ABSTRACT
The electrical activity of unipolar cells of the cardiac ganglion of Limulus has been examined with microelectrodes to determine the electrical properties and the functional relationship between unipolar cells.
Resting membrane potential in these cell averages −43 mV.
Correlated with each contraction of the heart there occurs a burst of activity which consists of a sustained depolarization of several seconds on which is superimposed a series of small 2–5 mV spikes.
Activity which occurs during the initial phase appears to be the result of presynaptic inputs to these cells. Spike activity during the recovery phase is probably endogenous to the cell from which we are recording.
The specific membrane resistance for the soma membrane averages 12 700 Ω. cm2. The time constant has a value of 19·6 ms. The specific membrane capacitance measures 1·54 μF/cm2.
External stimulation produces a number of different responses in the unipolar cells which are dependent upon a number of factors. These responses can be classified into at least three types: (a) a driven response similar to a spontaneous burst; (b) slowly rising potentials which may be antidromic spikes.
