Effects of heroin at different concentrations on electrophysiological properties of rat hippocampal CA1 pyramidal neurons

AIM: To investigate changes of electrophysiological properties of rat hippocampal CA1 pyramidal neurons in perfusion with heroin at different concentrations. METHODS: The intracellular recordings were made from CA1 pyramidal neurons of isolated hippocampal slices in perfusion with 0.03-0.3 mmol·L-1 heroin. Compared with control parametes before herion perfusion, the electrophysiological data obtained from identical neurons at 15 min after acute perfusion of the different concentration heroin were analyzed. RESULTS: With the increase of the heroin concentrations in perfusion, the absolute values of neuron resting potential and threshold potential decreased (P<0.05). In 0.3 mmol·L-1 heroin perfusion group，the amplitude of action potential decreased （P<0.05）, 10%-90% risetime and 10%-90% decaytime of spike potential elongated （P<0.05， P<0.01）, and I-V relation curve indicated membran slope resistance increased in 0.1-0.3 mmol·L^-1 perfusion group （P<0.05，P<0.01）. I-F relation curve showed that neuron average firing frequency recored at 15 min after 0.03 mmol·L^-1 heroin infusion was similar to the control frequency when intracellular stimulus intensity was 0.1-1.8 nA, however, firing frequency kept the higher level （P<0.05，P<0.01） in 1.9-2.0 nA vs the control frequence. It was evident that EPSPs of pyramidal neurons were inhibited in perfusion of three concentration heroin, especially in 0.3 mmol·L^-1. CONCLUSION: These results indicate acute heroin perfusion has a significantly influence on electrical activities of hippocampus CA1 pyramidal neurons.