A remotely operated pump for intracerebral micro-injection in the primate

A method is described for making small (2-6 microliters) localized intracerebral drug injections in the conscious monkey. A base plate and guide cannula are initially secured to the skull under general anaesthesia. A mechanical pump containing the drug solution and fitted with an injection needle is located on the base plate assembly. In the conscious animal the pump is triggered magnetically to deliver a predetermined volume into the target brain region.

A method for monitoring end-tidal CO2 during neurophysiological experiments on small laboratory animals

The Hewlett Packard Model 47210A Capnometer, intended for monitoring expired CO2 in human patients, can be modified for use in acute neurophysiological studies on small animals. The airway adaptor which would normally be attached to an endotracheal tube is modified and its internal volume is reduced to 0.2 ml, and is incorporated into a guinea pig head-holder. We have verified that the modification does not alter the Capnometer's accuracy. There is no significant increase in resistance in the airway when the adaptor is in place, and the waveform of instantaneous CO2 shows rapid changes on inspiration and expiration with well-resolved peaks and troughs. Measurement of arterial pCO2 suggests that the Capnometer and modified airway adaptor form an accurate system for obtaining a continuous record of end-tidal CO2 in small guinea pigs.

Estimation of thresholds for evoked potentials using a laboratory computer

To study drug effects on bioelectric activity evoked by near-threshold stimulation, we have developed a computerized threshold estimation technique. The procedure utilizes a laboratory computer (PDP 11/34) equipped with a standard laboratory interface with A/D and D/A capabilities. Program-controlled voltage pulses, delivered via D/A, are interfaced through a constant current stimulus isolation unit for electrical stimulation. One channel of activity is digitized at a user-defined rate and the signal is searched for a response. Responses were generally defined by a feature of the signal which was greater than a multiple of its standard deviation in the subthreshold signal. Using some a priori knowledge of the expected response and user-defined processing options, the program determines threshold on-line without pretrial test data. Program operation is illustrated with sensory evoked potentials in acutely prepared cats and hippocampal evoked potentials in chronically implanted rats.

A microperfusion chamber for brain slice pharmacology

The construction of a chamber for extracellular recording from submerged CNS tissue is described. Its operation is illustrated using hippocampal slices prepared from rat brains. The total volume of perfusing medium is less than 0.4 ml, and a drug solution can be uniformly distributed throughout this volume in less than 1 min. Drug-laden medium can also be rapidly replaced with fresh medium. The perfusing medium is continuously stirred with a jet of 95% O2-5% CO2, maintaining submerged slices viable for many hours. The system has exceptional advantages for investigating synaptic pharmacology of scarce and expensive drugs.

A microcomputer technique for the detailed analysis of animal behaviour

Movements and postures of animals may be described quantitatively and as such represent measures that may be used to, for example, detect drug-induced alterations in behaviour. However, because of the time-investment needed to generate such data, quantitative assessment of animal behaviour remains a major problem in psychopharmacology. The present communication outlines a microcomputer based method for obtaining frequency, real-time duration and latency measures from a large number of behavioural elements. When used in conjunction with a videotape recorder, this system enables one experimenter to obtain data from situations involving several interacting animals, thus representing an aid to increased data-logging efficiency using only equipment that is commonly found in many psychopharmacology laboratories.

A manually-operated brain tissue slicer suitable for neurotransmitter release studies

A simple, inexpensive device has been designed to prepare slices or prisms of brain tumor for metabolic and release experiments by means of a hand-operated method. It is particularly suitable for very rapid slicing of small, irregular pieces of brain tissue dissected from animals or specimens available at biopsy. This simple apparatus was produced as an alternative to the more widely used motor-driven tissue choppers. A comparison of the morphological and metabolic integrity of tissue produced by the new slicer and a conventional tissue chopper is presented. The hand tissue slicer has been used to measure the release of monoamine neurotransmitters and specific neuropeptides in vitro.

Digital reproduction of biopotential waveforms for neurophysiological studies

A simple biological signal generator capable of reproducing complex biopotential waveforms is described. It is constructed by a combination of digital and analog circuit components and can be used under different experimental conditions, such as in calibration of biomedical instrumentation systems, or simply as a function generator providing voltage outputs of various waveforms. The biopotential waveform to be generated is sampled at a high frequency and the samples are stored sequentially in a programmable read only memory (PROM). The samples are then fed in the same sequence to a digital-to-analog (D/A) converter and the resulting output is amplified and a DC offset is added. External controls are provided to adjust the DC offset, amplitude and repetition rate of the signal generated. The reproduced voltage signals are stable and superior in quality to those produced by conventional biological signal generators.

Two apparatus for detection of motility and water consumption of rodents

Two apparatus for time sequences data acquisition are described. The first is designed for detection of motility. It acts according to the principle of inertia. Movements of animal are transmitted to a plate supported by steel balls with a minimal resistance. Horizontal oscillations are detected using an electro-optical system. Very weak movements can be recorded. The second indirectly records feeding behavior (water intake) using also an optical detection of the air bubble passing through the glass-tube of the feeding-bottle. The long-term stability, accuracy and sensitivity of the apparatus are discussed. Examples of application are quoted.

Volumetric measure and lick count of liquid food intake of rats

A simple and relatively inexpensive lick counter-volumeter is described which automatically records liquid intake and drinking behavior of rats. It counts lick contacts while accurately measuring the rate of volume intake in constant unit volumes. The unit volumes are adjustable over a wide range. For a unit volume on the order of 60 microliter, the precision was 1.2% over a range of withdrawal rates from 1 to 10 ml/min. The average lick volume of rats consuming a liquid food was systematically lower by 18% during the second meal following a 15 hr fast when compared to that of the first. This change in average lick volume appears to reflect a change in the rat's motivation to drink the liquid food.