Nevzat Kahveci

Effects of intracerebroventricularly-injected morphine on anxiety, memory retrieval and locomotor activity in rats: involvement of vasopressinergic system and nitric oxide pathway.

Morphine has been shown to alter several behavioural processes. We aimed to investigate the effects of intracerebroventricular (i.c.v.) morphine on anxiety, memory retrieval and locomotor activity in rats and to elucidate the possible involvement of the vasopressinergic system and the nitric oxide (NO) pathway in these effects. Rats were pretreated with morphine (0.5, 5, 50 microg/5 microl; i.c.v.) or saline (5 microl; i.c.v.) 30 min before the elevated plus maze test, the probe trial of the Morris water maze and the open field test. Morphine (5 microg/5 microl; i.c.v.) induced significant anxiolytic effects in the elevated plus maze. None of the doses of morphine produced any effects in the probe trial of the Morris water maze and the open field. Pretreatment with an arginine vasopressin (AVP) V(1) receptor antagonist (25, 125 ng/5 microl; i.c.v.), an AVP V(2) receptor antagonist (25, 125 ng/5 microl; i.c.v.), or L-NAME, an NO synthase inhibitor (5, 25 microg/5 microl; i.c.v.) 30 min before morphine significantly prevented the anxiolytic effects of morphine. These results suggest that i.c.v. morphine has significant anxiolytic effects, probably mediated by both vasopressinergic system and NO pathway, but has no effect on memory retrieval or locomotor activity, at least at the applied doses.

The effects of sevoflurane and isoflurane on intracranial pressure and cerebral perfusion pressure after diffuse brain injury in rats.

Twenty-four adult male Wistar rats, weighing 220 to 290 g, were anesthetized with 30 mg/kg intraperitoneal sodium thiopental, then underwent a tracheostomy. After diffuse impact–acceleration brain injury (BI) was induced, each rat was paralyzed and mechanically ventilated with 30% O2 in nitrous oxide (N2O). The rats were assigned randomly to two groups, each of which received one of the two volatile anesthetic agents, sevoflurane or isoflurane. The anesthetics were administered at 0.5, 0.75, 1.0, and 1.25 minimal alveolar concentration (MAC) for 30 minutes each, respectively, and anesthesia was maintained at 0.75 MAC during the last hour of the study period. Intracranial pressure (ICP), mean arterial pressure (MAP), rectal and intrahemispheric temperatures, and end-tidal volatile anesthetic concentrations were monitored continuously throughout the 3 hours, with measurements recorded every 15 minutes. At baseline, there were no significant differences between the two groups regarding the monitored physiologic values. In the sevoflurane group, MAP fell significantly after 45 minutes, and a similar change was observed in the isoflurane group after 30 minutes (P < .05, P < .01, and P < .001, respectively). Intracranial pressure increased significantly at 45 minutes in the sevoflurane group (P < .01) and remained elevated from 60 minutes until the end of the study period (P < .01, P < .001). Although ICP increased in the isoflurane group, the change was not significant. Cerebral perfusion pressure (CPP) decreased in parallel with MAP, with the reduction in the sevoflurane group being more pronounced than that in the isoflurane group. The results demonstrated that, under the conditions of diffuse BI, animals that were anesthetized with sevoflurane had higher ICP and lower CPP levels than those anesthetized with isoflurane.

Experimental Subarachnoid Haemorrhage Models in Rats

There is no comprehensive and reliable model available in small animals that are suitable for the study of subarachnoid haemorrhage (SAH). In the study we reviewed the advantages and disadvantages of available SAH models in rats and presented our model. Experimental SAH was induced in a group of 350-450 g Sprague-Dawley rats. A 2 mm-diameter burr hole was drilled and, working under a microscope, haemorrhage was produced by transclival puncture of the basilar artery with a 20 microns thick piece of glass. The rats were assigned to either the experimental group (n: 7) or the control group (n: 7). Local cerebral blood flow (LCBF), intracranial pressure (ICP), and cerebral perfusion pressure (CPP) were measured for 60 min after SAH, after which the rats were decapitated. Microscopic examinations were done on three different segments of the basilar artery. There was a significant and sharp drop in LCBF just after SAH was induced (56.17 +/- 12.80 mlLD/min/100 g and 13.57 +/- 5.85 mlLD/min/100 g for baseline and post-SAH, respectively; p < 0.001), the flow slowly increased by the end of the experiment but never recovered to pre-SAH values (43.63 +/- 7.6 mlLD/min/100 g, p < 0.05). ICP (baseline 7.33 +/- 0.8 mmHg) increased acutely to 70.6 +/- 9.2 mmHg, and also returned to normal levels by 60 min after SAH. CPP (baseline 75.1 +/- 4.9 mmHg) dropped accordingly (to 21.0 +/- 6.3 mmHg) and then increased, reaching 70.1 +/- 4.9 mmHg at 60 min after SAH. Examinations of the arteries revealed decreased inner luminal diameter and distortion of the elastica layer. We present an inexpensive and reliable model of SAH in the rat that allows single and multiple haemorrhages and to study the early and late course of pathological changes.

