A subpopulation of reactive astrocytes at affected neuronal perikarya after hypophysectomy in adult rats

Interleukin-1 reduces food intake and body weight in rat by acting in the arcuate hypothalamus

A reduction in food intake is commonly observed after bacterial infection, a phenomenon that can be reproduced by peripheral administration of Gram-negative bacterial lipopolysaccharide (LPS) or interleukin-1beta (IL-1β), a pro-inflammatory cytokine released by LPS-activated macrophages. The arcuate nucleus of the hypothalamus (ARH) plays a major role in food intake regulation and expresses IL-1 type 1 receptor (IL-1R1) mRNA. In the present work, we tested the hypothesis that IL-1R1 expressing cells in the ARH mediate IL-1β and/or LPS-induced hypophagia in the rat. To do so, we developed an IL-1β-saporin conjugate, which eliminated IL-R1-expressing neurons in the hippocampus, and micro-injected it into the ARH prior to systemic IL-1β and LPS administration. ARH IL-1β-saporin injection resulted in loss of neuropeptide Y-containing cells and attenuated hypophagia and weight loss after intraperitoneal IL-1β, but not LPS, administration. In conclusion, the present study shows that ARH NPY-containing neurons express functional IL-1R1s that mediate peripheral IL-1β-, but not LPS-, induced hypophagia. Our present and previous findings indicate that the reduction of food intake after IL-1β and LPS are mediated by different neural pathways.

Absence of axonal sprouting following unilateral lesion in 125-day-old rat supraoptic nucleus may be due to age-dependent decrease in protein levels of ciliary neurotrophic factor receptor alpha

Within the supraoptic nucleus (SON) of a 35-day-old rat, we previously demonstrated a collateral sprouting response that reinnervates the partially denervated neural lobe (NL) after unilateral lesion of the hypothalamo-neurohypophysial tract. Others have shown a decreased propensity for axonal sprouting in an aged brain; therefore, to see if the SON exhibits a decreased propensity for axonal sprouting as the animal ages, we performed a unilateral lesion in the 125-day-old rat SON. Ultrastructural analysis of axon profiles in the NL of the 125-day-old rat demonstrated an absence of axonal sprouting following injury. We previously demonstrated that ciliary neurotrophic factor (CNTF) promotes process outgrowth from injured magnocellular neuron axons in vitro. Thus, we hypothesized that the lack of axonal sprouting in the 125-day-old rat SON may be due to a reduction in CNTF or the CNTF receptor components. To this point, we found that as the rat ages there is significantly less CNTF receptor alpha (CNTFRα) protein in the uninjured, 125-day-old rat compared to the uninjured, 35-day-old rat. We also observed that protein levels of CNTF and the CNTF receptor components were increased in the SON and NL following injury in the 35-day-old rat, but there was no difference in the protein levels in the 125-day-old rat. Altogether, the results presented herein demonstrate that the plasticity within the SON is highly dependent on the age of the rat, and that a decrease in CNTFRα protein levels in the 125-day-old rat may contribute to the loss of axonal sprouting following axotomy.

A rat model for pituitary stalk electric lesion-induced central diabetes insipidus: application of 3D printing and further outcome assessments

A stable and reproducible rat injury model is not currently available to study central diabetes insipidus (CDI) and the neurohypophyseal system. In addition, a system is needed to assess the severity of CDI and measure the accompanying neurobiological alterations. In the present study, a 3D-printed lesion knife with a curved head was designed to fit into the stereotaxic instrument. The neuro-anatomical features of the brain injury were determined by in vivo magnetic resonance imaging (MRI) and arginine vasopressin (AVP) immunostaining on brain sections. Rats that underwent pituitary stalk electrical lesion (PEL) exhibited a tri-phasic pattern of CDI. MRI revealed that the hyperintenseT1-weighted signal of the pituitary stalk was interrupted, and the brain sections showed an enlarged end proximal to the injury site after PEL. In addition, the number of AVP-positive cells in supraoptic nucleus (SON) and paraventricular nucleus (PVN) decreased after PEL, which confirmed the success of the CDI model. Unlike hand-made tools, the 3D-printed lesion knives were stable and reproducible. Next, we used an ordinal clustering method for staging and the k-means’ clustering method to construct a CDI index to evaluate the severity and recovery of CDI that could be used in other multiple animals, even in clinical research. In conclusion, we established a standard PEL model with a 3D-printed knife tool and proposed a CDI index that will greatly facilitate further research on CDI.

