Screw Electrodes Research Articles

Reduced conduction function in central nervous system by 2,5-hexanedione

In order to examine the involvement of the central nervous system (CNS) following administration of 2,5-hexanedione (2,5-HD) in rats, the present experiment was conducted using the auditory brainstem response (ABR) and somatosensory-evoked potentials (SEPs). Nine male Wistar rats were given 2,5-HD subcutaneously at 350 mg/kg/day, five days a week for three weeks. For the control group, nine male rats were employed. One week after the last administration, ABRs were measured from the scalp with subcutaneous needle electrodes under pentobarbital anesthesia. Click sounds of 61 and 86 dB sound pressure level were used in ABR measurement (61dB-ABR and 86dB-ABR, respectively). The SEP evoked by stimulation at the forepaw and the medulla oblongata (SEP and SEP-M) were recorded from the surface of the cerebral cortex using screw electrodes under immobilization. The significant findings observed in 2,5-HD-treated rats included: 1) delayed latencies of the Ist, IIIrd, IVth and Vth components of the 61dB-ABR and the Ist, IInd, IIIrd and Vth components of the 86dB-ABR; 2) increased interpeak latencies (IPLs) between III-V and I-V of the 61dB-ABR; 3) delayed latencies of the P1 and N1 components of the SEP and the N1 component of the SEP-M. The delays of IPL-III-V of the 61dB-ABR and the N1 component of the SEP-M were considered to reflect conduction disorders of the auditory and somatosensory afferent pathway in the CNS, respectively. Thus, the ABR may be a sensitive method to detect disorders in the CNS produced by neurotoxic substances.

Clinical Utility of Telemetered Intracardiac Electrograms in Diagnosing a Design Dependent Lead Malfunction

Inhibition of pacemakers due to false signals from malfunctioning pacing leads has been previously reported. Three cases are reported in which inappropriate pauses were observed shortly following implantation. In all three cases, active fixation leads with an electronically active screw and ring tip electrode were used. All leads were manufactured by Oscor Medical, St. Petersburg, Florida. In case one, models PY-61 (ventricle) and PY-51 (atrium) were used. In case two, models PY-61 were used in the ventricle and the atrium. In case three, models PY-52 were used both in the atrium and ventricle. Thresholds at the time of implantation were acceptable. In cases one and two, inappropriate pauses were noted following paced ventricular beats. In case three, inappropriate inhibition of the ventricular output was noted intermittently after some of the paced atrial beats. Spurious signals were identified as the cause of the apparent oversensing problem by using electrocardiograms with annotated telemetry information and noninvasively telemetered intracardiac electrograms. The amplitude of the spurious signals varied between 2 and 14 mV. In all cases, the problems resolved with time. A mechanism for the generation of false transients is proposed and the value of telemetered intracardiac electrograms is discussed.

Effects of cocaine on the brain-stem auditory evoked potential in the Long-Evans rat

The present study examined the effects of an acute psychoactive dose of cocaine hydrochloride (HCl) in the rat, using the brain-stem auditory potential (BAEP) as an objective, quantitative measure of this substance's effects on brain and auditory electrophysiology. The animals were 8 adult Long-Evans rats (4 female, 4 male). BAEPs were recorded from skull screw electrodes during a baseline period as well as 30–90 min after cocaine HCl treatment (10 mg/kg, i.p.). Normothermia was maintained to control for possible temperature-related effects. Cocaine's effects on the BAEP were examined over a broad range of stimulus intensities (intensity profiles) and repetition rates (rate profiles). Cocaine prolonged latencies of several BAEP components at low stimulus intensities and shortened these latencies at high stimulus intensities. The average BAEP threshold was alos increased by cocaine treatment. These results were not strong, but were suggestive of a recruitment type change in auditory function. Cocaine treatment had no convincing effects on the BAEP as a function of stimulus repetition rate.