Effects of different resuscitation fluids on tissue blood flow and oxidant injury in experimental rhabdomyolysis.

Objective:This study was performed to evaluate the effects of 0.9% saline (SAL), 0.9% saline + sodium bicarbonate + mannitol (SAL/BIC/MAN), and hypertonic saline-dextran (HSD) on hemodynamic variables, tissue blood flow, and oxidant injuries in experimental traumatic rhabdomyolysis (TR) in rats subjected allogeneic muscle extract infusion. Design:Prospective, randomized, experimental. Setting:Physiology experiment laboratory. Subjects:Male Sprague-Dawley rats, weighing 250–300 g. Interventions:All groups (n = 8 each) underwent femoral artery and vein catheterization. The animals in the TR, SAL, SAL/BIC/MAN, and HSD groups received an infusion of 2 mL of autologous muscle extract for 60 mins. After autologous muscle extract infusion, the SAL and HSD groups received 30 mL/kg 0.9% saline for 30 mins or 4 mL/kg HSD for 5 mins, respectively. The SAL/BIC/MAN group received 30 mL/kg 0.9% saline for 30 mins plus a bolus of 1 g/kg mannitol and a bolus of 2 mEq/kg sodium bicarbonate diluted in 1 mL of saline. At 2 hrs of autologous muscle extract infusion, erythrocyte flows in liver and kidney were measured by using a laser Doppler flowmeter. Then, blood samples and kidney and liver biopsies were taken to measure levels of glutathione and malondialdehyde. Measurements and Main Results:TR caused decreases in mean arterial pressure, tissue blood flow, and tissue glutathione and an increase in malondialdehyde. Rats in the HSD group had significant metabolic acidosis. SAL resuscitation did not correct tissue blood flow and prevent oxidant injury. HSD increased tissue blood flow, mean arterial pressure, and liver and kidney glutathione and decreased serum, liver, and kidney malondialdehyde. SAL/BIC/MAN resuscitation corrected all oxidant damage variables but did not increase tissue blood flow. SAL/BIC/MAN preserved serum malondialdehyde and liver glutathione better than the HSD did. Conclusions:HSD prevented oxidant injury and restored tissue blood flow but increased metabolic acidosis that followed autologous muscle extract infusion. SAL/BIC/MAN seems to be more effective than HSD in decreasing oxidant injury. Further research on the effects of the solute overload and metabolic acidosis due to HSD resuscitation on renal function in experimental rhabdomyolysis is warranted.

Hypertonic saline dextran alleviates hepatic injury in hypovolemic rats undergoing porta hepatis occlusion.

To monitor the ischemic and/or reperfusion injury after porta hepatis occlusion (Pringle maneuver) in livers subjected to hypotension, serum alanine amino transferase (ALT), liver malondialdehyde (MDA), and liver glutathione (GSH) levels were measured. MDA is a by-product of oxidant-induced lipid peroxidation, and GSH is an endogenous antioxidant. The effects of lactated Ringers (LR) and hypertonic saline (7.5%)/Dextran (6%; HSD) resuscitation on liver injury, if any, was investigated. Rats in sham (S, n = 8) and five other groups (n = 8) underwent femoral artery and vein catheterization and laparotomy. The hemorrhage and ischemia (HI) group was bled 30% of their blood volume and had their porta hepatis occluded for 30 min. The HI, LR, and HSD groups underwent both hemorrhage and occlusion. Thirty minutes after hemorrhage, the LR and HSD groups received either LR (equivalent to three times the shed blood) or HSD (10 mL/kg) resuscitation over 30 min. Both LR and HSD resuscitation lowered the increased ALT and liver tissue MDA seen in the HI group. ALT was decreased from 348 ± 93 IU/L in the HI group to 200 ± 98 IU/L in the LR and 139 ± 74 IU/L in the HSD groups. Liver tissue MDA was 353 ± 22 nmol/g/tissue in the HI group and LR decreased it to 261 ± 17 nmol/g/tissue, whereas HSD decreased it to 273 ± 20 nmol/g/tissue. The decrease in ALT and the increase in liver GSH were more pronounced with HSD resuscitation (P < 0.05). HSD seems to be more effective than LR in decreasing the liver tissue damage produced by total hepatic inflow occlusion under hypovolemic conditions.

