablation of mouse photoreceptors with selective photocoagulation

In this work, we investigated changes in the morphology of intrinsically photosensitive retinal ganglion cells (ipRGCs), M1 subtype, and pupillary light reflex following local and selective ablation of photoreceptors in mice. Laser photocoagulation was used to selectively destroy four patches of photoreceptors per eye at around 4 papillary diameters from the optic disc and at the 3, 6, 9, and 12 o'clock positions between the retinal vessels in the adult mouse retina, leaving cells in the inner retina intact. Morphological parameters of individual M1 cells specifically labeled by the antibody against melanopsin (PA1-780), including dendritic field size, total dendritic length, and dendritic branch number, were examined 1, 2, 4, and 8 weeks after photocoagulation with Neurolucida software. A considerable reduction in these parameters in M1 cells in the "lesioned areas" was found at all the four time points after photocoagulation, as compared with those in the "unlesioned areas". Although M1 cells in the lesioned areas showed significant changes as early as 1 week after laser treatment and the changes gradually increased, reaching a peak value at 2 weeks, morphological restoration was clearly seen in these cells over time. However, no difference in the morphological parameters of M1 cells was observed between the unlesioned areas of laser-treated mice and the corresponding areas of age-matched normal mice without laser lesions. Fluorescence intensity of the somata of melanopsin-positive M1 cells located inside the lesioned areas was significantly decreased at all the four time points after photocoagulation, whereas no changes in pupillary light reflex were detected at different light irradiations, indicating that photocoagulation-induced local photoreceptor loss and alterations of ipRGCs may be insufficient to cause abnormalities in non-image-forming (NIF) visual functions. The results suggest that intact photoreceptors could be crucial for maintaining the expression levels of melanopsin and normal morphology of M1 cells.

ON-Type Retinal Ganglion Cells are Preferentially Affected in STZ-Induced Diabetic Mice

Purpose

We investigate morphologic and physiologic alterations of ganglion cells (GCs) in a streptozocin (STZ)-induced diabetic mouse model.

Methods

Experiments were conducted in flat-mount retinas of mice 3 months after the induction of diabetes. Changes in morphology of four subtypes of GCs (ON-type RGA2 [ON-RGA2], OFF-type RGA2 [OFF-RGA2], ON-type RGC1 [ON-RGC1], and ON-OFF type RGD2 [ON-OFF RGD2]) were characterized in Thy1-YFP transgenic mice. Using whole-cell patch-clamp recording, passive membrane properties and action potential (AP) firing properties were further investigated in transient ON- and OFF-RGA2 cells.

Results

Morphologic parameters were significantly altered in the dendrites branching in the ON sublamina of the inner plexiform layer (IPL) for ON-RGA2 cells and ON-OFF RGD2 cells. Much less significant changes, if any, were seen in those arborizing in the OFF sublamina of the IPL for OFF-RGA2 and ON-OFF RGD2 cells. No detectable changes in morphology were seen in RGC1 cells. Electrophysiologically, increased resting membrane potentials and decreased membrane capacitance were found in transient ON-RGA2 cells, but not in transient OFF-RGA2 cells. Similar alterations in AP firing properties, such as an increase in AP width and reduction in maximum spiking rate, were shared by these two subtypes. Furthermore, in response to depolarizing current injections, both cells generated more APs suggesting an enhanced excitability of these cells in diabetic conditions.

Conclusions

These differential changes in morphology and electrophysiology in subtypes of GCs may be responsible for reduced contrast sensitivity known to occur during the early stage of diabetic retinopathy.

[The experiment study of endovascular denervation in treatment of cancer pain]

Objective: To assess the feasibility and safety of endovascular denervation (EDN) with a multi-electrode radiofrequency ablation catheter on beagles. Methods: A total of 18 beagles, (10.2±1.1) kg,of either gender,were provided by the Animal Center of Southeast University (SYXK (Su) 2016-0013). They were divided equally into three groups:the instant euthanizing group, the long-term follow-up group and the sham operation group. Beagles in the instant euthanizing group were euthanized immediately after EDN. Beagles in the long-term follow-up group were euthanized three months after EDN. Beagles in the sham operation group underwent sham operation and were euthanized three months later. Blood biochemistry was measured at baseline, and immediately, 15 days, 30 days and 90 days after the surgery. Computerized tomographic (CT) angiography was determined before the surgery and 60 days after the surgery. Digital subtraction angiography (DSA) was determined 90 days after the surgery. Histopathologic analyses were used to identify the changes of arterial wall and neuron cells. Results: Beagles in the long-term follow-up group and the sham operation group all underwent EDN successfully without accidental death. No abdominal aortic perforation and peripheral tissue necrosis were found at Necropsy. No vascular injuries were found by CTA and DSA in each group. There was no statistical difference in hematological analyses, 90 days after the surgery:white blood cell:(12.5±1.5)×10(9)/L vs (13.2±0.7)×10(9)/L, P=0.275; red blood cell:(7.0±0.6)×10(9)/L vs (6.3±0.4)×10(9)/L, P=0.089; total bilirubin:(2.9±0.4) μmol/L vs (3.0±0.6) μmol/L, P=0.681; glutamic-pyruvic transaminase:(40±11) U/L vs (37±6) U/L, P=0.168; glutamic oxalocetie transaminase:(51±11) U/L vs (48±9) U/L, P=0.221; urea nitrogen:(7.2±1.2) mmol/L vs (6.9±0.8) mmol/L, P=0.505; creatinine:(60±9) μmol/L vs (59±9) μmol/L, P=0.81; prothrombin time:(7.2±0.7) s vs (7.0±0.7) s, P=0.719. Histopathological analyses showed that there were hypercellular appearance of nerve bundle and thickened perineurium in EDN groups, while normal perineurium around nerve bundle in the sham operation group. Conclusion: EDN could be applied in beagles safely and feasibly.