Electrophysiological and morphological evidence for a diameter-based innervation pattern of the superior colliculus

Neurophysiological and morphological techniques were used to describe changes in the optic tract and superior colliculus (SC) in response to unilateral enucleation. Long-Evans, male (>250 g) rats were implanted with chronic bipolar stimulating electrodes located in the optic chiasm and a recording electrode located below the stratum griseum superficiale (SGS) and referenced to a skull screw electrode. In rats with satisfactory electrode placements ( n = 15), peaks corresponding to rapidly conducting presynaptic activity (Pre), rapidly conducting postsynaptic activity (N1), and slowly conducting postsynaptic activity (P3) were identified according to peak latency, polarity, stimulation threshold, and resistance to 100-Hz stimulation. These peaks diminished differentially over a 7 day (D 1–7) postenucleation period. Those peaks reflecting rapidly conducting axons (i.e., Pre, N1) decayed by D 2, whereas those reflecting slowly conducting axons (i.e., P3) persisted until D 4 and decayed completely by D 7. In a separate set of enucleated rats ( n = 25), the progression of degeneration in the SC was outlined morphologically from D 1–7 using both light and electron microscopy. Light microscopy of semithin epoxy sections indicated that degenerative changes, consisting largely of swollen axons and myelin debris, appeared first in the upper stratum opticum (SO) and lower SGS on D 1,2, progressed upward throughout the middle SGS by D 4, and finally involved the entire SGS and lower stratum zonale (SZ) by D 5–7. Electron microscopy, however, indicated that although degenerated terminals were seen in the lower SGS, at (D 1,2), the majority of degenerated synapses were restricted to the upper SGS at the later time points. Coupled with the electro-physiological data, these observations indicate that within the SGS, early degenerating, large diameter optic nerve fibers terminate below slower degenerating, smaller diameter fibers.

Dose-dependent effects of atropine sulfate on the brainstem and cortical auditory evoked potentials in the rat

Because brainstem auditory evoked potentials (BAEPs) are frequently recorded in anesthetized animals and humans, it is important to become familiar with the effects on the BAEP of drugs used during anesthesia, including pre-anesthetics. The dose-dependent and stimulus intensity-dependent effects on the BAEP of a pre-anesthetic, atropine sulfate, were studied in the unanesthetized rat. The animal subjects were 11 adult female Long-Evans rats. BAEPs in response to 0.1 ms clicks (12.5/s) were recorded from skull screw electrodes during a baseline period, as well as after saline and atropine treatments. Atropine sulfate was given i.p. in doses ranging from 0.250 to 40 mg/kg. Contrary to a prior report, doses in the standard pre-anesthetic range (i.e. 0.250–1.000 mg/kg) did not convincingly influence the BAEP. Only the highest dose (40 mg/kg) produced a significant and noteworthy change in the BAEP. This effect was characterized by significant amplitude increases in the P1, P2 and P3 components, but not in the P4, P5 and P6 components. This selective effect occurred at the highest stimulus intensity of 110 dB peak equivalent sound pressure level, but not at lower intensities. There were no convincing atropine-induced changes in BAEP latencies. Atropine-induced changes in the cortical auditory evoked potential (CAEP) were characterized by amplitude decrements. Thus, atropine seemed to have an excitatory effect on the BAEP and an inhibitory or depressive effect on the CAEP.

Acute effects of a Khat extract on the rat electroencephalogram

Rats chronically implanted with cortical screw electrodes were treated with three different oral doses of a Khat extract and the EEG recorded for 5 h. Several abnormalities in EEG patterns were observed, particularly after the administration of the largest dose (400 mg/kg). Spectral analysis of EEG showed a significant shift of frequencies towards faster, lower voltage activity following administration of the two smaller doses (50 and 100 mg/kg), reflecting a stimulant effect of the extract. The highest degree of cortical activation was observed following administration of the smallest dose. With the largest dose, an initial activation was followed by a state of EEG depression characterized by a high percentage of slow, high voltage waves. It is concluded that Khat extract in small doses has a stimulant effect on the rat brain, but with larger doses induces a state of depression.

