scholarly journals Reduction of spike generation frequency by cooling in brain slices from rats and from patients with epilepsy

2018 ◽  
Vol 39 (11) ◽  
pp. 2286-2294 ◽  
Author(s):  
Sadahiro Nomura ◽  
Hiroyuki Kida ◽  
Yuya Hirayama ◽  
Hirochika Imoto ◽  
Takao Inoue ◽  
...  
Keyword(s):  
Brain Temperature ◽  
Brain Slices ◽  
Intractable Epilepsy ◽  
Spike Frequency ◽  
Temporal Lobectomy ◽  
Resting Potential ◽  
Brain Cooling ◽  
Firing Threshold ◽  
Epileptic Discharge ◽  
Human Neurons

This study aimed to understand the mechanism by which brain cooling terminates epileptic discharge. Cortical slices were prepared from rat brains (n = 19) and samples from patients with intractable epilepsy that had undergone temporal lobectomy (n = 7). We performed whole cell current clamp recordings at approximately physiological brain temperature (35℃) and at cooler temperatures (25℃ and 15℃). The firing threshold in human neurons was lower at 25℃ (−32.6 mV) than at 35℃ (−27.0 mV). The resting potential and spike frequency were similar at 25℃ and 35℃. Cooling from 25℃ to 15℃ did not change the firing threshold, but the resting potential increased from −65.5 to −54.0 mV and the waveform broadened from 1.85 to 6.55 ms, due to delayed repolarization. These changes enhanced the initial spike appearance and reduced spike frequency; moreover, spike frequency was insensitive to increased levels of current injections. Similar results were obtained in rat brain studies. We concluded that the reduction in spike frequency at 15℃, due to delayed repolarization, might be a key mechanism by which brain cooling terminates epileptic discharge. On the other hand, spike frequency was not influenced by the reduced firing threshold or the elevated resting potential caused by cooling.

Morphological and Electrophysiological Properties of Principal Neurons in the Rat Lateral Amygdala In Vitro

2001 ◽  
Vol 85 (2) ◽  
pp. 714-723 ◽  
Author(s):  
E.S.L. Faber ◽  
R. J. Callister ◽  
P. Sah
Keyword(s):  
Cell Morphology ◽  
Brain Slices ◽  
Spike Trains ◽  
Spike Frequency ◽  
Morphological Properties ◽  
Spike Frequency Adaptation ◽  
Differential Distribution ◽  
Lateral Amygdala ◽  
Frequency Adaptation ◽  
Firing Properties

In this study, we characterize the electrophysiological and morphological properties of spiny principal neurons in the rat lateral amygdala using whole cell recordings in acute brain slices. These neurons exhibited a range of firing properties in response to prolonged current injection. Responses varied from cells that showed full spike frequency adaptation, spiking three to five times, to those that showed no adaptation. The differences in firing patterns were largely explained by the amplitude of the afterhyperpolarization (AHP) that followed spike trains. Cells that showed full spike frequency adaptation had large amplitude slow AHPs, whereas cells that discharged tonically had slow AHPs of much smaller amplitude. During spike trains, all cells showed a similar broadening of their action potentials. Biocytin-filled neurons showed a range of pyramidal-like morphologies, differed in dendritic complexity, had spiny dendrites, and differed in the degree to which they clearly exhibited apical versus basal dendrites. Quantitative analysis revealed no association between cell morphology and firing properties. We conclude that the discharge properties of neurons in the lateral nucleus, in response to somatic current injections, are determined by the differential distribution of ionic conductances rather than through mechanisms that rely on cell morphology.

scholarly journals Millimetre wave radiation activates leech nociceptors via TRPV1-like receptor sensitisation

2018 ◽  
Author(s):  
S. Romanenko ◽  
A. R. Harvey ◽  
L Hool ◽  
R. Begley ◽  
S. Fan ◽  
...  
Keyword(s):  
Brain Slices ◽  
Potassium Conductance ◽  
Resting Potential ◽  
Wave Radiation ◽  
60 Ghz ◽  
Membrane Excitability ◽  
Millimetre Wave ◽  
Conductive Heating ◽  
Exposure Levels

AbstractDue to new applications such as wireless communications, security scanning, and imaging the presence of artificially generated high frequency (30-300 GHz) millimetre-wave (MMW) signals in the environment is increasing. Although safe exposure levels have been set by studies involving direct thermal damage to tissue, there is evidence that MMWs can have an impact on cellular function, including neurons. Earlier in vitro studies have shown that exposure levels well below the recommended safe limit of 1mW/cm2 cause changes in the action potential (AP) firing rate, resting potential, and AP pulse shape of sensory neurons in leech preparations, as well as alter neuronal properties in rat cortical brain slices; these effects differ from changes induced by direct heating. In this paper we examine continuous MMW power (up to 80 mW/cm2 at 60 GHz) and evaluate the responses in the thermosensitive primary nociceptors of the medicinal leech (genus Richardsonianus Australis). The results show that MMW exposure causes an almost two-fold decrease in the threshold for activation of the AP compared with conductive heating (3.6±0.4 mV vs. 6.5±0.4 mV respectively). Our analysis suggests that MMW exposure mediated threshold alterations are not caused by enhancement of voltage gated sodium and potassium conductance. Moreover, it appears that MMW exposure has a modest suppressing effect on membrane excitability. We propose that the reduction in AP threshold can be attributed to sensitization of the TRPV1-like receptor in the leech nociceptor. In silico modelling supported the experimental findings. Our results provide evidence that MMW exposure stimulates specific receptor responses that differ from direct conductive heating, fostering the need for additional studies.

