Impact of video games on plasticity of the hippocampus.

The hippocampus is critical to healthy cognition, yet results in the current study show that action video game players have reduced grey matter within the hippocampus. A subsequent randomised longitudinal training experiment demonstrated that first-person shooting games reduce grey matter within the hippocampus in participants using non-spatial memory strategies. Conversely, participants who use hippocampus-dependent spatial strategies showed increased grey matter in the hippocampus after training. A control group that trained on 3D-platform games displayed growth in either the hippocampus or the functionally connected entorhinal cortex. A third study replicated the effect of action video game training on grey matter in the hippocampus. These results show that video games can be beneficial or detrimental to the hippocampal system depending on the navigation strategy that a person employs and the genre of the game.

Immunomodulatory effects of footshock in the rat.

Intermittent inescapable footshock (IIFS) treatment, administered to 3-month-old male rats, resulted in analgesia as well as discrete immunological and endocrine changes. The splenic lymphocyte proliferative response to concanavalin A (ConA) and phytohemagglutinin (PHA) was decreased by 20% and 41%, respectively. The primary IgM plaque forming cell (PFC) response to sheep red blood cells (SRBC), however, was not altered by IIFS administered either immediately or 24 h after injection of SRBC. IIFS also produced a significant (20-fold) increase in plasma corticosterone (CORT) as compared to non-shocked controls. The shock-induced suppression of splenic lymphocyte mitogenic response to PHA was blocked by 10 mg/kg naltrexone (NTX) administered immediately before IIFS. NTX alone had no effect on this mitogen response. However, NTX significantly attenuated the shock-induced rise in CORT even though NTX alone significantly elevated CORT in the non-shocked controls. These data suggest that IIFS alters cellular immune response but not the primary IgM PFC response (a measure of humoral immune function) and that the immunomodulatory effects may involve both an opioid and a corticosteroid component with respect to alterations in the splenic lymphocyte mitogenic response to PHA.

Neurobehavioral effects of the calcium ionophore A23187.

The divalent cationic ionophore A23187 (calimycin) facilitates the transport of calcium ions across biological membranes, resulting in an increase of cytosolic calcium. A23187 has been used extensively in vitro to activate calcium-dependent neurocellular processes. Because of its potential usefulness as a neurotoxicological probe, our laboratory conducted a series of studies to characterize the neurofunctional consequences of A23187 in the intact organism. In addition to approximating the LD50, the effects of acute parenteral administration of A23187 on conditioned avoidance, nociceptive shock threshold, open-field activity, consummatory behavior, body temperature and neuromotor function, including general activity, coordination, balance and grip strength, were assessed in the rodent. The LD50 of A23187, administered intraperitoneally to adult male rats, was 9.2 mg/kg. The predominant overt signs of toxicity included lethargy, limb weakness and apnea. Lower doses, from 0.5 to 0.03 mg/kg, produced a variety of more subtle neurobehavioral effects, including a selective depression of motor activity, a moderate elevation of shock threshold, altered conditioned avoidance behavior and hypothermia.

Postnatal neurobehavioral development in rats exposed in utero to caffeine.

Potential behavioral and teratogenic effects of caffeine were studied in Charles River CD albino rats. Caffeine in distilled water was given by gavage to pregnant rats (dams) at doses of 5, 25, 50 or 75 mg/kg on Days 3-19 of gestation. Concurrent controls received distilled water gavage (10 ml/kg) on the same days. Dams were allowed to deliver normally. Physical and behavioral observations were made on dams during gestation and lactation and on F1 offspring through 9 weeks of age. Caffeine decreased body weights and food intake and increased water intake in gestating dams but these effects dissipated during lactation. Spontaneous locomotor activity (PAC) and open field (OF) were increased immediately after caffeine gavage but not before. Parturition was slightly delayed. With analyses of data based on individual pups the following effects were noted. Pre- and post-weaning offspring body weights were decreased in females at 50 and 75 mg/kg and in males at 75 mg/kg. Incisor eruption was delayed in females at 5, 50 and 75 mg/kg and in males at all doses. Auditory startle developed earlier in the 5 mg/kg dose group but was delayed at 75 mg/kg for males only. Eye opening was delayed in both sexes at 25, 50 and 75 mg/kg. In females, vaginal opening was delayed at 5, 25 and 75 mg/kg and 9-week ovary weights were increased at 75 mg/kg. In postweaning males, food intake was decreased and water intake was increased with increasing dose. In males, PAC was decreased at 75 mg/kg only on Day 12. At 7 weeks of age, step-down passive avoidance was decreased at 5 and 25 mg/kg but increased at 50 and 75 mg/kg, and at 8 weeks of age, shuttlebox active avoidance was decreased with increasing dose. Maternal and offspring behaviors were only weakly correlated. Correction for litter effect in developmental data yielded fewer significant results and only at 50 and 75 mg/kg. The issue of whether it is always appropriate to correct for "litter effect" is discussed.

Neuromotor function in rats during subchronic dietary exposure to triphenyl phosphate.

The possibility that dietary exposure to triphenyl phosphate (TPP) may result in detectable neuromotor dysfunction was investigated. Young male Sprague-Dawley rats were fed diets containing TPP at levels of 0, 0.25, 0.50, 0.75 or 1.0% for 4 months. At approximately monthly intervals, a battery of behavioral tests was administered to assess different facets of neuromotor function including motility, balance, coordination and muscular strength. Treatment-related decrements in growth, in the absence of changes in food consumption, were found at all dietary levels above 0.25%. However, none of the behavioral measures used in this study were affected by the dietary treatment. It was concluded that there is no evidence of neuromotor toxicity following subchronic dietary exposure to TPP in the rat.

Multipup homing: a rapid test for olfactory discrimination in neonatal rats.

The multipup homing procedure (MHP) is a rapid test for olfactory discrimination performance that can be run on an entire 8-pup litter of neonatal rats in 8 min. Performance improved developmentally with age, and females tended to perform better than males. The MHP was examined for its usefulness in detecting early postnatal effects of low-level prenatal exposure to chlorpromazine (CPZ) or d-amphetamine (AMPH). CPZ increased response latencies in both males and females, but AMPH had no significant effects. The MHP appears promising for use in behavioral teratological assessment of neurobehavioral function.