Whole-cell recordings in freely moving rats

Intracellular recording, which allows direct measurement of the membrane potential and currents of individual neurons, requires a very mechanically stable preparation and has thus been limited to in vitro and head-immobilized in vivo experiments. This restriction constitutes a major obstacle for linking cellular and synaptic physiology with animal behavior. To overcome this limitation we have developed a method for performing whole-cell recordings in freely moving rats. We constructed a miniature head-mountable recording device, with mechanical stabilization achieved by anchoring the recording pipette rigidly in place after the whole-cell configuration is established. We obtain long-duration recordings (mean of approximately 20 min, maximum 60 min) in freely moving animals that are remarkably insensitive to mechanical disturbances, then reconstruct the anatomy of the recorded cells. This head-anchored whole-cell recording technique will enable a wide range of new studies involving detailed measurement and manipulation of the physiological properties of identified cells during natural behaviors.     

Real-time cortical cerebral blood flow follow-up in conscious,freely moving rats by laser Doppler flowmetry

This article describes a laser Doppler flowmetry (LDF) system that enables repeated measurements and thereby long-term followup of cortical cerebral blood flow (CBF) in awake and freely moving rats. The system consists of a specially designed flow probe adapter, a flow probe connector, and a LDF flow probe, which may thereby rotate through its own axis. During the experiment, the flow adapter is permanently mounted onto the rat's skull bone. A thin layer of skull bone is left intact at the site for cortical CBF measurements. The probe connector and the flow probe may be repeatedly detached and remounted to the adapter, which allows for cortical cerebral blood flow recording from exactly the same anatomical location. The laser Doppler flowmetry system enables stable cortical CBF recordings in the conscious rat while it moves freely in a bowl cage.     

Telemetric recording of neuronal activity

A telemetric system is described which allows the wireless registration of extracellular neuronal activity and vocalization-associated skull vibrations in freely moving, socially living squirrel monkeys (Saimiri sciureus). The system consists of a carrier platform with numerous guiding tubes implanted on the skull. Custom-made microdrives are mounted on the platform, allowing the exploration of two electrode tracks at the same time. Commercially available quartz-insulated platinum-tungsten microelectrodes are used. The electrodes can be moved over a distance of 8-10 mm by turning a screw on the microdrive. Vocalization-associated skull vibrations are recorded with a piezo-ceramic element. Skull vibration signal and the signals from the two microelectrodes are fed into separate transmitters having different carrier frequencies. The signals are picked up by an antenna in the animal cage and are sent to three receivers in the central laboratory. Here, the signals are transferred via an analog/digital interface to a personal computer for data analysis and to a video recorder for long-term storage. The total weight of the head mount including carrier platform, microdrive, electrodes, skull vibration sensor, three transmitters, and protection cap is 32 g. The transmitters are powered with two rechargeable lithium batteries, allowing about 8 h of continuous recording. Reliable signal transmission is obtained over a distance of about 2 m. Recording stability allows to follow the activity of specific neurons up to several hours, with no movement artefacts during locomotion.     

Techniques for recording renal sympathetic nerve activity in awake,freely moving animals

The methods described here allow recording of sympathetic nerve discharge in awake, freely moving animals, and follow a historical perspective of the different techniques developed over the years to record sympathetic discharge. The length of time each system is viable for recording varies from days to weeks. Also included are special hints for the surgical implantation of recording electrodes, types of recording electrodes and cables, as well as the minimum equipment necessary for recording sympathetic discharge. Lastly, a section on troubleshooting includes how to remove movement artifacts and extraneous noise, and minimize the destruction of leads common in recording in awake, freely moving animals. This article is written for the beginner or novice with an emphasis on what is needed when embarking on recording sympathetic nerve discharge in awake, freely moving animals.     

