1. ¹King's College London, Department of Psychology, Institute of Psychiatry, London, UK
2. ²King's College London, Division of Psychological Medicine and Psychiatry, Institute of Psychiatry, London, UK
3. ³Affective Disorder Unit, Bethlem Royal Hospital, Beckenham, Kent, UK

Correspondence: Professor V Kumari, King's College London, Department of Psychology, P078, Institute of Psychiatry, De Crespigny Park, London SE5 8AF, UK. Tel: +00 44 207 848 0233; Fax: +00 44 207 848 0860; E-mail: v.kumari@iop.kcl.ac.uk

Received 15 October 2007; Revised 11 December 2007; Accepted 11 December 2007; Published online 23 January 2008.

Abstract

Prepulse inhibition (PPI) of the startle response is sensitive to sex with women showing less PPI compared with age-matched men and varies according to the menstrual cycle in women. Relatively less is known about sex differences in prepulse facilitation (PPF). To examine further the roles of sex and circulating sex hormones, pre- (n=20) and postmenopausal women (n=20) were compared with men of similar ages (n=17, 18–40 years; n=18, 55–69 years). All participants were assessed on PPI and PPF, and provided saliva samples for measurement of 17-estradiol (estrogen) and testosterone. Premenopausal women showed less PPI compared with age-matched men, with no significant difference in PPF. Postmenopausal women did not differ in PPI but showed more PPF than age-matched men. There was less PPI and PPF in older, relative to young, men; pre- and postmenopausal women did not differ significantly. PPI showed no association with the levels of sex hormones. PPF showed small positive associations with both the levels of estrogen and testosterone, especially in young men. The present findings extend recent observations in mice showing less PPI in premenopausal, but not postmenopausal, female compared with male mice of similar ages (Ison and Allen, Behav Brain Res, 2007) to humans. There appear to be no substantial relationships between individual differences in endogenous levels of sex hormones and PPI; fluctuations within an individual may have a stronger role.