The Acomys cahirinus (spiny mouse) as a new model for biological and neurobehavioural studies.

Acomys cahirinus is a precocial murid and a comparison of its development with altricial species of the same family, such as the rat and mouse, may shed some light on the relationship between genetic and environmental factors in the development. The use of Acomys in neurobehavioural studies and its comparison with mouse and rat may be particularly profitable. Behavioural, differences particularly in the exploratory behaviour, are paralleled by differences in the brain anatomy. Therefore Acomys seems to be a new very promising tool for investigating neurological and behavioural developmental systems.

A toggle-floor box: the reliability of crossings in the evaluation of drug-induced locomotor changes in mice.

Various categories of the motor behavior were recorded using a video tape in mice subjected to a 10 min activity session in a toggle-floor box after an ip administration of saline solution, d-amphetamine (2 or 4 mg/kg), morphine (10 or 20 mg/kg) or scopolamine (0.5 or 1 mg/kg). While all the three drugs enhanced horizontal activity, in particular the crossing from one compartment to the other, rearing was inhibited, particularly by morphine. The results demonstrate that crossings, the behavioral category easily measurable automatically, represent a reliable index of the drug-induced hyperactivity.

[Comparative study of the brain of developed and underdeveloped neonatal rodents of the Muridae family]. / Sravnitel'noe issledovanie mozga u zrelo- i nezrelorozhdaiushchikhsia gryzunov iz semeistva myshinykh.

Morphological studies have been made of the neocortical and archicortical structures in the spiny mouse Acomys cahirinus, the only maturely born species from the family Muridae. The data obtained reveal highly developed hippocampus as compared to the neocortex in this mouse, in contrast to relationships found in other mice and rats.

Antihistaminics enhance morphine-, but not amphetamine- and scopolamine-induced hyperactivity in mice.

Three histamine H1-receptor antagonists, chlorpheniramine, diphenhydramine and tripelennamine, were tested alone or in combination with morphine, amphetamine and scopolamine on locomotor activity in mice. All three antihistaminics, at some dosage levels, enhanced morphine-induced hyperactivity, but did not change or even reduce locomotor stimulation induced by amphetamine and scopolamine. The results suggest that H1-blocking agents may specifically interact, though not necessarily directly, with opiate mechanisms in producing behavioural effects.

A comparative study of mossy fiber distribution in the brain of the precocial Acomys cahirinus and of the altricial Rattus norvegicus: neuroanatomical bases and behavioral correlates.

Acomys cahirinus, the spiny mouse, is the only precocial murid. Given the relatively advanced state of neural maturation at birth, this species is therefore of interest for comparative studies of brain and behavioural development. Previous work on this species has indicated that (i) hippocampal thickness (relative to body weight) is greater in adult Acomys than in rats and mice; (ii) the hippocampus appears laminated at birth, unlike that of related altricial species; (iii) the degree of olfactory bulb maturation at birth is greater in Acomys than in gerbils or rats. In the study reported, the distribution of hippocampal mossy fibers of Acomys was compared with that of Rattus norvegicus, in order to extend our earlier findings. In addition, the implied involvement of hippocampal mossy fibers in olfaction suggests a relation to our studies of exploratory behaviour in this species.

D-Amino acids influence ultrasonic calling in mice pups: effects of D-phenylalanine and D-leucine.

6-day-old mice pups were injected with D-amino acids (D-phenyl-alanine + D-leucine), and their ultrasonic distress vocalizations were measured. D-Amino acids, which exert opioid-like effects, reduce the number of ultrasonic calls without affecting the activity of the pups. This effect is reversed by naloxone, an opioid antagonist. The role of endogenous opioids in modulating early attachment is discussed.

Exploratory behavior of two species of murid rodents, Acomys cahirinus and Mus musculus: a comparative study.

The exploratory behavior of two species of murid rodents, Acomys cahirinus and Mus musculus, was compared in four experiments: In the first, the responses of the two species to a novel arena were studied. Mus was found to take longer to enter the arena, and to spend more time in the relatively familiar or safer start box, than was Acomys. The results suggest that Acomys may persevere longer in exploring particular areas, whereas Mus appear to explore in the open arena by using frequent shifts of attention. The second experiment investigated species differences in response to the addition of a small novel object. Although the species did respond differently, the major species differences seemed to be related more to the open arena than to the object. The third experiment tested the hypothesis that both species would explore more if there was somewhere to hide (e.g., an artificial burrow) than if there was not. It was found that Acomys treated the available artificial burrow as another novel object, while Mus, as predicted, spent more time hiding inside it than did Acomys. The fourth experiment investigated burrow use when a model "predator" was introduced: Both species increased their use of the burrow but some species differences were found. Mus responded to the model more by freezing, or running immediately into the burrow; Acomys responded more by fleeing.