Design and Assembly of an Ultra-light Motorized Microdrive for Chronic Neural Recordings in Small Animals

The ability to chronically record from populations of neurons in freely behaving animals has proven an invaluable tool for dissecting the function of neural circuits underlying a variety of natural behaviors, including navigation¹ , decision making ^2,3, and the generation of complex motor sequences^4,5,6. Advances in precision machining has allowed for the fabrication of light-weight devices suitable for chronic recordings in small animals, such as mice and songbirds. The ability to adjust the electrode position with small remotely controlled motors has further increased the recording yield in various behavioral contexts by reducing animal handling.^6,7Here we describe a protocol to build an ultra-light motorized microdrive for long-term chronic recordings in small animals. Our design evolved from an earlier published version⁷, and has been adapted for ease-of use and cost-effectiveness to be more practical and accessible to a wide array of researchers. This proven design ^8,9,10,11 allows for fine, remote positioning of electrodes over a range of ~ 5 mm and weighs less than 750 mg when fully assembled. We present the complete protocol for how to build and assemble these drives, including 3D CAD drawings for all custom microdrive components.     

Electrical activity of the lateral hypothalamus related to food-procuring movements of rats

On freely moving albino rats we demonstrated that, when fast food-procuring movements are performed, the mass electrical activity of the lateral hypothalamus (LH) is suppressed 1.6–2.0 sec before the movement beginning recorded with a photoelectrical device. Videorecording of the movements and recording of the spike activity of LH units showed that the latter are activated 1.0–0.1 sec before the movement initiation. The LH is considered a motivation-related structure, which serves as a source providing an increase in the excitability of the structures involved in the control of food-procuring movements and, further on, supporting this increased excitability. The LH is also a component of the mechanisms providing formation of the motor program. The role of the LH in the ensemble of motor centers, which organize and control voluntary movements, is discussed.     

A Wireless Multi-Channel Recording System for Freely Behaving Mice and Rats

To understand the neural basis of behavior, it is necessary to record brain activity in freely moving animals. Advances in implantable multi-electrode array technology have enabled researchers to record the activity of neuronal ensembles from multiple brain regions. The full potential of this approach is currently limited by reliance on cable tethers, with bundles of wires connecting the implanted electrodes to the data acquisition system while impeding the natural behavior of the animal. To overcome these limitations, here we introduce a multi-channel wireless headstage system designed for small animals such as rats and mice. A variety of single unit and local field potential signals were recorded from the dorsal striatum and substantia nigra in mice and the ventral striatum and prefrontal cortex simultaneously in rats. This wireless system could be interfaced with commercially available data acquisition systems, and the signals obtained were comparable in quality to those acquired using cable tethers. On account of its small size, light weight, and rechargeable battery, this wireless headstage system is suitable for studying the neural basis of natural behavior, eliminating the need for wires, commutators, and other limitations associated with traditional tethered recording systems.     

The electrophysiological characteristics and behavioral manifestations of hippocampal and thalamic spreading depression]

Behavioral manifestations of spreading depression (SD) were compared with SD electrophysiological characteristics in these structures. Carbon electrodes were suitable for recording DC slow potential changes in freely moving animal. It was shown that short (0.1 s) high-frequency (200 Hz) electrical stimulation of thalamus and hippocampus with intensity 50-300 microA easily triggered SD wave in these structures in narcotized and awake rats. The threshold of SD occurrence in dorsal hippocampus was the same or sometimes lower than that of the primary afterdischarge. Penetrating SD into ventral hippocampus provoked long latency seizure discharge and wet-dog shakings in awake rats. Intensity of locomotor activity accompanying bilateral hippocampal SD exceeded orienting response significantly. Contrary to hippocampus, thalamic SD was usually subseizure and unilateral phenomenon and had a clear tranquil effect on the rat locomotor activity. It was found that the rats didn't change the compartment preference after 20-45 SD waves in the thalamus or in the hippocampus.     