Transgene is specifically and functionally expressed in retinal inhibitory interneurons in the VGAT-ChR2-EYFP mouse

Ectopic transgene expression in the retina has been reported in various transgenic mice, indicating the importance of characterizing retinal phenotypes. We examined transgene expression in the VGAT-ChR2-EYFP mouse retina by fluorescent immunohistochemistry and electrophysiology, with special emphasis on enhanced yellow fluorescent protein (EYFP) localization in retinal neuronal subtypes identified by specific markers. Strong EYFP signals were detected in both the inner and outer plexiform layers. In addition, the ChR2-EYFP fusion protein was also expressed in somata of the great majority of inhibitory interneurons, including horizontal cells and GABAergic and glycinergic amacrine cells. However, a small population of amacrine cells residing in the ganglion cell layer were not labeled by EYFP, and a part of them were cholinergic ones. In contrast, no EYFP signal was detected in the somata of retinal excitatory neurons: photoreceptors, bipolar and ganglion cells, as well as Müller glial cells. When glutamatergic transmission was blocked, bright blue light stimulation elicited inward photocurrents from amacrine cells, as well as post-synaptic inhibitory currents from ganglion cells, suggesting a functional ChR2 expression. The VGAT-ChR2-EYFP mouse therefore could be a useful animal model for dissecting retinal microcircuits when targeted labeling and/or optogenetic manipulation of retinal inhibitory neurons are required.

Orexin-A Suppresses Signal Transmission to Dopaminergic Amacrine Cells From Outer and Inner Retinal Photoreceptors

Purpose

The neuropeptides orexin-A and orexin-B are widely expressed in the vertebrate retina; however, their role in visual function is unclear. This study investigates whether and how orexins modulate signal transmission to dopaminergic amacrine cells (DACs) from both outer retinal photoreceptors (rods and cones) and inner retinal photoreceptors (melanopsin-expressing intrinsically photosensitive retinal ganglion cells [ipRGCs]).

Methods

A whole-cell voltage-clamp technique was used to record light-induced responses from genetically labeled DACs in flat-mount mouse retinas. Rod and cone signaling to DACs was confirmed pharmacologically (in wild-type retinas), whereas retrograde melanopsin signaling to DACs was isolated either pharmacologically (in wild-type retinas) or by genetic deletion of rod and cone function (in transgenic mice).

Results

Orexin-A attenuated rod/cone-mediated light responses in the majority of DACs and inhibited all DACs that exhibited melanopsin-based light responses, suggesting that exogenous orexin suppresses signal transmission from rods, cones, and ipRGCs to DACs. In addition, orexin receptor 1 antagonist SB334867 and orexin receptor 2 antagonist TCS OX229 enhanced melanopsin-based DAC responses, indicating that endogenous orexins inhibit signal transmission from ipRGCs to DACs. We further found that orexin-A inhibits melanopsin-based DAC responses via orexin receptors on DACs, whereas orexin-A may modulate signal transmission from rods and cones to DACs through activation of orexin receptors on DACs and their upstream neurons.

Conclusions

Our results suggest that orexins could influence visual function via the dopaminergic system in the mammalian retina.

[Changes in peripheral blood 25 - hydroxyvitamin D3, Th17 cells, and CD4+ regulatory T cells and their clinical significance in patients with primary biliary cirrhosis]

Objective: To investigate the changes in peripheral blood 25-hydroxyvitamin D₃[25-(OH)D₃], CD4⁺regulatory T (Treg) cells, and Th17 cells in patients with primary biliary cirrhosis (PBC) and their mechanism of action in PBC. Methods: A total of 22 patients with PBC were enrolled and the male/female ratio was 1:21, with a mean age of 61±12 years. There were 7 healthy volunteers matched for age in the normal control group. Electrochemiluminescence immunoassay was used to measure the peripheral blood 25-(OH)D₃level in the PBC group and normal control group, and flow cytometry was used to analyze the changes in Th17 cells and CD4⁺Treg cells. The t-test, rank sum test, Pearson correlation analysis, or Spearman's rank correlation analysis was used for statistical analysis according to the type of the data. Results: The PBC group had a significantly lower serum 25-(OH)D₃level than the normal control group (9.49±3.65 vs 27.35±2.35 ng/ml,P< 0.01). Compared with the normal control group, the PBC group had a significantly higher percentage of Th17 cells (2.05%±1.17% vs 0.99%±0.12%,P< 0.01) and a significantly lower percentage of CD4⁺Treg cells (2.54%±1.14% vs 3.78%±0.51%,P< 0.05); there was a significant difference in Th17/Treg ratio between the PBC group and the normal control group (1.00±0.63 vs 0.26±0.02,P< 0.01). In the PBC group, peripheral blood 25-(OH)D3 was not correlated with Th17 cells or Th17/Treg ratio (r= -0.062 and -0.328,P> 0.05), while it was positively correlated with the percentage of CD4⁺Treg cells (r= 0.468,P< 0.05). Conclusion: Patients with PBC have significant reductions in peripheral blood 25-(OH)D₃and percentage of CD4⁺Treg cells, a significant increase in the percentage of Th17 cells, and immune unbalance of Th17 cells and CD4⁺Treg cells. 25-(OH)D₃can upregulate the percentage of CD4⁺Treg cells and thus affect the development and progression of PBC, and exogenous vitamin D may improve immune function in PBC patients.

