Modification of stroke susceptibility by genotype-dependent maternal influences. The influence of the prenatal and postnatal maternal environment on stroke susceptibility was evaluated by reciprocally crossing the spontaneously hypertensive (SHR) and the Dahl salt-sensitive (SS/Jr) inbred rat strains to produce reciprocal F1 hybrids that were nurtured, respectively, during prenatal and postnatal life by SHR or SS/Jr mothers. Following placement on a high-salt diet containing 8% NaCl at 35 days of age, F1 rats reared by SHR mothers had shorter survival times and were more likely to die with cerebral hemorrhage than F1s reared by SS/Jrs. Across reciprocal F1 female groups, enhanced susceptibility to stroke was associated with greater elevations of systolic blood pressure, but this association was not seen across reciprocal F1 male groups. There was also an association between blood pressure and stroke within each F1/gender subgroup: Rats eventually suffering strokes developed higher blood pressure after placement on the high-salt diet than rats that did not suffer stroke. Lower day 35 body weights (before exposure to the high-salt diet) were associated with greater likelihood of stroke both across the reciprocal F1 groups, and within three of the four F1/gender subgroups. The differences in stroke susceptibility between the reciprocal F1 groupings may be due to systematic differences in the prenatal and/or postnatal environments of SHR and SS/Jr mothers and may be mediated by variations in the nutritive capacity of the two inbred mothers. 