Effects of neonatal undernutrition and cold stress on behavior and biochemical brain parameters in rats.

This study was conducted to investigate the separate and combined effects of neonatal undernutrition (U) and cold stress (S) on the behavioral and cerebral development of postweaning rats. A severe U was imposed by feeding dams a low protein diet. Postweaning all pups were fed a control diet. S consisted of daily exposure to 5 degrees for 3 minutes from day 2 to 11. Behavioral data show that U animals, stressed (S) + nonstressed (NS), exhibited a significant deficit in reversal learning of T-maze at 21 days, an enhanced passive avoidance response, but no difference in active-avoidance at 35 days when compared to controls of the same age. S had no effect on behavior development. At death (110 days), the brains were dissected into five sections and assay for acetylcholinesterase (AChE) and cholinesterase (ChE) activities. Brain weights of U animals (NS + S) were significantly lower in all sections except dorsal cortex (DC). AChE and ChE activities were significantly higher in all sections (except DC) of U animals relative to controls. S resulted in lower cerebellar weight and ChE:AChE ratios in some sections. Our results suggest a delayed behavioral maturation in U animals and an association between early postweaning behavior and brain parameters in adult rehabilitated animals.

Prenatal undernutrition: effects on behavior, brain chemistry and neuroanatomy in rats.

The behavior and cerebral effects of prenatal protein-calorie undernutrition were investigated in newborn and postweanling rat pups. At birth, prenatally undernourished (PU) animals showed a deficit in body weight; however, by day 15 the difference was diminished and not significant. On days 13-18, PU pups required more trials for reversal learning of a water-escape response in a T-maze than control (C) pups; however, on days 31-35, there were no difference between groups when trained to learn an active-avoidance response. Assessment of brain development showed that at birth, DNA and protein content was severely reduced in PU animals; however, normalization was noted in regional sections of the brain at 35 days of age. Brainstem reticular cells from PU pups at birth show less dendritic arborization and less terminal branching cells from C pups. The results are discussed in terms of a delayed rate of maturation.

The effect of protein-free diet on blood pressure in the Wistar rat.

The relationship between blood pressure (BP) and an 18 day protein free diet (PFD) was studied in unanesthetized male Wistar rats beginning at 20 weeks of age. Following cessation of the 18 day diet, BP was monitored for 8 weeks. Both the PFD animals and a control diet (CD) group showed a reduction in BP from 20 weeks to 30 weeks. Reduction in BP for PFD animals was 3 times that of the CD animals across the diet period. The authors caution the reader in terms of generalizing across strains for this effect and suggest that a greater data base is needed before a definite statement can be made concerning the effects of a protein free diet on BP.

Effect of handling on maternal behavior following return of pups to the nest.

Handling rat pups during the 1st week after birth altered adult behavior in the open-field, whereas simply spearating the pups from their mothers during the same period produced differences in body weight at weaning. Observations of mother-infant interaction following pup treatment yielded different patterns of maternal behavior. Moreover, pups receiving early treatment were more active as adults in a novel environment and had a greater body weight at weaning. The quality of maternal care and the immediate effects of infantile stimulation on the mother-infant relation should be considered in specifying a mediating mechanism for the effects of early experience.

Interactive effects of parity and pup stress on the maternal behavior of Rattus norvegicus.

Litters of primiparous and multiparous rat mothers received 0,2, or 5 min of cold stress for the 1st 5 days postpartum. Primiparae showed increasing maternal responsiveness over the treatment period. Multiparae were initially maternally responsive to moderate stress cues from pups, but habituated to them over days. From Days 6 to 20, when pups were not stressed, lactation behavior of stressed groups declined in primiparous mothers but not in multiparous mothers.

Maternal behavior: a determinant of amphetamine toxicity in rats.

At 130 days of age, 31 female rats that had been subjected in infancy to handling, mother-separation, both, or neither, were injected with d-amphetamine (100 mg/kg, 50 mg/ml, i.p.). The subjects form handled, mother-present litters were the only group that showed increased latency to death. This finding indicated that the maternal behavior elicited by early handling, rather than early handling or maternal presence alone, resulted in reduced amphetamine toxicity in the offspring, tested in adulthood.

Effects of prior experience and 'functional disturbance' on acute and chronic tolerance to methylphenidate.

The degree of habituation or adaptation an animal has experienced prior to the administration of methylphenidate was found to be more crucial in determining the animal's response to the drug than chronic drug administration alone. Rats allowed to adapt in a Y-maze for 24 days showed less methylphenidate-induced activity than animals receiving chronic administration of saline or methylphenidate but no adaptation, when animals were injected with the drug and tested in the Y-maze on Day 25. Animals also were shown to develop tolerance to the methylphenidate-induced activity.