The Role of Retinal Dopamine in C57BL/6 Mouse Refractive Development as Revealed by Intravitreal Administration of 6-Hydroxydopamine

Purpose

Although retinal dopamine (DA) has been long implicated in myopia development, current studies demonstrate that retinal DA levels are unaltered in C57BL/6 mice with form-deprivation myopia. This work was undertaken to explore whether and how refractive development is perturbed in this mouse strain when retinal DA levels are reduced by 6-hydroxydopamine (6-OHDA) administration.

Methods

On two successive days, 6-OHDA was injected into the vitreous of P18 mice. Retinal DA levels were measured by HPLC and TH levels analyzed by quantitative Western blotting. To choose appropriate 6-OHDA doses that significantly reduce retinal DA levels, but cause minimal disturbance of overall retinal physiology, ERG analysis was performed. Refractive errors were measured using a photorefractor, and ocular biometry performed with optical coherence tomography and photokeratometry.

Results

Administration of 6-OHDA of 6.25 μg and 12.5 μg significantly reduced retinal levels of DA and TH, but without affecting ERG a- and b-wave amplitudes. With normal visual experience, 6-OHDA induced myopic refractive shifts in a dose-dependent fashion. Form deprivation induced further myopic shifts in 6-OHDA-injected eyes, but did not cause further decline in retinal DA. Furthermore, 6-OHDA administration resulted in a shorter axial length and a steeper cornea, whereas form deprivation led to a longer axial length, without changing the corneal radius of curvature.

Conclusions

Reducing retinal DA levels led to myopic refractive shifts in C57BL/6 mice, which mainly resulted from a steeper cornea. In addition to the DA-independent mechanism for form-deprivation myopia, there is a DA-dependent mechanism in parallel that underlies myopic refractive shifts under normal laboratory conditions in this mouse strain.

Multiple cone pathways are involved in photic regulation of retinal dopamine

Dopamine is a key neurotransmitter in the retina and plays a central role in the light adaptive processes of the visual system. The sole source of retinal dopamine is dopaminergic amacrine cells (DACs). We and others have previously demonstrated that DACs are activated by rods, cones, and intrinsically photosensitive retinal ganglion cells (ipRGCs) upon illumination. However, it is still not clear how each class of photosensitive cells generates light responses in DACs. We genetically isolated cone function in mice to specifically examine the cone-mediated responses of DACs and their neural pathways. In addition to the reported excitatory input to DACs from light-increment (ON) bipolar cells, we found that cones alternatively signal to DACs via a retrograde signalling pathway from ipRGCs. Cones also produce ON and light-decrement (OFF) inhibitory responses in DACs, which are mediated by other amacrine cells, likely driven by type 1 and type 2/3a OFF bipolar cells, respectively. Dye injections indicated that DACs had similar morphological profiles with or without ON/OFF inhibition. Our data demonstrate that cones utilize specific parallel excitatory and inhibitory circuits to modulate DAC activity and efficiently regulate dopamine release and the light-adaptive state of the retina.

Signaling mechanism for modulation by ATP of glycine receptors on rat retinal ganglion cells

ATP modulates voltage- and ligand-gated channels in the CNS via the activation of ionotropic P2X and metabotropic P2Y receptors. While P2Y receptors are expressed in retinal neurons, the function of these receptors in the retina is largely unknown. Using whole-cell patch-clamp techniques in rat retinal slice preparations, we demonstrated that ATP suppressed glycine receptor-mediated currents of OFF type ganglion cells (OFF-GCs) dose-dependently, and the effect was in part mediated by P2Y1 and P2Y11, but not by P2X. The ATP effect was abolished by intracellular dialysis of a Gq/11 protein inhibitor and phosphatidylinositol (PI)-phospholipase C (PLC) inhibitor, but not phosphatidylcholine (PC)-PLC inhibitor. The ATP effect was accompanied by an increase in [Ca(2+)]i through the IP3-sensitive pathway and was blocked by intracellular Ca(2+)-free solution. Furthermore, the ATP effect was eliminated in the presence of PKC inhibitors. Neither PKA nor PKG system was involved. These results suggest that the ATP-induced suppression may be mediated by a distinct Gq/11/PI-PLC/IP3/Ca(2+)/PKC signaling pathway, following the activation of P2Y1,11 and other P2Y subtypes. Consistently, ATP suppressed glycine receptor-mediated light-evoked inhibitory postsynaptic currents of OFF-GCs. These results suggest that ATP may modify the ON-to-OFF crossover inhibition, thus changing action potential patterns of OFF-GCs.