Effects of centrally-injected glucagon-like peptide-1 on pilocarpine-induced seizures, anxiety and locomotor and exploratory activity in rat.

Glucagon-like peptide-1 (7-36)-amide (GLP-1) is a gut peptide, which exerts significant effects on glucose homeostasis. GLP-1 and GLP-1 receptors are also widely distributed in the central nervous system. In the present study, we aimed to investigate the effects of intracerebroventricularly (i.c.v.)-injected GLP-1 on pilocarpine-induced seizures, anxiety and locomotor and exploratory activity in rat. Rats were pretreated with GLP-1 (1-1000 ng/5 microl; i.c.v.) or saline (5 microl; i.c.v.) 30 min before seizure induction by pilocarpine (2.4 mg/5 microl; i.c.v.) and with GLP-1 (1, 10, 100 ng/5 microl; i.c.v.) or saline (5 microl; i.c.v.) 30 min before the open field test or the elevated plus maze test. GLP-1 did not produce any protective effect against pilocarpine-induced seizures and did not also produce statistically significant differences in the number of squares visited (measure of locomotor activity) or number of rearings (measure of exploratory behaviour), compared to the saline-treated rats in the open field test. On the other hand, GLP-1 (1 ng and 10 ng; i.c.v.) induced an anxiogenic effect, indicated by a decrease in the time spent in open arms, an increase in the time spent in closed arms, and a decrease in the anxiety scores in the elevated plus maze test. Pretreatment with an arginine vasopressin (AVP) V(1) receptor antagonist (125 ng/5 microl; i.c.v.) and L-NAME (100 microg/5 microl and 200 microg/5 microl) significantly abolished the anxiogenic effect of GLP-1 (1 ng/5 microl; i.c.v.). These results suggest that, centrally-injected GLP-1 produces anxiogenic effects via NO pathway and AVP V(1) receptors, but does not have any effects on pilocarpine-induced seizures or locomotor and exploratory activity in the open field test.

An anatomical and pathological evaluation of middle cerebral artery occlusion in rats.

Abstract Adult male Sprague-Dawley rats (n = 87) weighing 350-400 g were used for studying the anatomy of the horizontal segment of middle cerebral artery and infarct area after occlusion of the artery. In the experimental group (n = 27) middle cerebral artery was coagulated 3-4 mm length from the origin of the lateral striate arteries to the inferior cerebral vein and divided. Control rats (n = 20) had all the surgical procedures except occlusion. Another group of rats (n = 40) were used to determine the anatomical variations of middle cerebral artery after intracarotid carbon black injection. Five major patterns of middle cerebral artery were observed and two of them were major and constituted 92.5% of rats. Twenty-four hours after middle cerebral artery occlusion, all animals were neurologically evaluated. On the third day after occlusion the brains were stained with 2% 2,3,5-triphenyltetrozolium chloride. The area of Infarction was assessed by computerized analysis method. In our study after determining the variations of the middle cerebral artery and Its branches in our strain of rats, we were able to achieve 92.5% grade III and IV infarcted area. [Neurol Res 2000; 22: 609-614]

Long-term cognitive effects of uridine treatment in a neonatal rat model of hypoxic-ischemic encephalopathy.