A miniature head-mounted two-photon microscope. high-resolution brain imaging in freely moving animals

Two-photon microscopy has enabled anatomical and functional fluorescence imaging in the intact brain of rats. Here, we extend two-photon imaging from anesthetized, head-stabilized to awake, freely moving animals by using a miniaturized head-mounted microscope. Excitation light is conducted to the microscope in a single-mode optical fiber, and images are scanned using vibrations of the fiber tip. Microscope performance was first characterized in the neocortex of anesthetized rats. We readily obtained images of vasculature filled with fluorescently labeled blood and of layer 2/3 pyramidal neurons filled with a calcium indicator. Capillary blood flow and dendritic calcium transients were measured with high time resolution using line scans. In awake, freely moving rats, stable imaging was possible except during sudden head movements.     

应激诱发的海马神经元突触增强参与大鼠的新环境学习

本文旨在研究应激对海马新环境空间学习记忆的损伤作用机制.在大鼠海马CA1区埋植电极,刺激schaffer侧枝记录CA1区树突层的兴奋性突触后场电位(field excitatory postsynaptic potential,fEPSP),探索应激对火鼠新环境空间学习的突触可塑性的影响.同时研究了再次新环境空间学习时...     

Neural basis for spatial memory in animals: what do hippocampal neurons tell us?

Recent studies relying on the recording of neuronal unit activity in freely moving rats show the existence of two populations of neurons signalling the animal's location or head direction: place cells found primarily in the hippocampus and head direction cells found in brain areas anatomically and functionally related to the hippocampus. The properties of these two neuronal populations suggest that their activity strongly depends upon information cues stemming from the spatial environment, and also suggest their involvement in spatial memory. Place cells and head direction cells would jointly participate in a neural network allowing the animal to orient in space and to store spatial locations in memory. This network would also be operating in humans, in particular for encoding specific events in episodic memory.     

Effect of chloral hydrate on in vivo KCl-induced striatal dopamine release in the rat

The release of striatal dopamine (DA) and its metabolites in response to locally-induced K⁺ depolarization was investigated in vivo in chloral hydrate-anesthetized and freely moving rats. KCl at concentrations of 30, 50, and 100 mM induced significant dose-dependent increases in extracellular DA overflow in both chloral hydrate-anesthetized and freely moving rats (P<0.05). Extracellular levels of dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5-HIAA) were decreased. The DA overflow in response to 30 mM KCl stimulation in anesthetized rats was significantly greater than that in freely moving rats (P<0.05). In addition, chloral hydrate anesthesia resulted in a significant decrease in extracellular levels of DOPAC and significant increases in extracellular levels of HVA and 5-HIAA in comparison with freely moving rats (P<0.05). Furthermore, the basal level of extracellular HVA in chloral hydrateanesthetized rats was significantly higher than that in freely moving rats. These results suggest that chloral hydrate anesthesia could have significant effects on the pharmacological response of the striatal dopaminergic neurons.     

An inexpensive electronic device for measuring electroantennogram responses to sex pheromone components with a voltmeter

ABSTRACT. An inexpensive, portable device which allows measurement of electroantennogram (EAG) maximum amplitudes with a voltmeter instead of an oscilloscope is described. Potential advantages of the device include more rapid recording, low-cost construction of additional EAG recording systems for a laboratory with several users, and portability allowing studies in the field and occasional bench top use. The device is intended for use in conventional EAG recording, where EAG signals with rapid depolarizations are being measured, and where the maximum amplitude of the EAG signal is the only parameter of interest.     

A motorized microdrive for recording of neural ensembles in awake behaving rats

The recording of neural ensembles in awake, behaving rats has been an extremely successful experimental paradigm, providing demonstrable scientific advances. Dynamic control of the position of the implanted electrodes is of key importance as mobile electrodes provide a better signal-to-noise ratio and a better cell/ electrode yield than nonmobile electrodes. Here we describe the use of low cost, soon to be commercially available dc motors to successfully control the depth of electrodes. The prototype designed is approximately 30 mm in diameter and 50 mm in length and weighed about 30 gms. This paper presents the results of linear displacements of electrodes achievable with this motorized microdrive.     