[Refractive development and form-deprivation induced myopic refractive error in CBA/CaJ mice]

Due to the advantages in genetic manipulation, mice have become one of the most commonly used mammalian models for the study of mechanisms underlying myopia development. However, the vast majority of laboratory mouse strains are incapable of synthesizing melatonin, a neurohormone that may play an important role in myopia generation in humans. The present study investigated refractive development profiles in the CBA/CaJ mouse, a strain proficient in melatonin, and determined whether and how its refractive development could be affected by form-deprivation. Eccentric infrared photoretinoscopy revealed that this animal could be stably refracted, and the refractive error underwent developmental changes, which increased with age in the hyperopic direction and eventually got stable approximately 9 weeks after birth. The absolute values of refractive error in CBA/CaJ mice were larger than those of age-matched C57BL/6 mice, whereas the time points when refractive error reached steady state were similar between the two strains. Five weeks of form-deprivation applied to 3-week-old CBA/CaJ mice by translucent occluder wear caused a significant myopic shift in refractive error, indicating that this strain could be adequately used as a myopia model.

Orexin-A differentially modulates AMPA-preferring responses of ganglion cells and amacrine cells in rat retina

By activating their receptors (OX1R and OX2R) orexin-A/B regulate wake/sleeping states, feeding behaviors, but the function of these peptides in the retina remains unknown. Using patch-clamp recordings and calcium imaging in rat isolated retinal cells, we demonstrated that orexin-A suppressed α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA)-preferring receptor-mediated currents (AMPA-preferring currents) in ganglion cells (GCs) through OX1R, but potentiated those in amacrine cells (ACs) through OX2R. Consistently, in rat retinal slices orexin-A suppressed light-evoked AMPA-preferring receptor-mediated excitatory postsynaptic currents in GCs, but potentiated those in ACs. Intracellular dialysis of GDP-β-S or preincubation with the Gi/o inhibitor pertussis toxin (PTX) abolished both the effects. Either cAMP/the protein kinase A (PKA) inhibitor Rp-cAMP or cGMP/the PKG blocker KT5823 failed to alter the orexin-A effects. Whilst both of them involved activation of protein kinase C (PKC), the effects on GCs and ACs were respectively eliminated by the phosphatidylinositol (PI)-phospholipase C (PLC) inhibitor and phosphatidylcholine (PC)-PLC inhibitor. Moreover, in GCs orexin-A increased [Ca(2+)]i and the orexin-A effect was blocked by intracellular Ca(2+)-free solution and by inositol 1,4,5-trisphosphate (IP3) receptor antagonists. In contrast, orexin-A did not change [Ca(2+)]i in ACs and the orexin-A effect remained in intracellular or extracellular Ca(2+)-free solution. We conclude that a distinct Gi/o/PI-PLC/IP3/Ca(2+)-dependent PKC signaling pathway, following the activation of OX1R, is likely responsible for the orexin-A effect on GCs, whereas a Gi/o/PC-PLC/Ca(2+)-independent PKC signaling pathway, following the activation of OX2R, mediates the orexin-A effect on ACs. These two actions of orexin-A, while working in concert, provide a characteristic way for modulating information processing in the inner retina.

Hyperactivity of ON-type retinal ganglion cells in streptozotocin-induced diabetic mice

Impairment of visual function has been detected in the early stage of diabetes but the underlying neural mechanisms involved are largely unknown. Morphological and functional alterations of retinal ganglion cells, the final output neurons of the vertebrate retina, are thought to be the major cause of visual defects in diabetes but direct evidence to support this notion is limited. In this study we investigated functional changes of retinal ganglion cells in a type 1-like diabetic mouse model. Our results demonstrated that the spontaneous spiking activity of ON-type retinal ganglion cells was increased in streptozotocin-diabetic mice after 3 to 4 months of diabetes. At this stage of diabetes, no apoptotic signals or cell loss were detected in the ganglion cell layer of the retina, suggesting that the functional alterations in ganglion cells occur prior to massive ganglion cell apoptosis. Furthermore, we found that the increased activity of ON-type ganglion cells was mainly a result of reduced inhibitory signaling to the cells in diabetes. This novel mechanism provides insight into how visual function is impaired in diabetic retinopathy.

Upregulation of glutamate-aspartate transporter by glial cell line-derived neurotrophic factor ameliorates cell apoptosis in neural retina in streptozotocin-induced diabetic rats

AIMS

Dysfunction of glutamate uptake, largely mediated by the glutamate-aspartate transporter (GLAST), may lead to retinal cell apoptosis in diabetic retinopathy. The aim of this study is to examine how cell apoptosis and the expression level of GLAST in neural retina of a diabetic rat model are changed and whether the neuroretinal apoptosis could be ameliorated by the administration of glial cell line-derived neurotrophic factor (GDNF).

METHODS

Diabetes was induced by intraperitoneal injection of streptozotocin (STZ) in Sprague-Dawley rats. GLAST protein expression levels were determined by Western blotting, whereas apoptosis of retinal neurons was evaluated by TUNEL staining. To assess the role of GDNF in ameliorating the STZ-induced retinal changes, GDNF/GDNF with siRNA directed against GLAST was injected into the vitreous after STZ injection.

RESULTS

In rat retinas 4 weeks after the onset of STZ-induced diabetes, TUNEL-positive cells were significantly increased, whereas GLAST levels were significantly reduced. Intraocular administration of GDNF at the early stage of diabetes remarkably increased the GLAST levels and decreased TUNEL-positive signals in the retinas. These effects of GDNF were largely abolished by coadministration of GLAST siRNA.

