Vitamin D Improves Cognitive Impairment and Alleviates Ferroptosis via the Nrf2 Signaling Pathway in Aging Mice.

Ferroptosis is an iron-dependent mode of cell death associated with the occurrence and development of age-related neurodegenerative diseases. Currently, there are no effective drugs available to prevent or treat these aging-related neurodegenerative diseases. Vitamin D (VD) is an antioxidant and immunomodulator, but its relationship with ferroptosis in aging-related neurodegenerative diseases has not been extensively studied. In this study, we aimed to investigate the role of VD in learning and memory in aging mice. To examine whether VD protects aging hippocampal neurons, we used physiologically active 1,25(OH)2D3. We established aging models in vivo (C57BL/6 mice) and in vitro (HT22 cells) using D-galactose (D-gal). The results demonstrated that VD could improve learning and memory in mice aged via the use of D-gal, and it reduced damage to hippocampal neurons. VD could regulate ferroptosis-related proteins (increasing GPX4 expression and decreasing ACSL4 and ALOX15 protein expression levels), increasing GSH levels, reducing MDA and intracellular and mitochondrial ROS levels, as well as total iron and Fe2+ levels, and improving mitochondrial morphology, thereby alleviating ferroptosis in aging hippocampal neurons. Additionally, VD activated the VDR/Nrf2/HO-1 signaling pathway, thereby inhibiting ferroptosis. Notably, when the VDR was knocked down, VD lost its ability to activate Nrf2. Consequently, inhibiting Nrf2 decreased the protective effect of VD against ferroptosis in aged hippocampal neurons. In summary, VD activates the Nrf2/HO-1 signaling pathway through the VDR, effectively preventing ferroptosis induced by aging in hippocampal neurons.

TESOT: a teaching modality targeting the learning obstacles in global medical education.

In higher education, it is a great challenge for instructors to teach international medical students (IMSs) efficiently. These students usually have different learning obstacles and learning style preferences from domestic students. Thus it is necessary to use teaching modalities targeting the specific characteristics of IMSs. Accordingly, we have developed a teaching modality composed of classical teacher-centered approach (TCA), enriched with components of student-centered approach (SCA) and online interactions targeting the learning characteristics of IMSs, which we defined as TESOT (an acronym made of the underlined words' initials). Aside from the online interactions that provide both answers to questions raised by students and guidance throughout a course, this modality contains additional in-classroom components (i.e., pre-lecture quiz, student-led summary, and post-lecture quiz). The effectiveness of this modality was tested in the nervous system module of the Physiology course for IMSs. The final exam scores in the nervous system module in the year taught with TESOT were higher than those earned by students taught with a classical TCA modality in preceding 2 yr. The improvement of teaching effectiveness is attributable to increasing communication, bridging course contexts, and meeting diverse learning style preferences. These results indicate that TESOT as an effective teaching modality is useful for enhancing efficiency of teaching IMSs.

Effects of Intranasal Oxytocin on Pup Deprivation-Evoked Aberrant Maternal Behavior and Hypogalactia in Rat Dams and the Underlying Mechanisms.

Oxytocin (OT), a hypothalamic neuropeptide, applied through nasal approach (IAO), could improve maternal health during lactation that is disrupted by mother-baby separation; however, the regulation of IAO effects on maternal behaviors and lactation as well as the underlying mechanisms remain unclear. Using lactating rats, we observed effects of intermittent pup deprivation (PD) with and without IAO on maternal behaviors and lactation as well as the activity of OT neurons in the supraoptic nucleus (SON) and the activity of hypothalamic pituitary-adrenal axis, key factors determining the milk-letdown reflex during lactation and maternal behaviors. The results showed that PD reduced maternal behaviors and lactation efficiency of rat dams as indicated by significantly longer latency to retrieve their pups and low litter's body weight gains during the observation, respectively. In addition, PD caused early involution of the mammary glands. IAO partially improved these changes in rat dams, which was not as significant as IAO effects on control dams. In the SON, PD decreased c-Fos and increased glial fibrillary acidic protein (GFAP) filaments significantly; IAO made PD-evoked c-Fos reduction insignificant while reduced GFAP filament significantly in PD dams. IAO tended to increase the levels of phosphorylated extracellular signal-regulated kinases (pERK) 1/2 in PD dams. Moreover, PD+IAO significantly increased plasma levels of dam adrenocorticotropic hormone and corticosterone but not OT levels. Lastly, PD+IAO tended to increase the level of corticotropin-releasing hormone in the SON. These results indicate that PD disrupts maternal behaviors and lactation by suppressing the activity of hypothalamic OT-secreting system through expansion of astrocytic processes, which are partially reversed by IAO through removing astrocytic inhibition of OT neuronal activity. However, the improving effect of IAO on the maternal health could be compromised by simultaneous activation of hypothalamic pituitary-adrenocortical axis.

