Yurttas Oguz

Recovery cycle of the blink reflex and exteroceptive suppression of temporalis muscle activity in migraine and tension-type headache.

Brain stem interneuronal excitability can be assessed by recording the recovery cycle of the blink reflex and exteroceptive suppression of temporalis muscle activity. Abnormal endogenous pain control mechanisms due to disturbed brain stem interneuronal activity have been implicated in the pathogenesis of tension‐type headaches. The blink reflex, exteroceptive suppression of temporalis muscle activity, and the recovery curve of both the R2 component of the blink reflex and the ES2 component of the exteroceptive suppression of the temporalis muscle activity were studied in 20 patients with migraine without aura, 32 patients with tension‐type headache, and 20 normal controls. In our study, the blink reflex was elicited by stimulation of the supraorbital nerve; the exteroceptive suppression of the temporalis muscle activity was elicited by applying electrical shocks to the labial commissure, both on the lower and upper sides. The recovery cycle was established by delivering paired shocks at different interstimulus intervals. Comparisons were made between normal control subjects, patients with migraine without aura, and patients with tension‐type headache. The latency of R1, R2, and R2′, the amplitude and size of the R2 and R2′ components of the blink reflex, the latency and duration of the ES1 and ES2 components, and the recovery curve of the ES2 component of the temporalis muscle activity did not differ between groups. However, the recovery curve of the R2 component of the blink reflex diminished in patients with tension‐type headache compared with the other groups. Our findings indicate reduced excitability of the brain stem interneurons in patients with tension‐type headache.

Visual evoked potentials and optic nerve histopathology in normal and diabetic rats and effect of ginkgo biloba extract

Abstract. The purpose of this study was to test the possible therapeutic role of ginkgo biloba extract on the impairment of visual function and pathological histology of the optic nerve caused by early diabetes. Ginkgo biloba extract entraps oxygenated free radicals and is also a strong inhibitor of the platelet activation factor (PAF). For this purpose, VEP recordings and optic nerve histopathology were studied on alloxan diabetic and normal Swiss albino rats in four experimental groups. The VEP recordings showed no statistical significance between diabetic and normal rats. However, the amplitudes were significantly increased in diabetic animals with ginkgo biloba extract compared with the diabetics, supposing an impression of axonal protection. But the amplitude values were decreased in normal rats treated with the same extract compared with normal animals, assuming a toxic activity. Optic nerve ultrastructural findings also confirmed these VEP changes. It was concluded that this extract could be encouraging for human clinical trials of diabetes.

Withdrawal of antiepileptic drugs in adult patients free of seizures for 4 years: A prospective study

We aimed to assess the relapse rate of epilepsy, prospectively attributable to antiepileptic drug (AED) withdrawal in seizure-free patients and to determine the risk factors for seizure recurrence. Seventy-nine patients with epilepsy who were seizure-free for at least 4 years were enrolled into the study. The AEDs were tapered by one-sixth every 2 months. The EEG and clinical examination were performed at the beginning; at each visit during discontinuation and 2, 6, 12, 24, and 36 months after the complete drug withdrawal. For each patient, records were obtained of the main demographic and clinical variables. A total of 49 patients completed the discontinuation programme. Twenty-eight patients (57%) relapsed while 21 of those (42.8%) did not suffer a relapse at the end of the study period. In patients discontinuing treatment, the probability of relapse was 21.4% during the tapering period (especially in the last months), 28.6% at 1 month, 14.3% at 3 months, 3.6% at 6 months, 7.1% at 12 months, 17.8% at 24 months, and 7.1% at 36 months. The age at onset of epilepsy and the duration of active disease were found to affect the risk of relapse. Although drug withdrawal could be considered in adult patients free of seizures for 4 years, the final decision should be tailored to the patients clinical, emotional, and socio-cultural profile.

The Effect of Ginkgo Biloba Extract on Eeg Spectra in Experimental Diabetes: No Relation to Lipid Peroxidation

Forty four Swiss albino rats aged two months, weighing 180-250 g, were used in the experiment. They were divided into four equal groups as control, alloxan-diabetic, diabetic + GbE and control + GbE. After the onset of experimental period, diabetic + GbE and control + GbE groups received ginkgo biloba extract and the other groups were given saline solution for ten weeks. Diabetic and diabetic + GbE groups were made diabetic by injecting alloxan on 16th day. Spectral analysis of EEGs recorded from parietal lobes of all groups of rats were computed by Fast Fourier Transform (FFT) algorithm. Their amplitude maxima were found to occupy the frequency bands of 1-2, 2-4, 4-6, 6-8, 8-16 and 16-30 Hz. Significant amplitude increase was found in 1-2 and 2-4 Hz frequency bands in diabetic + GbE group compared with control, but no differences were found for other groups.

The effect of developmental exposure to cadmium (Cd) on visual evoked potentials (VEPs) and lipid peroxidation.

Pregnant Swiss albino rats were divided into three groups: control (C), gestational exposure of Cd (G-Cd), and gestational/postnatal exposure of Cd (GP-Cd) groups. Control animals received tap water, and the rats of GP-Cd group received Cd as CdC12 in their drinking water during the experimental period. The G-Cd group was given Cd during pregnancy, but given tap water after birth. Twenty-two days after birth, 15 rats (for each group) were taken from their mothers and continued to be treated with Cd (GP-Cd group) or tap water (C and G-Cd groups) for an additional 38 days. On postnatal day (PND) 60, flash visual evoked potentials (FVEPs) were recorded with disc electrodes attached with collodion 0.5 cm in front of and behind bregma. The mean latencies on N1, P2, and P3 were prolonged in the GP-Cd group compared with controls. The mean latency of P3 was also significantly different between G-Cd and GP-Cd groups. P1-N1 and N1-P2 amplitudes of VEPs were significantly decreased in the GP-Cd group compared with control group. N1-P2 amplitude of the G-Cd group was significantly lower than that of the control group. Thiobarbituric acid reactive substances (TBARS) were determined as an indicator of lipid peroxidation. Our data showed that pre- and postnatal Cd treatment caused a significant increase of lipid peroxidation in the brain.