CONCLUSIONS

GDNF, administrated at the early stage of diabetes, could rescue retinal cells from neurodegeneration by upregulating the expression of GLAST.

Cellular localization of P2Y₆ receptor in rat retina

Extracellular nucleotides exert their actions via two subfamilies of purinoceptors: P2X and P2Y. Eight mammalian P2Y receptor subtypes (P2Y(1,2,4,6,11,12,13,14)) have been identified. In this work, the localization of P2Y(6) was studied in rat retina using double immunofluorescence labeling and confocal scanning microscopy. Immunostaining for P2Y(6) was strong in the outer plexiform layer and was diffusely distributed throughout the full thickness of the inner plexiform layer. In addition, P2Y(6) immunoreactivity was clearly observed in many cells in the inner nuclear layer and the ganglion cell layer. In the outer retina photoreceptor terminals, labeled by VGluT1, and horizontal cells, labeled by calbindin, were P2Y(6)-positive. However, no P2Y(6) immunostaining was detected in bipolar cells, labeled by homeobox protein Chx10. In the inner retina P2Y(6) was localized to most of GABAergic amacrine cells, including dopaminergic and cholinergic ones, stained by tyrosine hydroxylase (TH) and choline acetyltransferase (ChAT) respectively. Some of glycinergic amacrine cells, but not glycinergic AII amacrine cells, were also labeled by P2Y(6). Moreover, P2Y(6) immunoreactivity was seen in almost all ganglion cells, labeled by Brn3a. In Müller glial cells, stained by cellular retinaldehyde binding protein (CRALBP), however, no P2Y(6) expression was found in both somata and processes. We speculate that P2Y(6) may be involved in retinal information processing in different ways, probably by regulating the release of transmitters and/or modulating the radial flow of visual signals and lateral interaction mediated by horizontal and amacrine cells.

Distribution of somatostatin receptor 5 in mouse and bullfrog retinas

Somatostatin (SRIF), as a neuroactive peptide in the CNS, may act as a neuromodulator through activation of five specific receptor subtypes (sst(1)-sst(5)). In this work we conducted a comparative study of the expression of sst(5) in mouse and bullfrog retinas by immunofluorescence double labeling. Basically, the expression profiles of sst(5) in the retinas of the two species were similar. That is, in the inner retina sst(5) was localized to dopaminergic and cholinergic amacrine cells, stained by tyrosine hydroxylase (TH) and choline acetyltransferase (ChAT) respectively, and cells in the ganglion cell layer, whereas in the outer retina immunostaining for sst(5) was observed in horizontal cells. However, a more widespread, abundant distribution of labeling for sst(5), as compared to mouse retina, was seen in bullfrog retina: strong labeling for sst(5) was diffusely distributed in both outer and inner plexiform layers (OPL and IPL) in the bullfrog retina, but the labeling was only observed in the IPL of the mouse retina. In addition, bullfrog photoreceptors, both rods and cones, but not mouse ones, were labeled by sst(5). In combination with the experiments showing that SRIF-immunoreactivity was mainly found in the inner retina, our results suggest that SRIF, released from SRIF-containing cells in the inner retina, may play a neuromodulatory role in both outer and inner retina mediated by volume transmission via sst(5) in bullfrog retina, while the SRIF action may be largely restricted to the mouse inner retina.

Expression of sigma receptor 1 mRNA and protein in rat retina

Sigma receptor (sigmaR), known as a unique nonopiate, nonphencyclidine brain receptor, can bind diverse classes of psychotropic drugs, neurosteroids and other synthetic compounds, such as (+)pentazocine, etc. Two types of sigmaRs have been identified: sigmaR1 and sigmaR2. In this work, we examined the expression of sigmaR1 in rat retina by reverse transcription-polymerase chain reactive (RT-PCR) analysis and immunofluorescence double labeling. RT-PCR analysis showed that sigmaR1 mRNA was present in rat retina. Furthermore, labeling for sigmaR1 was diffusely distributed in the outer and inner plexiform layers. The sigmaR1-immunoreactivity (IR) was also observed in many cells in the inner nuclear layer and the ganglion cell layer. In the outer retina sigmaR1 was expressed in all horizontal cells labeled by calbindin. In contrast, no sigmaR1-IR was detected in several subtypes of bipolar cells, including rod-dominant ON-type bipolar cells, types 2, 3, 5 and 8 bipolar cells, labeled by protein kinase C (PKC), recoverin and hyperpolarization-activated cyclic nucleotide-gated potassium channel 4 (HCN4) respectively. In the inner retina, most of GABAergic amacrine cells, including dopaminergic and cholinergic ones, stained by tyrosine hydroxylase (TH) and choline acetyltransferase (ChAT) respectively, expressed sigmaR1. Some glycinergic amacrine cells were also labeled by sigmaR1, but glycinergic AII amacrine cells were not labeled. In addition, sigmaR1-IR was seen in almost all somata of the ganglion cells retrogradely labeled by fluorogold. These results suggest that sigmaR1 may have neuromodulatory and neuroprotective roles in the retina.

