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Biomedical subjects

H Feer

Publications and source records attributed to H Feer.

At least 19 recordsLinked to original sources
PubMed1991

Genetic and environmental influences on reactive and spontaneous locomotor activities in rats.

Paired groups of rats (derived from divergent, selective breeding or living in divergent environmental conditions) were compared with regard to locomotor activities. Intrapair differences were found to vary non-systematically, depending upon whether the rats were initially exposed to a test-environment with or without a slight environmental modification (reactive activities), or were allowed to habituate extensively to the environment (spontaneous activity). Since the behavioral patterns were found to represent distinct entities, this pointed to the necessity of differentiating clearly between spontaneous and reactive activities and indicated, once again, that both genetic and environmental influences are important in these behaviors and must be taken into account. Accepting and controlling for these variables makes it possible to use the factor of individual differences in laboratory animal behavior to advantage.

Animals↗
PubMed1990

Competition for sucrose-pellets in triads of male Wistar rats: disinhibitory effect of individual housing in poor-performing rats.

Within triads of male Wistar rats, some animals almost completely abstain from competition for palatable sucrose-pellets (so-called poor-performing rats). Individual housing temporarily helped these rats to behave more competitively. Such changes in the poor-performing rats' competition-scores are discussed in relation to previously described, isolation-induced alterations in serotonergic and noradrenergic neurotransmission.

Animals↗
PubMed1990

Competition for sucrose-pellets in triads of male Wistar rats: effects of acute and subchronic chlordiazepoxide.

Within triads of male Wistar rats, some animals almost completely abstain from competition for palatable sucrose pellets (so-called poor-performing rats), whereas other rats consistently win the competition (so-called high-performing rats). Subchronic (5 mg/kg; 5 consecutive days), but not acute (0.1-20 mg/kg), treatment with chlordiazepoxide temporarily helped poor-performing rats to behave more competitively. This finding, considered together with parallel studies (using high-performing rats), suggested that chlordiazepoxide's beneficial effect was only demonstrable when the poor-performing rats had become tolerant to the drug's initial sedative effect.

Animals↗
PubMed1989

Selective breeding in rats for extreme densities of platelet 3H-imipramine binding sites: evidence against a trait hypothesis.

Some investigators suggest that the number of platelet 3H-imipramine binding sites is genetically determined and that the reduced 3H-imipramine binding observed in some studies of depression represents a trait marker. Others believe that 3H-imipramine binding is state-dependent because 3H-imipramine binding has been reported to normalize after clinical recovery. We used a genetic selection paradigm in rats to approach this question from another direction. While breeding 10 generations of rats, we used either extremely high or extremely low density of platelet 3H-imipramine binding sites as a selection criterion. We were unsuccessful in producing two distinct rat sublines. These data do not support a predominant genetic influence on 3H-imipramine binding.

Animals↗
PubMed1989

Behavioral effects of yohimbine and chlordiazepoxide: dependence on the rat's previous familiarization with the test conditions.

The effects of yohimbine and chlordiazepoxide on locomotor activity in an open field were found to depend on the rat's previous habituation to the test environment: chlordiazepoxide induced a locomotor activation in nonhabituated, but not in habituated rats; yohimbine activated in habituated rats only. In a further study, carried out in the rat's homecage (habituated conditions), the effect of both drugs on competition for sucrose pellets was assessed: yohimbine, but not chlordiazepoxide, helped so-called poor-performing rats to temporarily overcome their typical abstention from competition. The presence or absence of drug effects, obviously depending on the rat's previous familiarization with the test environment, are discussed with view to Gray's concept of the behavioral inhibition system.

Animals↗
PubMed1988

Genetic and environmental influences on behavioral and neurochemical aspects of emotionality in rats.

