Prenatal stress influences 8-OH-DPAT modulated startle responding and [3H]-8-OH-DPAT binding in rats

The present study was to investigate some aspects of the 5-HT1A receptor system in adult-aged rats (50-60 days) that were either exposed to prenatal stress (PS) or not exposed to prenatal stress (CON). In the first series of experiments, rats were pretreated with vehicle, the 5-HT1A agonist 8-OH-DPAT or the 5-HT1A antagonist, WAY-100635 and exposed to 120 acoustic startle stimuli (95 dB) using a 30 s inter-trial interval. 8-OH-DPAT produced a dose-dependent increase in acoustic startle responding in CON and PS rats, with the PS rats exhibiting greater responding than CON rats. WAY-100635 depressed startle amplitudes only in the CON group. Finally, radioligand binding studies using [3H]-8-OH-DPAT indicated a significant decrease in receptor density in hippocampal homogenates from PS rats but no difference in [3H]-8-OH-DPAT binding from homogenates of the amygdala. Our results are consistent with earlier reports indicating that prenatal stress alters the serotonergic system. Specifically, our results indicate that gestational exposure to chronic mild stress enhances startle amplitudes following 8-OH-DPAT administration, prevents the depression in startle amplitudes following WAY-100635 administration and reduces [3H]-8-OH-DPAT binding in hippocampal preparations.