Natriuretic peptide receptors are expressed in rat retinal ganglion cells

Natriuretic peptides (NPs) exert their actions through three membrane-bound receptors, which are known as NP receptors (NPRs: NPR-A, NPR-B and NPR-C). In this work we examined the expression of three NPRs in rat retinal ganglion cells (GCs), retrogradely labeled and intracellularly dye-injected, by double immunofluorescence labeling. In vertical sections, almost all GCs, retrogradely labeled by cholera toxin B, were stained by antibodies against the three NPRs. The labeling for three NPRs was observed mainly on the membranes of the somata of GCs, whereas the staining for NPR-A was also seen in the cytoplasm. Moreover, with tangential sections, almost all cells located in the ganglion cell layer were NPR-A, B, C immunoreactive. By combining with intracellular injection of Neurobiotin into GCs in whole mount retinas that enables to identify ON-, OFF- and ON-OFF-types of GCs according to arborization of their dendrites in the inner plexiform layer, we further demonstrated that NPRs were expressed in these major types of GCs.

Natriuretic peptides are localized to rat retinal amacrine cells

Natriuretic peptides (NPs) may act as neuromodulators through activation of three specific receptor subtypes (NPRs). In the present study we examined the expression of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and C-type natriuretic peptide (CNP) on different subtypes of retinal amacrine cells (ACs) in rat by immunofluorescence double labeling. All three NPs were moderately expressed in dopaminergic and cholinergic ACs, stained by tyrosine hydroxylase (TH) and choline acetyltransferase (ChAT), respectively. The immunostaining appeared on the membrane, cytoplasm and somatodendritic compartments of these ACs. In AII glycinergic ACs, labeled by parvalbumin (PV), however, only faint punctate staining, if any, was seen. These results suggest that NPs could be produced in ACs and play a neuromodulatory role in the inner retina. Together with a previous immunocytochemical study, showing that NPR-B is present in cultured rat GABAergic ACs, our results further suggest that NPs produced in ACs may also modulate their own activity.

5-HT2A receptors are differentially expressed in bullfrog and rat retinas: a comparative study

Expression of 5-hydroxytryptamine (5-HT) 2A receptor (5-HT2A) was studied in bullfrog and rat retinas by immunocytochemistry. In the bullfrog retina, 5-HT2A-immunoreactivity was observed in both the outer and inner plexiform layers (OPL and IPL). Double labeling experiments further showed that 5-HT2A was expressed in Müller cells stained by GFAP. Labeling for 5-HT2A was strong in the somata and endfeet and relatively weak in the major processes and fine branchets of Müller cells. In contrast, 5-HT2A immunoreactivity was hardly detected in the rat retina, and no rat Müller cells were labeled. Furthermore, immunocytochemical assay demonstrated that labeling for 5-HT was present in amacrine cells and displaced amacrine cells in the inner retina of bullfrog, but not in the rat retina. These results suggest that 5-HT may modulate retinal information processing via activating 5-HT2A expressed in neuronal and glial elements in bullfrog, but that such modulation is unlikely to occur in rat.

A modified electrocardiographic algorithm for differentiating typical atrioventricular node re-entrant tachycardia from atrioventricular reciprocating tachycardia mediated by concealed accessory pathway

Non-invasive prediction of tachycardia mechanism is becoming clinically important in the era of catheter ablation for curing supraventricular tachycardia. Twelve-lead electrocardiograms (ECGs) during sinus rhythm and atrioventricular node re-entrant tachycardia (AVNRT) or atrioventricular reciprocating tachycardia (AVRT) with a narrow QRS complex were obtained from 154 consecutive adult patients who had received successful radiofrequency catheter ablation. The ECGs of initial 104 patients were analysed by three observers without knowledge of the electrophysiological diagnosis. The two arrhythmias were accurately diagnosed in 68% of cases. Three criteria were found to be discriminators of tachycardia mechanism by univariable analysis. Pseudo r/Q/S waves predicated AVNRT in 92% of cases (sensitivity 71%; specificity 95%). Retrograde P wave predicated AVRT in 86% of cases (sensitivity 75%; specificity 85%), RP interval > or =100 ms in 93% (sensitivity 71%; specificity 94%) and ST-segment elevation in lead aVR in 83% (sensitivity 71%; specficity 83%). According to the initial results, we proposed a modified stepwise ECG algorithm which used pseudo r/S/Q waves, RP interval and ST-segment elevation in lead aVR during tachycardia. Two observers assessed the modified algorithm in the remaining 50 patients. The algorithm was able to correctly diagnose the tachycardia mechanism in 84% and 87%, respectively. Using the modified algorithm can improve the accuracy and simplify the differential diagnosis between typical AVNRT and AVRT via concealed accessory pathway in adult patients.

Expression of the dopamine transporter in rat and bullfrog retinas

We examined the expression of the dopamine transporter in rat and bullfrog retinas by immunohistochemistry. In both species, the dopamine transporter was strongly expressed in somata and processes of all dopaminergic amacrine cells. In contrast, no immunoreactivity for dopamine transporter was observed in cholinergic amacrine cells. In rat dopaminergic interplexiform cells, dopamine transporter immunoreactivity was also observed on the ascending processes terminating in the outer plexiform layer. Furthermore, the labeling for dopamine transporter diffusely appeared in both outer and inner plexiform layers. This expression profile of the dopamine transporter suggests that dopamine may be taken up not only in the synapses but also extrasynaptically by dopamine transporter, diffusely distributed in both plexiform layers.

