Low-level cadmium exposure increases one-way avoidance in juvenile rats.

Twenty-seven pregnant rats from three genetic lines, Roman High Avoidance (RHA), Roman Low Avoidance (RLA), and Satinder's Heterogeneous Stock (SHS), received daily SC injections of either 0.075 mg/kg CdCl2 (low dose), 0.225 mg/kg CdCl2 (high dose), or an equivalent volume of saline vehicle (control) throughout gestation. Cd-exposed progeny from the RHA genetic line weighed significantly less than RHA control progeny (pd 35-44); however, SHS progeny from the low-dose group weighed significantly more than progeny from any other group (pd 14-44). Unconditioned escape response (UER) level was determined on pd 39. Progeny from the high-dose group required a significantly lower UER level as compared to the low-dose group. Acquisition of conditioned avoidance responses was tested from pd 41 to 44. There were significant differences due to dose for one-way avoidance responses. Cd-related differences in one-way avoidance were restricted to progeny from the SHS genetic line. SHS progeny from the high-dose group demonstrated significantly more one-way responses when compared to the control group. Differences in avoidance responses are discussed in relation to Cd-induced hypernociception. The concentration of Cd in the liver and kidney of dams and progeny was determined by Inductively Coupled Plasma spectroscopy (ICP). There were significant dose-related differences in Cd concentration in maternal tissues.

Emotional reactivity and alcohol preference among genetic crosses of the Maudsley and Roman rats.

The relationship between open-field emotional reactivity and alcohol preference was investigated in crosses of the Maudsley and Roman rat lines. No significant differences were found in any of the behaviors between the respective reciprocal crosses. The scores on the two variables showed a positive correlation between open-field defecation (OFD) and alcohol preference. The findings confirmed a prediction for the relationship between OFD and alcohol preference in these genetic crosses. In light of the previous findings it would seem that OFD and alcohol preference are not directly related to each other, and emotional reactivity acts as a mediating process between the two behaviors. However, in these genetic crosses the observed relationship between OFD and alcohol preference can be explained by a possible genetic overlap between the mechanisms mediating these two behaviors.

Cannabis use and sensation-seeking orientation.

Cannabis use and its relationship with sensation-seeking orientation was investigated in 48 college and university students of both sexes. Users and nonusers were matched for sex, age, and education. Cannabis users scored higher on all the four subscales of the sensation-seeking scale (SSS). Analysis of covariance controlling for the use of alcohol, cigarettes, and LSD decreased the level of significance between the user and nonuser groups on all the subscales and the total SSS scores; however, the differences between the user and nonuser remained significant on the disinhibition subscale and the total SSS scores.

Differential effects of pre- and/or post-natal d-amphetamine on avoidance response in genetically selected lines of rats.

Effects of pre- and post-natal d-amphetamine on avoidance response were investigated in genetically selected lines of rats. Pregnant animals of the Roman high- and low avoidance (RHA and RLA) lines were administered daily either 3 mg/kg d-amphetamine or physiological saline from day 7 to 20 of gestation. Either-way avoidance learning was studied in prenatally treated offspring over four days of training and subsequently under the effects of four dosages of d-amphetamine. Prenatal intervention with d-amphetamine contributed significantly to avoidance learning over four days of training. A significant genetic line X prenatal treatment X dose response interaction was found in one-way and two-way responses. Results were discussed in terms of inverted-U arousal function, and it is proposed that the prenatal amphetamine intervention may affect baseline levels of physiological arousal. This effect may enhance or impair learning depending upon the nature of the response and the genetic line.

Open-field emotional reactivity and alcohol intake in rats.

The relationship between open-field emotional reactivity and alcohol intake was investigated. Randomly selected, high and low open-field defecation (OFD) groups from each of the MNR, MR and RCA genetic lines of rats were used. No functional relation between OFD as a measure of emotional reactivity and alcohol intake was found. Differences in alcohol intake among genetic lines were confirmed. It is concluded that emotional reactivity is a mediating process related independently to both OFD and alcohol intake.

Ontogeny and interdependence of genetically selected behaviors in rats: avoidance response and open field.

Ontogeny and interdependence of genetically selected avoidance and open-field behaviors were investigated in six genetic lines, involving 1,018 animals, and three developmental models (longitudinal, cross sectional, and generational). In selected lines, behaviors varied with age, depending upon the genetic selection; in the control (random bred) line, no such effects were found. Between the lines selected for high (RHA) and low (RLA) rates of two-way-active avoidance, ontogenetic differences in the selected behavior emerged as the animals grew older, whereas between the lines selected for high (MR) and low (MNR) frequency of open-field defecation, the differences in the selected behavior were present at all stages of development. In unconditioned escape response to footshock, which shows an inverse relation to avoidance response in the RHA and RLA lines, and in general activity (number of sections crossed in an open field), which shows inverse relation to defecation in the MNR and MR lines, the differences were present at all stages. The relation between avoidance response and open-field defecation (emotional reactivity) was not linear but suggestive of curvilinear inverted-U-function.

