Figure 5.

Prepulse inhibition thresholds in quiet are modified in opposite directions by the loss (–/–) or increased activity Ld'T (KI) of α9 nAChRs, yet responses do not differ significantly in background noise. In quiet, (A) α9 nAChRs (–/–) or (B) Ld'T KI animals can inhibit their acoustic startle with a prepulse at 80 dB, and did not inhibit their startle with a prepulse at 30 dB (edges of psychometric function). However, the threshold for inhibiting their startle response 50% of the time (A′ = 0.75) is higher for α9 (–/–) null animals (A) and lower for α9 KI animals (B) (C) Mean PPI thresholds (defined as prepulse level at A′ = 0.75) and SEM values are shown for (A) α9 nAChRs (–/–) or B) Ld'T KI, and each of the groups contained 12 mice. There was a significant threshold increase for α9 nAChR KI animals when compared to littermate controls) and there was a trend for α9 nAChRs (–/–) to have lower thresholds in quiet (t, trend; ^*p < 0.05). (D,E) When prepulse inhibition of the acoustic startle reflex was tested in 60 dB background noise (BBN), α9 nAChRs (–/–) or Ld'T KI mice were able to inhibit their startle reflex when tested with a prepulse of 80 dB, but did not inhibit their startle with a prepulse at 50 dB; yet unlike the quiet condition, there was no significant difference between (D) α9 nAChR (–/–) or (E) Ld'T KI mice in their response, as shown in bar graph form with means and SEMs in (F).