Parasitological assessment of wild ring-tailed coatis (Nasua nasua) from the Brazilian Atlantic rainforest.

Image 1.

Seizure suppression by asynchronous non-periodic electrical stimulation of the amygdala is partially mediated by indirect desynchronization from nucleus accumbens.

Electrical stimulation (ES) of the nervous system is a promising alternative for the treatment of refractory epilepsy. Based on the understanding that seizures are the expression of neural hypersynchronism, our group developed and tested a non-standard form of low-energy temporally unstructured ES termed NPS (Non-periodic stimulation), with pseudo-randomized inter-pulse intervals. Previous investigation demonstrated that NPS applied to the amygdala has a robust anticonvulsant effect against both acute and chronic seizures, and suggested that its therapeutic effect is based on direct desynchronization of ictogenic neural circuits. Further mechanistic investigation using functional magnetic resonance imaging has shown that NPS also activates nucleus accumbens (NAc) in seizure-free rats, raising the hypothesis of an alternative therapeutic mechanism: NPS-enhanced indirect inhibition / desynchronization of ictogenic circuits by NAc. In order to investigate this idea, here we evaluated behavior and cortical electrographic activity from animals submitted to pentylenetetrazole (PTZ) induced seizures, treated with NPS and with or without bilateral electrolytic lesion of NAc. NPS-treated animals with bilateral lesion of NAc expressed unexpected straub tail in addition to other stereotypical convulsive behavior, displayed increased susceptibility to PTZ (lower drug threshold), and had a much longer electrographic seizure, with a greater number of spikes, firing at a higher rate. Moreover, analysis of spike morphology showed an increase in amplitude and slope in these animals, suggesting that ablation of NAc results in disinhibition and/or increase of neural synchronism within ictogenic circuits. NPS had no therapeutic effect whatsoever in lesioned animals, while it displayed a mild anticonvulsant effect in those with intact brains. Results corroborate the notion that NAc has a key role in controlling aberrant epileptiform activity in ictogenic circuits through indirect polysynaptic connections that may enroll the ventral pallidum and ventral tegmental area. They also point to the possibility that NPS may enhance this effect, putatively by benefiting from the structure's property of detecting saliences.

Asynchronous, bilateral, and biphasic temporally unstructured electrical stimulation of amygdalae enhances the suppression of pentylenetetrazole-induced seizures in rats.

A promising alternative for the treatment of refractory epilepsy is electrical stimulation (ES) of the central nervous system. Based on the premise that epilepsy is a result of neural hypersynchronization, we have previously demonstrated that a novel non-standard form of electrical stimulation with randomized inter-pulse intervals, termed non-periodic stimulation (NPS), applied to the amygdala is robustly anticonvulsant. This investigation also suggested that NPS attains its therapeutic effect by desynchronization of epileptiform activity. Here, we further explored the desynchronization hypothesis by testing how the efficacy of NPS in the suppression of convulsive behaviors depends on morphological, spatial, and temporal parameters of stimulus. For this purpose, we varied the number of pulse phases (monopolar versus bipolar square pulses), side of stimulation (right versus left), number of application hemispheres (unilateral versus bilateral), and interhemispheric temporal synchronicity (synchronous versus asynchronous), while measuring the impact on the anticonvulsant action of NPS. Wistar rats received a controlled infusion of the convulsant agent pentylenetetrazole (PTZ, 10 mg/min), together with one of six variations of NPS applied to the amygdala. A stimulated PTZ-free group of animals was also performed as a positive control. Latency to convulsive behavior was used to measure seizure threshold. Animals receiving NPS displayed significant higher threshold for forelimb clonus and generalized tonic-clonic seizures for all patterns. Thresholds seemed to increase gradually from mono to biphasic, unilateral to bilateral, and synchronous to asynchronous stimuli. Thus, combined biphasic, bilateral, and asynchronous stimulation resulted in the greatest seizure threshold. PTZ free animals did not develop any observable convulsive behavior or other uncommon motor activity. These results confirm that NPS has anticonvulsant properties and that biphasic, bilateral, and asynchronous stimulation enhances its efficacy. The fact that lack of synchronism between stimuli of each hemisphere maximizes NPS anticonvulsant power is evidence to desynchronization as tool for suppression of seizures.

