Ethological analysis of mother-pup interactions and other behavioral reactions in rats: effects of malnutrition and tactile stimulation of the pups

Abstract

Mother-pup interaction, as well as other behavioral reactions were studied during the lactation period in 24 litters of Wistar rats and their dams fed either a 16% (control -C; 12 litters) or a 6% (malnourished -M; 12 litters) protein diet. The diets were isocaloric. Throughout lactation there was a 36.4% weight loss of M dams and a 63% body weight deficit in the M pups when compared to control pups. During this period, half of the litters were exposed daily to additional tactile stimulation (CS or MS), while the other half were submitted to normal rearing conditions (CN or MN). The tactile stimulation of pups (handling) consisted of holding the animal in one hand and gently touching the dorsal part of the animals body with the fingers for 3 min. A special camera and a time-lapse video were used to record litter behavior in their home cages. Starting at 6 p.m. and ending at 6 a.m., on days 3, 6, 12, 15, 18 and 21 of lactation, photos were taken at 4-s intervals. An increase in the frequency (154.88 ± 16.19) and duration (455.86 ± 18.05 min) of suckling was observed throughout the lactation period in all groups compared to birth day (frequency 24.88 ± 2.37 and duration 376.76 ± 21.01 min), but the frequency was higher in the C (84.96 ± 8.52) than in the M group (43.13 ± 4.37); however, the M group (470.2 ± 11.87 min) spent more time suckling as compared with the C group (393.67 ± 13.09 min). The M dams showed a decreased frequency of resting position throughout the lactation period (6.5 ± 2.48) compared to birth day (25.42 ± 7.74). Pups from the C group were more frequently observed separated (73.02 ± 4.38) and interacting (258.99 ± 20.61) more with their mothers than the M pups (separated 66.94 ± 5.5 and interacting 165.72 ± 12.05). Tactile stimulation did not interact with diet condition, showing that the kind of stimulation used in the present study did not lead to recovery from the changes induced by protein malnutrition. The changes in mother-pup interaction produced by protein malnutrition of both may represent retardation in neuromotor development and a higher dependence of the pups on their mothers. These changes may represent an important means of energy saving and heat maintenance in malnourished pups.

Early Postnatal Protein-Calorie Malnutrition and Cognition: A Review of Human and Animal Studies

“…Protein or protein-calorie malnutrition imposed during lactation changes the quantity and quality of mother-pup interactions and may lead to long-lasting adverse effects on the behavior of rats in the adult life [40–42]. Reported data have been shown that malnourished mothers spend more time in the nest [41], take longer to gather the pups in the pup retrieval test [40] and change the eating pattern [43].…”

“…Reported data have been shown that malnourished mothers spend more time in the nest [41], take longer to gather the pups in the pup retrieval test [40] and change the eating pattern [43]. Like the mothers, the malnourished pups also presented changes in the behavior as compared to well-nourished pups, mainly by expressing more time in the nest, less time exploring the environment, less time separated in groups and more time in ultrasonic calls [42,44]. …”

Maternal low-protein diet decreases brain-derived neurotrophic factor expression in the brains of the neonatal rat offspring

“…A multitude of animal studies have delved into the effects of prenatal PEM during gestation and postnatal PEM on behavioral abnormalities in the adult progeny [92, 110]. The protein malnourished rat pups subjected to prenatal and postnatal PEM exhibit greater nesting period and passive [5] but lesser locomotor and exploratory behavior [111] during the preadolescent period while exhibiting aggressive and dominance behavior traits in adulthood [112]. Prenatal and postnatal PEM is also associated with deficits in spatial learning and memory in adult rats despite allowing nutritional recovery [113].…”

Efeitos da desnutrição protéica pós-natal no desempenho de ratos em diferentes tarefas de aprendizagem e memória

“…Esta perda de peso das mães desnutridas pode ser atribuída a um maior gasto energético na amamentação e nos cuidados com os filhotes sem a ingestão correspondente (DE OLIVEIRA, 1985). Alguns estudos mostram que as mães desnutridas passam mais tempo amamentando e menos tempo descansando fora do ninho do que as mães controle (LEVITSKY et al, 1975;RIUL et al, 1999), levando a um maior consumo de energia nesses animais. Outros revelaram que ratas lactantes que recebem dieta com Discussão ________________________________________________________________________________________ deficiência de proteína tendem a consumir menor quantidade de alimento (LIMA et al, 1993;CAMBRAIA et al, 1997;RIUL et al, 1999).…”