Effects of excessive glucocorticoid receptor stimulation during early gestation on psychomotor and social behavior in the rat.

Severe psychological stress in the first trimester of pregnancy increases the risk of schizophrenia in the offspring. To begin to investigate the role of glucocorticoid receptors in this association, we determined the effects of the glucocorticoid dexamethasone (2 mg/kg), administered to pregnant rats on gestation days 6-8, on maternal behaviors and schizophrenia-relevant behaviors in the offspring. Dams receiving dexamethasone exhibited increased milk ejection bouts during nursing. Offspring of dexamethasone-treated dams (DEX) showed decreased juvenile social play and a blunted acoustic startle reflex in adolescence and adulthood, effects that were predicted by frequency of milk ejections in the dams. DEX offspring also showed increased prepulse inhibition of startle and reduced amphetamine-induced motor activity, effects not correlated with maternal behavior. It is postulated that over-stimulation of receptors targeted by glucocorticoids in the placenta or other maternal tissues during early gestation can lead to psychomotor and social behavioral deficits in the offspring. Moreover, some of these deficits may be mediated by alterations in postnatal maternal behavior and physiology produced by early gestational exposure to excess glucocorticoids.

Contribution of orosensory stimulation to strain differences in oil intake by mice.

Little is known about why animals differ in daily intake of oils. Here, we tested the hypothesis that the oral acceptability of oil is a key determinant of daily intake. To this end, we examined short- and long-term ingestive responses of eight mouse strains (FVB/NJ, SWR/J, SM/J, C57BL/6J, BALB/cJ, 129P3/J, DBA/2J and AKR/J) to Intralipid, a stable emulsion of soybean oil. In Experiment 1, we compared orosensory responsiveness (as indicated by initial licking rates) of eight mouse strains to a range of concentrations of Intralipid and sucrose. We included sucrose because there are two natural alleles of Tas1r3 (the gene that encodes the T1R3 sweet taste receptor), and strains with the Tas1r3Sac-b allele exhibit higher daily intake of sucrose and oil than strains with the Tas1r3Sac-d allele. All strains exhibited concentration-dependent increases in lick rates for both sucrose and Intralipid, but the extent of these increases varied greatly across strains. The strains with the Tas1r3Sac-b allele licked more vigorously for sucrose at concentrations < or =0.3 M, but not for Intralipid at any concentration. In Experiment 2, we ran the mice through 24-h preference tests, in which they had a choice between water and each of four concentrations of Intralipid (1, 5, 10 and 20%). The strains differed greatly in daily intake of Intralipid, particularly at the 1 and 5% concentrations. Regression analyses revealed that strain differences in orosensory responsiveness reliably predicted strain differences in daily intake of 1 and 5% Intralipid, but not 10 or 20% Intralipid. These findings indicate (i) that Tas1r3 genotype does not modulate orosensory stimulation from oil, (ii) that orosensory stimulation contributes to strain differences in daily intake of dilute oil emulsions, but not concentrated ones, and (iii) that daily intake of concentrated oil emulsions is controlled primarily by post-oral satiety mechanisms.