Intracellular recording of rat neuron activity at the medial preoptic area of the hypothalamus using triangular wave microelectrode oscillation.

A triangular wave microelectrode oscillating apparatus was constructed to evaluate an intracellular recording of rat neuron activity in the medial preoptic area (POA) of the hypothalamus. In this apparatus, electrodes passed a current with a frequency of 1.0 to 1.8 kHz and a voltage of 2.2 to 3.2 V and produced micro-oscillation of the electrode tip. The electrode was inserted into a neuron of the rat POA in vivo. In vivo recording of the activity of the rat POA neuron was possible. By means of electrical stimulation of the median eminence arcuate of the hypothalamus, an intracellular recording of antidromic, orthodromic or non-responding neuron was also possible. As a result, various components of the action potential such as the resting, threshold and spike potentials, and depolarization and repolarization such as after-hyperpolarization and after-depolarization were observed. The resting potentials ranged from 45 to 90 mV, and POA neurons possessed action potentials of almost the same magnitude. Several problems, however, remain to be solved. In general, the time available for the intracellular recordings is too short. The cells survive only for 15 minutes at the longest and may die in only a few minutes. An improvement of the apparatus was mandatory.