Anisomycin administered in the olfactory bulb and dorsal hippocampus impaired social recognition memory consolidation in different time-points.

To identify an individual as familiar, rodents form a specific type of memory named social recognition memory. The olfactory bulb (OB) is an important structure for social recognition memory, while the hippocampus recruitment is still controversial. The present study was designed to elucidate the OB and the dorsal hippocampus contribution to the consolidation of social memory. For that purpose, we tested the effect of anisomycin (ANI), which one of the effects is the inhibition of protein synthesis, on the consolidation of social recognition memory. Swiss adult mice with cannulae implanted into the CA1 region of the dorsal hippocampus or into the OB were exposed to a juvenile during 5 min (training session; TR), and once again 1.5 h or 24 h later to test social short-term memory (S-STM) or social long-term memory (S-LTM), respectively. To study S-LTM consolidation, mice received intra-OB or intra-CA1 infusion of saline or ANI immediately, 3, 6 or 18 h after TR. ANI impaired S-LTM consolidation in the OB, when administered immediately or 6h after TR. In the dorsal hippocampus, ANI was amnesic only if administered 3 h after TR. Furthermore, the infusion of ANI in either OB or CA1, immediately after training, did not affect S-STM. Moreover, ANI administered into the OB did not alter the animal's performance in the buried food-finding task. Altogether, our results suggest the consolidation of S-LTM requires both OB and hippocampus participation, although in different time points. This study may help shedding light on the specific roles of the OB and dorsal hippocampus in social recognition memory.

Sleep pattern and learning in knockdown mice with reduced cholinergic neurotransmission.

Impaired cholinergic neurotransmission can affect memory formation and influence sleep-wake cycles (SWC). In the present study, we describe the SWC in mice with a deficient vesicular acetylcholine transporter (VAChT) system, previously characterized as presenting reduced acetylcholine release and cognitive and behavioral dysfunctions. Continuous, chronic ECoG and EMG recordings were used to evaluate the SWC pattern during light and dark phases in VAChT knockdown heterozygous (VAChT-KDHET, n=7) and wild-type (WT, n=7) mice. SWC were evaluated for sleep efficiency, total amount and mean duration of slow-wave, intermediate and paradoxical sleep, as well as the number of awakenings from sleep. After recording SWC, contextual fear-conditioning tests were used as an acetylcholine-dependent learning paradigm. The results showed that sleep efficiency in VAChT-KDHET animals was similar to that of WT mice, but that the SWC was more fragmented. Fragmentation was characterized by an increase in the number of awakenings, mainly during intermediate sleep. VAChT-KDHET animals performed poorly in the contextual fear-conditioning paradigm (mean freezing time: 34.4±3.1 and 44.5±3.3 s for WT and VAChT-KDHET animals, respectively), which was followed by a 45% reduction in the number of paradoxical sleep episodes after the training session. Taken together, the results show that reduced cholinergic transmission led to sleep fragmentation and learning impairment. We discuss the results on the basis of cholinergic plasticity and its relevance to sleep homeostasis. We suggest that VAChT-KDHET mice could be a useful model to test cholinergic drugs used to treat sleep dysfunction in neurodegenerative disorders.

Sleep pattern and learning in knockdown mice with reduced cholinergic neurotransmission

