Mesenteric mast cell degranulation is not essential for conditioned taste aversion

The possible role of mesenteric mast cell degranulation as the mediator of the initial UCS effects in the complex sequences leading to conditioned taste aversion (CTA) was studied. Both LiCl and Compound 48/80, a potent mast cell degranulator, produced CTA to 10% sucrose. Whereas the Compound 48/80 groups displayed massive mast cell degranulation, neither the LiCl treated nor saline control groups demonstrated any histologically determinable alterations. Administration of the antihistamine chlorpheniramine at dosages known to block radiation-induced CTA before the sucrose CS-UCS pairings did not block either LiCl- or Compound 48/80-induced CTA; the antihistamine actually facilitated the aversion. However, pretreatment with the antihistamine did not alter mesenteric mast cell morphology.

Activity and acquisition/extinction comparisons of brown- and white-coated litter mates

Initial experiments were conducted to determine the effect of coat color on behavior. “Wild” brown- and white (albino)-coated litter mates from 5 brother-sister bred pairs which were the offsprings of albino rats bred with wild dump rats ( Rattus norvegicus) were compared directly on several behavioral measures. No significant differences existed between coat colors for juvenile and adult ambulatory activity, acquisition rates for a lever-pressing task or for weaning and adult body weights. The brown-coated rats extinguished the lever responses more quickly than their white-coated litter mates. Sex differences tended towards significance for the activity measures and were significant for the body weights.

No evidence for relationship between biorhythms and industrial accidents

According to the popular biorhythm model accidents are more likely to occur during the "critical days" of three sine wave-like cycles that display periodicities of 23 days, 28 days, and 33 days. Analyses of 400 mining accidents from two separate industries demonstrated that the number of employees who were involved with accidents on their individual critical days of the different cycles did not differ significantly from chance expectancy. Furthermore the number of employees involved in accidents when their cycles were in ascending phases (presumably associated with positive behaviors) did not differ significantly from the number of employees who were involved in accidents when their cycles were in the descending phases, presumably associated with negative behaviors. We have found neither empirical nor theoretical support for the biorhythm model.

Cajal-Retzius cells as electrostatic guides for migrating neurons

A model is presented to explain one of the possible functions of the Cajal-Retzius cells which are known to mature perinatally but not to survive into late infantile life. In this model the processes of the Cajal-Retzius (C. R.) cells and the ventricular surface act as a transient capacitor-like mechanism during neural migration. Neurons which are connected to the ventricular surface during migration by an end foot are consequently guided by the Cajal-Retzius cell processes located in the upper strata of the cortical molecular layer. Once the end foot is severed migration stops and differentiation begins. When the period of migration nears completion postnatally, the mechanism is destroyed as these cells die or lose their connection with the cortical pial surface. Calculations are given to support the feasibility of this model.

Oral taurine effects on inhibitory behavior: response transients to step-like schedule changes

Rats habituated to DRL 6-s schedules that required response inhibition in order to obtain reward did not alter their total responses or efficiency ratios (response/reinforcement) when placed ad libitum (orally) on 0.9% taurine (1.1 +/- 0.4 g/kg/24-h) relative to controls. In three separate experiments, taurine-administerd rats did show significantly poorer adjustment profiles (higher response/reinforcement ratios) during the 15 min immediately following step-like increases in inhibition time demand to DRL 12 s. The effect was transient and was not signficant in subsequent sessions. Taurine rats had been habituated to a DRL schedule intended to induce "frustration" before and step-change did not differ from the taurine group maintained on the normal DRL schedule. No significant differences were noted between taurine and control groups, either before or after taurine administration or before or after the step-change in inhibition demand, with respect to defecation in the test chamber, daily fluid consumption, body weight or total responses. We concluded that oral taurine may inhibit learning during labile periods of adjustment following sudden changes of input demand but does not influence a well learned or established response pattern. These results imply taurine's role in the brain as a "stabilizer" against short-term input fluctuations.

Weak inhibitory behavioral effects of postnatal! preweaning taurine injections in rats

The behavior of rats injected once every 2 days between Postnatal Days 4 and 20 with 62.5 mug/g or 125 mug/g body weight of taurine was compared with saline- or .5 M NaCl-injected litter-mate controls. Taurine-injected rats ran significantly less in the running wheel test and displayed lower response/reinforcement ratios following step-like changes in DRL reinforcement schedules. The quicker adjustments to the changes in DRL schedules did not occur immediately but during sessions following the change. We concluded that taurine administration during early juvenile development could weakly influence adult inhibitory behavior.

Physiological changes associated with changing fixed ratio schedules in rats

In two experiments rats, which had been gradually adjusted to a fixed ratio 50 (FR 50) reinforcement schedule over 10 sessions and then suddenly were placed on a FR 125 schedule on Session 11, showed a significant decrease ( p < .05) in circulating blood eosinophil levels compared to groups which had been similarly shaped up to but maintained on a FR 50 schedule. The changes presumably occurred within a 35- to 40-min. period following the schedule change. Significant positive correlations were noted between the amount of disruption in the response pattern observed in the records of the group that had been shifted from FR 50 to FR 125 and number of fecal boluses on the last day, duration of the bar-press per response, and thyroid-thymus nodule weights.

Prenatal exposure to an elf rotating magnetic field, ambulatory behavior, and lunar distance at birth: a correlation

A significant correlation of 877 between lunar distance at the time of birth and the number of squares traversed in a open-field situation 21 to 25 days later was found for 19 litters that had been exposed continuously during their prenatal development to a 0.5 Hz, 3 to 30 gauss Rotating Magnetic Field (RMF), over a year. RMF-exposed litters that were born on or near lunar perigees traversed fewer squares in an open field than those born on or near apogees. RMF-exposed litters tested “blind” also showed the relationship between lunar distance at time of birth and later open-field activity. 12 control litters did not show a significant correlation (.101).