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Journal Article 2001; 22(6): 449-452 PubMed PMID: 11781543 Citation  Keywords:  Animals, Body Weight, Circadian Rhythm:physiology, Leptin:blood, Male, Melatonin:metabolism, Pineal Gland:metabolism, Rats, Rats, Wistar,.   

OBJECTIVES: Exogenous and endogenous melatonin decrease leptin release. It is not known whether melatonin also has an effect on circadian release pattern of leptin. So, this study was planned to investigate the possible changes in the circadian release of leptin following pinealectomy.

METHODS: A group of rats were surgically pinealectomized while some others were exposed to sham operation. The animals were decapitated at 13.30 p.m. and 01.30 a.m. Serum leptin levels were measured by radioimmunoassay.

RESULTS: Serum leptin levels at 13.30 p.m. were lower than the values at 01.30 a.m. in both pinealectomized (P<0.002) and sham rats P<0.001). Serum leptin levels measured at 13.30 p.m. and 01.30 a.m. were significantly elevated (P<0.05 and P<0.01, respectively) in the pinealectomized rats in comparison to sham animals.

CONCLUSION: The circadian release of leptin does not seem to be regulated by melatonin release from the pineal gland whereas melatonin, physiologically released, may have a decreasing effect on leptin release....

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Journal Article 2001; 22(4): 255-262 PubMed PMID: 11524633 Citation  Keywords:  Animals, Circadian Rhythm:drug effects, Drug Administration Schedule, Growth Hormone:blood, Insulin-Like Growth Factor I:metabolism, Male, Melatonin:administration & dosage, Oscillometry, Osmolar Concentration, Pineal Gland:physiology, Rats, Rats, Wistar,.   

BACKGROUND: A relationship between circadian GH-IGF-I axis activity and pineal gland function in rats is not sufficiently elucidated, particularly in the aspect of melatonin (MEL) participation with relation to a possible mechanism of these dependencies.

OBJECTIVE: Influence of pinealectomy and long-term MEL administration on circadian GH-IGF-I axis function in male rats was evaluated. An attempt was also made to determine whether the effect of exogenous MEL is dependent on the pineal gland presence.

METHODS: Studies were performed in 192 sexually mature male Wistar rats, which were subjected to pinealectomy or sham operation. In half of the animals from each group MEL (Sigma, USA) in dose of 50 microg/ 100g b.m. was administrated intraperitoneally (daily between 5 and 6 pm during a 4-week period). Blood for RIA assays of MEL, GH and IGF-I concentrations was collected every 3 hours during a day-beginning at 8 am (rats killed by decapitation).

RESULTS: Significant influence of pinealectomy and exogenous MEL on a daily profile of endogenous MEL in rats was confirmed. Distinct, dependent on the time of the day anomalies in circadian oscillations of GH and IGF-I showing positive correlation with changes in endogenous MEL concentrations were also shown. GH rhythm was suppressed in a group of rats with removed pineal gland; after pinealectomy distinct decrease and after MEL use - distinct increase of GH and IGF-I concentrations during the day were observed. It had influenced mean daily concentrations and values of amplitude of circadian GH and IGF-I oscillations in all studied groups of animals. In rats with preserved pineal gland the effect of exogenous MEL action was more intensified.

CONCLUSIONS: Pineal gland can influence circadian function of GH-IGF-I axis, and in mechanism of this dependence, changes in endogenous MEL concentrations seem to play an important role. Administration of MEL in rats after pinealectomy only partly prevents changes of GH-IGF-I axis function caused by gland removal, which can indicate participation of other pineal gland substances in generating disturbances. Influence of exogenous MEL on GH-IGF-I axis function during the day is dependent on the presence of pineal gland, which can be connected with indirect and/or direct influence of administrated hormone on this gland....

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Journal Article 2018; 39(3): 209-218 PubMed PMID: 30431738 Citation  Keywords:  Animals, Behavior, Animal, Blood-Brain Barrier:metabolism, Brain:diagnostic imaging, Brain Edema:etiology, Disease Models, Animal, Evans Blue, Intracranial Hypertension:etiology, Locomotion, Male, Myelin Sheath:pathology, Permeability, Rats, Rats, Wistar,.   

OBJECTIVES: This paper presents our own rat model of the cellular brain edema, induced by water intoxication (WI). The basic principle of the model is an osmotic imbalance in the cell membrane followed by an intracellular flow of sodium and simultaneous accumulation of water leading to the subsequent increase of BBB permeability. METHODS: The usefulness of the model was tested in precisely specified conditions whose results were clearly expressed. The procedure determined both how WI induces cellular edema as well as the disturbances caused by cellular edema. RESULTS: The evidence of existing cellular edema with increased BBB permeability was proved by intracellular accumulation of intravital dye with a large molecular size; increased brain-water content was confirmed by using the dry/wet weight method and by the decrease in CT density; the elevated intracranial pressure (ICP) due to the expanding volume was determined by continuous monitoring the ICP; the structural lesions were proved by identification of the myelin disintegration; and the impaired nervous functions was demonstrated by the of open field test method. CONCLUSION: Our experimental model can help the future studies of pathophysiology of cellular brain edema and is suitable for testing neuroprotective agents....

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Journal Article 2018; 39(4): 310-314 PubMed PMID: 30531705 Citation  Keywords:  Age Factors, Animals, Behavior, Animal:drug effects, Brain Edema:physiopathology, Erythropoietin:pharmacology, Locomotion:drug effects, Male, Motor Activity:drug effects, Neuroprotective Agents:pharmacology, Rats, Rats, Wistar, Recombinant Proteins:pharma.   

OBJECTIVES: Effect of recombinant human erythropoietin (rhEPO) on spontaneous motor activity was tested in young rats after intraperitoneal (i.p.) administration of rhEPO, followed by induction of cellular brain edema (CE). Induced changes in the spontaneous horizontal locomotor activity was studied by open field test (OFT). METHODS: CE was induced by water intoxication (WI) using standard method of fractional hyperhydration accompanied with desmopressin administration. Using the accepted method of OFT average time spent in locomotion (s) was determined. 48 young rats at the age of 25, and 35 days were divided into three groups - controls, rats after WI (OFT followed after 44 hours), and rats administered with rhEPO prior to application WI (OFT after 48 hours). RESULTS: In 35-day-old rats rhEPO administration increased the spontaneous locomotor activity, previously decreased by cellular edema. In 25-day-old rats, rhEPO administration prior to the induced CE, decreased spontaneous locomotor activity. CONCLUSION: Presented results demonstrate the neuroprotective capacity of rhEPO, manifested by elimination of the suppressive influence of CE on the locomotion in 35-day-old rats. In 25-day-old rats the neuroprotective effect was not present. These results confirmed that the 10 day interval in the development may represent a different stage of brain maturation in the relation to the neuroprotective effect of rhEPO....

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