Showing papers on "Pinealectomy published in 2009"

Melatonin promotes neurogenesis in dentate gyrus in the pinealectomized rat.

Abstract: It was previously shown that pinealectomy causes delayed loss of pyramidal neurons in rat hippocampal layers CA1/3 and that this is reversed by melatonin supplementation. Here, we used immunohistologic detection of doublecortin, a protein expressed in newborn neurons, to determine if melatonin supplementation promotes neurogenesis after pinealectomy. It was found that melatonin supplementation significantly increased the number of doublecortin immunoreactive neurons in the dentate gyrus over the postsurgical intervals of 2, 4, 6, 8, 10 and 17 months. The increase was most evident at 6 months postsurgery and thereafter, and was apparent despite a severe decline in doublecortin-labeled cells over the 17 month postsurgical interval in all groups of rats. Doublecortin immunoreactive cells were not observed in the pyramidal layer itself. These results indicate that melatonin promotes neurogenesis in the dentate gyrus of pinealectomized rats. However, it is equivocal that these newborn neurons migrate to the pyramidal layer and account for the reappearance of neurons at this location in these rats. This study provides further evidence for a role of melatonin in promoting neurogenesis, adding another role to its already remarkably pleiotropic profile. The scope and significance of this newly discovered role remains to be determined.

Mucosal strengthening activity of central and peripheral melatonin in the mechanism of gastric defense.

Abstract: This review summarizes the involvement of centrally and peripherally applied melatonin, a major hormone of pineal gland, in the mechanism of gastric mucosal integrity, gastroprotection and ulcer healing. Melatonin was originally shown to attenuate gastric mucosal lesions but the controversy exists in the literature as to whether melatonin derived from the pineal gland, considered as the major source of this indole or rather that locally generated from L-tryptophan within gastric mucosa, plays predominant role in the mechanism of gastrointestinal integrity. Both, intragastric (i.g.) and intracerebroventricular (i.c.v.) administration of melatonin and its precursor, L-tryptophan to rats without or with removed pineal gland by pinealectomy attenuates in the dose-dependent manner the formation of on gastric lesions induced by topical irritants and water immersion restraint stress (WRS). Melatonin accelerated the gastric ulcer healing and this was accompanied by the rise in gastric blood flow (GBF), the plasma melatonin and gastrin levels, the mucosal generation of PGE(2) and luminal NO content. Pinealectomy, which suppresses the plasma melatonin levels, markedly aggravated the gastric lesions induced by WRS. Concurrent supplementation of pinealectomized animals with melatonin or L-tryptophan, the melatonin precursor, attenuated the lesions induced by WRS. Treatment with luzindole, an antagonist of Mel(2) receptors, or with L-NNA, the NO-synthase inhibitor, significantly attenuated melatonin- and L-tryptophan-induced protection and the acceleration of ulcer healing and the accompanying increase in the GBF and luminal content of NO. We conclude that 1) exogenous melatonin and that released from the L-tryptophan attenuate lesions induced by topical irritant such as ethanol and WRS via interaction with MT(2) receptors and due to an enhancement of gastric microcirculation, probably mediated by NO and PG derived from cNOS, iNOS and COX-2 overexpression and activity, and 2) the pineal gland plays an important role in the limitation of WRS-induced gastric lesions and acceleration of ulcer healing via releasing melatonin predominately at night time, that exerts gastroprotective and ulcer healing actions.

Pinealectomy in the chicken: a good model of scoliosis?

Abstract: The phenomenon of spinal deformity in the pinealectomized chicken has led researchers to postulate a disturbance of melatonin activity as a potential cause of adolescent idiopathic scoliosis (AIS). More recently, structural differences between curves seen in this model and those seen in scoliosis have been highlighted suggesting the deformities observed are not as similar as first thought. We examined melatonin levels, and the radiological and histological characteristics of scoliosis after pinealectomy in chickens. They underwent pinealectomy (P) at 2 days of age, sham surgery (S) or served as controls (C). Mean melatonin levels were 32.9 pmol/L (P), 175 pmol/L (S) and 227.3 pmol/L (C). Scoliosis developed in 75% of chickens after pinealectomy and 38% after a sham procedure. Nineteen percent of unoperated controls also developed scoliosis. A lower melatonin level was associated with the development of scoliosis (p ≤ 0.001), but exceptions were seen with levels up to 265 pmol/L observed in one case. Most of the curves occurring spontaneously and after sham surgery and almost half after pinealectomy were short angular curves: distinct from those resembling idiopathic scoliosis. These occur over one or two segments and are characterized by marked apical wedging, frequently associated with subluxation or dislocation. The intervertebral joint in the chicken is more like a synovial joint histologically than an intervertebral disc. This study highlights important differences between the chicken and the human, and between their respective spinal deformities. Caution is advised when drawing conclusions regarding the pathogenesis of AIS from this model.