Naloxone influences ultrasonic calling in young mice.

The ultrasonic calls produced by three day old mice when separated from the nest mother and siblings increase in number when naloxone is injected.

Archicortex and neocortex in the precocial murid Acomys cahirinus. A comparison with two altricial species: Mus musculus and Rattus norvegicus.

A morphological analysis of some structures of the archicortex and neocortex was performed in the Acomys cahirinus (spiny mouse), the only precocial murid. The data obtained indicate that the spiny mouse brain is an interesting case of a largely developed hippocampus with respect to the neocortex when compared to the brains of the mouse and rat. The precocious pups of the spiny mouse present the peculiarity among Murids of an early olfactory imprinting.

Rooting and the development of male sexual behavior in two inbred mouse strains.

The sexual development of C57BL 6/J and SEC/IReJ male mice was studied during twice-weekly pairings with estrus females from 5 weeks of age. SEC were far slower to begin copulating than C57 and their responses to the female included a much higher frequency of rooting. Rooting, where the male's snout is pushed below the female's flank and jerked upwards, declines over tests as the full copulatory pattern develops. SEC also spent a higher proportion of their time in close contact with the female and groomed her more than C57. Both strains showed more rapid development of copulation if testing was delayed until 10 weeks of age, especially if they had exposure to female scent during this maturation period. The frequency of rooting and the speed of development are inversely related in these strains, but in segregating hybrid populations no such relationship is maintained. It is argued that the slowness of SEC's development cannot be ascribed to low sexual motivation. The significance of rooting remains obscure, but it seems possible that it may represent an aspect of exploratory behavior that is highly developed in SEC and some other strains.

Ontogenic and genetic variability in the morphology of the somatosensory cortex in developing C57BL/6 and SEC/Re1J mice.

At seven days of age, inbred strains such as SEC/Re1J and C57BL/6 present clear variations of a number of behavioral and electrophysiological parameters. The present investigation was carried out in order to provide anatomical evidence of the interstrain variability in maturation during the first postnatal week by analysing the morphological characteristics of cortical areas in seven day old SEC/Re1J and C57BL/6 mice. The somatosensory cortex was chosen on the basis of its easy localization in histological preparations, its postnatal plasticity and its functional importance during ontogeny. Different measures were performed in areas 1, 3 and 40: cortical depth, depth of layers, grey/cell coefficient, and cellular volumes. The main interstrain differences were observed in areas 1 and 40 and interpreted either in terms of ontogenic variability or, alternatively, in terms of phenotypic characteristics of the brain cortex in inbred mice. Conversely, the level of maturation in area 3 was found remarkably similar in both strains. The relationship between morphological parameters and other measures of the postnatal development is discussed.

A study of several genetic biochemical markers in Sherpas with description of some variant phenotypes.

Gene frequencies for 23 genetic biochemical markers have been determined in one sample of Sherpas and two smaller samples, one of Tibetans living in Nepal and one of 'mixed' Nepalese. Sherpas presented a high GPT1 (0.71) and an appreciable incidence of HbE (about 2%). Variant phenotypes for PGM1, PHI, PepB and C were observed.

Lipid malnutrition and early development: A study of motor reflexes and electrocorticographic activity in the mouse.

The effects of malnutrition on the ontogeny of reflex and electrocorticographic (ECoG) activities were studied in the progeny of mice fed with diets deficient in essential fatty acids (EFA-deprived) during the last week of pregnancy. Previous findings suggested that prenatal deficiency in essential fatty acids may result in extensive modifications of brain lipid biochemistry. The present findings indicate that postnatal maturation of malnourished mice occurs at a later age for a number of motor reflex activities and for the ECoG patterns. The results also indicate that the study of malnutrition through a selective prenatal dietary deficiency presents a number of advantages in relation to postnatal undernutrition attained by varying the litter size.