Prepulse inhibition (PPI) represents an attenuation of the startle reflex following the presentation of a weak prepulse at brief intervals prior to the startle eliciting pulse. It has been shown that increases in striatal dopamine levels decrease PPI; because dopamine release is sensitive to estrogen, it is likely that PPI varies across the menstrual cycle. Cross-sectional studies looking at estrogen effects suggest that this may be true. In this study, we compare effects of menstrual phase on PPI in a between-group design (men, follicular phase women, and luteal phase women) as well as a within-subjects design (women across the two phases). The study found a between-group as well as a within-subjects effect of phase on PPI. PPI in follicular phase women did not differ significantly from PPI in men. However, PPI was reduced in luteal women compared to follicular women. These data provide evidence that ovarian hormones affect sensorimotor gating.

Prepulse inhibition (PPI) is an acoustic startle paradigm that has been used as an operational measure of sensorimotor gating. Many patients with schizophrenia have impaired PPI, and several lines of evidence suggest that PPI may represent a heritable endophenotype in this disease. We examined startle magnitude and latencies in 40 schizophrenia patients, 58 first-degree relatives of these patients and 100 healthy controls. After removing low-startlers, we investigated PPI and startle habituation in 34 schizophrenia patients, 43 relatives and 86 control subjects. Heritability analyses were conducted using a variance-component approach. We found significant heritability of 45% for PPI at the 60-ms interval and 67% for startle magnitude. Onset latency heritability estimates ranged between 39% and 90% across trial types, and those for peak latency ranged from 29% to 68%. Heritability of startle habituation trended toward significance at 31%. We did not detect differences between controls and either schizophrenia patients or their family members for PPI, startle magnitude or habituation. Startle latencies were generally longer in schizophrenia patients than controls. The heritability findings give impetus to applying genetic analyses to PPI variables, and suggest that startle latency may also be a useful measure in the study of potential endophenotypes for schizophrenia.

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