Effects of ketamine anesthesia on the rat brain-stem auditory evoked potential as a function of dose and stimulus intensity

Because ketamine is both an abused substance and a commonly used veterinary anesthetic, its effects on brain and sensory functions are of interest. The present study examined the dose-dependent effects of ketamine anesthesia in the rat, using the brain-stem auditory evoked potential (BAEP) as an objective, quantitative measure of this substance's acute effects on brain and sensory electrophysiology. The animal subjects were 11 young adult female Long-Evans rats. BAEPs were recorded from skull screw electrodes during a baseline period as well as after saline and ketamine treatments. Ketamine was administered (i.p.) in 2 serial doses. The first dose (100 mg/kg) was followed 30–40 min later by a second dose (also 100 mg/kg). Equal volumes of normal saline were also injected serially. An interval of 1–2 weeks occurred between the saline and ketamine treatments, with treatment order counterbalanced. Normothermia was maintained to control for possible temperature-related effects. Ketamine produced prolongations in the latencies of all BAEP components (P1 through P6) that were statistically significant relative to baseline values. These latency shifts were progressively greater for waves P1 through P4 (shifts in P5 and P6 approximated the P4 shift). The effect of the second ketamine injection was to nearly double the latency shifts. Ketamine also had significant and complex effects on BAEP amplitudes that were dependent on dose and stimulus intensity. The resukts of the present study challenge the belief that the BAEP is resistant to the effects of anesthetics and suggest that the BAEP is useful in characterizing the CNS and sensory effects of these pharmacological agents.

Effect of body temperature on the ventilatory responses in the lizard Gallotia galloti

A new technique for recording ventilatory frequency on small lizards is described. This is based on the record of the electrical potential that spontaneously atises during the ventilatory cycle between an active steel needle electrode, implanted in the membrane of the nasal cavity, and a reference stainless steel screw electrode implanted on the parietal bone. The nasal ventilatory signal coming from these electrodes, together with a simultaneous record of the electromyogram of intercostal muscles, was used to investigate the pulmonary ventilation of the lizard Gallotia galloti over the body temperature range 5–35 °C. The results suggest that the ventilation pattern of this lizard begins with a passive expiration, in which electromyographic activity is not present, followed by an active expiration and then an active inspiration, these being separated by a shorter muscullar resting period. The active expiration lasts longer than the active inspiration over all the range of body temperatures studied. The ventilatory frequency increases exponentially with body temperature. The duration of the muscular activity during the ventilatory cycle, in the 10–35 °C range of body temperature, is approximately half the ventilatory period and decreases exponentially with body temperature at half the rate at which the ventilatory period decreases. The duration of several electromyographic events recorded during the ventilatory cycle also decreases exponentially with body temperature.

Superior colliculus lesions and flash evoked potentials from rat cortex

It is generally assumed that the primary response of the rat flash evoked potential (FEP) is activated by a retino-geniculate path, and that the secondary response reflects input to the cortex by way of the superior colliculus (SC) or other brainstem structures. In the present study, male Long-Evans rats were implanted with monopolar screw electrodes placed over the left visual cortex, and a pair of twisted monopolar depth electrodes, which were used to produce electrolytic lesions, were placed in each SC. One half of the animals did not receive the electrolytic treatment (controls). FEP waveforms were obtained from all animals prior to treatment and 2 and 5 days after treatment. Histological analysis was performed to verify electrode placement and determine lesion size. Electrolytic lesions resulting in massive destruction of the SC produced no decrement in any portion of the rat FEP but did produce an increase in amplitude of the N2P3 component. The data show that the secondary response is not generated by SC in rats, but that SC may modulate amplitude of the response.

