Infantile Rats Research Articles

Effects of Melatonin on the Cerebellum of Infant Rat Following Kaolin-Induced Hydrocephalus: a Histochemical and Immunohistochemical Study.

Hydrocephalus is a developmental disorder causing abnormally collected cerebrospinal fluid within the cerebral ventricles. It leads to bigger skulls and many dysfunctions related to the nervous system. Here, we addressed whether exogenous melatonin administration could reverse the clinical features of kaolin-induced hydrocephalus in infantile rats. A controlled double-blinded study was conducted in 2-week-old 45 Wistar albino rats, which were divided into three groups: Group A, the control group, received intracisternal sham injection with solely the needle insertion; group B, the hydrocephalus group, was treated with isotonic NaCl after kaolin injection; and group C, the hydrocephalus + melatonin group, was given i.p. exogenous melatonin at a dose of 0.5mg/100g body weight after kaolin injection. Histological and immunohistochemical analyses were performed after the induction of hydrocephalus and melatonin administration. Glial fibrillary acidic protein was stained by immunohistochemical method. TUNEL method was used to define and quantitate apoptosis in the cerebellar tissues. Statistical analysis was performed by nonparametric Kruskal-Wallis H test, and once significance was determined among means, post hoc pairwise comparisons were carried out using Mann-Whitney U test. We found that melatonin administration significantly ameliorated ratio of substantia grisea area/substantia alba area in the cerebellum of infantile rats. Histologically, there was a significant reduction in the number of cerebellar apoptotic cells after the hydrocephalus induced by kaolin (P < 0.05). Our results clearly revealed that the histopathological changes in the cerebellum were reversed by systemic melatonin administration in infantile rats with kaolin-induced hydrocephalus. Nevertheless, further studies are needed to suggest melatonin as a candidate protective drug in children with hydrocephalus.

Prenatal Exposures of Male Rats to the Environmental Chemicals Bisphenol A and Di(2-Ethylhexyl) Phthalate Impact the Sexual Differentiation Process.

The increasing incidence of reproductive anomalies, described as testicular dysgenesis syndrome, is thought to be related to the exposure of the population to chemicals in the environment. Bisphenol A (BPA) and di(2-ethylhexyl)phthalate (DEHP), which have hormonal and antihormonal activity, have attracted public attention due to their presence in consumer products. The present study investigated the effects of BPA and DEHP on reproductive development. Timed-pregnant female rats were exposed to BPA and DEHP by gavage from gestational days 12 to 21. Results showed that prenatal exposures to test chemicals exerted variable effects on steroidogenic factor 1 and GATA binding protein 4 protein expression and increased (P < .05) sex-determining region Y-box 9 and antimüllerian hormone protein in the infantile rat testis compared with levels in the control unexposed animals. Pituitary LHβ and FSHβ subunit protein expression was increased (P < .05) in BPA- and DEHP-exposed prepubertal male rats but were decreased (P < .05) in adult animals relative to control. Exposure to both BPA and DEHP in utero inhibited (P < .05) global DNA hydroxymethylation in the adult testis in association with altered DNA methyltransferase protein expression. Together the present data suggest that altered developmental programming in the testes associated with chemical exposures are related to the disruption of sexual differentiation events and DNA methylation patterns. The chemical-induced effects impact the development of steroidogenic capacity in the adult testis.