Impaired cholinergic neurotransmission can affect memory formation and influence sleep-wake cycles (SWC). In the present study, we describe the SWC in mice with a deficient vesicular acetylcholine transporter (VAChT) system, previously characterized as presenting reduced acetylcholine release and cognitive and behavioral dysfunctions. Continuous, chronic ECoG and EMG recordings were used to evaluate the SWC pattern during light and dark phases in VAChT knockdown heterozygous (VAChT-KDHET, n=7) and wild-type (WT, n=7) mice. SWC were evaluated for sleep efficiency, total amount and mean duration of slow-wave, intermediate and paradoxical sleep, as well as the number of awakenings from sleep. After recording SWC, contextual fear-conditioning tests were used as an acetylcholine-dependent learning paradigm. The results showed that sleep efficiency in VAChT-KDHET animals was similar to that of WT mice, but that the SWC was more fragmented. Fragmentation was characterized by an increase in the number of awakenings, mainly during intermediate sleep. VAChT-KDHET animals performed poorly in the contextual fear-conditioning paradigm (mean freezing time: 34.4±3.1 and 44.5±3.3 s for WT and VAChT-KDHET animals, respectively), which was followed by a 45% reduction in the number of paradoxical sleep episodes after the training session. Taken together, the results show that reduced cholinergic transmission led to sleep fragmentation and learning impairment. We discuss the results on the basis of cholinergic plasticity and its relevance to sleep homeostasis. We suggest that VAChT-KDHET mice could be a useful model to test cholinergic drugs used to treat sleep dysfunction in neurodegenerative disorders.

Reduced hippocampal GABAergic function in Wistar audiogenic rats

Epilepsy is a neurological disorder associated with excitatory and inhibitory imbalance within the underlying neural network. This study evaluated inhibitory γ-amino-butyric acid (GABA)ergic modulation in the CA1 region of the hippocampus of male Wistar rats and Wistar audiogenic rats (aged 90 ± 3 days), a strain of inbred animals susceptible to audiogenic seizures. Field excitatory postsynaptic potentials and population spike complexes in response to Schaffer collateral fiber stimulation were recorded in hippocampal slices before and during application of picrotoxin (50 µM, 60 min), a GABA A antagonist, and the size of the population spike was quantified by measuring its amplitude and slope. In control audiogenic-resistant Wistar rats (N = 9), picrotoxin significantly increased both the amplitude of the population spike by 51 ± 19 percent and its maximum slope by 73 ± 21 percent. In contrast, in slices from Wistar audiogenic rats (N = 6), picrotoxin caused no statistically significant change in population spike amplitude (33 ± 46 percent) or slope (11 ± 29 percent). Data are reported as means ± SEM. This result indicates a functional reduction of GABAergic neurotransmission in hippocampal slices from Wistar audiogenic rats.

Reduced hippocampal GABAergic function in Wistar audiogenic rats.

Epilepsy is a neurological disorder associated with excitatory and inhibitory imbalance within the underlying neural network. This study evaluated inhibitory γ-amino-butyric acid (GABA)ergic modulation in the CA1 region of the hippocampus of male Wistar rats and Wistar audiogenic rats (aged 90 ± 3 days), a strain of inbred animals susceptible to audiogenic seizures. Field excitatory postsynaptic potentials and population spike complexes in response to Schaffer collateral fiber stimulation were recorded in hippocampal slices before and during application of picrotoxin (50 µM, 60 min), a GABA A antagonist, and the size of the population spike was quantified by measuring its amplitude and slope. In control audiogenic-resistant Wistar rats (N = 9), picrotoxin significantly increased both the amplitude of the population spike by 51 ± 19% and its maximum slope by 73 ± 21%. In contrast, in slices from Wistar audiogenic rats (N = 6), picrotoxin caused no statistically significant change in population spike amplitude (33 ± 46%) or slope (11 ± 29%). Data are reported as means ± SEM. This result indicates a functional reduction of GABAergic neurotransmission in hippocampal slices from Wistar audiogenic rats.

Computerized invasive measurement of time-dependent intraocular pressure.