Convulsant component of a depressant benzodiazepine

The convulsant influence of high doses of diazepam, in the presence of the benzodiazepine receptor antagonist Ro 15-1788, was studied in rats. Animals were implanted with permanent cortical screw electrodes for EEG recording. EEG spiking and accompanying clonic activity was observed in rats receiving ≥ 20 mg/kg diazepam, followed 10 minutes later by Ro 15-1788 (20 mg/kg). Pentylenetetrazole and picrotoxin seizure thresholds, measured during constant rate iv infusion, were significantly lowered by pretreatment with diazepam (250 mg/kg) and Ro 15-1788 (20 mg/kg) administered 30 and 20 minutes, respectively, before seizure threshold measurement. It is proposed that this convulsive activity of diazepam is mediated through the picrotoxinin receptor.

Auditory middle latency responses in the guinea pig

Auditory middle latency responses (latencies 6 to 50 msec in guinea pigs) were recorded from eight awake, restrained guinea pigs. Before recording, screw electrodes were implanted in the skull in a coronal plane in line with the bregma. Another electrode, which served to monitor auditory brainstem responses, was placed 1 cm posterior to the bregma. All electrodes were referenced to a lead positioned 2 cm anterior to the bregma. During the recording session, click stimuli of various repetition rates and intensity levels were delivered monaurally in a closed sound system. Auditory brainstem responses were monitored to ensure normal functioning of the peripheral auditory system. Responses from electrodes at the midline and over the temporal area ipsilateral to the stimulus ear were greatly attenuated or absent. From an electrode over the temporal area contralateral to the stimulus ear, two positive peaks occurred at latencies of approximately 12 and 27 msec. A negative trough was identified at approximately 17 msec. Latency and amplitude functions for this waveform were determined for various stimulus levels. Response amplitude increased as stimulus repetition rate was decreased. Anesthesia greatly altered waveform structure and prolonged peak latencies. These effects were more marked at stimulus repetition rates faster than 10/sec than at slower rates. Properties of the guinea pig middle latency response are compared with those previously reported for cats and humans.

Effects of α- and β-adrenergic receptor antagonists on retrograde amnesia produced by frontal cortex stimulation

This study assessed the effects of adrenergic antagonists on the development of retrograde amnesia. Animals were trained on either a one-trial inhibitory (passive) avoidance task or a visual discriminated avoidance Y-maze. Thirty minutes prior to training animals received an injection of the β-adrenergic antagonists propranolol (0.5 mg/kg), saline, or one of the following α -adrenergic antagonists: phentolamine (10 mg/kg), piperoxane (5 mg/kg), or phenoxybenzamine (2 mg/kg). Shortly after training, the animals received frontal cortex stimulation (5 mA/1 sec) through implanted cortical screw electrodes. The results indicate that pretreatment of rats with any of these α - and β -adrenergic antagonists attenuates the production of retrograde amnesia. These findings add further support to the view that an adrenergic response to amnestic treatments may be a component of a restricted set of biological systems that are involved in retrograde amnesia.

Morphological evidence that feline SMR and human Mu are analogous rhythms

In cats implanted with epidural screw electrodes over sensorimotor cortex, various recording montages were used to observe the waveform of the sensorimotor rhythm (SMR). It was found that in bipolar recordings spanning the crus, SMR exhibited a wicket-shaped waveform comparable in shape and polarity to the human mu rhythm. Based on previously reported topographic and functional similarities of feline SMR and human mu, and on the present data demonstrating morphological similarities, it appears that feline SMR is the first proven feline model of a spontaneous human ieeg rhythm.