Three pairings of rats (two derived from divergent, selective breeding and one from divergent environmental conditions) were compared with regard to behavioral and hormonal parameters. Striking differences were observed: results obtained in our own laboratory as well as those found in a review of the literature pointed to higher emotionality (e.g., increased defecation and corticosterone secretion, etc.) in Roman low-avoidance, Wistar-Kyoto and group-housed rats, as compared to their respective counterparts, Roman high-avoidance, spontaneously hypertensive, and individually housed Wistar rats. Concomitant receptor binding studies reviewed here (3H-diazepam- and 3H-imipramine-binding sites) have revealed, however, less consistent intrapair differences.

Animals↗
PubMed1988

Static magnetic fields decrease nocturnal pineal cAMP in the rat.

Magnetosensitivity of the rat's pineal cyclic adenosine monophosphate (cAMP) system was investigated. During their dark phase, rats were exposed for one hour to a static magnetic field (MF) inverting the horizontal component of the natural MF. MF-exposed animals showed a 38% decrease in pineal cAMP content (1.21 pmol/pineal gland) compared to a non-exposed control group (1.96 pmol/pineal gland).

Animals↗
PubMed1988

Isolation-induced locomotor hyperactivity and hypoalgesia in rats are prevented by handling and reversed by resocialization.

Differences in locomotor activity in the open field were found between individually and group-housed rats (isol greater than soc). Daily handling, initiated at postnatal day 1, was without effect in group-housed rats but prevented the isolation-induced hyperactivity. For tail-flick latency, strikingly similar differences (isol greater than soc; prevention by handling) have been observed. The isolation-induced aberrations in both locomotor reactivity in a novel environment and in pain sensitivity could be reversed by subsequent resocialization. This indicates that the altered sensitivities to external stimuli are caused by the environmental manipulation.

Animals↗
PubMed1988

Competition for sucrose-pellets in triads of male Wistar rats: the individuals' performances are differing but stable.

After having individually been accustomed to consume palatable sucrose-pellets, the individual's competition-rate for sucrose-pellets within its familiar triad has been observed in male Wistar rats. In this fixed-triad, food competition paradigm high-performing rats (high competition-rate, majority of pellets consumed), medium-performing rats (medium competition-rate, consumption of some pellets) and poor-performing rats (almost completely abstaining from competition with only rare incidence of pellet consumption) can be distinguished. Intra-group rank-orders, defined according to the individuals' competition-rates (expressed as a score), were present in many triads and, once established, these were stable over months. No additional differences were observed between high- and poor-performing rats, neither when these were individually tested in an open field or in the elevated plus-maze, nor with regard to the preference for a sucrose solution.

Animals↗
PubMed1988

Competition for sucrose-pellets in triads of male Wistar rats: effects of three serotonergic drugs.

1. Within triads of rats, individuals can be discerned according to their competition for sucrose-pellets as a high-, a medium- and a poor-performing animal. 2. The competition-rates, expressed as scores, are affected by serotonergic drugs: upon inhibiting tryptophan-hydroxylase, the characteristic abstention of the poor-performing rats can temporarily be overcome; quipazine, on the other hand, leads to a dose-dependent decrease in the competition-rate of high-performing rats. 3. Such findings are indicative for a regulatory effect of some serotonergic mechanisms on a competition-behavior evoked within the familiar social context.

Animals↗
PubMed1987

Chronic methamphetamine and its withdrawal modify behavioral and neuroendocrine circadian rhythms.

Chronic methamphetamine (MA) administration via the drinking water not only induced hyperactivity, but phase delayed the rat rest-activity cycle under entrained conditions. The minimum and/or maximum of the rhythms in eating, drinking, body weight, core body temperature and plasma/urine corticosterone were delayed. The different phase shifts of peak and trough values can also be a result of modulation in the wave form of the rhythms. The fall, but not the rise, of nocturnal pineal melatonin secretion occurred 4 hours earlier in MA-treated rats than in controls: this pattern was still present 1 week after withdrawal, but no longer after 4 weeks withdrawal. Neither chronic MA nor its withdrawal had any effect on plasma thyrotropin. These patterns after chronic MA intake fall into two groups: those rhythms whose peak and/or trough are delayed and those that are not. We thus interpret chronic MA application as modulating the eating rhythm (though not directly through rhythmic MA levels in the CNS), and that this in turn changes all food-dependent rhythms. In contrast, the circadian rhythms of melatonin and thyrotropin remain independent.