Rectal temperature measurement results in artifactual evidence of selective brain cooling

2001 ◽  
Vol 281 (1) ◽  
pp. R108-R114 ◽  
Author(s):  
Shane K. Maloney ◽  
Andrea Fuller ◽  
Graham Mitchell ◽  
Duncan Mitchell
Keyword(s):  
Rectal Temperature ◽  
Brain Temperature ◽  
Brain Cooling ◽  
Selective Brain Cooling ◽  
Blood Temperature ◽  
Arterial Blood ◽  
The Status ◽  
Conscious Sheep ◽  
Surrogate Measures ◽  
Arterial Blood Temperature

Selective brain cooling (SBC) is defined as a brain temperature cooler than the temperature of arterial blood from the trunk. Surrogate measures of arterial blood temperature have been used in many published studies on SBC. The use of a surrogate for arterial blood temperature has the potential to confound proper identification of SBC. We have measured brain, carotid blood, and rectal temperatures in conscious sheep exposed to 40, 22, and 5°C. Rectal temperature was consistently higher than arterial blood temperature. Brain temperature was consistently cooler than rectal temperature during all exposures. Brain temperature only fell below carotid blood temperature during the final few hours of 40°C exposure and not at all during the 5°C exposure. Consequently, using rectal temperature as a surrogate for arterial blood temperature does not provide a reliable indication of the status of the SBC effector. We also show that rapid suppression of SBC can result if the animals are disturbed.

scholarly journals A-38 Examining Cognitive Differences of Pre- and Post- Surgery in Pediatric Epilepsy

2019 ◽  
Vol 34 (6) ◽  
pp. 897-897
Author(s):  
I Cernokova ◽  
D Bearden ◽  
A Gordon ◽  
K Ono
Keyword(s):  
Block Design ◽  
Verbal Ability ◽  
Intractable Epilepsy ◽  
Temporal Lobectomy ◽  
Pediatric Epilepsy ◽  
Verbal Iq ◽  
Post Surgery ◽  
Neuropsychological Evaluations ◽  
Domain Block ◽  
Perceptual Reasoning

Abstract Objective Intractable epilepsy is often associated with cognitive difficulties in the language domain. Few studies examining verbal domains of cognitive functioning indicate a small increase of verbal skills post-surgery. The current study compared Verbal IQ and Performance IQ domains in pediatric populations before and after open resection surgery. Method Participants included 31 epilepsy patients (age 5-20 years old; M = 12.23 years pre-surgery; M = 14.72 years post-surgery; 20 males, 11 females) who underwent neuropsychological evaluations prior to and following an open brain resection surgery (i.e., temporal lobectomy, temporal resection, frontal lobectomy). Cognitive ability was assessed by Weschler Abbreviated Scale of Intelligence (WASI) in order to analyze differences between pre-surgical and post-surgical cognitive function, specifically verbal comprehension and perceptual reasoning ability. Results No statistically significant differences were found, using a One-way ANOVA, between the two groups; however, a downward trend was noted for the Verbal IQ (VIQ) domain, F(1, 25) = 2.624, p = 0.118, including the verbal subtests vocabulary, F(1, 23) = 2.203, p = 0.151, and similarities, F(1, 24) = 1.678, p = 0.207. No differences or trends were noted within the Performance IQ (PIQ) domain, block design, or matrix reasoning. Conclusions Findings indicated that participants verbal ability decreased after epilepsy surgery when compared to prior evaluations. This is not consistent with previous research, which stated an increase in verbal abilities following surgical resection. Variable time between surgery and re-evaluation might account for discrepancies. Further, no differences in nonverbal reasoning abilities were noted. Results indicated a need for further research in open brain resection surgeries and the outcome of verbal processing.

scholarly journals Intractable Temporal Lobe Epilepsy (TLE) From Tuberculoma; Microneurosurgical Management of by Amygdalohippocampectomy with Lesionectomy Plus Standard Anterior Temporal lobectomy: A Case Report and Short Review of Literature

2019 ◽  
Vol 16 (2) ◽  
pp. 106-109
Author(s):  
Forhad Hossain Chowdhury ◽  
Mohammod Raziul Haque ◽  
AFM Momtazul Haque
Keyword(s):  
Temporal Lobe Epilepsy ◽  
Temporal Lobe ◽  
Medial Temporal Lobe ◽  
Venous Malformation ◽  
Intractable Epilepsy ◽  
Complex Partial Seizure ◽  
Temporal Lobectomy ◽  
Mesial Temporal Sclerosis ◽  
Low Grade ◽  
Presenting Symptoms

