Early protein malnutrition changes learning and memory in spaced but not in condensed trials in the Morris water-maze

Abstract

Early protein malnutrition induces structural, neurochemical and functional changes in the central nervous system leading to alterations in cognitive and behavioral development of rats. The aim of the present study was to investigate the effects of protein malnutrition during lactation on acquisition and retention of spatial information using different training procedures (spaced x condensed trials). Rats treated with 16% (well-nourished) or 6% (malnourished) protein diets during the lactation phase and nutritionally recovered until 70 days of age were tested in the Morris water-maze in procedures of 1 trial/day (spaced trials), 4, 8, 12 trials/day (intermediate density) and 24 trials/day (condensed trials), completing 24 trials at the end of training. Seven and 28 days after the training the animals were tested again in just one trial to assess long-term memory. The results showed that protein malnutrition caused deficits on the spatial learning and memory in spaced but not in intermediate and condensed trials procedure. Seven and 28 days after the training there was an increase in the latency to find the platform but only malnourished animals submitted to 1 trial/day had significantly higher latency as compared with well-nourished controls. One of the possible hypotheses is that the effect protein malnutrition only in the procedure of spaced trials could be due to deficits in memory consolidation. It is suggested that these deficits can be the result of alterations produced by protein malnutrition in the hippocampal formation or in long-lasting emotional and/or motivational aspects of the rat's behavior.

Behaviour of postnatally growth-impaired mice during malnutrition and after partial weight recovery

“…17 Spatial memory in a Morris water maze was impaired in rats after early protein malnutrition with subsequent recovery, however only when spaced trials were applied. 21 No results indicating cognitive impairment in early protein malnourished animals were found in the present study as far as working memory in the Y maze and short-term memory in a one trial OR task are concerned. These results are in line with the idea that nutritional rehabilitation may help reduce cognitive deficits.…”

“…13 A range of methods have been applied to induce the nutritional deficit: temporal maternal separation, manipulation of litter size, restriction of maternal protein-energy intake, or the surgical ligation of the dam's nipples to impair lactation. [14][15][16][17] Reported effects of postnatal protein malnutrition induced by these methods in rodent offspring include changes in social, aggressive, and maternal behaviour, 18,19 exploratory behaviour and anxiety, 20 altered learning and memory capacities, 21,22 differences in the behavioural response to the administration of drugs, 23,24 and the response threshold to aversive stimuli. 16 The extent and persistence of effects of a limited period of PEM on brain development, behaviour and cognition are not entirely explored; however, they seem to be partly reversible later in life.…”

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

“…In addition to changes in typical behaviors of social interaction, malnourished rats have learning difficulties in tasks that involved complex strategies or required the animal’s attention to many environmental stimuli, as shown in previous studies by our group [31,32,34,46]. …”

“…Although some studies do not show significant differences in performance between well-nourished and early malnourished rats in spatial learning and memory tasks [53–55]; some other studies with rats subjected to severe malnutrition in early life and/or extended until after the lactation period, covering thus the entire critical period of central nervous system development, showed that these animals take longer to learn the task and have more difficulty to retain the information learned [31,32,34,46,49,56,57]. …”

Early postnatal protein malnutrition causes resistance to the anxiolytic effects of diazepam as assessed by the fear-potentiated startle test

“…Early postnatal protein malnutrition affects learning (acquisition) and memory (retention) in the distal but not in the proximal cue version of the Morris water maze and changes learning and memory in spaced but not in condensed trials in the same test (Fukuda et al 2002;Valadares and Almeida 2005).…”