Several methods have been described to measure intraocular pressure (IOP) in clinical and research situations. However, the measurement of time varying IOP with high accuracy, mainly in situations that alter corneal properties, has not been reported until now. The present report describes a computerized system capable of recording the transitory variability of IOP, which is sufficiently sensitive to reliably measure ocular pulse peak-to-peak values. We also describe its characteristics and discuss its applicability to research and clinical studies. The device consists of a pressure transducer, a signal conditioning unit and an analog-to-digital converter coupled to a video acquisition board. A modified Cairns trabeculectomy was performed in 9 Oryctolagus cuniculus rabbits to obtain changes in IOP decay parameters and to evaluate the utility and sensitivity of the recording system. The device was effective for the study of kinetic parameters of IOP, such as decay pattern and ocular pulse waves due to cardiac and respiratory cycle rhythm. In addition, there was a significant increase of IOP versus time curve derivative when pre- and post-trabeculectomy recordings were compared. The present procedure excludes corneal thickness and error related to individual operator ability. Clinical complications due to saline infusion and pressure overload were not observed during biomicroscopic evaluation. Among the disadvantages of the procedure are the requirement of anesthesia and the use in acute recordings rather than chronic protocols. Finally, the method described may provide a reliable alternative for the study of ocular pressure dynamic alterations in man and may facilitate the investigation of the pathogenesis of glaucoma.

Computerized invasive measurement of time-dependent intraocular pressure

Several methods have been described to measure intraocular pressure (IOP) in clinical and research situations. However, the measurement of time varying IOP with high accuracy, mainly in situations that alter corneal properties, has not been reported until now. The present report describes a computerized system capable of recording the transitory variability of IOP, which is sufficiently sensitive to reliably measure ocular pulse peak-to-peak values. We also describe its characteristics and discuss its applicability to research and clinical studies. The device consists of a pressure transducer, a signal conditioning unit and an analog-to-digital converter coupled to a video acquisition board. A modified Cairns trabeculectomy was performed in 9 Oryctolagus cuniculus rabbits to obtain changes in IOP decay parameters and to evaluate the utility and sensitivity of the recording system. The device was effective for the study of kinetic parameters of IOP, such as decay pattern and ocular pulse waves due to cardiac and respiratory cycle rhythm. In addition, there was a significant increase of IOP versus time curve derivative when pre- and post-trabeculectomy recordings were compared. The present procedure excludes corneal thickness and error related to individual operator ability. Clinical complications due to saline infusion and pressure overload were not observed during biomicroscopic evaluation. Among the disadvantages of the procedure are the requirement of anesthesia and the use in acute recordings rather than chronic protocols. Finally, the method described may provide a reliable alternative for the study of ocular pressure dynamic alterations in man and may facilitate the investigation of the pathogenesis of glaucoma.

An electrographic analysis of the synchronous discharge patterns of GEPR-9s generalized seizures.

Previous results from our Laboratory have shown a synchronous discharge pattern (less than 1 ms apart) in monopolar recordings from electrodes placed in the cortex, inferior colliculus, and medulla of seizing GEPR-9s. However, the wave morphology of the ictal EEG is quite different for electrodes placed in different anatomical structures. These results lead us to hypothesize that wave morphology was indicative of neural circuitry involved in the GEPR9 seizure and that volume conduction was accounting for synchronous epileptiform EEG pattern. We decided to approach the problem by using a set of two experiments. Experiment 1: Perform a complete precollicular transection in GEPR-9s before inducing seizure in order to observe changes in EEG morphology after forebrain circuitry removal. Experiment 2: A novel methodological approach using a three-dimensional bipolar array enabled the reconstruction of a vector indicative of to which direction is voltage increasing. Such time-varying vector is indicative of the source direction of the high-amplitude epileptiform EEG signal. By placing such an array of electrodes, used to record the 3 bipolar EEGs, in the forebrain, midbrain, and hindbrain, we were able to use a simple intersection method to infer source localization. Our results suggest that the slow wave component of the GEPR9 epileptiform ictal EEG pattern is associated with a midbrain-forebrain circuit while the spike component is associated with a midbrain-hindbrain substrate. These results are supported by experiment 1 in which only the spike component of EEG remained after the precollicular transection.

Vasopressinergic hypothalamic neurons are recruited during the audiogenic seizure of WARs.