Melatonin treatment decreases c-fos expression in a headache model induced by capsaicin.

Abstract: The aim of the present work was to analyze c-fos response within the trigeminal nucleus caudalis (TNC) of pinealectomized rats and animals that received intraperitoneal melatonin, after intracisternal infusion of capsaicin, used to induce intracranial trigeminovascular stimulation. Experimental groups consisted of animals that received vehicle solution (saline–ethanol–Tween 80, 8:1:1, diluted 1:50) only (VEI, n = 5); animals that received capsaicin solution (200 nM) only (CAP, n = 6); animals submitted to pinealectomy (PX, n = 5); sham-operated animals (SH, n = 5); animals submitted to pinealectomy followed by capsaicin stimulation (200 nM) after 15 days (PX + CAP, n = 7); and animals that received capsaicin solution (200 nM) and intraperitoneal melatonin (10 mg/kg) (CAP + MEL, n = 5). Control rats, receiving vehicle in the cisterna magna, showed a small number of c-fos-positive cells in the TNC (layer I/II) as well as the sham-operated and pinealectomized rats, when compared to animals stimulated by capsaicin. On the other hand, pinealectomized rats, which received capsaicin, presented the highest number of c-fos-positive cells. Animals receiving capsaicin and melatonin treatment had similar expression of the vehicle group. Our data provide experimental evidence to support the role of melatonin and pineal gland in the pathophysiology of neurovascular headaches.

Rat pinealectomy: a modified direct visual approach

Abstract: PURPOSE: To report a new, direct visual approach for rat pinealectomy. METHODS: Eighty adult female rats (Rattus norvegicus albinus EPM-1 strain) were weighted and anesthetized intraperitoneally with 15 mg/kg xylazine and 30 mg/kg ketamine. The animal was fastened to a dissection table, an incision was made in the skin and the subcutaneous tissue, bringing the lambda into view. The skullcap was opened with a dental drill, bringing the cerebral hemispheres and the superior sagittal sinus into view. The pineal gland, located under the venous sinus, was removed in a single piece using tweezers. Next, the bone fragment was returned to its place and the surgical layers were sutured. RESULTS: This new technique is easy to be done, avoids bleedings and removes only the pineal gland without damage to the remaining encephalon. In addition it makes possible the achievement of a sham surgery, allowing the pineal gland to remain intact. CONCLUSION: The proposed technique intends to facilitate studies aiming to better understanding the complexity and importance of the pineal gland on reproductive and other body systems.

Melatonin prevents peritoneal adhesions in rats.

Abstract: Background and Aim: Intra-abdominal adhesions are important postoperative complica- tions following abdominal surgery The adhesions that develop form the basis of more advanced pathology such as intestinal obstruction or infertility Melatonin is secreted from the pineal gland in a circadian pattern; this molecule has potent antioxidant characteristics and has beneficial effects in many models of inflammation The aim of this study was to evaluate the effects of melatonin on peritoneal adhesions created in rats Methods: Atotal of 28 Sprague-Dawley male rats were used and divided into four groups In the first phase of the study, pinealectomy (PINX) was performed on half the animalsAn incision was made and sutured in the cecum of all experimental animals in all groups 15 days after the PINX procedure Some animals were given melatonin orally at a dose of 5 mg/kg daily following the adhesion operation and continued for 15 days The rats were anesthetized and the abdomen opened after the 15th day (on day 30 of the study) After adhesion scoring based on macroscopic inspection, tissue samples were obtained from the sutured region of the cecum to measure malondialdehyde and hydroxyproline Results: Peritoneal adhesion density was significantly higher in the PINX group compared to the control animals; exogenously administered melatonin significantly reduced adhesion formation The degree of adhesion was also significantly lower in the intact rats given melatonin compared to the control group Conclusion: Antioxidant activity increases in the oxidative process We conclude that melatonin may be an important molecule in preventing peritoneal adhesions

Daily rhythms of spike coding in the rat supraoptic nucleus.

