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    Serum cortisol levels following acute experimental spinal cord injury
    (Via Medica, 2009) Gezici, Ali Riza; Karakas, Alper; Ergun, Ruchan; Gunduz, Bulent
    Background and purpose: Cortisol has neuroprotective effects. We monitored the serum cortisol levels after cervical and thoracic spinal cord injury (SCI) in four groups of rats. Materials and methods: Forty male Sprague-Dawley rats were randomized to four groups. The control group received neither laminectomy nor SCI. The sham group received laminectomy without SCT. The cervical spinal trauma group received a C5-C6 laminectomy and spinal trauma at this level. The thoracic spinal trauma group received a T6-T7 laminectomy and spinal trauma. Blood samples were drawn 2, 6, 12 and 24 hours after surgeries and assayed immediately. Results: The level of cortisol in the cervical spinal trauma group was highest at the second hour of the experiment and the lowest in control and sham-operated groups at the same time. At the sixth hour, cortisol levels increased in control and sham operated groups decreased, but increased in thoracic and cervical groups decreased, but increased in thoracic and cervical groups. After the 24(th) hour, serum cortisol levels in thoracic and cervical groups decreased but did not change significantly in control and sham-operated animals. Conclusion: Activation of endogen cortisol secretion of the organism starts immediately after the SCI injury and throughout the experiment the serum cortisol levels in neurotrauma groups remained high compared with the control and sham-operated groups. At the beginning, the level of neurological lesion (cervical or thoracic) affected differently the level of serum cortisol at a statistically significant level but this difference disappeared at the 6(th) hour.
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    Serum Leptin Levels Following Acute Experimental Spinal Cord Injury
    (Taylor & Francis Ltd, 2009) Gezici, Ali Riza; Ergun, Ruchan; Karakas, Alper; Gunduz, Bulent
    Background/Objective: Spinal cord injury influences many hormones that are known to be involved in the modulation of neurotrophic, neurogenic, and neuroprotective events. Recent studies showed that leptin could be neuroprotective, enhancing neuronal survival in vitro and in vivo. The objective of this study was to evaluate the pattern of the serum leptin levels in rats during acute traumatic SCI. Methods: Forty male Sprague-Dawley rats were divided randomly into 4 groups. In the control group, neither laminectomy nor SCI was performed; only laminectomy was performed without SCI in the sham group. In the cervical and thoracic spinal trauma groups, laminectomies were performed following the same trauma procedure. Blood samples were drawn 2, 6, 12, and 24 hours after the procedures and assayed immediately. Results: In the first 2 hours, levels of leptin were similar in control and sham-operated groups and higher in neurotrauma groups (P < 0.05). At the sixth hour, leptin levels increased in the sham-operated group, decreased in the neurotrauma groups (P < 0.05), and did not change in the control group (P > 0.05). At the 12th hour, the levels of leptin increased in all groups (P > 0.05). At the 24th hour, they decreased in the control, sham-operated, and cervical groups (P < 0.05); levels did not change in the thoracic group (P > 0.05). The decrease was higher in the control group than in the other groups (P < 0.05). Conclusions: Activation of endogenous leptin secretion started immediately after the SCI. The level of neurologic lesion (either cervical or thoracic regions) affected the levels of serum leptin differently, but with the exception of the first 12-hour period, this difference did not reach a statistically significant level.