The Wistar Audiogenic Rat (WAR) is a genetic model of reflex epilepsy with seizures induced by high-intensity sound stimulation (120 dB SPL). In spite of the known neural substrates involved in WAR seizure phenotype, neuroendocrine hypothalamic neurons were never investigated. In this work, AVP immunohistochemistry in the hypothalamus and radioimmunoassay (RIA) in plasma and in hypothalamic and hypophysial tissues were performed on both controls and WARs in order to evaluate the dynamics of AVP release due to seizure induction. Susceptible animals (WARs) displayed at least tonic-clonic convulsions followed by clonic spasms, while resistant Wistar rats (R) had no convulsive behavior. Animals were sacrificed at 3 instances: basal condition (without stimulus) and at 3 and 10 min after sound stimulation. For the immunohistochemistry AVP study, brains were harvested and processed by the avidin-biotin-peroxidase detection method. Optic densitometry was used for quantifying AVP labeling in supraoptic (SON) and paraventricular (PVN) hypothalamic nuclei. SON presented higher densitometry levels (%D--relative to background) for both WARs and R when compared to PVN. Nevertheless, both nuclei presented a marked decrease, referenced to basal levels, in %D for WARs at 3 min (approximately 35%) against a discrete change for R (approximately 90%). RIA results were significantly higher in the hypophysis of WARs when compared to R rats, at 3 min. Also, at 3 min, plasma AVP in WARs (89.32 +/- 24.81 pg/mL) were higher than in R (12.01 +/- 2.39 pg/mL). We conclude, based on the AVP releasing profiles, that vasopressinergic hypothalamic neurons are recruited during the audiogenic seizure of WARs.

Baroreflex function in conscious rats submitted to iron overload.

Our hypothesis is that iron accumulated in tissue, rather than in serum, may compromise cardiovascular control. Male Fischer 344 rats weighing 180 to 220 g were divided into 2 groups. In the serum iron overload group (SIO, N = 12), 20 mg elemental iron was injected ip daily for 7 days. In the tissue iron overload group (TIO, N = 19), a smaller amount of elemental iron was injected (10 mg, daily) for 5 days followed by a resting period of 7 days. Reflex heart rate responses were elicited by iv injections of either phenylephrine (0.5 to 5.0 microg/kg) or sodium nitroprusside (1.0 to 10.0 microg/kg). Baroreflex curves were determined and fitted to sigmoidal equations and the baroreflex gain coefficient was evaluated. To evaluate the role of other than a direct effect of iron on tissue, acute treatment with the iron chelator deferoxamine (20 mg/kg, iv) was performed on the TIO group and the baroreflex was re-evaluated. At the end of the experiments, evaluation of iron levels in serum confirmed a pronounced overload for the SIO group (30-fold), in contrast to the TIO group (2-fold). Tissue levels of iron, however, were higher in the TIO group. The SIO protocol did not produce significant alterations in the baroreflex curve response, while the TIO protocol produced a nearly 2-fold increase in baroreflex gain (-4.34 +/- 0.74 and -7.93 +/- 1.08 bpm/mmHg, respectively). The TIO protocol animals treated with deferoxamine returned to sham levels of baroreflex gain (-3.7 +/- 0.3 sham vs -3.6 +/- 0.2 bpm/mmHg) 30 min after the injection. Our results indicate an effect of tissue iron overload on the enhancement of baroreflex sensitivity.

A comprehensive electrographic and behavioral analysis of generalized tonic-clonic seizures of GEPR-9s.

