Figure 4.

Instantaneous firing of hippocampal neurons can be affected by the ambient oxygen level in the hypoxic cycle. (A) The time period during which the ambient O₂ level was above the mean (15.5%) was regarded as high supply of O₂, while the time period during which the O₂ was below the mean was designated as lower supply of O_2. In the first 5 min of intermittent hypoxia (IH), the level of oxygen supply had no clear effect on the firing of both the putative pyramidal neurons (B) and the putative interneurons (C). However, in the last 5 min of 8 h IH treatment, both putative pyramidal neurons (D) and putative interneurons (E) tended to fire more during the period of higher oxygen supply. The data were from 50 putative pyramidal neurons and 12 putative interneurons (six rats). Wilcoxon's paired signed rank test for pyramidal neurons; Paired Student's t-test for interneurons; *P < 0.05.