The behaviour of immature and mature rats exposed prenatally to anti-ganglioside antibodies.

Three behavioural experiments were carried out in rats born to mothers injected with anti-ganglioside antibodies between days 16 and 19 of their pregnancies. Immature animals were slower to habituate to an open-field arena and took longer to learn sequence maze when no cues were provided than did offspring of mothers who had received normal serum. The latter difference disappeared when the way through the maze was cued. In a third experiment mature rats, exposed prenatally to the antibody, showed superior adaptation on a visual discrimination task compared to their controls. It was concluded that antiganglioside modifies sensory rather than motor mechanisms in the rat.

The effect of increased brain GABA produced by amino-oxyacetic acid on arousal in rats.

Previous work has reported behavioral arousal in the rat to be inversely related to cortical GABA production. Therefore the effects of an increase in brain GABA levels, induced by amino-oxyacetic acid, on measures of behavioural arousal such as rearing and ambulation were examined. The increase in GABA was immediately associated with decreased rearing, however the behaviour was later indistinguishable from control values while the levels of brain GABA remained raised. It was suggested that the return to normal behaviour that occurred while brain GABA levels were increased, reflected an interaction between excitatory and inhibitory systems, and that a compensation had occurred to return the balance to normal. The pre-treatment with alpha-methyl-p-tyrosine, known to deplete brain noradrenaline and dopamine, prevented the characteristic return of normal behaviour that followed the injection of amino-oxyacetic acid. This data is consistent with GABA and noradrenaline or dopamine-mediated systems interacting in the control of behavioural arousal. The depletion of serotonin with p-chloro-phenylalanine did not prevent the characteristic recovery of behaviour that followed the injection of amino-oxyacetic acid.

Short intertrial intervals impair water maze performance in old Fischer 344 rats.

Male and female Fischer 344 rats (N = 55) aged approximately 18, 21, and 24 months were tested for spatial learning in the water maze with intertrial intervals of 1-4 min (Massed) or 23-33 min (Spaced). Animals tested in the Massed condition showed an age-related impairment on trials to criterion; rats aged 24 months performed more poorly than younger subjects. Spaced animals did not differ at any age nor did they differ from 18- or 21-month-old Massed subjects. The youngest rats in both groups were comparable to animals aged 7-8 months tested under Massed conditions. Tests on swim distance, swim speed, and escape latency produced similar results. Our data suggest that acquisition deficits in 24-month-old rats tested with long intertrial intervals are due at least in part to increased susceptibility to fatigue and/or thermal stress. Caution should be used, therefore, when interpreting age-related impairments in water maze performance.

Pulse jitter retards kindling without affecting brain-stimulation reward.

Convulsions in rats bar-pressing for electrical stimulation of the brain can interfere with the behavioural evaluation of the properties of the reward substrate. If seizure activity involves the synchronous activation of populations of neurons, then the regular timing of pulses may be important in epileptogenesis produced by electrical stimulation. In the first experiment we found that behaviourally derived, charge-duration functions collected from three self-stimulating rats with lateral hypothalamic electrodes were not affected by introducing a controlled, 50% jitter to the interpulse interval of self-stimulation trains. In the second experiment, we kindled two groups of 6 rats with once-daily, 1.0 s bursts of either regularly timed or jittered pulses to the amygdala until full motor seizures developed. Although both groups eventually attained Class 5 convulsions, the time to first seizure was about two days longer with jittered pulses. Thus, while the circuitry that accumulates input from self-stimulation is not affected by the irregularity of asynchronous pulses, the jitter does seem to retard the development of seizures.

Intra-individual patterns of hormonal and affective adaptation to work demands: an n = 2 study of junior doctors.

