QUANTITATIVE EEG IN THREE PHARMACOLOGICAL MODELS OF PSYCHOSIS Tomáš Páleníèek, Michaela Fujáková, Martina Kutová, Martin Brunovský,Vìra Bubeníková-Valešová, Jiøí Horáèek Adress: Prague Psychiatric Center, Ústavní 91, 181 03 Prague 8 -Bohnice email: palenicek@pcp.lf3.cuni.cz METHODS This work is supported by projects MEYSCR 1M0517, MHCR NR-8785-3, MHCR MZ0PCP2005 and MHCR NR-8792-3. EEG POWER SPECTRA STATISTICS I. BEHAVIORAL EXPERIMENTS ANIMALS AND DRUGS INTRODUCTION II. EEG SPECTRAL ANALYSIS AND EEG COHERENCES RESULTS (EEG experiments) CONCLUSIONS 1) STEREOTACTIC SURGERY 2) EEG RECORDING 2) EEG SIGNAL ANALYSIS Rats were stereo-tactically implanted with 14 silver electrodes under halothane anesthesia, 7 days before EEG recording. 12 active electrodes were implanted on the surface of the cortex in homologous areas of the right and left hemispheres (Fig. 1A/C). Coordinates for implanting electrodes were adapted from the stereotactic atlas The Rat Brain – Fourth Edition (Paxinos et al., 2003) (Fig. 1C). The reference electrode was implanted above the olfactory bulb and the ground electrode subcutaneously in the occipital region. All electrodes were fixed to the skull with dental cement (Dentalon). After the operation, animals were placed individually in each cage. The day before EEG recording a connector was mounted to the electrodes under a short time total halothane anesthesia. All EEG recordings were performed between 09:00 and 14:00. Rats were connected with a cable to 21-channel BrainScope amplifier system (Unimedis, Prague). After the first 10 minutes of baseline EEG record drugs were administered and recording was kept for another 30 min with Ketamine, 70 min with 2C-B and 30 min with Amphetamine. Animals were able to move freely in the cage during all EEG recording (Fig. 1B). EEG data were stored on a PC hard disk for off line processing. Two types of artifact-free EEG data (each in total length of 30 sec) were carefully chosen by visual inspection for further processing. The first type was taken from artifact-free epochs of the baseline EEG record, the second type of artifact-free data was taken from record after drug administration. A Fast Fourier transformation (FFT) was applied on selected data to obtain the auto-spectra of individual electrodes and cross-spectra of selected electrode pairs in the following frequency bands: delta (1.0 – 3.5 Hz), theta (4.0 - 7.5 Hz), alpha (8 – 12 Hz), beta1 (12 – 15 Hz), beta2 (15 - 17.5 Hz), beta 3 (18 – 25 Hz) and high beta (25.5 – 30 Hz). EEG coherence was derived from auto- spectral and cross-spectral values for 15 electrode pairs intra-hemispherally (between F3/C3, F3/P3, F3/P5, F3/T3, F3/T5, C3/P3, C3/P5, C3/T3, C3/T5, P3/P5, P3/T3, P3/T5, P5/T3, P5/T5, T3/T5 on the left hemisphere and analogically on the right hemisphere) and 6 homologue electrode pairs inter-hemispherally (between F3/ F4, C3/C4, T3/T4, P3/P4, P5/P6, T5/T6 electrode pairs interhemispherally). Behavioral data were analyzed by one way analysis of variance (ANOVA) with Bonferroni post hoc test by Sigmastat 3.0 software. Differences between groups with P<0.05 and lower were considered as statistically significant. EEG Data were analyzed by Neuroguide Deluxe software v. 2.3.7. (© 2002 - 2007 Applied Neuroscience, Inc.), the differences between groups with p < 0, 05 (paired T-Test) were considered as significant. Each animal served as a self control in the EEG experiment. Our results demonstrate that all drugs at doses that are behavioral active induced changes in QEEG. Ketamine had mainly excitatory effect on the cortical EEG activity and also induced global increases in functional connectivity, except the onset of its action in delta band, where fronto-temporal decrease in coherence was observed. 2C-B produced changes in QEEG parameters which have a similarly biphasic trend like in the locomotor experiments. During the onset there was a decreas in functional connectivity between frontal and temporal cortex, later this was reversed and there was also a hypersynchrony similarly like with Ketamine. Contrary Amphetamine produced only minimal changes in QEEG, however again a slight fronto-temporal decrease in coherence was observed. Several similarities can be found with data from schizophrenic patients, mainly the decreased fronto-temporal coherence. All experiments were carried out on male Wistar rats (200-300 g). 