Lateralized audiogenic seizure: motor asymmetries exhibited and the effects of interrupted stimulation

Sensitized SJL/J mice were monaurally tested for susceptibility to sound-induced seizure. The acoustic stimulation was interrupted for 15 s at various points during the biphasic pattern of running which these mice characteristically exhibit before seizing. Asymmetries of run directions and side of fall were noted. In addition, a dramatic reduction in seizure incidence was found when the interruption either extended into the period when the later burst of running would have occurred or began during this running burst. Finally, the results indicate that the latencies to the later running burst and the subsequent seizure are determined at or about the time of the onset of the first burst of running.     

Recovery of susceptibility following audiogenic seizure in mice.

The rate at which SJL/J mice recover susceptibility following an initial sound-induced seizure was examined. Fewer than 15% of the subjects seized when retested after a 2-min delay, and only 50% reseized after a 10-min delay. The likelihood of a second seizure was enhanced if the initial seizure exhibited a rapid progression to clonus. During the retest, seizures progressed more slowly than during the initial test, which indicates that recovery was not complete even if a second seizure was induced. Finally, recovery of seizure susceptibility was prevented as long as the subject continued to be exposed to intense auditory stimulation following the initial convulsion, an effect previously noted by Alexander and Kopeloff (1980). The findings are discussed in terms of a recently proposed central inhibitory model of the recovery of audiogenic seizure susceptibility.     

Independence of uniphasic and biphasic audiogenic seizure progressions in mice

DBA/2J mice were monaurally or binaurally tested for susceptibility to sound-induced seizure. Two seconds following the beginning of running, one group of binaurally tested mice had acoustic stimulation interrupted for 15 s. These mice later seized when the stimulation was readministered. Their seizure progression closely resembled the behavior exhibited by noninterrupted binaurally stimulated mice and did not shift to the biphasic motor pattern of monaurally stimulated subjects. We conclude that the single burst of running of a binaurally tested mouse is qualitatively different from either of the two bursts of running exhibited by monaurally tested mice.     

Maternal stress and pituitary-adrenal manipulations during pregnancy in rats: effects on morphology and sexual behavior of male offspring.

The purpose of the present study was to determine whether the demasculinizing and feminizing effects of prenatal stress (i.e., stress applied to the mother during pregnancy) in rats reported previously are mediated by activation of the maternal pituitary-adrenal axis. Neither whole-body restraint, with or without hyperthermia, nor ACTH treatment during the last third of gestation had any reliable effect on masculine or feminine sexual behavior in male Sprague-Dawley offspring, although these treatments produced maternal pathology and evidence of maternal adrenocorticoid release. Significant littermate similarity was found for almost every morphological and behavioral measure. Failure to control for the litter variable may account for many previously reported effects of prenatal stress on sexual behavior in rats. The discrepancy between the present and earlier findings is discussed in terms of methodological and theoretical considerations.     

Roles of anoxia and noise-induced hearing loss in the postictal refractory period for audiogenic seizures in mice.

The present series of experiments demonstrated a postictal refractory period for audiogenic seizures in DBA/2J mice, which was not related to hearing loss but apparently was related to anoxia. Unlike many previous studies, Experiment 1 controlled for the effects of noise exposure upon hearing sensitivity and demonstrated reduced susceptibility to subsequent audiogenic seizures for at least 1 hr after initial clonic-tonic convulsions. The postictal refractory period was shown to result from the occurrence of seizures per se, not from noise exposure alone. Experiment 2 demonstrated deficiencies of sensorimotor functions that accompanied reduced postictal seizure susceptibility. The two phenomena had similar time courses of recovery, which suggested a common mechanism, probably anoxia, associated with the initial convulsions. In support of this view, Experiment 3 showed that recovery from both phenomena was expedited by allowing subjects to breathe increased O2. The role of anoxia in fatal convulsions was suggested by the finding that subjects experiencing clonic-tonic convulsions in a high-O2 environment survived without exception. In contrast, seizures of air-breathing controls were almost always fatal. Taken together, the data indicate that the postictal reduced susceptibility to audiogenic seizures was closely related to metabolic depletion (in particular, anoxia). The pattern of recovery of susceptibility further suggests that the effects of anoxia impair the spread of seizure activity through the central nervous system, although the initiation of seizures is also affected for a short time.     