Neuroimaging of white matter abnormalities in pediatric hydrocephalus

Hydrocephalus (HCP) is a severe pathologic condition in which the ventricular system enlarges in response to abnor- mal cerebrospinal fluid production and absorption mechanisms. While accumulating evidence implicates damage to various white matter (WM) structures as one of the major neurobiological mechanisms underlying poor behavioral outcomes in children with HCP, current evaluation of such damage remains limited. Diffusion tensor imaging (DTI) is a unique magnetic resonance technique that exploits differences in the diffusion properties of water molecules in different tissue. Anisotropic diffusion prop- erties, as measured by DTI, are strongly influenced by the micro-structural components of WM and thus can help to assess the properties in tissue constituents, tissue microstructure and cytoarchitecture. Initial clinical studies have shown that DTI is a sen- sitive imaging tool for investigating WM damage as well as the extent of recovery in HCP. A key study has shown that the periventricular WM and corona radiata in children between 12-18 years exhibited increased pre-operative fractional anisotropy (FA) driven by a slightly increased axial diffusivity and a more dramatic decreased radial diffusivity. Post-operatively the FA in these regions returned to normal in most patients. In contrast, the corpus callosum was found to have low FA pre-operatively which did not respond to cerebrospinal fluid diversion surgery. A more recent study reported a similar lower FA and higher mean diffusivity in the corpus callosum in infants. However, the abnormalities in the internal capsule were found to be more heterogeneous. Longitudinal study showed that most DTI measurements returned to normal post-operatively. In experimental studies, similar abnormalities in DTI were found in both neonatal and infantile rats with induced HCP. These findings correlated with increased astrocyte and microglial reactivity and reduced myelination. This review also discusses interpretations regarding the different patterns of DTI abnormalities seen in HCP in different WM regions. Overall, support is growing for DTI as a useful non-invasive imaging tool in the diagnosis and treatment of pediatric hydrocephalus.

Histological evaluation of the prefrontal cortex of infantile Wistar rats exposed to nicotine during the embryonic period

Exposure to nicotine in utero is neuroteratogenic, predisposing the developing brain to cell injury and many forms of neurological and neurobehavioural problems that persist after birth. The current study examined some of the histological effects of prenatal nicotine exposure on the prefrontal cortex of infantile rats. Primiparous Wistar rats were mated, and pregnancy was confirmed. A daily dose of 0.03 mg/kg of nicotine was administered intra-peritoneally to each treated rat for five consecutive days during their first two weeks of gestation. The rate of development and maturation of brain cells was reduced, as well as a reduction in the population of cells, though no apparent reduction of brain weight or morphological changes was noticed.Keywords: prenatal nicotine, prefrontal cortex, infantile rats

The expression of α-smooth muscle actin during the lung injury induced by hyperoxia

To explore the expression of α-smooth muscle actin (α-SMA) during the lung injury induced by hyperoxia in infantile rats. Sixty-four male Sprague-Dawley (SD) rats about 3 weeks were randomly assigned into normal control group which exposured to room air [fraction of inspired oxygen (FiO(2)) was 0.21] and hyperoxia exposure group (95%O(2)) according to random digits table. Eight rats in each group were randomly sacrificed at day 1, 7, 14 and 21.Pulmonary tissue remodeling was observed by hematoxylin-eosin (HE) staining. Immunohistochemistry method was performed to evaluate the expression of α-SMA in pulmonary tissue, further Western blotting was also made to determine the expression of α-SMA. The early histopathologic changes after HE were inflammation and edema in pulmonary tissue, while the later changes were interstitial hyperplasia and fibroblast proliferation. The expression of α-SMA was very slight in bronchial epithelium, alveolar epithelium and alveolar interstitium in normal control group, but increased with the time of hyperoxia exposure prolonged and peaked at 21st day. Western blotting detected that the expression of α-SMA after hyperoxia exposure for 1 day and 7 days in hyperoxia exposure group presented no difference compared with normal control group (1.02±0.12 vs. 1.00±0.13, 1.05±0.14 vs. 0.99±0.12, both P>0.05), but the expression of α-SMA after hyperoxia exposure for 14 days and 21 days was increased compared with normal control group (1.27±0.21 vs. 1.05±0.15, 2.26±0.28 vs. 1.05±0.14, P<0.05 and P<0.01). Pulmonary fibrosis remodeling was caused by hyperoxia exposure. The expression of α-SMA in pulmonary tissue in hyperoxia exposure groups obviously increased, and could play an important role in pulmonary fibrosis remodeling.

Vascular and Cardiac Effects of Stress in Albino Rats of Different Sex and Age Groups

Stress exposure induced similar cardiac effects in male and female infantile rats, but vascular reactions to stress in males were more pronounced than in females. In mature male rats (but not in females), both cardiac and vascular responses to stress decreased in comparison with infantile animals. In adult rats, cardiac effects of stress were more pronounced than the vascular response; females demonstrated greater cardiac response and less significant vascular reactions than males. Aging was accompanied by a decrease in the cardiac response and increase in the vascular reaction to stress. These changes were more significant in females than in males. In contrast to infantile and adult animals, old females demonstrated greater vascular response to stress than male rats. The observed sex-dependent changes in the ontogeny of vascular and cardiac response to stress are discussed in light of sex- and age-related peculiarities of hypertension development.