Abstract: Novel measures of coding based on interspike intervals were used to characterise the rhythms of single unit activity in the supraoptic nucleus during the day/night cycle in urethane-anaesthetised rats in vivo. Both continuously firing and phasic cells showed significant (P < 0.001) diurnal rhythms of spike frequency and in the irregularity of firing, as quantified by the log interval entropy (ENT). Comparison of rhythms in log interval ENT showed that the amplitude of the rhythms was greater for the continuously firing cells than for the phasic cells (P = 0.002). Rhythms persisted after hypertonic stimulation or pinealectomy and both treatments reduced the amplitude significantly only for the continuously firing cell group. By contrast, the mesor (i.e. mid-point of the rhythm) was reduced only for the phasic cell group. A similar analysis applied to the activity of cells of the suprachiasmatic nucleus showed that, after pinealectomy, there was a significant rhythm in ENT (P < 0.001) but not firing rate; however, the amplitude of the rhythm in ENT was attenuated (P = 0.047). Diurnal changes in the electrical activity of supraoptic cells are consistent with previously reported circadian changes in magnocellular neuropeptide release. Differences between continuous and phasic cell groups in the effects of osmotic stimulation on rhythmic activity indicate that the two cell types differ in their coding of osmolality and zeitgeber time information. The different effects of pinealectomy on the supraoptic and suprachiasmatic nuclei suggest that removal of endogenous melatonin unmasks a difference in circadian coding between the two nuclei.

Testosterone and melatonin effects on adrenal cortex of orchiectomized and pinealectomized rats.

Abstract: The study aimed to examine the effects of pinealectomy (PX) and melatonin on adrenal cortex of orchiectomized rats and to explain whether the testosterone action on adrenal cortex is modified by the pineal gland. Neither PX (53 days) nor melatonin administration (10 days) had an effect on the structure as well as on the studied functional parameters of the adrenal gland--corticosterone output by homogenates, 11 beta-hydroxylase and 5 alpha-reductase activities, liver corticosterone metabolism and serum corticosterone level. On the contrary, PX of 14 months duration resulted in an increase in 5 alpha-reductase activity. Testosterone administration into orchiectomized rats lowered corticosterone output and liver corticosterone metabolism and these effects were unaffected by PX or melatonin. Testosterone lowered 5 alpha-reductase and 11 beta-hydroxylase activities, the effects not modified by PX, however, after melatonin administration activities of these enzymes were similar as in orchiectomized rats. Obtained results cast doubts on a physiological role of the pineal gland and its principal hormone--melatonin--in regulation of adrenocortical structure and secretory activity and suggest that testosterone action on the rat adrenal cortex is not modified by the pineal gland.

The effect of pinealectomy and leptin hormone on the proliferation and apoptosis activation in Syrian hamster testis in different photoperiods.

Abstract: The effects of pinealectomy and leptin hormone on proliferative and apoptotic processes in the epithelia of testicular seminiferous tubules of Syrian hamsters have been investigated. Proliferative and apoptotic processes were assessed semi-quantitatively by proliferating cell nuclear antigen (PCNA) and caspase-3 immune stainings. Animals used in the study were divided into four groups; control, pinealectomy (PinX), leptin-treated (10 microg/mL/day/kg body weight, intraperitoneally) and pinealectomy + leptin groups. Half of the hamsters in each group were exposed to short and the other half to long photoperiods for 8 weeks. In short photoperiod, PCNA activity especially in spermatogonia was significantly higher in the pinealectomy and leptin-treated groups compared with the control group. Histological score (HSCORE) value of PCNA in the PinX + leptin group was lower than those of PinX and leptin-treated groups. HSCORE value of caspase-3 in PinX and PinX + leptin groups was increased. In the long photoperiod, PCNA activation in the PinX group was significantly lower than the control group while the differences between the controls and other groups were not significant. The difference between the increases in caspase-3 activity in the PinX and control groups was significant. Thus, it was observed that photoperiods had no effect on the proliferation activity in the control groups. The inhibiting effect of short photoperiod on testis was not observed throughout 8 weeks. PinX eliminated the inhibiting effect of short photoperiod but did not alter the stimulating effect of long photoperiod. Leptin did not show any effect in long photoperiod but decreased proliferation by stimulating melatonin in short photoperiod.

Pinealectomy in rat: an illustrative case

Abstract: The pineal body is known to be a vital component in the regulation of seasonal reproduction. The pineal complex may consist of two parts in rats, i.e. the small deep pineal and the large superficial pineal. As commonly used techniques of pinealectomy remove the superficial pineal only, we illustrated the surgical technique for pinealectomy on our rat specimen in this report.

Estradiol and melatonin effects on adrenal cortex of ovariectomized and pinealectomized rats.

Abstract: Studies on the effect of pinealectomy (PX) and melatonin on adrenal cortex of ovariectomized and estradiol replaced rats were performed. Neither PX nor melatonin replacement changed corticosterone output by adrenal homogenate, 11 beta-hydroxylase activity, liver corticosterone metabolism or serum corticosterone level, however, melatonin increased adrenal 5 alpha-reductase activity. On the other hand, PX of 14 months duration resulted in an increase in intraadrenal 5 alpha-reductase activity. PX did not modify estradiol effect on rat adrenal cortex, while concomitant estradiol-melatonin administration increased corticosterone output by adrenal homogenate. Stimulatory effect of estradiol on liver corticosterone metabolism was observed only in the presence of pineal gland or exogenous melatonin. In non of experiments, 45 nmole/ml of melatonin added into incubation medium stimulated adrenal 5 alpha-reductase activity. Obtained results cast doubt on a physiological role of melatonin in regulation of adrenocortical secretory activity in ovariectomized rats and suggest that estradiol effect on the adrenal cortex is not mediated by the pineal gland.