Response of the hypothalamo-corticotropic system to metyrapone in pigeons

Chronic catheterization and miniature recording device allowed plasma corticosterone (B) and hypothalamic multiunit activity (MUA) to be simultaneously obtained from freely behaving, awake pigeons, before and for 4 hrs after intravenous injection of metyrapone. Injection of vehicle (tartric acid : 100 mg/4 ml/kg) led to MUA and B profiles quite similar to stress-induced responses, i.e., a rapid and sustained rebounding increase in hypothalamic firing rate and, shifted by 5-10 min, in plasma B. These responses were progressively attenuating for 90-120 mn. Metyrapone administration induced first a rapid and short MUA and B increase. Then both parameters drastically decreased near zero for about 2 hrs and were slowly restored to initial values within 3-4 hrs. It is suggested that metyrapone treatment inhibited both peripheral (B synthesis) and central (hypothalamic neurons) levels of the corticotropic axis.     

Single unit activity of dopaminergic neurons in freely moving cats

Single unit activity was recorded from the area of the substantia nigra in freely moving cats. A sub-population of these neurons had the following characteristics: long action potential durations (2–4 msec); relatively slow discharge rates (2–6 spikes/sec); firing as single spikes along with periods of bursting activity in which spike amplitude successively decreased; suppression of unit activity by systemic injection of apomorphine and increased activity after systemic injection of haloperidol. These characteristics are similar to those of identified dopamine neurons recorded in chloral hydrate anesthetized or peripherally paralyzed rats. Therefore, based upon these physiological and pharmacological similarities, this study represents the first systematic report providing evidence for recording the activity of dopaminergic neurons in freely moving cats. In addition, when these cells were studied across the sleep-waking cycle they displayed little variation in firing rates between waking, slow wave sleep and REM sleep.     

双电极绑定技术记录在体大鼠海马CA1区长时程增强

目的:探讨双电极绑定条件下记录大鼠在体海马CA1区长时程增强的可行性。方法:雄性Wistar大鼠乌拉坦麻醉;脑立体定位仪上埋置脑室导管;安装自制的刺激/记录绑定电极;引导基础性场兴奋性突触后电位(fEP-SP);强直刺激诱导长时程增强(LTP)。结果:绑定后的刺激和记录电极能可靠地引起海马CA1区fEPSP,fEPSP的出现率几乎100%;基础性fEPSP记录可保持长时间稳定;高频刺激成功诱导出LTP并维持达3h以上,诱导率约67%;双脉冲易化记录稳定、可靠;脑室注射β淀粉样蛋白(Aβ)对LTP显示出明显的压抑作用。结论:采用双电极绑定技术进行在体海马LTP记录简便易行、节省资源、引导fEPSP和诱导LTP的成功率较高,有望成为一项重要的研究学习和记忆机制的电生理辅助手段。     

An image-free opto-mechanical system for creating virtual environments and imaging neuronal activity in freely moving Caenorhabditis elegans

Non-invasive recording in untethered animals is arguably the ultimate step in the analysis of neuronal function, but such recordings remain elusive. To address this problem, we devised a system that tracks neuron-sized fluorescent targets in real time. The system can be used to create virtual environments by optogenetic activation of sensory neurons, or to image activity in identified neurons at high magnification. By recording activity in neurons of freely moving C. elegans, we tested the long-standing hypothesis that forward and reverse locomotion are generated by distinct neuronal circuits. Surprisingly, we found motor neurons that are active during both types of locomotion, suggesting a new model of locomotion control in C. elegans. These results emphasize the importance of recording neuronal activity in freely moving animals and significantly expand the potential of imaging techniques by providing a mean to stabilize fluorescent targets.     

Telemetry system to record force and EMG from cat ankle extensor and tibialis anterior muscles

The purpose of this technical note is to present the design of an eight-channel telemetry system of dimensions and weight small enough to record muscular forces and EMGs simultaneously from gastrocnemius, soleus, plantaris and tibialis anterior muscles of a freely moving cat. All schematics for constructing the telemetry device are shown in detail. Using this system, we were successful in measuring force and EMG data of all four instrumented muscles in freely moving animals. The telemetry system presented here has the advantage over a conventional cable system that recordings may be obtained at any time in the freely moving animal without interference by an experimenter.