A mechanographic method for measurement of muscle tone in the conscious rat. The calf muscle stretch response in reserpine-induced rigidity

A simple mechanographic method for the measurement of muscle tone in awake rats is presented. It utilizes principles corresponding to those in clinical assessment of tone and it has been applied to an animal model of Parkinson's disease: the reserpine-treated rat. The rat was restrained by a plastic cylinder and by metal cuffs at the ankles. The hind feet were repeatedly dorsiflexed by an electromechanical manipulator and the resulting calf muscle tension was indirectly measured with a strain-gauge system. The relative contributions to the stretch response from the different muscle groups acting on the ankle joint in the awake and untreated rat and during reserpine-induced rigidity are described. Very little active tension was found in the untreated rat. After treatment with reserpine, continuous activation of the muscle was found in EMG recordings and there was a sharp increase in the tension recorded during stretch. The static response to the increased isometric stretch was augmented. An additional, tonic response to ramp stretch was elicited at all stretch velocities. There was no evidence for phasic responses to rapid stretch in reserpine-induced rigidity. The amplitude of the myomechanogram was thus found to be independent of the ramp stretch velocity. Subsequent injection of apomorphine abolished the increased stretch response. It is demonstrated that changes in muscle tone could be followed during drug treatment and that the method can be used in investigations of the pathophysiological mechanisms behind the disorders of muscle tone.

A sensitive optoelectronic displacement transducer for the neurophysiological laboratory

This paper describes a simple and convenient way of making a sensitive displacement transducer for routine use in the neurophysiological laboratory. It is based upon a commercially available optoelectronic integrated circuit and requires only simple electronic and mechanical fabrication. Its sensitivity is such that it may be used to monitor movements down to approximately 100 nm over a bandwidth of 8 kHz without additional filtering or averaging. Further electronic filtering or computer averaging will extend its sensitivity. It has many potential uses, two examples of which are provided.

A mechanographic method for measurement of locomotor activity in rats. Effects of dopaminergic drugs and electric stimulation of the brainstem

A simple treadmill arrangement has been developed to quantify the quadruped or hindleg locomotor activity in rats. The method provides information on the accumulated distance passed by the rat in the treadmill but also on the temporal distribution of locomotion and the stepping cycle. It can be used with intact rats but also during stereotaxically guided electric stimulation of the brain. The accumulated locomotion produced by apomorphine showed a partly linear relation to the dose and the results were comparable to those found with other methods. The locomotor effect of brainstem stimulation was enhanced by apomorphine. This method combines the advantages of several other methods and is well suited as a tool for the analysis of nervous regulation of locomotor activity.

Micropipette puller design: form of the heating filament and effects of filament width on tip length and diameter

Though the ultrafine short tips provided by our micropipette puller are helpful for many preparations, longer tips are still needed for some cases where target cells for intracellular work are deeply embedded in tissue. Because the original 'loop' type of heating filament proved unsuitable for widening to provide the longer tips, we studied simpler forms of heating filaments. By comparison with the common loop design, a rectangular trough filament proved to have many advantages without any significant disadvantage. In particular, this type of filament may be used at varying widths to provide long tips as well as short ones. Thus our micropipette puller can now provide tip lengths that extend upward by continuous gradations from about 6 to 27 mm, while maintaining tip diameter in the ultrafine range of 0.1 micrometer or less. These long tips have proved more reliable and free from bending than long tips traditionally provided by the Livingston puller. By using narrow filaments in conjunction with other parameters that influence tip size, tips have also formed with diameters up to 1.5 micrometers and lengths of only 2-3 mm.

Estimation of volume fractions in nervous tissue with an image analyzer

The calculation of volume fractions in nervous tissue is a method often used in neuroanatomy. In ontogenetic studies and problems concerning aging, as well as after experimental procedures, volume fractions are calculated in order to quantify the results. Grey level index (GLI) and grey cell coefficient (GCC) are different parameters correlated to the volume density of cellular elements in nervous tissue. The grey cell coefficient (GCC) is defined as the volume fraction of cellular elements in a griseum (grey matter area) and is estimated by a basic stereological method (point counting) from observations in two dimensions. The grey level index (GLI), measured with an automatic image analyzer, is the areal proportion of projected profiles of all stained elements within a volume given by the area of the measuring field and the thickness of section. GLI and GCC are compared in specimens obtained by a special histological procedure, and a method to estimate volume fractions by means of GLI-measurement is described.