This study records noise-free intracerebral EEG of the genetically epilepsy prone rat (GEPR-9), along with behavioral correlates, during a seizure on unanesthetized freely behaving unrestrained animals. The GEPR-9 exhibits acoustically triggered generalized tonic-clonic seizures, and often times the EEG, recorded with conventional techniques, has resulted in data with imbedded movement artifact. For noise-free video-EEG recordings, we used a previously developed system that consists of a head connector with a FET preamplifier and battery, signal conditioning device (5000x gain, 1 Hz-100 Hz filters), A/D converter and video/PC-PC/video computer boards for recording image data. Each animal was implanted with three monopolar/referential electrodes chosen among the following areas: cortex, inferior colliculus, reticular formation and caudal medulla. The video-EEG data were quite similar for all recorded animals: (1) basal desynchronized EEG before sound stimulus; (2) increase in EEG frequency after stimulus and before seizure onset; (3) high-amplitude polyspikes during massive myoclonic thrusts with or without a very fast running episode; (4) an electrodecremental response during tonic extension; (5) wave and spike complex during forelimb and hindlimb tonic rigidity and posttonic clonus; (6) low-amplitude EEG during postictal depression. Time sequenced spectral analysis also highlights the epileptiform EEG pattern during seizure with high reproducibility between animals. While testing seizure naive GEPR-9s, there was a clear evolution from modest epileptiform EEG activity on the first acoustic stimulation to progressively higher amplitude, duration and frequency epileptiform EEG activity throughout seizure repetition.

Baroreflex function in conscious rats submitted to iron overload

Our hypothesis is that iron accumulated in tissue, rather than in serum, may compromise cardiovascular control. Male Fischer 344 rats weighing 180 to 220 g were divided into 2 groups. In the serum iron overload group (SIO, N = 12), 20 mg elemental iron was injected ip daily for 7 days. In the tissue iron overload group (TIO, N = 19), a smaller amount of elemental iron was injected (10 mg, daily) for 5 days followed by a resting period of 7 days. Reflex heart rate responses were elicited by iv injections of either phenylephrine (0.5 to 5.0 µg/kg) or sodium nitroprusside (1.0 to 10.0 µg/kg). Baroreflex curves were determined and fitted to sigmoidal equations and the baroreflex gain coefficient was evaluated. To evaluate the role of other than a direct effect of iron on tissue, acute treatment with the iron chelator deferoxamine (20 mg/kg, iv) was performed on the TIO group and the baroreflex was re-evaluated. At the end of the experiments, evaluation of iron levels in serum confirmed a pronounced overload for the SIO group (30-fold), in contrast to the TIO group (2-fold). Tissue levels of iron, however, were higher in the TIO group. The SIO protocol did not produce significant alterations in the baroreflex curve response, while the TIO protocol produced a nearly 2-fold increase in baroreflex gain (-4.34 ± 0.74 and -7.93 ± 1.08 bpm/mmHg, respectively). The TIO protocol animals treated with deferoxamine returned to sham levels of baroreflex gain (-3.7 ± 0.3 sham vs -3.6 ± 0.2 bpm/mmHg) 30 min after the injection. Our results indicate an effect of tissue iron overload on the enhancement of baroreflex sensitivity.

A low protein diet causes an increase in the basal levels and variability of mean arterial pressure and heart rate in Fisher rats.

The correlation between nutrition and cardiovascular related disorders is a well-established fact. Previous work from our Laboratory has suggested a significant compromise of cardiovascular reflexes in conscious rats submitted to a low-protein (LP) diet. Our working hypothesis is that the basal level of mean arterial pressure (MAP), variability of the mean arterial pressure (VMAP), heart rate (HR) and variability of heart rate (VHR) are altered in rats submitted to a protein restricted diet. Two experimental groups were used: control group (normal protein 15%, NP) and malnourished group (low-protein 6%, LP). In order to verify the efficiency of the dietary restriction we measured body weight, total blood protein, plasma albumin, urea and glucose. Our experiments demonstrated that the malnourished rats presented augment levels of basal MAP (LP 122+/-2 mmHg vs. NP 113+/-1 mmHg) and of VMAP (LP 12.8+/-1.5mmHg vs. NP 9+/-1mmHg) when compared to the control group. We observed similar increased levels, in the malnourished group, for both HR (LP 429+/-8 bpm vs. NP 381+/-7bpm) and VHR (LP 67.6+/-8.3bpm vs. NP 44.4+/-4.9bpm). Our results suggest a correlation between the LP diet in Fisher rats and the increased basal levels of mean arterial pressure, HR and their respective variability.

Assessment of the seizure susceptibility of Wistar Audiogenic rat to electroshock, pentyleneterazole and pilocarpine.