Hypoxic-ischemic encephalopathy (HIE), is the most common brain disorder in neonates during the perinatal period, which, to date, can only be managed to some extent by hypothermia. Uridine is the principal circulating pyrimidine in humans which is utilized as a precursor for membrane phospholipid biosynthesis. Uridine has recently been shown to provide clinical benefit in treatment of Alzheimers disease due to its involvement in increasing number of brain synapses along with other phospholipid precursors. We previously showed that uridine treatment ameliorated brain damage by reducing apoptosis in a rat model of neonatal HIE. The aim of the present study was to investigate the effects of uridine administration on cognitive functions during periadolescent period in rats subjected to hypoxic-ischemic (HI) brain damage in neonatal period. Male newborn rats were subjected to HI insult on postnatal day 7 (P7) and were injected intraperitoneally with either saline or uridine (500mg/kg) for three consecutive days. Part of pups in each group were sacrificed on P10 to collect brain samples for active Caspase-3 analyses and the remaining pups were raised through P40 to evaluate early reflexes, sensorimotor coordination and learning and memory functions by Negative Geotaxis (NG), Beam Walking (BW) and Morris Water Maze (MWM) tasks, respectively. Confirming our previous findings, we showed that uridine administration reduced apoptotic cell damage on P10. No significant difference was observed between uridine and saline groups in early reflexes or sensorimotor coordination. On the other hand, rats receiving uridine displayed improved learning and memory in MWM during periadolescent period. We conclude that uridine treatment improves learning and memory in the long term by, probably, reducing apoptotic cell death in early newborn period. This is the first study to show beneficial cognitive effects of uridine in rats with brain damage.

Effects of Interrupted and Uninterrupted Occlusion of the Basilar Artery on Cerebral Blood Flow, and on Neurological and Histological Outcome in Rats with Subarachnoid Hemorrhage

Most neurosurgeons consider temporary vessel occlusion for aneurysmal clipping an effective technique that facilitates dissection between the aneurysm and the parent vessel. It is generally believed that repeated short periods of cerebral ischemia are safer for the brain than a single long episode. The aim of this study was to identify whether interrupted and uninterrupted vessel occlusion differs with regard to changes in brain tissue and cerebral hemodynamics after subarachnoid hemorrhage (SAH). Fifty Spraque Dawley rats (300–350 g) were placed under general anaesthesia and ventilated. The basilar artery was exposed through a transclival approach. Baseline local cerebral blood flow (LCBF) values was measured, and then the basilar artery was punctured, causing subarachnoid hemorrhage (SAH). Group I (n = 24) was subjected to 60 min of interrupted basilar artery occlusion, defined as 5 min of reperfusion after every 10 min of occlusion, group II (n = 26) 60 min of uninterrupted artery occlusion. Three days after completion of the experiment, each rat was neurologically evaluated and decapitated. Coronal brain slices were obtained and stained to assess infarct volume. Immediately after SAH, LCBF fell by 58% in group I, and by 52% in group II. In group I, each ischemic insult brought a similar reduction in LCBF, and after each release of the occlusion there was a rapid rise in flow. In group II, the LCBF values dropped initially and remained at low levels until the end of the study. The 2, 3, 5 triphenyltetrazolium chloride stained sections showed similar volumes of brainstem infarction in both groups (38.3 ± 9.2 mm 3 vs. 34.3 ± 8.7 mm 3, respectively; p > 0.05). The results suggest that there is no neuroprotective advantage to either interrupted or uninterrupted temporary blockage of blood flow during neurovascular procedures after SAH in the basilar artery region.

Uridine treatment protects against neonatal brain damage and long-term cognitive deficits caused by hyperoxia

Exposure to excessive oxygen in survivors of preterm birth is one of the factors that underlie the adverse neurological outcome in later life. Various pathological changes including enhanced apoptotic activity, oxidative stress and inflammation as well as decreased neuronal survival has been demonstrated in animal models of neonatal hyperoxia. The aim of the present study was to investigate the effect of administering uridine, an anti-apoptotic agent, on cellular, molecular and behavioral consequences of hyperoxia-induced brain damage in a neonatal rat model. For five days from birth, rat pups were either subjected continuously to room air (21% oxygen) or hyperoxia (80% oxygen) and received daily intraperitoneal (i.p.) injections of saline (0.9% NaCl) or uridine (500mg/kg). Two-thirds of all pups were sacrificed on postnatal day 5 (P5) in order to investigate apoptotic cell death, myelination and number of surviving neurons. One-thirds of pups were raised through P40 in order to evaluate early reflexes, sensorimotor coordination and cognitive functions followed by investigation of neuron count and myelination. We show that uridine treatment reduces apoptotic cell death and hypomyelination while increasing the number of surviving neurons in hyperoxic pups on P5. In addition, uridine enhances learning and memory performances in periadolescent rats on P40. These data suggest that uridine administered during the course of hyperoxic insult enhances cognitive functions at periadolescent period probably by reducing apoptotic cell death and preventing hypomyelination during the neonatal period in a rat model of hyperoxia-induced brain injury.