Distinctive morphology of hippocampal CA1 terminations in orbital and medial frontal cortex in macaque monkeys

The fine morphology of hippocampal connections to the orbital and medial frontal cortex (OMFC) was investigated by placing injections of anterograde tracers in the CA1 in two monkeys. The axons terminated mainly in layers 2 and 3, of areas 11, 13, 14c, 25, and 32, and were widely divergent in these layers, traversing 2-4 mm. Boutons were scattered along the main axon, but also occurred as distinctive small, spherical clusters of terminations ("mini-clusters"; diameter <50 microm). Occasional larger terminal arbors were observed in layer 3 and these were often unusually tortuous or convoluted. These features may imply a specialized microcircuitry of hippocampal-OMFC connections, including an origin from a particular subpopulation of CA1 projection neurons.

Expression of glycine receptor and transporter on bullfrog retinal Müller cells

The expression of the glycine receptor (GlyR) alpha1, alpha2 and beta subunits and glycine transporter (GlyT) on Müller cells was studied in bullfrog retina using double immunofluorescence labeling and confocal scanning microscopy. Double labeling of glial fibrillary acidic protein (GFAP), a specific marker for Müller cells, and the GlyR subunits showed that almost all Müller cells moderately expressed GlyR alpha1 and weakly GlyR beta, whereas no immunoreactivity for GlyR alpha2 was observed. The labeling for GlyR alpha1 and GlyR beta appeared in somata, major processes, endfeet and branchlets of the Müller cells. Müller cells were also GlyT1-labeled. Consistent with previous electrophysiological results, these findings suggest that Müller cells may be involved in modulation of glycinergic transmission by reciprocal interactions with retinal neurons through GlyR and GlyT.

Transgenic mice expressing a fluorescent in vivo label in a distinct subpopulation of neocortical layer 5 pyramidal cells

The neuronal components of cortical circuits have been characterized on the basis of their morphological and functional properties, and further refined by correlation of marker proteins with particular cell types. This latter approach has been very fruitful for GABA-containing neurons, but comparable diagnostic markers for subpopulations of excitatory pyramidal cells have been more elusive. An emerging new approach consists of transgenic mice that express fluorescent proteins under the control of promoters that are active in specific cell types. Here, we analyzed a line of transgenic mice that carries a transgene consisting of regulatory sequences of the potassium channel Kv3.1 and enhanced yellow fluorescent protein (EYFP). In these mice, a set of neurons in neocortical layer 5 expresses high levels of the transgenic marker protein. EYFP-expressing, and nonexpressing layer 5 cells were easily identified in living tissue under conditions suitable for patch-clamp electrophysiology. By using immunolabeling, retrograde Fast Blue labeling and electrophysiological recordings with biocytin injections, we identified the fluorescent neurons as a population of pyramidal cells with distinct morphological and electrophysiological properties when compared with nonfluorescent neighboring layer 5 pyramidal cells. The most prominent morphological difference between these two populations was a much smaller number of apical oblique dendrites in EYFP-positive as compared with the EYFP-negative cells. The most prominent electrophysiological feature was a steady spike frequency adaptation in EYFP-positive cells, whereas EYFP-negative cells responded to a depolarizing current injection with a closely spaced spike doublet followed by constant frequency firing. The in vivo labeled transgenic mice provide an experimental tool for further functional differentiation of these populations of layer 5 pyramidal cells.

Direct projections from CA1 to the superior temporal sulcus in the monkey, revealed by single axon analysis

Anterograde tracer injections in the middle sector of CA1 in macaque monkeys demonstrate a direct projection to the fundus of the anterior superior temporal sulcus, in area IPa. Terminations are predominantly in layer 3. With regard to both terminal and arbor configuration, these hippocampal-cortical connections are morphologically similar to corticocortical connections to temporal association cortex. This report provides additional evidence of direct CA1 connections to particular multimodal cortical areas.

Proof of the mysterious efficacy of ginseng: basic and clinical trials: effects of red ginseng on learning and memory deficits in an animal model of amnesia

Ameliorating effects of red ginseng on learning and memory deficits due to hippocampal lesions and aging were reviewed; the performance of young rats with selective hippocampal lesions with or without red ginseng (p.o.), and aged rats with or without red ginseng (p.o.) in the spatial learning tasks was compared with that of sham-operated or intact young rats. Each rat was tested with 3 types of spatial learning tasks (distance movement task, DMT; random reward place search task, RRPST; and place learning task, PLT) in a circular open field using intracranial self-stimulation (ICSS) as reward. The results in the DMT and RRPST indicated that motivational and motor activity of young rats with hippocampal lesions with and without ginseng and aged rats with and without ginseng were not significantly different from that of control young rats. However, young rats with hippocampal lesions without ginseng and aged rats without ginseng displayed significant deficits in the PLT. Treatment with red ginseng significantly ameliorated place-navigation deficits in young rats with hippocampal lesions in the PLT. Similarly, red ginseng improved performance of aged rats in the PLT. The results, along with previous studies showing significant effects of red ginseng on the central nervous system, suggest that red ginseng ameliorates learning and memory deficits through effects on the central nervous system, partly through effects on the hippocampal formation. However, its mechanisms are still unclear, and further studies are required.