This paper examines the detailed pattern of hormonal and affective response to natural variations in work demands, in relation to a taxonomy of adaptive response based on Frankenhaeuser's (1986) psychobiological analysis of coping modes and Hockey's (1993) regulatory control model. Two junior doctors were monitored every day over a 7-week period of work on a cardio-thoracic surgery ward. Measurements were made for each morning and afternoon work period of self-rated workload, effort and affective state, and the level of urinary catecholamines and cortisol. The de-trended data were analysed separately for the two individuals, using multivariate methods. Following reduction of work variables by principal components analysis, canonical correlation analyses were carried out for each individual. These revealed differences in the patterns of adaptation to two distinctive work contexts (enabling and demanding work) across the two doctors, as identified through loadings on two significant pairs of canonical variates. As expected, enabling work (high medical demands, with high personal resources) was associated with active coping in both subjects (low fatigue, high effort/adrenaline and low cortisol). However, demanding work (high general demands) was associated with marked differences between them in the pattern of loadings. One subject showed the strain pattern normally associated with effortful engagement in difficult tasks (high anxiety and fatigue, high effort/adrenaline), though without the anticipated reduction in cortisol. The response pattern of the other individual was indicative of passive coping (high anxiety and cortisol, with no effort/adrenaline component). The findings are interpreted in terms of the role of personal coping styles on the adaptive response to work demands. The use of canonical correlation methods with intra-individual data sets, although relatively unusual, appears to provide potentially valuable evidence on the nature of individual differences in the process of psychobiological response to stress underlying work-health relationships.

Heart rate as an indicator of stress in surgeons and anaesthetists.

Ambulatory monitoring of heart rate was used as one indication of psychological stress among 8 doctors involved in cardio-thoracic surgery and 8 doctors performing anaesthesia in the same operating theatre. Twenty-three days of recording were available and the heart rate traces were related to observations of activities made by the authors. Comparisons of mean heart rates are made for these and other occupations. Certain sorts of activities are shown to increase and decrease heart rate. The value of heart rate as an indicator of psychological stress in field studies is discussed.

Clustering individuals as a way of dealing with multiple predictors in occupational stress research.

As the number and type of variables thought to affect the amount of stress experienced by an individual in the workplace increase, and as these effects are often found to be nonlinear and to interact with each other, the forms of statistical analyses employed present different costs and benefits. The use of cluster analysis as a preliminary means of categorizing individuals is described as the least artificial and empirically most accurate means of deriving groups that can lead to hypotheses and hypothesis testing using the more conventional means of analysis of variance. Such a methodology is described as it was applied to an investigation of the effects of demands, attitudes to demands, supports-constraints, and trait neuroticism upon job satisfaction and scores on the General Health Questionnaire for a sample of psychiatric nurses.

Some determinants of stress in psychiatric nurses.

This paper reports the results of an empirical study of psychological stress in nurses employed in a large Special Hospital and caring for mentally disturbed patients who may be a danger to themselves or to others. Such an environment would appear to be dangerous and stressful and the findings of this study show that this sample of nurses do indeed report relatively high levels of stress when compared to some other employed samples. Relationships between psychological distress, anxiety and depression and aspects of their jobs, such as job demands, supports and constraints, are discussed. Individual differences in experiences of stress are also considered.

Bidirectional multisite seizure propagation in the intact isolated hippocampus: the multifocality of the seizure "focus".

Localizing the seizure focus is difficult and frequently, multiple sites are found. This reflects our poor understanding of the fundamental mechanisms of seizure generation and propagation. We used multisite electrophysiological recordings in two seizure models and voltage-sensitive dye imaging, to spatiotemporally characterize the initiation and propagation of seizures in an intact epileptogenic brain region, the isolated hippocampus. In low-magnesium perfusate, seizures always originated in the temporal region, and propagated along the septotemporal axis to the septal region. After the seizure spread across the hippocampus, the bursts within a seizure became bidirectional, with different propagation patterns at different frequencies. When the intact hippocampus was separated along the septotemporal axis, independent bidirectional activity was observed in the two halves, and region-specific cuts to the tissue reveal that the CA3 region is critical for seizure generation and propagation. In a second seizure model, using focal tetanic stimulation of the septal and temporal CA3 region, seizures always originated at the stimulated site with bidirectionality later developing at different frequencies, as noted in the low magnesium model, behavior compatible with coupled neuronal network oscillators. These data provide novel insights into the dynamic multifocality of seizure onset and propagation, revealing that the current concept of a single seizure "focus" is complex.