Oxytocin Removes Estrous Female vs. Male Preference of Virgin Male Rats: Mediation of the Supraoptic Nucleus Via Olfactory Bulbs.

Social functions of oxytocin (OT) have been explored extensively; however, relationship between the effect of intranasally applied OT (nasal OT) on the social preference (SP) and intracerebral actions of endogenous OT remains unclear. To resolve this question, we first observed effects of nasal OT on the SP of virgin young adult male rats toward unfamiliar virgin estrous female (EF) vs. virgin male rats. The results showed that the test male rats exhibited significantly more times and longer duration accessing the female than the male, which were acutely eliminated by nasal OT. Then, we examined the approaches mediating nasal OT effects on the activity of potential brain targets in Western blots and found that nasal OT activated the olfactory bulbs (OBs) and the supraoptic nucleus (SON), but not the piriform cortex, amygdala and hippocampus as shown by significant changes in the expression of c-Fos and/or phosphorylated extracellular signal-regulated protein kinase (pERK) 1/2. Moreover, microinjection of TTX into the OBs blocked nasal OT-evoked increases in pERK1/2 levels as well as the molecular association between ERK1/2 and OT-neurophysin in the SON. Electrolytic lesions of the lateral olfactory tract did not significantly change the basal levels of pERK 1/2 in the SON; however, upon nasal OT, pERK 1/2 levels in the SON reduced significantly. Lastly, microinjection of L-aminoadipic acid (gliotoxin) into the SON to reduce OT levels reduced the duration of the test male's accessing the EF and blocked the nasal OT-evoked increase in the duration of test male's accessing the male while significantly increasing pERK1/2 levels in the amygdala. These findings reveal for the first time that nasal OT acutely eliminates virgin males' SP to EFs via the OB-SON route and that OT neurons could mediate the social effects of nasal OT by suppressing social phobia generated in the amygdala.

Interactions of the Mechanosensitive Channels with Extracellular Matrix, Integrins, and Cytoskeletal Network in Osmosensation.

Life is maintained in a sea water-like internal environment. The homeostasis of this environment is dependent on osmosensory system translation of hydromineral information into osmotic regulatory machinery at system, tissue and cell levels. In the osmosensation, hydromineral information can be converted into cellular reactions through osmoreceptors, which changes thirst and drinking, secretion of antidiuretic vasopressin (VP), reabsorption of water and salt in the kidneys at systemic level as well as cellular metabolic activity and survival status at tissue level. The key feature of osmosensation is the activation of mechanoreceptors or mechanosensors, particularly transient receptor potential vallinoid (TRPV) and canonical (TRPC) family channels, which increases cytosolic Ca2+ levels, activates osmosensory cells including VP neurons and triggers a series of secondary reactions. TRPV channels are sensitive to both hyperosmotic and hyposmotic stimuli while TRPC channels are more sensitive to hyposmotic challenge in neurons. The activation of TRP channels relies on changes in cell volume, membrane stretch and cytoskeletal reorganization as well as hydration status of extracellular matrix (ECM) and activity of integrins. Different families of TRP channels could be activated differently in response to hyperosmotic and hyposmotic stimuli in different spatiotemporal orders, leading to differential reactions of osmosensory cells. Together, they constitute the osmosensory machinery. The activation of this osmoreceptor complex is also associated with the activity of other osmolarity-regulating organelles, such as water channel protein aquaporins, Na-K-2Cl cotransporters, volume-sensitive anion channels, sodium pump and purinergic receptors in addition to intercellular interactions, typically astrocytic neuronal interactions. In this article, we review our current understandings of the composition of osmoreceptors and the processes of osmosensation.

Effects of norepinephrine on the electrical activities of pain-related neurons in the rat nucleus accumbens.

This study examined the effects of norepinephrine (NE) and phentolamine on the electrical activities of pain-excited neurons (PENs) and pain-inhibited neurons (PINs) in the nucleus accumbens (NAc) of Wistar rats. Trains of electric pulses applied to the right sciatic nerve were used to provide noxious stimulation, and the discharges of PENs and PINs were recorded using a glass microelectrode. Our results revealed that in response to noxious stimulation, NE decreases the evoked discharge frequency of PENs and increases the evoked discharge frequency of PINs in the NAc of healthy rats, whereas phentolamine produced opposite responses. These results demonstrate that NE is involved in the modulation of nociceptive information transmission in the NAc.