Effects of nonsaponin fraction of red ginseng on learning deficits in aged rats

Previously we reported that oral application of red ginseng significantly ameliorated learning deficits in aged rats and young rats with hippocampal lesions. In the present study, we investigated the effects of the nonsaponin fraction of red ginseng on learning deficits in aged rats in behavioral studies and those on long-term potentiation (LTP) in the hippocampal CA3 subfield in young rats in electrophysiological studies. In the behavioral studies, three groups of rats [aged rats with and without oral administration of the nonsaponin fraction of red ginseng and young rats] were tested with the three types of spatial-learning task [distance movement task (DMT), random-reward place search task (RRPST), and place-learning task (PLT)] in a circular open field. The results in the DMT and RRPST indicated that motivational and motor activity was not significantly different among the three groups of rats. However, performance of the aged rats without nonsaponin was significantly impaired in the PLT when compared with the young rats. Treatment with nonsaponin significantly ameliorated deficits in place-navigation learning in the aged rats in the PLT. In the electrophysiological studies, effects of nonsaponin on the LTP in the CA3 subfield of the hippocampal slices were investigated in vitro. Pretreatment with nonsaponin significantly augmented the increase in population spike amplitudes in the CA3 subfield after LTP induction. These results suggest that the nonsaponin fraction of red ginseng contains important substances to improve learning and memory in aged rats and that this amelioration by nonsaponin might be attributed partly to augmentation of LTP in the CA3 subfield.

Connections between the anterior inferotemporal cortex (area TE) and CA1 of the hippocampus in monkey

In addition to the trisynaptic perforant pathway from entorhinal cortex to CA1, there are multiple direct parallel pathways between several cortical regions and CA1. These may be supposed to function cooperatively, in conjunction with the perforant pathway; but neither the functional nor anatomical organization of the extended network is well understood. In this report, we further investigate the connections between anterior inferotemporal cortex (area TE) and CA1. Injections of tracer substances demonstrate that part of the dorsal subdivision of TE sends projections to CA1, but does not receive reciprocating projections back. This contrasts with the bi-directional connections between the more ventral subdivision, TEav, and CA1, as reported by previous studies (and corroborated by tracer injections in this report). The corticohippocampal projections from dorsal TE are likely to be unimodal visual. They partially converge in the posterior portion of CA1 with connections from posterior TE and from the inferior parietal lobule, perhaps constituting a network related to visual or visuospatial processes.

Inferior parietal lobule projections to anterior inferotemporal cortex (area TE) in macaque monkey

Parietal cortical areas have generally been considered as part of the dorsal stream and, as such, only indirectly connected with inferotemporal cortex. In this report we demonstrate, by using the anterograde tracer BDA, that much of the inferior parietal lobule (IPL) has direct connections to anterior-ventral TE (TEav) around the anterior middle temporal sulcus (amts). Connections from area PG terminate in layers 1 and 5 as well as 4; and those from area PF, target layer 6 of TEav, with a small secondary focus in layer 4 of anterior-dorsal TE. Connections from areas PG and PF are relatively sparse; but those from the mid-IPL region (approximately area PFG), which terminate in layer 4, are light to moderate. In confirmation of these results, injections of retrograde tracers in TEav produce labeled neurons in the IPL. These are most numerous in layer 3 at the border of areas PG and PFG, but also occur in layer 5/6. These laminar patterns are more complex than the classical 'feedforward' or 'feedback' patterns associated with early sensory areas. Branched collaterals are common; and three of seven reconstructed axons branched to both TEav and to the lateral bank of the occipito-temporal sulcus, itself a major source of inputs to TEav. The existence of connections from the IPL preferentially to TEav and the amts provides another example where direct 'bypass' connections operate in parallel with multiple indirect routes. It provides further evidence for the differential connectivity of subdivisions within anterior TE and is consistent with recent evidence from functional magnetic resonance imaging studies that the region around the amts may be part of a network involved in three- dimensional shape, which is distributed across both 'what' and 'where' processing streams.

Red ginseng ameliorated place navigation deficits in young rats with hippocampal lesions and aged rats

Effects of hippocampal lesions and aging on spatial learning and memory and ameliorating effects of red ginseng on learning deficits were investigated in the following two experiments: performance of young rats with selective hippocampal lesions with red ginseng by mouth (p.o.; Experiment 1) and aged rats with red ginseng (p.o.; Experiment 2) in the spatial tasks was compared with that of sham-operated or intact young rats. Each rat in these two behavioral experiments was tested with the three types of spatial-learning tasks (distance movement task, DMT; random-reward place search task, RRPST; and place-learning task, PLT) in a circular open field using intracranial self-stimulation as reward. The results in the DMT and RRPST tasks indicated that motivational and motor activity of young rats with hippocampal lesions with and without ginseng were not significantly different from that of sham-operated young rats in Experiment 1. However, young rats with hippocampal lesions displayed significant deficits in the PLT task. Treatment with red ginseng significantly ameliorated place-navigation deficits in young rats with hippocampal lesions on the PLT task. Similarly, red ginseng improved performance of aged rats on the PLT task in Experiment 2. The results, along with previous studies showing significant effects of red ginseng on the central nervous system, suggest that red ginseng ameliorates learning and memory deficits through effects on the central nervous system, partly through effects on the hippocampal formation.