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. 2021 Jun 4;15:663633. doi: 10.3389/fncir.2021.663633

Figure 2.

Figure 2

Intraseptal microinjection of NBQX affects power and frequency of reticular stimulation-induced hippocampal theta wave activity in a dose-dependent fashion. (A,B) Time course of effect of intraseptal microinjection of vehicle and NBQX on the reticular stimulation-induced suppression of the CA1 population spike (PS) and (C,D) the power of the concomitant theta wave activity. The RPO was stimulated at an intensity that evokes 4–5 Hz theta wave activity (labeled as ‘T’ V). The stimulation was initiated at the time point shown in (A) and was subsequently maintained throughout the recording except for intermittent periods when T + 1 V stimulation was applied. The plot in (A) corresponds to (a) 2 min before the onset of RPO stimulation (−24 min and −23 min), (b) 10 min following the onset of RPO stimulation, and before microinjection of vehicle (−22 min to −12 min), and (c) 10 min following vehicle microinjection (−11 min to −1 min). NBQX (10 or 20 μg/μl, 0.5 μl) was microinjected 10 min after vehicle microinjection (A). This corresponds to 0 min in the plot (B). The time course in (B) reflects 10 min before and 20 min after NBQX microinjection. Panels (C,D) are built as in (A,B) except power is not illustrated for the period before RPO stimulation since theta wave activity was not observed in this period. Furthermore, theta wave activity was lost around ~30 s to 1 min in four of six experiments following microinjection NBQX 20 μg/μl. In absence of overt theta, the peak FFT power in the theta range was used for drawing the plots. The FFT parameters and PS were computed in 1 min block. Power was expressed as a ratio of the average power in the 10 min preceding microinjection of vehicle. (C) As the effect of vehicle on PS and theta parameters was similar in both NBQX experiments, the vehicle data were combined for the two groups (n = 12). Note that the higher dose of NBQX attenuated theta power (D) but not the suppression of PS (B). (E) Histogram of FFT theta peak power (ratio) before and after microinjection of vehicle and NBQX. The histograms represent the average of RPO-induced theta peak power in two contiguous minutes before microinjection and the average of peak RPO-induced theta peak power in two contiguous minutes in the 5 min period after microinjection. (F) Histograms showing FFT theta peak frequency before and after microinjection of NBQX at T + 1 V. Since NBQX 20 μg/μl evoked a loss of theta on RPO stimulation at intensity ‘T’, higher stimulation intensity at T + 1 was applied at 20 min after NBQX treatment to evoke theta wave activity which was then used for analysis. The theta frequency observed at 20 min post-NBQX was compared with the corresponding theta frequency evoked at T + 1 stimulation applied before the onset of time course investigations (Basal). Data are mean ± S.E.M. Significant difference (p < 0.05): (A) @vs. corresponding PS amplitude at −24, −23 min, one-way repeated measures (RM) ANOVA followed by Newman-Keuls post hoc test. (D) Time course: *NBQX20 vs. corresponding −2, −1 min, and &NBQX20 vs. NBQX10, two-way RM ANOVA followed by Bonferroni post hoc test. (E,F) Histograms: *vs. pre-NBQX20 or Basal, two-tailed paired t-test.