Maturation-dependent spontaneous healing of partial thickness cartilage defects in infantile rats

Partial-thickness articular cartilage defects (PTCDs) do not heal spontaneously and are thought to be a predisposing factor for the development of osteoarthritis. Younger and smaller animals have a better healing capacity for many types of injuries including those to articular cartilage. Our aim was to examine the longitudinal histological changes of immature murine articular cartilage after the creation of small PTCDs and to compare them to PTCDs in mature cartilage. Single linear PTCDs were created in 3-week-old and 16-week-old rats in the direction of joint motion. At 6 and 12weeks after PTCD creation, histological changes were examined in the defect sites and surrounding cartilage. Immature cartilage showed a higher repair capability than mature cartilage. Although repaired immature cartilage had fibrocartilage, it exhibited better quality than any PTCD model, except for a fetus model and comparable quality to full-thickness cartilage defects (FTCD) after bone marrow stimulation. Elucidation of the underlining mechanisms that immature cartilage possesses for repairing PTCDs is necessary in order to aid the prevention or develop treatment for osteoarthritis.

Development of an experimental model of cholestasis induced by hypoxic/ischemic damage to the bile duct and liver tissues in infantile rats

We aimed to develop experimental models of hypoxia/ischemia-induced cholestasis using neonatal and infantile rats. Hypoxia/ischemia was induced in the bile duct (BD) by injecting prostaglandin (PG) at birth and/or by coagulation of the hepatic artery (CHA) at about 3weeks after birth. The rats were divided into 6 groups: control; PG-injected; sham-operated with or without PG; CHA; and CHA+PG. CHA was also performed in adult rats. Liver specimens and blood samples were obtained at 5weeks after birth, and immunohistochemical and biochemical examinations were performed. (1) BD proliferation with fibrosis (BDPF) was found in the intrahepatic portal tract in the CHA and CHA+PG groups. Low-grade BDPF was observed in the PG group. (2) Cyst formation in the extrahepatic BD (EBD) was observed in the porta hepatis of some rats in the CHA and CHA+PG groups. In these groups, the number of peribiliary vascular plexuses (PVPs) decreased. BD proliferation and infiltration of inflammatory cells were observed in the EBD wall in the CHA+PG group. (3) Ki-67 was expressed in BD and EBD cells in the CHA+PG group. (4) BDPF was not detected in adult rats with CHA. (5) Serum liver function tests indicated obstructive changes in the EBD in the CHA and CHA+PG groups. Reduced blood flow in the EBD during infancy induced BDPF and obstructive changes in the EBD, which may, along with immature PVP and inflammatory changes in the EBD, contribute to hypoxia/ischemia of the EBD.

Neuroprotective effect of memantine on hippocampal neurons in infantile rat hydrocephalus

The effect of memantine administration on hippocampal neurons of the infantile rats with kaolin induced hydrocephalus was investigated. Hydrocephalus was induced by injecting kaolin into the cisterna magna of 3-weeks old Sprague-Dawley rat pups. One group received a single daily dose of 20mg/kg memantine i.p. following hydrocephalus induction for a period of two weeks. By the end of the two-week period, animals were radiologically evaluated by magnetic resonance imaging and then sacrificed to get their cerebrums removed. Both immunohistochemical analysis of nitric oxide synthase activity and quantification of spared neurons in CA1, CA2 and CA3 regions of hippocampus were performed. In hydrocephalus-induced rats considerable neuronal loss associated with significantly increased nitric oxide synthase immunoreactivity were determined in all hippocampal regions. However, memantine treated rats showed significantly higher number of spared neuron counts and reduced nitric oxide synthase immunoreactivity in CA1 and CA2 regions compared with the non-treated rats. The findings of the study show that hippocampal neurons may constitute important targets for injury secondary to hydrocephalic process in experimental infantile hydrocephalus. Early anti-excitotoxic treatment with memantine seems to have a neuroprotective effect especially in the CA1 and CA2 subunits of the hippocampus.