Noradrenergic mechanism involved in the nociceptive modulation of nociceptive-related neurons in the caudate putamen.

Norepinephrine (NE) participates in pain modulation of the central nervous system. The caudate putamen (CPu) is one region of the basal ganglia that has been demonstrated to be involved in nociceptive perception. Our previous work has shown that microinjection of different doses of norepinephrine into the CPu produces opposing effects in the tail-flick latency (TFL) of rats. However, the mechanism of action of NE on the pain-related neurons in the CPu remains unclear. The present study examined the effects of NE and the alpha-adrenoceptor antagonist phentolamine on the pain-evoked response of pain-excitation neurons (PENs) and pain-inhibition neurons (PINs) in the CPu of rats. Trains of electric impulses were used for noxious stimulation, and were applied to the sciatic nerve. The electrical activities of pain-related neurons in the CPu were recorded by a glass microelectrode. The results revealed that intra-CPu microinjection of NE (8microg/2microl) increased evoked firing frequency of PEN and shortened the firing latency, but decreased the evoked firing frequency of PIN and prolonged the inhibitory duration (ID). Intra-CPu administration of phentolamine (4microg/2microl) showed the opposite effects. The above results suggest that NE in the CPu modulates nociception by affecting the baseline firing rates of PENs and PINs.

MK-801 changes the role of glutamic acid on modulation of algesia in nucleus accumbens.

Dizocilpine maleate (MK-801) causes the blockage of the glutamic acid (Glu) receptors in the central nervous system that are involved in pain transmission. However, the mechanism of action of MK-801 in pain-related neurons is not clear, and it is still unknown whether Glu is involved in the modulation of this processing. This study examines the effect of MK-801, Glu on the pain-evoked response of pain-excitation neurons (PENs) and pain-inhibition neurons (PINs) in the nucleus accumbens (NAc) of rats. The trains of electric impulses applied to the sciatic nerve were used as noxious stimulation. The electrical activities of PENs or PINs in NAc were recorded by a glass microelectrode. Our results revealed that the lateral ventricle injection of Glu increased the discharged frequency and shortened the discharged latency of PEN, and decreased the discharged frequency and prolonged the discharged inhibitory duration (ID) of PIN in NAc of rats evoked by the noxious stimulation, while intra-NAc administration of MK-801 produced the opposite response. On the basis of above findings we can deduce that Glu, MK-801 and N-methyl-D-aspartate (NMDA) receptor are involved in the modulation of nociceptive information transmission in NAc.

Microinjection of different doses of norepinephrine into the caudate putamen produces opposing effects in rats.

It has been proven that norepinephrine (NE) regulates antinociception through its action on alpha-adrenoceptors located in brain nuclei, spinal cord, and peripheral organs. However, the supraspinal mechanism of noradrenergic pain modulation is controversial. The present study was aimed at investigating the nociceptive effects induced by injecting different doses of NE and phentolamine into the caudate putamen (CPU) of rats. The thermal pain threshold of the rats was measured by performing a tail-flick test. The tail-flick latency (TFL) was measured at 2-60 min after microinjection of the drugs. Our results revealed that the thermal pain threshold increased (long TFL) after the administration of a low dose of NE (2 microg/2 microl) and decreased (short TFL) after injection of a high dose of NE (8 microg/2 microl). In contrast, the pain threshold decreased after the administration of a low dose of phentolamine (1 microg/2 microl), while it increased after injection of a high dose of phentolamine (4 microg/2 microl). These results indicated that the injection of different doses of NE in the CPU of the rats produced opposite effects on the pain threshold, as determined by the tail-flick tests.

Cholecystokinin-8 antagonizes electroacupuncture analgesia through its B receptor in the caudate nucleus.