Interaction among d-amphetamine, scopolamine and genotype in avoidance behavior of rats.

Effects of d-amphetamine and scopolamine were investigated on either-way avoidance in two genetic lines. In the either-way task, the animal has the option to respond in either of the two directions available. Differences between the genetic lines were statistically significant under the effects of scopolamine, but were absent under the effects of d-amphetamine. It seems that scopolamine is more likely to disrupt responsiveness to visual stimuli in the low-avoidance line and this difference in responsiveness is influenced by bidirectional genetic selection.

Genetically heterogeneous and selected lines of rats: behavioral and reproductive comparison.

Avoidance learning, open-field, and reproductive behaviors of a genetically heterogeneous stock (derived from a four-way cross of selected lines) were compared with the corresponding behaviors of the parental lines. The heterogeneous stock showed heterosis on the body development, fertility rate, litter size at birth and at weaning, and directional dominance on the avoidance learning and open-field measures.

Interaction among scopolamine, conditioned stimulus modality, genotype, and either-way avoidance behavior of rats.

Effects of scopolamine were investigated on either-way avoidance in three genetic lines under auditory and visual conditioned stimuli (CS). In the either-way task, the animal has the option to respond in either of the two directions available. In the genetic line selected for high-avoidance the effects of scopolamine were similar with both auditory and visual CS modes. In the genetic line selected for low-avoidance, and in the genetically heterogeneous line, the effects of the drug were different between the auditory and visual CS. It is suggested that scopolamine is more likely to disrupt responsiveness to visual stimuli, which have become less effective in the low-avoidance line during the course of genetic selection.

Long-term effects of preweaning taurine injections in rats: interactions with strain and gender.

A comparison was made of MR, MNR, and RCA strains that had been injected with either 62.5 mg/kg of taurine or comparable volumes of physiological saline between postnatal Days 8 and 20 and later tested at 100 days of age in an open field and 1-way shock avoidance situations. Taurine-injected rats displayed significant elevation in defecation score in the open field. In addition a significant Treatment X Strain interaction was due to the larger defecation numbers displayed by the taurine-injected MR rats relative to the saline-injected MR rats.

Scopolamine interacts with reactions to cat and genotypic emotional reactivity in rat.

In the presence or absence of a cat the effects of scopolamine hydrobromide were investigated on approach, freezing and defecation behaviors of the bidirectionally selectively bred rat strains for emotional reactivity. Compared to the baseline behavior (absence of cat and scopolamine), both the genetic lines showed decrease in approach and increase in freezing in the presence of cat. Scopolamine in the absence of cat did not affect any of the behaviors of the nonreactive strain but increased approach and decreased freezing in the reactive strain. The presence of both cat and scopolamine affected both the strains but differently, i.e., showing no significantly change in the nonreactive, but increase in freezing and decrease in approach in the reactive strain, as compared to the respective baselines.

Oral intake of morphine in selectively bred rats.

Oral intake of morphine was investigated in selectively bred strains of rats. It was possible to induce all the five genetic lines to consume morphine in distilled water. Withdrawal of morphine resulted in significant decrease in the body weights of all the genetic lines in both the experiments. Significant drug-preference behavior was found only in three genetic lines with a common characteristic of relatively high emotional reactivity as compared to the two lines not showing such a behavior.

Sensory responsiveness and avoidance learning in rats.

Analysis of sensory responsiveness and avoidance learning was carried out in three experiments using five rat strains. There were significant differences among the strains in response to electric footshock. Also the strain-specific shock intensity as unconditioned stimulus (US) elicited significantly higher rates of avoidance learning as compared with the rates of avoidance learning under an equal but average level of shock intensity as US. In general, discrete auditory and visual sensory modes as conditioned stimuli (CS) produced almost the same rate of avoidance learning. The proportion of variation in avoidance learning attributable to strains was significant under all six experimental conditions except no-discrete CS and strain-specific US condition.

Differential effects of morphine on two-way avoidance in selectively bred rat strains.

Effects of morphine administration were investigated on avoidance behavior in five rat strains. Strain-dependent facilitation or suppression of avoidance acquisition was found in animals tested 1 h after the last administration of morphine. Significant strain differences were found in the incidences of sexual stimulation, diarrhea and wetness, reactivity, and death due to toxicity.

Interactions of age, sex and long-term alcohol intake in selectively bred strains of rats.

The alcohol consumption by five genotypes of rats was studied in two experiments. Alcohol intake was age-dependent in rats bred for high emotional reactivity and avoidance conditionability. Differences in consumption by sex appeared to be primarily due to differences in body weight.