Effects of hyperoxia on inflammatory response in lung of infantile rats

To investigate the effects of hyperoxia on inflammatory response in lung of infantile rats. Forty 21-day-old male Sprague-Dawley (SD) rats were randomly divided into five groups: room-air control group and 12, 24, 48, 72 hours hyperoxia groups, with the rats continuously exposed to room-air and oxygen (92%-94%) respectively. The rats were sacrificed by depletion method, and lung tissue was obtained for bronchoalveolar lavage. The contents of malondialdehyde (MDA) and the activities of myeloperoxidase (MPO) in lung tissue were assayed by thiobarbituric acid or chromometry, and the concentrations of tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6) and IL-10 in bronchoalveolar lavage fluid (BALF) were measured by enzyme linked immunosorbent assay (ELISA). The lung pathology was examined, and lung injury score was assessed. Compared with the room-air control group, the contents of MDA [(2.24+/-0.43) mmol/g vs. (1.57+/-0.31) mmol/g] and the activities of MPO [(1.24+/-0.25) U/g vs. (0.69+/-0.22) U/g] from lung tissue were elevated at 12 hours and 24 hours of hyperoxia exposure, respectively, and they further increased with prolongation of hyperoxia exposure (P<0.05 or P<0.01). The values of TNF-alpha [(135.2+/-44.0) ng/L vs. (94.5+/-22.3) ng/L], IL-6 [(73.1+/-14.2) ng/L vs. (55.7+/-17.3) ng/L] and IL-10 [(67.9+/-21.7) ng/L vs. (48.2+/-7.6) ng/L] in BALF were all higher at 24 hours of hyperoxia exposure than those of the room-air control group (P<0.05 or P<0.01), but decreased at 48 hours of hyperoxia exposure compared with those of 24-hour hyperoxia exposure group [TNF-alpha: (105.4+/-17.0) ng/L, IL-6: (54.3+/-17.4) ng/L, IL-10: (50.9+/-6.9) ng/L, all P<0.05]. Lung injury scores were higher at 12 hours of hyperoxia exposure as compared with those of the room-air control group (4.5+/-1.4 vs. 1.3+/-0.5), and it further increased with prolongation of hyperoxia exposure (P<0.05 or P<0.01). Hyperoxia can lead to lung inflammatory injury in infantile rats, and the expressions of TNF-alpha, IL-6 and IL-10 in BALF may reach the peak at 24 hours of hyperoxia exposure.

Chronic low dose Adderall XR® down-regulates cfos expression in infantile and prepubertal rat striatum and cortex

We previously reported that treatment of prepubertal male rats with low, injected or oral, doses of methylphenidate stimulated cfos, fosB and arc expression in many areas of the developing brain. In the present study our objective was to determine whether the widely prescribed psychostimulant Adderall XR® (ADD) exerted similar effects in infantile and prepubertal rat brain. We report here, for the first time, that low threshold doses of oral ADD, an extended-release mixture of amphetamine salts, now routinely used for the treatment of Attention Deficit Hyperactivity Disorder (ADHD), also increased cfos expression in infantile (postnatal day 10; PD10) and prepubertal (PD24) rat brain. These threshold doses were correlated with blood levels of amphetamine determined by liquid chromatography–mass spectrometry. Moreover, we observed that chronic treatment with oral ADD (1.6 mg/kg; ×14 days) not only significantly down-regulated cfos expression following a final challenge dose of ADD in prepubertal (PD24) rat striatum and cortex, quantified in terms of FOS immunoreactivity (FOS-ir), but did so at a daily dose that was without effect with methylphenidate (MPH); that is a much higher oral dose of MPH (7.5 mg/kg; ×14 days) failed to induce down-regulation of cfos expression. Similar experiments in infantile rats (PD10), but using a threshold injected dose of ADD (1.25 mg/kg sc) also significantly reduced striatal and cingulate cortical FOS-ir. An additional finding in the prepubertal rats was that oral ADD-induced FOS-ir was observed in the cerebral cortex following doses lower than the threshold dose necessary to increase FOS-ir in the striatum. This was not the case in the PD10 rats. In conclusion, our efforts to calibrate biological responses, such as immediate early gene expression, to clinically relevant blood levels of stimulants confirmed that expression of cfos is very sensitive to repeated low doses of Adderall XR®. It is now feasible to examine whether other genes are also affected in these young rats and if the changes we report are reversible. The implications of such studies should be relevant to the putative effects of psychostimulant treatment of very young children.