OBJECTIVES: The analgesic effect of electroacupuncture (EA) stimulation has been proved. However, its mechanism of action is not clear. It has been well-known that cholecystokinin-8 (CCK-8) is a neuropeptide which is mainly related to the mediation of pain. The caudate nucleus was selected to determine if the release of CCK and the neural activity in this nucleus were involved in producing EA analgesia. MATERIALS AND METHODS: Radiant heat focused on the rat-tail was used as the noxious stimulus. The pain threshold of rats was measured by tail-flick latency (TFL). EA stimulation at the bilateral Zusanli (ST 36) acupoints of rats was used to investigate the effects of EA analgesia. The electrical activities of pain-excited neurons (PEN) and pain-inhibited neurons (PIN) in the caudate nucleus were recorded with a glass microelectrode. The present study examined the antagonistic effects of the intracerebral ventricular injection of CCK-8 on EA analgesia and reversing effects of CCK-B receptor antagonist (L-365,260) injection into the caudate nucleus on CCK-8. RESULTS: The radiant heat focused on the tail of rats caused an increase in the evoked discharge of PEN and a reduction in the evoked discharge of PIN. EA stimulation at the bilateral ST 36 acupoints of rats resulted in the inhibition of PEN, the potentiation of PIN, and prolongation of TFL. The analgesic effect of EA was antagonized when CCK-8 was injected into the intracerebral ventricle of rats. The antagonistic effect of CCK-8 on EA analgesia was reversed by injection of CCK-B receptor antagonist (L-365,260) into the caudate nucleus of rats. CONCLUSIONS: Our results suggest that CCK-8 antagonize EA analgesia through its B receptor.

Cholinergic mechanism involved in the nociceptive modulation of dentate gyrus.

Acetylcholine (ACh) causes a wide variety of anti-nociceptive effects. The dentate gyrus (DG) region of the hippocampal formation (HF) has been demonstrated to be involved in nociceptive perception. However, the mechanisms underlying this anti-nociceptive role have not yet been elucidated in the cholinergic pain-related neurons of DG. The electrical activities of pain-related neurons of DG were recorded by a glass microelectrode. Two kinds of pain-related neurons were found: pain-excited neurons (PEN) and pain-inhibited neurons (PIN). The experimental protocol involved intra-DG administration of muscarinic cholinergic receptor (mAChR) agonist or antagonist. Intra-DG microinjection of 1 microl of ACh (0.2 microg/microl) or 1 microl of pilocarpine (0.4 microg/microl) decreased the discharge frequency of PEN and prolonged firing latency, but increased the discharge frequency of PIN and shortened PIN inhibitory duration (ID). Intra-DG administration of 1 microl of atropine (1.0 microg/microl) showed exactly the opposite effects. According to the above experimental results, we can presume that cholinergic pain-related neurons in DG are involved in the modulation of the nociceptive response by affecting the discharge of PEN and PIN.

[Study on protective effect of vitamin E for ovarian grandlose cells and its mechanism in aged rats].

AIM: To observe the effect of vitamin E (VE) on ovarian apoptosis-related protein Bcl-2 and Bax and its impact on antioxidant capacity in aged female rats and to study the senility-delaying effect and mechanism of VE on ovary. METHODS: Natural aging female rats were given different doses of exogenous VE. Then apoptosis regulatory protein Bcl-2, Bax expression in ovarian grandlose cells were detected by using immunohistochemical methods and Western blot. The contents of serum total superoxide dismutase (SOD) activity and malondialdehyde (MDA) were detected by using biochemical methods. RESULTS: Contrasted with adult control group, the level of Bcl-2 expression in Senile control group was lower and the level of Bax expression was higher (P < 0.01), Serum SOD activity decreased and the level of MDA significantly increased (P < 0.01). Contrasted with senile control group, the level of Bcl-2 expression increased in VE group, the level of Bax expression decreased (P < 0.05), the level of MDA expression significantly decreased (P < 0.01). CONCLUSION: VE can regulate apoptosis-related protein Bcl-2, Bax expression and confront free radical damage which contribute to a protective effect for ovarian grandiose cells.

Morphine dependence changes the role of droperidol on pain-related electric activities in caudate nucleus.

Droperidol causes the blockage of the dopamine receptors in the central nervous system that are involved in pain transmission. However, the mechanism of action of droperidol in pain-related neurons is not clear, and it is still unknown whether opioids are involved in the modulation of this processing. The present study examines the effect of droperidol on the pain-evoked response of pain-excitation neurons (PENs) and pain-inhibition neurons (PINs) in the caudate nucleus (Cd) of rats. The trains of electric impulses applied to the sciatic nerve were used as noxious stimulation. Our results revealed that droperidol decreased the frequency of PEN discharge, and increased the frequency PIN discharge evoked by the noxious stimulation in the Cd of normal rats, while administration of droperidol to morphine-dependent rats produced the opposite response. Those demonstrated that droperidol is involved in the modulation of nociceptive information transmission in Cd, and there were completely opposite responses to painful stimulation between normal and morphine-dependent rats after administration of droperidol.