Sex-dependent regulation of hepatic CYP3A by growth hormone: Roles of HNF6, C/EBPα, and RXRα

Sex-based differences in the pharmacological profiles of many drugs are due in part to the female-predominant expression of CYP3A4, which is the most important CYP isoform responsible for drug metabolism. Transcription factors trigger the sexually dimorphic expression of drug-metabolizing enzymes in response to sex-dependent growth hormone (GH) secretion. We investigated the roles of HNF6, C/EBPα, and RXRα in the regulation of human female-predominant CYP3A4, mouse female-specific CYP3A41, and rat male-specific CYP3A2 expression by GH secretion patterns using HepG2 cells, growth hormone receptor (GHR) knockout mice as well as rat models of orchiectomy and hypophysectomy. The constitutive expression of HNF6 and RXRα was GH-dependent, and GHR deficiency decreased HNF6/C/EBPα complex levels and increased HNF6/RXRα complex levels. Feminine GH secretion induced the binding of HNF6 and C/EBPα to the CYP3A4 and Cyp3a41 promoters and HNF6/C/EBPα complex levels was more efficiently compared with masculine pattern. Additionally, a greater inhibition of the binding of RXRα to the CYP3A4 and Cyp3a41 promoters and HNF6/RXRα complex levels was observed by feminine GH secretion, but less inhibition was observed by masculine pattern. The binding of HNF6, C/EBPα, and RXRα to the CYP3A2 promoter was not directly regulated by androgens. RXRα completely abolished the synergistic activation of the CYP3A4, Cyp3a41, and CYP3A2 promoters by HNF6 and C/EBPα. The results demonstrate that sex-dependent GH secretion patterns affect the expressions and interactions of HNF6, C/EBPα, and RXRα as well as their binding to CYP3A genes. RXRα mediates the sex-dependent influence of GH on CYP3A expression as an important signalling molecule.

Assessment of the rate of spinal motor axon regeneration by choline acetyltransferase immunohistochemistry following sciatic nerve crush injury in mice

OBJECT

The purpose of this study was to examine whether choline acetyltransferase (ChAT) staining can be used for assessing the rate of motor neuron regeneration at an early phase of axon outgrowth.

METHODS

The authors developed a new sciatic nerve crush model in adult mice. In this model, in addition to performing a sciatic nerve crush injury, the authors excised the ipsilateral lumbar L3-6 dorsal root ganglion (DRG), which resulted in degeneration of the sensory fibers entering into the sciatic nerve. Crushed nerve sections obtained at Day 3 or Day 7 postinjury were analyzed by means of immunostaining.

RESULTS

The immunostaining showed that ChAT, a motor axon-specific antigen, was totally co-localized with growth-associated protein 43 (GAP-43), which is expressed in regenerating nerves and transported into growth cones.

CONCLUSIONS

Our results suggest that measuring the length of motor axon outgrowth by ChAT immunostaining is reliable. ChAT staining provides a more convenient method for evaluating the rate of motor axon outgrowth in a mixed nerve.

Existence of different types of senile plaques between brain and spinal cord of TgCRND8 mice

Conflicting findings exist regarding the formation of diffuse and dense-core β-amyloid (Aβ) plaques in Alzheimer's disease (AD). In the present study, we characterized Aβ plaque types in the brain and spinal cord of TgCRND8 mice, which express a transgene incorporating both the Indiana mutation (V717F) and the Swedish mutations (K670N/M671L) in the human amyloid-β protein precursor (APP) gene. By combining immunohistochemistry and thioflavin S staining, we were able to define dense-core and diffuse plaques in neocortex of the brain and spinal cord of 9 week-, 5 month-, 10 month- and 20-month-old TgCRND8 mice. The senile plaques in the neocortex were predominantly dense-core plaques, even in the youngest mice. However, diffuse plaques were instead detected in spinal cord of the mice, regardless of age. Our results that relative predominance of dense-core plaques in the neocortex and diffuse plaques in the spinal cord of TgCNRD8 mice of all disease durations argue against the notion that diffuse plaques may represent an early stage in the evolution of dense-core plaques. Furthermore, we also found that the ratio of Aβ42/Aβ40 of the brain was much higher than that of the spinal cord by Aβ ELISA assay. Our findings strongly indicate that diffuse and dense-core plaques may form via independent processes in AD and Aβ42 is more prone to form dense-core plaques than is Aβ40.