Effect of Age and Sex on Blood Pressure, Development of Renal Hypertension, and Concentration of Nitric Oxide in the Blood of Albino Rats

The mean blood pressure did not depend on the sex of animals and was characterized by the same ontogenetic changes in males and females. The mean blood pressure in infantile and, particularly, in old rats was higher than in adult animals. The increase in blood pressure in old rats was accompanied by a decrease in NO production. Infantile rats were least resistant to the development of renal hypertension. The degree of hypertension in infantile and adult females was lower than in males. However, the concentration of NO in these females was higher than in male rats. Aging was accompanied by inversion of sex differences in the resistance to renal hypertension. The severity of hypertension in old females was greater than in males. It was accompanied by a significant age-related decrease in NO concentration in female animals. Our results indicate that NO plays an important role in sex differences in the resistance of infantile, adult, and old rats to hypertension, while the decrease in NO concentration during aging leads to blood pressure elevation in females and males.

Expression of caspase-3 and FasL in the hippocampns of the infantile rats with recurrent seizures

Objective To investigate the expression of caspase-3 and FasL in the hippocampus of the infantile rats with recurrent sei-zures. Methods 72 of 20-day-old Sprague-Dawley rats were randomly divided into two groups, control group and seizure group. Seizures in rats were induced by inhalant flurothyl daily in six consecutive days. Brain tissue was sampled at different time points (the 1st day, 3rd day and 7th day) after last seizure. The expressions of caspase-3 and FasL proteins in the hippocampus were detected by immunohistochemistry, and the expression of caspase-3 mRNA was measured by reverse transcription- polymerase chain reaction (RT-PCR). Results The caspase-3 protein, FasL protein and caspnse-3 mRNA levels were obviously increased at the 1st, 3rd and 7th day after recurrent seizure in the hippocampus of the rat(P<0.01). Conclusions Caspase-3 and FasL are participated in the infantile brain injury after recurrent seizures. Key words: Convulsions△/ME/PA; Hippocampus/ME/PA; Caspnses/ME; Antigens, CD95

The protective effects of ginkgo biloba extract 761 on cultured large retinal ganglion cells in infantile rats

Objective To investigate the protective effects of ginkgo biloba extract (EGb) 761 on retinal ganglion cells (RGC) in rats,and to establish a method to define the rat RGC using fluorogold as a fluorescence dye.Methods RGC of 12 20-day-old Sprague-Dawley rats were labeled by injecting fluorogold into superior colliculus.The eyeball enucleation was performed 6 days later.Retinal stretched preparation was obtained from one eye to observe the label result under fluorescence microscope,and the retina from the other eye was detached to make the cell suspension to observe the configuration of stained RGC under the contrast fluorescence microscope.The cell suspension was divided into the control group and Egb761 groups with the concentration of 0.03%,0.10%,0.30%,1.00%,and 3.00%.Trypan blue dye was used to evaluate cells viability and the survival rate of the large retinal ganglion cells was calculated.Results The sign of the RGC was clear after labeled by fluorogold.The characteristics of large RGC were obvious.After detachment,large RGC died quickly in the cell suspension and the fluorescence disappeared.The result of Trypan blue staining indicated that large RGC died rapidly in the cell suspension.Large RGC in EGb761 group showed significantly better survival rates than that in control group at different time sites (P<0.01) in a dose-dependent manner (P<0.01).Conclusions EGb761 has a significant protective effect on large RGC cultivated in vitro,and retrolable method to identify RGC is feasible. Key words: Ginkgetin/therapeutic use; Ginkgolides/therapeutic use; Retinal ganglion cells/drug effects! Animal experimentation

Neonatal Exposure to Bisphenol A Alters Reproductive Parameters and Gonadotropin Releasing Hormone Signaling in Female Rats