The Effect of Hypercholesterolemia on SEPs Recorded from Rats

Twenty-four albino rats, weighing 180-200 g were studied. Twelve of them were fed with a diet containing 1% cholesterol for 12 weeks and the others were fed with a normal lab diet for the same period. As a result, plasma cholesterol level was found in the diet group 134.04 +/- 21.11 mg/dl with respect to control 72.72 +/- 10.5 mg/dl. In the two groups, following left posterior tibial nerve (PTN) stimulation, SEPs were recorded from central (Cz) referenced to frontal (Fz). In the hypercholesterolemic group, the first negative component (N24) was found to be prolonged (p less than .001) and the peak-to-peak amplitudes (N24P40, P40N80) were observed to be decreased (p less than .001). These results have shown that the latency and amplitude can be changed by hypercholesterolemia.

SEP spectral analysis of cholesterol rich rats.

In this study, twenty four albino rats, weighing between 180 and 200 g were tested. One half was fed with a diet containing 1% cholesterol for 12 weeks and the other half was fed with a normal lab diet for the same period. After the experimental period, the plasma cholesterol level in the diet group was 134.04 +/- 21.11 mg/dl compared with the control group 72.72 +/- 10.5 mg/dl. In the two groups, SEPs were recorded from central (Cz) referenced to frontal (Fz) following left posterior tibial nerve (PTN) stimulation. Amplitude spectra of SEPs were computed by Fast Fourier Transform (FFT) algorithm. Their amplitude maxima were found to occupy the frequency bands of 1-3.5, 4-5, 6-7, 8-10, 11-12, 13-20, 20.5-36 and 36 Hz and above. The decibel (dB) values of the maxima were statistically lower for hypercholesterolemia than for the normals in the all the frequency bands.

The effect of cadmium (Cd) treatment on somatosensory evoked potentials (SEPs) and conduction velocity in alloxane-induced diabetic rats: relation to lipid peroxidation.

Fifty-two healthy Swiss male albino rats, aged three months, were divided into four groups: Control (C), diabetic (D), cadmium (Cd), and diabetic + Cd (D+Cd). Diabetes was induced in D and D+Cd groups by administration of alloxane (5 mg/100 g). Cd and D+Cd groups were injected with CdCl2 i.p. (2 mg/kg/week) for 2 months. Somatosensory evoked potentials (SEPs) of the four groups were recorded following left posterior tibial nerve (PTN) stimulation. The mean latencies of P1, N1, P2 and N2 components were prolonged in all experimental groups compared with the control group. P1N1 and N1P2 amplitudes were significantly decreased in Cd and D+Cd groups in comparison with the control group. P2N2 amplitude was significantly decreased in the Cd group compared with the control group. In addition, conduction velocities and action potential amplitudes were determined from the sciatic nerves. The means of peripheral conduction velocities and action potential amplitudes were decreased significantly in all the experimental groups in comparison with the control group. Thiobarbituric acid reactive substances (TBARS), an indicator of lipid peroxidation, were increased in the kidneys and sciatic nerves of all experimental groups compared with the control group. A significant increase in the TBARS level of the brain was found in the Cd and D+Cd groups.

The effect of cadmium on visual evoked potentials in alloxane-induced diabetic rats : Relation to lipid peroxidation

Abstract Fifty-two healthy male Swiss albino rats, aged three months, were used in this study. They were divided into four groups: control (c), diabetic (D), cadmium (Cd), and diabetic + Cd (D+Cd). A diabetic condition was induced in D and D + Cd groups by administration of alloxane (5 mg/100 g). After this treatment, Cd and D + Cd groups were injected intraperitoneally with CdCl2 (2 mg/kg week). At the end of the 2-month experimental period, flash visual evoked potentials (FVEPs) of the four groups were recorded with disk electrodes attached with electrode paste 0.5 cm in front of and behind the bregma. The mean latencies off the P1, N1, P2, N2 and P3 components were significantly prolonged in the diabetic group compared with the control group. The mean latencies of P3 in the D + Cd group and of P1 and P3 in the Cd group were longer than those of the control group. P2N2 amplitude of Cd and D + Cd groups were significantly increased compared with the control group. On the other hand, thiobarbituric acid-reactive substances (TBARS) were determined as an indicator of lipid peroxidation. Our data showed that Cd treatment and diabetic condition caused a significant increase of lipid peroxidation in kidney, brain, retina and lens.

The Effects of Oxygenated Free Radicals on Vep Spectral Components in Experimental Diabetes

In this experimental research, 33 Swiss albino rats were studied. They were divided into three equal groups as control, alloxan-diabetic (diabetic group) and alloxan-diabetic rats treated with ginkgo biloba extract (diabetic-GbE group). After two months of diabetes and before ophthalmoscopically visible diabetic retinopathy, flash VEPs of three groups were recorded and spectral analysis of VEPs was computed by Fast Fourier Transform (FFT) algorithm. Comparing the results of diabetic and diabetic-GbE groups with control group, we observed a significant increase in the amplitude (dB) of 5 Hz frequency for the left and right responses of rats. At some frequencies, we also found important differences between diabetic-GbE and control groups.