Behavioral effects of microwave reinforcement schedules and variations in microwave intensity on albino rats

The objective of this exploratory investigation was to determine the interactive effects of fixed-ratio scheduling of microwave reinforcement in tandem with changes in microwave intensity. Nine albino rats were conditioned to regulate their thermal environment with microwave radiation while living in a Skinner (operant conditioning) Box in which the ambient temperature was about 27.13 degrees F at the beginning of the session. Each rat obtained a 6-sec. exposure of microwave radiation on a fixed-ratio schedule of MW reinforcement, the values of which varied from FR-1 to FR-30. Intensities of MW radiation were 62.5 W, 125 W, 250 W, and 437.5 W. Sessions lasted for 8 to 9 hr. over an approximate 13-mo. period. The effects of the intensity of microwave reinforcement varied as a function of the ratio value of the schedule used. Continuous reinforcement (FR-1) produced the lowest over-all rates, whereas FR-15, and FR-25 produced the highest over-all rates. Relatively higher thermal-behavior rates occurred under 62.5 W than under any of the other MW intensities for FR-1, FR-15, and FR-25, whereas FR-10 and FR-30 ratios produced intermediate rates of thermal responding which were constant for all values of MW intensity. These data are explained in terms of interactive effects between the "local" satiation or deprivation properties of the MW intensity and the ratio requirements of the schedule of MW reinforcement.     

Behavioral effects of testosterone in relation to social rank in the male rabbit

The role of gonadal androgens in favoring the adaptation to environmental pressure, including social organization, is well known. In the rabbit, testosterone administration increases marking behavior, and its level can be affected by agonistic interaction. In this experiment, we studied the effect of subcutaneous administration of testosterone propionate (TP) (3 mg/d for 6 days) in male rabbits belonging to the same social group (6 groups of 4 animals). In 2 additional groups (4 animals each), males were injected with almond oil. The animals were observed for 6 days in seminatural conditions, then treated with TP (or oil) and observed for another 6 days. The dominant/subordinate frequency ratio of behavioral patterns was used to rank the animals. The testosterone plasma concentration was correlated with agonistic behavior after the first period of social interaction. A significant increase of marking, digging, and defensive activity was observed after TP administration in all animals independent of rank, whereas this increase was not present in animals treated with oil. Agonistic and interactive behaviors increased significantly after TP treatment only in the first‐ranking animals. This indicates the influence of social rank in the modification of behaviors involving interactions among subjects Aggr. Behav. 29:269–278, 2003. © 2003 Wiley‐Liss, Inc.     

Behavioral risks during the transition from high school to college

The transition from high school to college is an important developmental milestone that holds the potential for personal growth and behavioral change. A cohort of 2,245 students was recruited during the summer before they matriculated into college and completed Internet-based surveys about their participation in a variety of behavioral risks during the last 3 months of high school and throughout the 1st year of college. Alcohol use, marijuana use, and sex with multiple partners increased during the transition from high school to college, whereas driving after drinking, aggression, and property crimes decreased. Those from rural high schools and those who elected to live in private dormitories in college were at highest risk for heavy drinking and driving after drinking.     

Simple disturbance of the dam in the neonatal period can alter haloperidol-induced catalepsy in the adult offspring

Three experiments were performed to determine whether apparently minimal disturbances of dams and litters would influence haloperidol-induced akinesia. In Experiment I, Long-Evans hooded rats (a) were left unmanipulated, (b) received nestcage relocation and observation, (c) received nestcage relocation/observation and maternal separation, or (d) received nestcage relocation/observation and pup handling. The male adult offspring received open-field testing and later received forepaw-on-dowel catalepsy testing following saline, morphine (20 mg/kg), or haloperidol (2 mg/kg). In Experiment II, hooded rats received (a) no manipulation, (b) nestcage relocation, (c) maternal separation, or (d) pup handling. At weaning, dams were tested in the open-field. Activity wheel locomotion of the offspring was assessed following saline or haloperidol for 3 days/week for 3 weeks; then, 5 and 7 days later, rats received haloperidol (0.5 mg/kg) and catalepsy testing. In both experiments, manipulations involving the dam reduced the offsprings' haloperidol-induced catalepsy, but, in Experiment II, a history of haloperidol administration distinguished between the effects of nestcage relocation and maternal separation. In Experiment III, Swiss albino mice received (a) no treatment, (b) nestcage relocation and maternal separation, (c) relocation/separation and mild cold stress of pups, (d) relocation/separation and pup handling, or (e) relocation/separation and severe cold stress of pups. Adult male mice received saline or haloperidol (2.5 mg/kg) and inclined grid catalepsy testing. Mice receiving relocation/separation and mice receiving relocation/separation and severe cold stress showed enhanced catalepsy versus control mice. Thus, it was concluded that seemingly innocuous events in infancy can influence the intensity of extrapyramidal side effects of neuroleptics in adulthood.