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    The effects of leptin hormone on locomotor activity in Syrian hamsters (Mesocricetus auratus)
    (Tubitak Scientific & Technological Research Council Turkey, 2011) Gunduz, Bulent; Karakas, Alper
    The suprachiasmatic nucleus (SCN) generates and controls the circadian rhythms in mammals including the rhythm of locomotor activity. Leptin is a hormone secreted by adipose tissue that informs the brain about the fat stores. SCN neurons express leptin receptors. Here we investigated the effects of 3 different leptin administrations on the locomotor activity of the Syrian hamsters maintained in constant darkness. Animals were intraperitoneally (ip) injected (4 mu g/kg), subcutaneously (sc) infused (4 mu g/kg), or intra-SCN infused (0.4 mu g/kg) with leptin for 3 days at circadian time 10 whereas the controls received saline (0.9% NaCl) at the same time in order to eliminate stress factors. Our results demonstrate that the locomotor activity of the hamsters can be phase advanced by the external leptin administrations. Leptin affected the level of phase-shifts in an administration method-dependent manner. The biggest phase advance was observed in intra-SCN infusion (P = 0.001), and the smallest was in the ip injection (P = 0.041) group. The wheel-turn amounts did not change significantly in the groups before and after the leptin administrations (P = 0.233); however, the period lengths increased (P = 0.011) significantly after leptin administrations. These results suggest for the first time that in vivo leptin administrations may change the rhythm of locomotor activity in adult male Syrian hamsters.
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    The Effects of Pinealectomy and Melatonin Implants on Circadian Locomotor Activity Responses of the Mongolian Gerbils Exposed to Rapid Photoperiodic Transitions
    (Journal Neurological Sciences, 2010) Gunduz, Bulent; Karakas, Alper
    The jet-lag syndrome and the shift-work malaise take place by rapid changes in photoperiod and disturb people's life frequently. In the present study; we wanted to simulate these conditions. Control, pinealectomized and melatonin including silastic tube implanted Mongolian gerbils were respectively exposed into long (14L:10D), short (8L:16D), constant darkness (0L:24D) and constant light (24L:0D) photoperiods in order to investigate the effects of photoperiod, pineal gland and melatonin hormone in the photoperiodic reentrainment of this species. Gerbils showed an light/dark cycle entrained locomotor activity rhythm in long and short photoperiods, free-running in constant darkness and arrhythmic locomotor activity in constant light. The period lengths were similar to each other in the groups (p>0,05). Gerbils were reentrained by the changes in photoperiod nevertheless pinealectomy and melatonin implants did not make any significant influence on this reentrainment (p>0,05). Locomotor activity amounts varied in a group-photoperiod-dependent manner. These data suggest that photoperiod but not the pineal gland and constant release melatonin hormone is effective on the activity rhythm of the Mongolian gerbil.
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    The effects of the intraamygdalar melatonin injections on the anxiety like behavior and the spatial memory performance in male Wistar rats
    (Elsevier, 2011) Karakas, Alper; Coskun, Hamit; Kaya, Aliye; Kucuk, Aysegul; Gunduz, Bulent
    In the present study, the effects of intraamygdalar administrations of melatonin (1 and 100 mu g/kg), saline and diazepam on the anxiety-like behavior and spatial memory performance in pinealectomized and sham-pinealectomized Wistar rats were investigated. The animals were tested by open field and elevated plus maze tests for anxiety-like behavior, and Morris water maze test for spatial memory. In open field, (a) diazepam was more effective in reducing the anxiety, (b) control subjects were more mobile than pinealectomized subjects and (c) 100 mu g/kg melatonin administrations reduced the velocity of the animals. In elevated plus maze, (a) 100 mu g/kg melatonin administrations increased the distance totally travelled and (b) enhanced the time spent in open arms, however, after the pinealectomy, 1 mu g/kg melatonin administrations decreased it and (c) control animals were less mobile than pinealectomized ones. In Morris water maze, (a) diazepam group travelled more distance than the others in control condition whereas, in pinealectomy condition high dose of melatonin and saline groups travelled more distance than the others, (b) in pinealectomy condition subjects who received 100 mu g/kg melatonin also travelled more distance than those who received 1 mu g/kg melatonin and diazepam, (c) the subjects who received 1 mu g/kg spent less time than those who received other treatments, and (d) in control condition subjects who received 100 mu g/kg melatonin were slower than those who received the other treatments. In conclusion, melatonin administration to amygdala decreased the anxiety; however, spatial memory performance of the rats was impaired by the pinealectomy and melatonin administrations. (C) 2011 Elsevier B.V. All rights reserved.