In the first LEE011 supplier session, 120-dB startle stimuli were presented to the mice 10 times, with random inter-trial intervals . In the second session, startle responses to stimuli at various intensities were assessed. Five white noise stimuli at 70 to 120 dB were presented in quasi-random order and with random inter-trial intervals . In the prepulse inhibition session, mice experienced five types of trial: no stimulus; startle stimulus only; prepulse 70 dB and pulse 120 dB; prepulse 75 dB and pulse 120 dB; and prepulse 80 dB and pulse 120 dB. Each trial was performed 10 times in quasi-random order and with random inter-trial intervals . In the final session, a 120-dB startle stimuli was presented to the mice 10 times with random inter-trial intervals . The total duration of an auditory startle response test was about 35 to 40 min. After each trial, the holding chambers were washed with tap water, wiped with a paper towel, and dried. To confirm the assay accuracy, the hippocampal homogenate spiked with known amounts of the steroids was prepared and its concentration of steroid was determined . Satisfactory accuracy was obtained, supporting the accuracy of determined hippocampal steroid content in Table 1. To determine the potential physiological significance of nanomolar concentrations of hippocampal CORT, we BAY-60-7550 PDE inhibitor investigated CORT effects on dendritic spine density and morphology in hippocampal ��acute�� slices. It should be noted that CORT levels were depleted in control ��acute�� slices, containing only 1.9 nM CORT following 2 h recovery incubation in ACSF. Treatment with exogenous 10 nM CORT for 1 h significantly increased the total spine density compared with control slices .On the other hand, treatment with 100 nM CORT only slightly increased the total spine density. Morphological changes in spine head diameter induced by 1 h CORT administration were also assessed. Spines were classified into three categories based on head diameters: small-head spines : middle-head spines : and large-head spines . Morphological categorization of spines into three subclasses enabled complex responses in spine subpopulations upon CORT application to be distinguished. Treatment with 10 nM CORT significantly increased the density of small-head spines from 0.58 to 0.81 spines/mm, while the density of middle-head spines and large-head spines was not significantly altered .