Effects of intracranial surgery on pineal lipid droplets, on other structures, and on melatonin secretion.

Abstract: Unique effects of sham-pinealectomy [intracranial surgery (IS)] which include reduced functional activity of the adrenal gland and suppressed circadian rhythms of the adrenal medulla, and which are reversed by pinealectomy, have been reported in rodents. To clarify the mechanisms, we investigated whether or what changes occur in pineal functional activity after IS. Sixty-six male rats of normal and IS groups were used at 50 days of age. The pineal gland was first examined by quantitative electron microscopy. The Sudan III-stained lipid droplet content of the pinealocytes and plasma melatonin level were then investigated using the same animals. In IS rats, the lipid droplet content of the pinealocytes decreased in both the dark and light phases 14 days after surgery. Mean volumetric ratio of nucleus, nucleolus, and mitochondria tended to increase in IS rats. The mean plasma concentration of melatonin showed apparent day-night changes, but no significant changes because of IS, 36 h and 14 days after surgery. But in the dark phase 14 days after surgery, plasma melatonin levels showed increased dispersion of values (P < 0.04). Thus, after IS the lipid content of pinealocytes showed changes not closely related to those of plasma melatonin level. From these and other results it is speculated that IS effects are dissimilar to usual stress responses, that day-night rhythms of functional activities of the pineal and adrenal medulla are differently controlled, and that pineal gland-dependent IS effects are most probably induced by changed sensitivity/states of target mechanisms to the pineal hormone melatonin.

Effect of pinealectomy on reproductive functions of male rats

Abstract: Objective To investigate the effect of pinealectomy on the reproductive functions of young rats.Methods Yong SD rats were randomly divided into sham operation group,pinealectomy group and melatonin administration group.We observed the reproductive actions and the weight of reproductive organs of rats after 1 month.Results The reproductive actions and the weight of epididymis increased significantly after pinealectomy.Conclusion The pineal inhibits the reproductive functions of young rats.

Rat pinealectomy. A modified direct visual approach 1 Pinealectomia em ratos. Técnica modificada com visualização direta

Abstract: Purpose: To report a new, direct visual approach for rat pinealectomy. Methods: Eighty adult female rats (Rattus norvegicus albinus EPM-1 strain) were weighted and anesthetized intraperitoneally with 15 mg/kg xylazine and 30 mg/kg ketamine. The animal was fastened to a dissection table, an incision was made in the skin and the subcutaneous tissue, bringing the lambda into view. The skullcap was opened with a dental drill, bringing the cerebral hemispheres and the superior sagittal sinus into view. The pineal gland, located under the venous sinus, was removed in a single piece using tweezers. Next, the bone fragment was returned to its place and the surgical layers were sutured. Results: This new technique is easy to be done, avoids bleedings and removes only the pineal gland without damage to the remaining encephalon. In addition it makes possible the achievement of a sham surgery, allowing the pineal gland to remain intact. Conclusion: The proposed technique intends to facilitate studies aiming to better understanding the complexity and importance of the pineal gland on reproductive and other body systems.

Reformulating schizophrenia: The importance of evolutionary theories

Abstract: body deficiency may be responsible for IS. Pinealectomy chickens may produce postoperative scoliosis, which is similar to human IS. Recently, scoliosis was found produced in pinealectomy rat maintained in a bipedal mode [1]. However, the concentration of human plasma melatonin in scoliosis patients was not significantly lower than that in normal ones [2]. These studies lead to the hypothesis, that melatonin signaling dysfunction may play a key role in the pathogenesis of IS [3]. Besides, clinical observation and family study has supported that the heredity is one of the causes of IS [4]. It is well-known that the mutation of genes which participate in melatonin signal transmission may cause melatonin signaling dysfunction. And the dysfunction of melatonin may disturb the function of central nervous system, including hypothalamus, brain stem, cerebellum and spinal cord, thus affecting the balance of body and the heterauxesis of spine. Taken together, the mutation of some molecules, such as receptors or some regulating factors, will lead to scoliosis by hampering melatonin signal transduction [5]. This hypothesis may push further insight into the strategy for screening children with high risk of developing IS. It means that gene therapy may be used to prevent genesis of scoliosis by screening blood sample.