The example recording illustrate a situation that clinically should be avoided, namely the development of arrhythmias with a clear tendency towards a systolic heart block what can happen when a heart with already strong contractions, here induced by adrenalin, is additionally stimulated with heart glycosides.

The substances can be applied to the isolated heart in a broad range of freely selectable concentrations and in all combinations. Mathematical algorithms simulate the physiologically appropriate reactions – also under unusual combinations of drugs. 
The force of the heart contractions is continuously recorded on a chart recorder. Parts of the recordings can be selected and stored for later data analysis.

In a separate drug laboratory the correct adjustment of the desired drug solutions can be trained by diluting high concentrated drugs from commercially available vials in physiological solution (Krebs solution). The gravimetric concentration and molecular weight are indicated on the ampoule packages to calculate the correct dilution – which will be checked.

SimNerv offers a fully equipped, realistically appearing laboratory on the computer screen for the induction and recording of compound action potentials. The experiments are performed with isolated preparations of the frog’s sciatic nerve which is particularly well suited illustrate the particular features and critical aspects of these clinically most relevant recordings of any electrical activity. 

The example recordings on the oscilloscope screen illustrate the alteration of action potential amplitude in the refractory period in response on double pules of varying delay.

The “SimNerv” laboratory includes a stimulator, an oscilloscope, a recording chamber and a Petri dish with two already prepared nerves. All stimulation and recording parameters of the virtual devices are freely adjustable. Mathematical algorithms guarantee for the appropriated reactions of the virtual nerves under all stimulus conditions, also considering the biological diversity of the preparations. 

For the experiments one of the nerves has to be taken out of the Petri-dish (by mouse click) and placed on the electrodes in the recording chamber (open and close with click on the lid) The position of the electrodes can be changed and the temperature of the recording chamber can be adjusted. A thread can be taken to set a nerve ligature (fully reversible).

The stimulator delivers voltage pulses of variable AMPLITUDE and DURATION. When TWIN are selected also the DELAY between the onsets of two successive stimuli can be adjusted. The POLARITY switch allows to invert the direction of the current flow corresponding to an exchange of the stimulus electrodes.

The simple double-beam storage oscilloscope displays the stimulus (channel 1), simultaneously with the compound action potential (channel 2) measured as the potential difference between the two recording electrodes by means of a differential amplifier. The sensitivity of both oscilloscope channels (mV/DIV) as well as their common time-base (ms/DIV) can be adjusted via the rotary switches.

SimNeuron offers virtual laboratories for voltage-clamp and current-clamp experiments in an easy to overlook lab design towards a better understanding of the relations between ion currents and membrane potentials including a neuron editor showing the mathematical equations also allowing modification and the neuron parameters.

The labs come along with a so-called “Standard Neuron” and a “Pacemaker Neuron” both of pre-defined parameters. Additional neurons with random parameters values can be obtained. The neuron editor allows to generate and safe own neurons with self-defined membrane parameters.

The current-clamp lab is for recordings of membrane potential changes on external currents and the voltage-clamp lab is for recording of ion-currents when the neuron is clamped to defined membrane potentials. 

Direct comparison of voltage-clamp and current clamp data from the same neuron can be of great help for a better understanding how neuronal sensitivity and activity is determined by ion channels’ activation and inactivation characteristics. Use of the neuron editor can become of particular value towards a deeper understanding of the consequences of ion channel modifications and alterations of passive membrane properties on the neuron’s dynamics.

The figure shows the neuron editor with the full set of mathematical equations and numerical values of all neuron parameters. All parameter values can be changed, reflected in the corresponding diagrams of leak currents or voltage and time dependent activation and inactivation.