High Antifouling Property of Ion-Selective Membrane: toward In Vivo Monitoring of pH Change in Live Brain of Rats with Membrane-Coated Carbon Fiber Electrodes

The objective of this study was to investigate under controlled conditions the effects of fentanyl on the rat locus coeruleus catechol oxidation current. Using differential normal pulse voltammetry combined with electrochemically treated carbon fiber electrodes to measure the catechol oxidation current, catecholamine metabolism can be reliably monitored. Male Sprague–Dawley rats weighing 500–600 g had carbon fiber electrodes implanted into the locus coeruleus under halothane – O2 – air anesthesia with controlled ventilation and muscle relaxation. Experiments consisted of four groups of rats given the following treatments: (A) saline (n = 6); (B) fentanyl, 10 μg∙kg−1 i.v. (n = 6); (C) naloxone, 800 μg∙kg−1 i.v. followed 2 min later by fentanyl, 10 μg∙kg−1 (n = 5); (D) clonidine, 200 μg∙kg−1 i.p. (n = 6). There was no significant change in the catechol oxidation current following saline. Fentanyl produced a significant (ANOVA, p < 0.05) decrease in the catechol oxidation current (maximum 32 min postinjection was 75.8 ± 4.6% of baseline). This decrease was prevented by a prior injection of naloxone. Clonidine produced a significant decrease in catechol oxidation current (maximum 40 min postinjection was 54.1 ± 7.0% of baseline). Systolic blood pressure was significantly decreased following clonidine and there were no significant changes in arterial blood gases throughout the experiments. The α2-adrenergic agonist clonidine and the opioid fentanyl produced a decrease in locus coeruleus catechol oxidation current measured by in vivo voltammetry, which monitors catecholamine turnover.Key words: catecholamine, clonidine, fentanyl, opiates, locus coeruleus, in vivo voltammetry.

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Carbon fiber electrodes for intracellular recording and stimulation

Journal of Neural Engineering ◽

10.1088/1741-2552/ac3dd7 ◽

2021 ◽

Author(s):

Yu Huan ◽

Jeffrey P Gill ◽

Johanna B Fritzinger ◽

Paras R Patel ◽

Julianna M Richie ◽

...

Keyword(s):

Carbon Fiber ◽

Intracellular Recording ◽

Neural Circuit ◽

New Technology ◽

Extracellular Recording ◽

Glass Microelectrode ◽

Carbon Fiber Electrodes ◽

Intracellular Stimulation ◽

Good Signal

Abstract Objective. To understand neural circuit dynamics, it is critical to manipulate and record many individual neurons. Traditional recording methods, such as glass microelectrodes, can only control a small number of neurons. More recently, devices with high electrode density have been developed, but few of them can be used for intracellular recording or stimulation in intact nervous systems. Carbon fiber electrodes (CFEs) are 8 micron-diameter electrodes that can be assembled into dense arrays (pitches ≥ 80 µm). They have good signal-to-noise ratios (SNRs) and provide stable extracellular recording both acutely and chronically in neural tissue in vivo (e.g., rat motor cortex). The small fiber size suggests that arrays could be used for intracellular stimulation. Approach. We tested CFEs for intracellular stimulation using the large identified and electrically compact neurons of the marine mollusk Aplysia californica. Neuron cell bodies in Aplysia range from 30 µm to over 250 µm. We compared the efficacy of CFEs to glass microelectrodes by impaling the same neuron’s cell body with both electrodes and connecting them to a DC coupled amplifier. Main Results. We observed that intracellular waveforms were essentially identical, but the amplitude and SNR in the CFE were lower than in the glass microelectrode. CFE arrays could record from 3 to 8 neurons simultaneously for many hours, and many of these recordings were intracellular, as shown by simultaneous glass microelectrode recordings. CFEs coated with platinum-iridium could stimulate and had stable impedances over many hours. CFEs not within neurons could record local extracellular activity. Despite the lower SNR, the CFEs could record synaptic potentials. CFEs were less sensitive to mechanical perturbations than glass microelectrodes. Significance. The ability to do stable multi-channel recording while stimulating and recording intracellularly make CFEs a powerful new technology for studying neural circuit dynamics.

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