BackgroundBisphenol A (BPA) is a component of polycarbonate plastics, epoxy resins, and polystyrene and is found in many products. Several reports have revealed potent in vivo effects, because BPA acts as an estrogen agonist and/or antagonist and as an androgen and thyroid hormone antagonist.ObjectivesWe analyzed the effects of neonatal exposure to BPA on the reproductive axis of female Sprague-Dawley rats.MethodsFemale rats were injected subcutaneusly, daily, from postnatal day 1 (PND1) to PND10 with BPA [500 μg/50 μL (high) or 50 μg/50 μL (low)] in castor oil or with castor oil vehicle alone. We studied body weight and age at vaginal opening, estrous cycles, and pituitary hormone release in vivo and in vitro, as well as gonadotropin-releasing hormone (GnRH) pulsatility at PND13 and in adults. We also analyzed two GnRH-activated signaling pathways in the adults: inositol-triphosphate (IP3), and extracellular signal-regulated kinase1/2 (ERK1/2).ResultsExposure to BPA altered pituitary function in infantile rats, lowering basal and GnRH-induced luteinizing hormone (LH) and increasing GnRH pulsatility. BPA dose-dependently accelerated puberty onset and altered estrous cyclicity, with the high dose causing permanent estrus. In adults treated neonatally with BPA, GnRH-induced LH secretion in vivo was decreased and GnRH pulsatility remained disrupted. In vitro, pituitary cells from animals treated with BPA showed lower basal LH and dose-dependently affected GnRH-induced IP3 formation; the high dose also impaired GnRH-induced LH secretion. Both doses altered ERK1/2 activation.ConclusionsNeonatal exposure to BPA altered reproductive parameters and hypothalamic–pituitary function in female rats. To our knowledge, these results demonstrate for the first time that neonatal in vivo BPA permanently affects GnRH pulsatility and pituitary GnRH signaling.

O.065 Pathology of AD-related inflammatory and oxidative stress mediators in Kaolin-induced hydrocephalus model of the aged rat

The present study describes the biochemical changes, morphological development and the cerebrospinal fluid dynamics of the kaolin-induced hydrocephalus in the adult rat. Two, 4 and 6 weeks after microsurgical kaolin instillation into the rat cisterna magna the basal intracranial pressure and the cerebrospinal fluid outflow resistance were measured. To determine possible biochemical changes in the rat cerebrum, brain stem and cerebellum the concentrations of glutamine, glutamate, glutathione, aspartate, GABA, alanine and taurine were measured by high pressure liquid chromatography. In addition, ventriculomegaly and syringomyelia were assessed, measuring the lateral ventricles and central canals by means of an image-processing computer program. It could be shown that the acute phase of kaolin-induced hydrocephalus in the first 4 weeks is characterised by a high basal intracranial pressure, a considerably increased CSF outflow resistance and a rise in brain water content in the fourth week. The changes in the concentrations of amino acids were moderate. Glutamine was increased and taurine was decreased in the cerebrum and alanine was increased in the brain stem. The chronic phase, however, is defined by normal basal pressure, declining outflow resistance, progression of ventriculomegaly and distinct changes in the biochemical parameters such as a remarkable decrease of glutamate, glutamine and taurine in the cerebellum, a decrease of taurine and alanine plus an increase in glutamine in the cerebrum and an increase of alanine in the brain stem. Moreover, cerebral metabolism in the adult rat seems to be more resistant to the effects of hydrocephalus than metabolism in neonatal and infantile rats.

Effects of ghrelin on neuronal activity in the ventromedial nucleus of the hypothalamus in infantile rats: An in vitro study

Ghrelin is an endogenous ligand for the growth hormone (GH) secretagogue (GHS) receptor (GHS-R) and a potent stimulant for GH secretion even in infantile rats before puberty. Although the ventromedial nucleus of the hypothalamus (VMH) might be a site of action for ghrelin to induce GH release, the electrophysiological effect of ghrelin on VMH neurons in infantile rats remains to be elucidated. Thus, the purpose of the present study was to investigate the effect of ghrelin on VMH neurons using hypothalamic slices of infantile rats. Ghrelin excited a majority of VMH neurons in a concentration-dependent manner. VMH neurons that were excited by GH releasing peptide-6 (GHRP-6), a synthetic GHS, were also excited by ghrelin and vice versa. Repeated application of ghrelin to the same VMH neuron decreased progressively the excitatory responses depending on the number of times it was administered. The excitatory effect of ghrelin on VMH neurons in normal artificial cerebrospinal fluid (ACSF) persisted in low Ca2+-high Mg2+ ACSF. The present results indicate that (1) ghrelin excites a majority of VMH neurons dose-dependently and postsynaptically and (2) the excitatory effects of ghrelin are mimicked by GHRP-6 and desensitized by repeated applications of ghrelin.

