International Review of Neurobiology: Supplement 1: Neurobiology of the Trace Metals Zinc and Copper S (International Review of Neurobiology. Supplement) by Carl C. Pfeiffer

Author:Carl C. Pfeiffer
Language: eng
Format: mobi
Tags: Internal Medicine, Basic Sciences, Medical eBooks, Science & Math, Anatomy, Neurology, Medical Books, Biological Sciences, Medicine, Neuroscience, Physiology, Basic Science
ISBN: 9781483144467
Publisher: Academic Press
Published: 2013-10-21T21:00:00+00:00

VI. Zinc

The gross symptoms of severe zinc deficiency in several species have been well described. These symptoms include growth retardation, anorexia (which occurs early), seborrhea, loss of hair (which occurs later), testicular atrophy and parakeratosis (Prasad, 1966; Prasad and Oberleas, 1970). Behavioral changes, though less-well-described, are equally characteristic. Most notable are the apathy, lethargy, and decreased activity associated with prolonged periods of zinc insufficiency (Apgar, 1968a, b; Caldwell et al., 1970). Decreased sexual activity on the part of both males and females and sterility in adult males has also been shown (Whitenack et al., 1970). Most of these symptoms have been demonstrated in several species, including man (Prasad, 1966; Prasad and Oberleas, 1970).

Chester and Quarterman (1970) have studied the eating habits of zinc-deprived rats. Under the conditions of their experiments the voluntary food consumption of zinc-deprived rats decreased to 30% of the controls. Day-to-day feed intake became more variable and cyclical. Forced-feeding zinc-deficient rats rapidly induced signs of ill-health. Reducing the protein content resulted in increased food intake and disappearance of the cyclical pattern of intake but did not increase growth. Zinc-deprived rats responded to a zinc-supplemented diet within 1–2 hours with increased food intake and were able to discriminate between zinc-sufficient and zinc-deficient diets. This discrimination dissipated after 6 days of repletion, after which time they ate about equal quantities of each diet. This ability to discriminate dietary zinc was also not apparent if protein-free diets were offered (Humphries and Quarterman, 1968).

Quantitative measures of behavior were only recently studied (Caldwell and Oberleas, 1969). These studies were divided between prenatal and postnatal investigations. The postnatal observations made on moderately severely deficient rats which were placed on the diet at 30 days of age for 48 days prior to testing. They were compared with paired-fed rats who were matched for weight prior to the start of dietary treatment.

In all three measures of behavior, namely, open field (Munn, 1950), platform avoidance-conditioning test (Tenen, 1966), and Lashley III water maze (Lashley, 1929) the performance of the zinc-deficient animals was significantly inferior to that of the zinc-supplemented animals. The results of the open field shown in Table I indicate reduced emotionality levels for the zinc-supplemented subjects. The differential was greatest for the first day of testing but persisted throughout the three trials (F = 4.62, df 1 and 22, p < .05). Performance in the conditioned-avoidance test for the first ten trials (two trial blocks) is shown in Table II. All conditioning had occurred during this time period though 50 trials (10 trial blocks) were run on each subject. The differences between treatment groups for performance were statistically in favor of the zinc-supplemented animals (F = 4.82, df 1 and 22, p < .05). In addition a significantly larger proportion of conditioned responses were made by the zinc-supplemented animals (χ2 = 21.04, p < .001) for all trial blocks.

TABLE I

POSTNATAL OPEN FIELD TESTS

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