A simple apparatus to assess cutaneous thermal sensitivity

A simple contact stimulator designed to provide quantitative assessments of thermal sensitivity of digital skin is described. The skin is tested at its normal resting temperature and thermal thresholds are given as the least differences in temperature between the skin and the stimulator which give rise to warm or cool sensations.

A differential displacement transducer for measuring relative movement in biological systems

This article describes a modified and improved version of the displacement transducer design originally presented by Sandeman (1968). The present design generates a high frequency electric field in the bathing solution. Relative displacement is detected within this field by measuring the differential voltage between two small diameter wire-sensing electrodes, which can be attached to different biological structures. By placing one of the sensing electrodes at a fixed point within the bath, absolute displacement can also be measured. A brief theoretical discussion and complete design are presented for the differential displacement transducer. The method presented here is more sensitive and versatile than the original approach.

Action potentials recorded by fluid electrodes

Using bullfrog's sciatic-peroneal nerve, action potentials recorded by fluid electrodes were studied under a variety of conditions. Action potential obtained by the adjacent fluid electrodes was diphasic, and its amplitude was directly proportional to the impedance between the fluid electrodes. The number of peaks of action potential was equal to that of the partition between recording fluid electrodes, and the peak latencies were increased in proportion to the distance between both partitions of the adjacent fluid electrodes at the first and at the move positions. These findings suggest that action potentials may be generated wherever the impedance of the conducting medium changes suddenly.

Rapid freezing of neural tissues for electron microscopy: a specimen carrier for correlative electrophysiological studies

The employment of rapid freezing of fresh tissue for electron microscopic studies of nervous tissue is receiving increasing attention. We report here on the design of a specimen carrier for use with freezing machines. This apparatus permits electrical stimulation and recording of responses closely comparable to those obtained in ordinary in vitro conditions. The essential features of this apparatus are that it employs miniature suction electrodes for stimulation and recording, a detachable well for mounting the specimen in Ringer's solution and a detachable cap for maintaining the specimen in a physiologic state suitable for freezing. This specimen carrier was designed for sympathetic ganglia but could be used with other types of neural tissue for correlative electrophysiological and morphological or biochemical studies.

LEDs: convenient, inexpensive sources for visual experimentation

This article presents the electrical and optical properties of LEDs for use as visual stimulators in neurophysiological and psychophysical research. one particular circuit is considered in detail which should enable an investigator with minimal technical expertise to build a high quality and versatile stimulator within a few hours and at a minimal cost. Improved circuits and anticipated developments in LED technology are discussed.

Recording of spontaneous activity with photoetched microelectrode surfaces from mouse spinal neurons in culture

A matrix of photoetched gold conductors integrated into the floor of a tissue culture chamber has been used to record from mammalian spinal cord neurons grown on the insulation layer of the multielectrode plate. Spontaneous activity has been monitored from tissue microfragments less than 150 micrometers in diameter and from thin sheets of spinal cell aggregates. Maximum spike amplitudes of 360 microV with signal-to-noise ratios of 8:1 have so far been achieved and the spontaneous activity maintained for several days. Recording electrode impedances measured between 4 and 7 M omega at 1 kHz. Conductor tips were deinsulated with laser pulses that formed shallow craters 2 micrometers deep and 12 micrometers in diameter. Addition of colloidal gold or platimum black was not necessary to achieve satisfactory recordings.

Double-lumen flow-through swivel for chronic experiments with unrestrained monkeys

Two modifications of a flow-through swivel are described for prolonged infusions into and simultaneous blood-sampling from chronically implanted catheters of large, unrestrained animals, e.g., rhesus monkeys. In addition, both offer easy access to the catheters proximal to the swivel and to the lumen of the reinforced nylon tubing which connects the animal to the swivel.

A device for the automated monitoring of stereotypic behavior

1. A novel rotation sensing device has been developed which consists of a linear potentiometer attached to the top of a spherical testing chamber. The potentiometer constantly monitors the precise angular position of the animal inside the chamber. 2. This device allows the automated monitoring of direction and rate of rotation, as well as a variety of other stereotypic behaviors. 3. The effects of morphine, apomorphine and amphetamine on motor activity were assessed by the apparatus.