This work evaluates the seizure susceptibility of nai;ve female Wistar Audiogenic rats (WARs), a genetic model of reflex epilepsy in which seizures are induced by high-intensity sound stimulation (120 dB SPL), to other pro-convulsive stimuli: transauricular electroshock (ES), pentylenetetrazole (PTZ) and pilocarpine (PILO). Normal Wistar rats from the main breeding stock of the Institute of Biological Sciences, UFMG were taken as controls. Electroshock seizures were induced through a pair of ear-clip electrodes (10 mA, at a frequency of 60 Hz, applied for 1 s). In order to test WAR susceptibility to chemically induced seizures, animals were treated either with PTZ (37.5 mg/kg i.p.) or PILO (200, 270 and 300 mg/kg i.p.). Seizure severity was evaluated by appropriate behavioral severity index scales (SI) specific to each epilepsy model and tested for statistical significance using the non-parametric Mann-Whitney Rank Sum test. Results show a significantly greater susceptibility of WARs for ES (SI(WAR)=3+/-3/3, SI(Wistar)=1+/-1/1; median+/-interquartile range 25%/75%, P<0.01) and PTZ (SI(WAR)=4+/-4/4, SI(Wistar)=1+/-1/4; median+/-interquartile range 25%/75%, P<0.02), as indicated by significantly higher SI scores and shorter latencies for seizure onset (T(WAR)=71+/-7 s, T(Wistar)=94+/-8 s; P<0.05 Student t-test, mean+/-S.E.M.). Although PILO also caused higher SI scores in WARs (WAR(200 mg)=1+/-1/1, Wistar(200 mg)=1+/-1/1; WAR(270 mg)=1.5+/-1/2, Wistar(270 mg)=1+/-1/1.25; WAR(300 mg)=9+/-1/9, Wistar(300 mg)=4+/-1.5/7.5; median+/-interquartile range 25%/75%), statistically significant differences were not observed. In conclusion, our results show that WARs have an inherited broader predisposition for seizures.

Glass pipette-carbon fiber microelectrodes for evoked potential recordings

Current methods for recording field potentials with tungsten electrodes make it virtually impossible to use the same recording electrode also as a lesioning electrode, for examples for histological confirmation of the recorded site, because the lesioning procedure usually wears off the tungsten tip. Therefore, the electrode would have to be replaced after each lesioning procedure, which is a very high cost solution to the problem. We present here a low cost, easy to make, high quality glass pipette-carbon fiber microelectrode that shows resistive, signal/noise and elctrochemical coupling advantages over tungsten electrodes. Also, currently used carbon fiber microelectrodes often show problems with electrical continuity, especially regarding electrochemical applications using a carbon-powder/resin mixture, with consequent low performance, besides the invonvenience of handling such a mixture. We propose here a new method for manufacturing glass pipette-carbon fiber microelectrodes with several advantages when recording intracerebral field potentials.

Low-cost automatic activity data recording system

We describe a low-cost, high quality device capable of monitoring indirect activity by detecting touch-release events on a conducting surface, i.e., the animal's cage cover. In addition to the detecting sensor itself, the system includes an IBM PC interface for prompt data storage. The hardware/software design, while serving for other purposes, is used to record the circadian activity rhythm pattern of rats with time in an automated computerized fashion using minimal cost computer equipment (IBM PC XT). Once the sensor detects a touch-release action of the rat in the upper portion of the cage, the interface sends a command to the PC which records the time (hours-minutes-seconds) when the activity occured. As a result, the computer builds up several files (one per detector/sensor) containing a time list of all recorded events. Data can be visualized in terms of actograms, indicating the number of detections per hour, and analyzed by mathematical tools such as Fast Fourier Transform (FFT) or cosinor. In order to demonstrate method validation, an experiment was conducted on 8 Wistar rats under 12/12-h ligh/dark cycle conditions (lights on at 7:00 a.m.). Results show a biological validation of the method since it detected the presence of circadian activity rhythm patterns in the behavior of the rats.