Non-dipping, ie failure to lower blood pressure during sleep, has been found to be more prevalent in diabetic than in non-diabetic subjects. However, the reasons remain to be clarified. Diabetic patients may wake up more frequently during the night (for instance, due to nocturia). This may result in inclusion of awake blood pressure measurements in the night-time average and thus erroneously raise this average, causing misclassification of patients as non-dippers. However, nondipping in diabetes may be due to blunted effect of sleep itself on blood pressure secondary to autonomic neuropathy. We undertook this study in order to further clarify this question. We studied 23 diabetic patients, and 23 matched controls who underwent 24-h ambulatory blood pressure monitoring, and reported taking an afternoon nap. Afternoon nap, by virtue of its short duration,

Rats from two strains, inbred for their sensitivity or resistance to experimental hypertension, showed marked differences in behaviour in certain standardized experimental situations. Rats from the resistant strain explored the environment of their cage more, crossed over more frequently into an adjacent cage and behaved more aggressively to another rat after a painful stimulus, than rats from the sensitive strain. Although it is too early to define in exact terms the relationship between these behavioural differences and the mechanisms of the experimental hypertension in one strain and the resistance in the other, these observations support the hypothesis that central nervous functions play a role in the pathogenesis of human ‘essential’ hypertension.