Patient presenting as a case of Temporal Lobe Epilepsy (TLE) are usually resistant to antiepileptic drugs and surgery is the treatment of choice. This type of epilepsy may be due to Mesial Temporal Sclerosis (MTS), tumors [i.e. low grade glioma, Arterio-venous Malformation (AVM) etc], trauma, infection (Tuberculosis) etc. Here we report a case of surgically treated TLE that was due to a large tuberculoma in medial temporal lobe. Intractable epilepsy caused by tuberculoma is rare. The only presenting symptoms was Complex partial seizure (Psychomotor epilepsy) for which the patient underwent scalp EEG (Electro Encephalography) and MRI (Magnetic resonance imaging) of brain. The patient was managed by amygdalohippocampectomy with lesionectomy plus standard anterior lobectomy. Postoperatively she was on anti-tubercular therapy and on carbamazepine. The case was seizure and disease free till last follow up. Journal of Surgical Sciences (2012) Vol. 16 (2) : 106-109

Integration of jugular venous return and circle of Willis in a theoretical human model of selective brain cooling

2007 ◽  
Vol 103 (5) ◽  
pp. 1837-1847 ◽  
Author(s):  
Matthew A. Neimark ◽  
Angelos-Aristeidis Konstas ◽  
Andrew F. Laine ◽  
John Pile-Spellman
Keyword(s):  
Venous Return ◽  
Mild Hypothermia ◽  
Brain Temperature ◽  
Circle Of Willis ◽  
Human Model ◽  
Anterior Communicating Artery ◽  
Moderate Hypothermia ◽  
Brain Cooling ◽  
Bioheat Equation ◽  
Selective Brain Cooling

A three-dimensional mathematical model was developed to examine the induction of selective brain cooling (SBC) in the human brain by intracarotid cold (2.8°C) saline infusion (ICSI) at 30 ml/min. The Pennes bioheat equation was used to propagate brain temperature. The effect of cooled jugular venous return was investigated, along with the effect of the circle of Willis (CoW) on the intracerebral temperature distribution. The complete CoW, missing A1 variant (mA1), and fetal P1 variant (fP1) were simulated. ICSI induced moderate hypothermia (defined as 32–34°C) in the internal carotid artery (ICA) territory within 5 min. Incorporation of the complete CoW resulted in a similar level of hypothermia in the ICA territory. In addition, the anterior communicating artery and ipsilateral posterior communicating artery distributed cool blood to the contralateral anterior and ipsilateral posterior territories, respectively, imparting mild hypothermia (35 and 35.5°C respectively). The mA1 and fP1 variants allowed for sufficient cooling of the middle cerebral territory (30–32°C). The simulations suggest that ICSI is feasible and may be the fastest method of inducing hypothermia. Moreover, the effect of convective heat transfer via the complete CoW and its variants underlies the important role of CoW anatomy in intracerebral temperature distributions during SBC.

Predictive value of Wada memory scores on postoperative learning and memory abilities in patients with intractable epilepsy

2006 ◽  
Vol 104 (1) ◽  
pp. 20-26 ◽  
Author(s):  
Fani Andelman ◽  
Svetlana Kipervasser ◽  
Miri Y. Neufeld ◽  
Uri Kramer ◽  
Itzhak Fried
Keyword(s):  
Right Hemisphere ◽  
Memory Loss ◽  
Intractable Epilepsy ◽  
Significant Negative Correlation ◽  
Temporal Lobectomy ◽  
Contralateral Hemisphere ◽  
Wada Test ◽  
Anterior Temporal Lobectomy ◽  
Ipsilateral Hemisphere ◽  
Neuropsychological Evaluations

Object Surgery for refractory epilepsy often bestows significant relief but may cause memory impairment. The risk of postoperative memory loss can be determined by the intracarotid amobarbital procedure, or the Wada test. Chemical inactivation of the hemisphere on the side of the lesion is usually performed first, followed by inactivation of the contralateral hemisphere. Patients who demonstrate adequate memory capacity of the contralateral hemisphere following deactivation of the ipsilateral hemisphere are considered good candidates for anterior temporal lobectomy. Evidence for the contribution of deactivating the contralateral healthy hemisphere remains inconclusive. Methods The authors analyzed results in 32 patients with intractable epilepsy who had undergone a bilateral Wada test followed by an anterior temporal lobectomy and in whom the findings of both pre- and postsurgical neuropsychological evaluations were available. The Wada memory scores were correlated with the difference in scores between pre- and postsurgical standardized memory test scores. Conclusions Analyses revealed no significant relationship between the Wada memory scores in the contralateral hemisphere and postsurgical changes in memory abilities. There was, however, a significant negative correlation between the Wada memory score in the ipsilateral hemisphere and postsurgical memory changes, particularly in patients with right hemisphere epileptogenic lesions (p = 0.0007). The results of this study are discussed vis-à-vis two theories of hippocampal function, and the authors stress the importance of the functional status of the surgical hemisphere in the prediction of postsurgical memory changes.

Sign in / Sign up

Export Citation Format

Share Document