Properties of somatosensory evoked cortical potentials in alert, chronic cats

Somatosensory evoked cortical potentials in alert, chronic cats were studied (i) to determine the relative responsiveness of primary somatosensory and late, nonspecific evoked potentials to stimulus intensity and (ii) to observe the long-term effects on late responses of ablating the somatosensory cortex. Screw electrodes were first implanted in the skull bilaterally over the primary somatosensory area and along the marginal and suprasylvian gyri. Recordings revealed two positive-negative late responses, designated P 1- N 1 and P 2- N 2, at the nonspecific sites. Primary and P 1- N 1 responses proved to be about equally sensitive to stimulus intensity and considerably more sensitive than P 2- N 2 responses in a stimulus range of 0.3 to 9 mA. In two succeeding operations, spaced a few weeks apart, left and right somatosensory areas were ablated. Postablation records showed that each nonspecific electrode that registered prelesion responses also displayed postlesion responses. In several animals, P 1- N 1 amplitude was enhanced above prelesion levels after both unilateral and bilateral ablations, whereas P 2- N 2 was consistently diminished after bilateral ablations. There thus appear to be two distinguishable late potentials along the marginal and suprasylvian gyri in awake, alert cats, differentiable by their sensitivity to stimulus intensity and to lesions of the primary somatosensory area.

A technique for EEG recording in the awake parakeet

the proper stereotaxic instrument for thespecies, (2) some degree of surgical sophistication,(3) sterile surgical conditions, (4) an accurate atlas of thespecies' brain and cranial bones, and (5) an anestheticduring the recording session. One of the standardtechniques used to circumvent some of these problems isto use stainless steel screw electrodes that are screwedinto the skull and held by dental acrylic. However, theparakeet skull is extremely thin and fragile-asis the casewith most small birds. This precluded the use of screwelectrodes and prompted the development of alternativeand somewhat simpler methods for attaching electrodesto the parakeet. These procedures may be ofparticularvalue in view of the recent interest in avian sleepprocesses and sensory processes (Van Twyver & Allison,1972; Dooling & Saunders. 1974).The skin covering the underside of the lower beak inthe parakeet is thin. This enables one to insert a 30-ga,Kynar-coated solid wire through the underside of themandible into the oral cavity and wrap it tightly aroundthe lateral portion of the lower beak. (See lower half ofFigure 1.) The length of wire wrapped around the beakis stripped to permit good electrical contact. Thisprocedure is applied to both sides of the parakeet'sbeakto provide both a ground and a reference electrode. Theinsulated portions of these beak electrode wires are ledto the back of the bird'shead, pulled taut, and threadedthrough the side holes ofa standard three-poletransistorplug as indicated in the upper half ofFigure I.A number of types of skull electrodes have been usedin combination with these beak electrodes. Theseinclude a 2 mm in diam coil of silver wire or a disk ofsilver foil, dental screws, and inverted wire nails.Regardless of the electrode type, it is attached to theskull using the following general procedures.The bird's head is cleaned with alcohol, and anincision is made along the medial axis of the scalpextending from the cere about 2 ern posteriorly. Theskin is pulled back, the skull surface wiped clean with acotton swab, and the electrode cemented to the skullwith conventional dental acrylic. The electrode lead isthen led to the third pole of the transistor plug. The

A simple electrode to record fetal EEG for optimal signal analysis

A simple EEG electrode for Intrauterine use In the human fetus is described. The stainless steel screw electrode possesses low noise characteristics, is constructed from commercially available material, and is easily attached to the fetal head during labor. Principles of optical signal analysis as an improved method of spectral analysis of the fetal EEG are also presented. The optical system provides visual display and hard copy output of the fetal EEG.

Influence of fatigue on sleep.

FATIGUE is thought to influence the humoral factors which increase and decrease the sensitivity of the sleep control centres. We have studied the influence of somatic fatigue on sleep, especially paradoxical sleep, in seventeen adult male albino rats with chronically implanted electrodes. The rats were anaesthetized with ‘Nembutal’ (35 mg/kg intraperitoneally) and a pair of screw electrodes were placed on the skull, overlying the frontal and occipital cortices. The electromyograph (EMG) was recorded by surgical needles inserted into the neck muscles and the electrocardiogram (ECG) by a surgical needle electrode in a posterior paw, referred to the neck muscle. Respiration was recorded by a pneumographic method, using a short rubber tube filled with active charcoal. To record eye movement, two stainless steel electrodes fixed to a plastic plate were inserted into the eyeball from the outside of the orbit.