Yael Lavi-Avnon

The reward system and maternal behavior in an animal model of depression: a microdialysis study

Rationale and objectivesFlinders sensitive line (FSL) rats, an animal model of depression, display a different pattern of maternal behavior compared to Sprague-Dawley (SD) controls. In this study, we examined the rewarding value of mother–infant interaction for FSL dams.Materials and methodsIn the main study, we measured monoamine levels in the nucleus accumbens (NAc) of early postpartum FSL and SD dams during an interaction with pups, using the microdialysis technique. In addition, we compared the preference patterns of FSL and SD rats using the conditioned place preference paradigm, with pups as the unconditioned stimuli.ResultsDopamine (DA) levels in dialysates from the NAc of SD dams but not FSL dams were elevated while interacting with pups but the metabolism of DA to dihydroxyphenylacetic acid was greater in FSL than in SD dams. While SD dams showed a conditioned preference for a region that was associated with SD pups, FSL dams did not show a preference for regions associated either with SD or FSL pups, but water deprived FSL rats demonstrated a preference to a region associated with water, eliminating an alternative explanation of learning deficit in FSL rats.ConclusionsTaken together, these results suggest that FSL dams are less rewarded by pups, compared to control dams.

Weight gain and maternal behavior in CCK1 deficient rats

The OLETF rat model of obesity has been extensively studied as an adult model of hyperphagia-induced obesity. In order to better understand the early circumstances that make OLETF pups obese, we investigated body weight from postnatal day (PND) 1 and examined diurnal maternal behavior over the first three postpartum weeks by undisturbed observations. Male and female OLETF rats weighed significantly more than LETO controls from PND 1 until adulthood. Differences in nursing behavior were observed only in the third postnatal week: OLETF dams exhibited more frequent nursing. OLETF dams displayed less self-directed behaviors and activity, over the entire postpartum period examined. Taken together, these data demonstrate that OLETF males and females are heavier from birth and suggest that maternal factors may contribute to weight differences between the strains.

Immobility in the swim test and observations of maternal behavior in lactating flinders sensitive line rats

In order to elucidate the relationship between maternal behavior and depression, the Flinders sensitive line (FSL) model of depression was studied and compared to Sprague-Dawley (SD) controls. Immobility in the swim test was measured, as an index for depressive-like behavior, and frequencies of maternal and non-maternal behaviors were recorded using short un-intrusive observations in the home cage. Lactating FSL rats displayed higher levels of immobility in the swim test compared to controls, indicating depressive-like behavior. In addition, compared to SD rats, FSL dams showed less frequent pup licking and non-nutritive contact with pups during the first and third weeks of lactation. In the third postpartum week, FSL dams showed less frequent nursing postures and more frequent self-directed behaviors. Thus, lactating FSL dams exhibit both depressed-like behavior and some abnormalities in maternal behavior.

Stress and pain responses in rats lacking CCK1 receptors

UNLABELLED CCK involvement in stress- and pain-responsiveness was examined by studying the behavior of infant (11-12-days-old) and adult OLETF rats that do not express CCK1 receptors. Infant odor- and texture-preferences were also assessed. We hypothesized that OLETF rats will show behavioral patterns similar to those previously observed after CCK1 antagonist administration. Rate of separation-induced ultrasonic vocalization was significantly greater in OLETF compared to controls, in two separate studies. Infant pups of the two strains did not differ in odor- and texture-preference tests. OLETF rats showed consistently longer hot-plate paw-lift (as infants, in two separate studies) and paw-lick (as adults) latencies. SUMMARY OLETF pups vocalized in isolation more than controls and showed relative hypoalgesic responses, evident also in adulthood, in concordance with the pharmacological literature.