4-bromo-2,5-dimethoxyphenethylamine hydrochloride (2C-B.HCl; 97-98%, synthesized at Charles University in Prague, Faculty of Pharmacy in Hradec Králové, CZR) Ketamine hydrochloride (Narketan) and Amphetamine sulphate (Sigma Aldrich) were dissolved in physiological solution and were injected subcutaneously or intraperitonealy (Ketamine) in a volume of 2 ml/kg. The doses used were 10 and 50 mg/kg for 2C-B, 9 and 30 mg/kg for Ketamine and 1 and 4 mg for Amphetamine. Only high doses will be shown in results from EEG experiments. Animals were tested in two behavioral tests, in the open field and in the test of prepulse inhibition (PPI) of acoustic startle reaction. In the open field, locomotor activity was registered for 30 min with the automatic video tracking system Ethovision color pro v 3.1.1.(Noldus); trajectory length in cm was analyzed. The PPI was measured in startle chamber SR-LAB (San Diego instruments). The percentage of inhibition of the startle reaction was (7) evaluated in the PPI test. Methods were in detail described elsewhere . RESULTS (behavioral experiments) Figure 1. A) B) C) Position of implanted electrodes on the brain surface and skull (A), the rat with implanted electrodes mounted to the registration system (B). The coordinates (C) were calculated from Bregm: 5 mm anteriorly and +/- 2 mm laterally for frontal association cortex (F3/F4), 2.2mm anteriorly and +/- 3.2 mm laterally for the primary motor cortex (C3/C4), 3.8 mm posteriorly and +/- 2.5 mm laterally or the first parietal association cortex (P3/P4), 4.5 mm posteriorly and +/- 4.5 mm laterally for the second parietal association cortex (P5/P6), 3.6 mm posteriorly and +/-7.2 mm laterally for the temporal association cortex (T3/T4) and 8.3mm posteriorly and 5.8 mm laterally for the secondary auditory cortex (T5/T6). EEG COHERENCE All three drugs were behaviorally active. Ketamine did not change the locomotion of animals, however there was a marked deficit in the PPI. Amphetamine on the contrast produced hyperlocomotion, but did not influenced the PPI. 2C-B had a biphasic effect on locomotion, initially it leaded to hypolocomotion during the onset of its action, subsequently it increased the locomotion. 2C-B also induced significant defficits in the PPI. Ketamine administration leaded to massive increase in the power spectra thorough the cortex in all bands, indicating a global cortical excitation. Contrary Amphetamine did not produced many changes, there was an increase in the power in the temporal cortex and frontal regions in delta band, and a significant decrease of relative power in beta and high beta bands globally. 2C-B had a biphasic effect in time, initially it induced an increase in the absolute power in beta and high beta bands contrary later there was an increase of power in slow waves bands (delta and theta) and a decrease in the relative power in alpha, beta and high beta bands. Ketamine induced massive increase in coherence thorugh the spectrum during the onset as well as during the maximum of its effects. The only decrease observed was in the delta band between frontal and tempral regions during the onset of its action. 2C-B during the onset of its action decreased fronto-temporal and fronto-parietal coherence almost thorough the spectrum except the delta band. Further in beta band it increased interhemispheral coherence. Later on the effect was reversed, there was an overall increase in fronto-temporal and fronto-parietal coherence in theta, alpha and high beta bands and a decrease of interhemispheral coherence in beta band. Amphetamine induced only small changes in coherence, the most prominent was the decrease of fronto-temporal coherence in the left hemisphere ih the high beta band. Schizophrenics reveal many abnormalities in classical and quantitative electroencephalography (QEEG). Regarding the EEG coherence a marker of functional connectivity, data (1-4) from literature are incoherent. Some indicate an increase in coherence, others a decrease in coherence (mainly between frontal and temporal regions) . To our knowledge no one studied cortical EEG coherence in animal models of psychosis. 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