Sexually Dimorphic Modulation of GABAA Receptor Currents by Melatonin in Rat Gonadotropin-Releasing Hormone Neurons

Gonadotropin-releasing hormone (GnRH) neurons represent the final output neurons in the central control of reproduction. gamma-Amino butyric acid (GABA), one of the major regulators of GnRH neurons, depolarizes GnRH neurons isolated from adult rats via GABA(A) receptors. The presence of GABA(A) receptors in GnRH neurons has also been demonstrated morphologically. Furthermore, the pineal hormone melatonin is involved in the regulation of reproductive function, including the timing of the luteinizing hormone surge. The suprachiasmatic nucleus and the GABAergic system in the medial preoptic area are considered as possible sites of the action of melatonin. Until now, however, a direct action of melatonin on GnRH neurons has not been reported. Therefore we examined the effect of melatonin on GABA(A) receptor currents in GnRH neurons isolated from GnRH-EGFP transgenic rats by means of perforated patch-clamp experiments. The GABA(A) receptor currents were modulated by melatonin in a sex-specific manner. In GnRH neurons from adult males, melatonin augmented these currents in 67% of the neurons examined, but attenuated the currents in only 19% of them. These modulations were blocked by the melatonin receptor antagonist luzindole, suggesting an involvement of melatonin receptors. The modulation by melatonin was not observed in GnRH neurons isolated from infantile rats. These findings indicate that GABA affects the excitability of GnRH neurons in adult rats through GABA(A) receptors, and that melatonin modifies this excitability via melatonin receptors in a sex-specific manner.

Melatonin ameliorates blood–brain barrier permeability, glutathione, and nitric oxide levels in the choroid plexus of the infantile rats with kaolin-induced hydrocephalus

Hydrocephalus is a disabling disease for children, but current data concerning the effects of melatonin on ventricular enlargement are still limited. We have investigated the changes in the choroid plexuses (CPs) of ventricles and blood–brain barrier (BBB) of hydrocephalic rats. Forty-five Swiss Albino rats at age 2 weeks were divided into three equal groups: control, hydrocephalus, and melatonin-treated hydrocephalus groups. Hydrocephalus was induced by kaolin injection into the cisterna magna of all pups except control group and melatonin was given at a daily dose of 0.5 mg/100 g body weight for 4 weeks. At the end of the study, one animal from each group was examined using a gamma camera to study the disruption of BBB due to hydrocephalus. All animals were then killed for assay of glutathione (GSH) and nitric oxide (NO), as well as histological study of the CPs during the hydrocephalus. We observed an increased BBB activity was found in hydrocephalus group, while melatonin reversed these changes. It was found that NO concentration was elevated in hydrocephalus group and melatonin partly abolished the increased levels of NO. In contrast, GSH levels were significantly decreased in hydrocephalus group, while melatonin increased the tissue GSH level ( p < 0.01). Histologically, there was a significant alteration in the CPs of the ventricles of hydrocephalic animals, but it was regressed after melatonin treatment in consistent with the gross morphological changes related to hydrocephalus. In conclusion, our results clearly demonstrated for the first time the neuroprotective effects of melatonin upon hydrocephalus-induced CP changes in infantile rats, but further studies are needed to suggest melatonin as a candidate protective drug in children.

The effect of hydrocephalus on lower esophageal sphincter smooth muscle reactivity: experimental study

Purpose The aim of this study was to assess the pharmacophysiological significance of the enteric nervous system for the mechanical responses of lower esophageal sphincter (LES) in infantile rats with kaolin-induced hydrocephalus. Material and methods Hydrocephalus was created in 7-day-old rats by injection of kaolin into the cisterna magna. After 10 days, rats were decapitated. Contractile (KCl, carbachol) and relaxant (isoprenaline, papaverine) responses were determined by using in vitro muscle technique in isolated LES smooth muscle strips. Results The receptor-mediated contractile and relaxant response to carbachol and isoprenaline in the LES smooth muscle was impaired in rats with hydrocephalus. There was no significant difference in the KCl and papaverine response in hydrocephalic and sham operated rats. Conclusion Our findings suggest that hydrocephalus may impair receptor-mediated contractile and relaxant activity of LES smooth muscle leading to gastroesophageal reflux.