Animals↗
PubMed1987

Open field and elevated plus-maze: a behavioural comparison between spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats and the effects of chlordiazepoxide.

An interstrain comparison was conducted between male spontaneously hypertensive rats and Wistar-Kyoto rats, in both the open field and the elevated plus-maze. Wistar-Kyoto rats, as compared to the hypertensive animals, showed, beside an attenuated locomotor activity in both test situations, a higher reaction to aversive environments (less entries into the central area of the open field and less visits to the open arms of the elevated plus-maze). Chlordiazepoxide, as potent anxiolytic, increased (1) general activity, (2) the frequency of entries into the open area of the open field, and (3) the number of visits to the open arms of the elevated plus-maze in both rat strains.

Animals↗
PubMed1986

Temporal distribution of [3H]-imipramine binding in rat brain regions is not changed by chronic methamphetamine.

Specific binding of [3H]-imipramine in the rat suprachiasmatic nuclei, occipital cortex and caudate putamen underwent significant and replicable changes throughout 24 hr under a light-dark cycle or under constant conditions. Daily variations were also found in the medial and dorsal raphe nuclei and the lateral hypothalamus. Methamphetamine, a psychoactive drug with marked effect on circadian rhythms in physiological and hormonal parameters and adrenergic receptors, did not have any significant effect on imipramine binding rhythms in eight discrete brain regions. Thus a drug known to reduce serotoninergic neurotransmission did not change characteristics of the modulatory binding site related to serotonin uptake.

Animals↗
PubMed1985

Weak 50-Hz electromagnetic fields activate rat open field behavior.

Rats were tested in an open field after previous exposure to a weak, 50-Hz electromagnetic field of the same order of magnitude as the earth's magnetic field. Animals exposed to the artificial field at the beginning of the light phase showed 40% more rearing activity than controls, together with a slight increase in ambulation and a tendency towards less defecation and a shortened rearing latency. A replication experiment yielded the same results. Animals exposed at the beginning of the dark phase manifested no significant changes in open field activity. The results show that weak electromagnetic stimuli can modify some behavioral responses, and that these responses are sensitive to circadian phase.

Animals↗
PubMed1985

Similarities in feeding behavior of chronic methamphetamine treated and withdrawn rats to VMH lesioned rats.

During chronic methamphetamine (M) administration and after drug withdrawal, total daily food intake, water consumption and body weight increase was measured. Additionally, food intake in the early light phase provided an index of normal circadian rhythmicity. A parallel development of tolerance to the anorexic effect of M and increased feeding in the early light phase occurred. A further abnormal behavior of both chronic M-treated and withdrawn rats was the lack of preference reversal when given free access to concentrated vs. diluted glucose solutions. Both disturbed circadian feeding rhythmicity and inhibition of the glucose preference reversal are found in rats with ventromedial hypothalamic (VMH) lesions. Reduced food intake and diminished body weight increase is a characteristic of lateral hypothalamic lesions. By analogy, chronic M-treatment could be considered to induce a functional state similar to lesions of the medial and lateral hypothalamus, each with a different time course.

Animals↗
PubMed1985

3H-Imipramine binding sites in platelets of hospitalized psychiatric patients.

The density of platelet 3H-imipramine binding sites has been proposed as a biological marker in psychiatry. We report the range of platelet 3H-imipramine binding in 55 psychiatric patients and 11 control subjects. All blood samples were withdrawn at 2300 h (on the day of hospital admission for patients). With the use of a slight modification of a previously described 3H-imipramine binding method, a mean B max of 1,510 fmole/mg protein (range: 390-5,560; median: 1,450) and a mean Kd of 2.0 nM (range: 0.6-17.0; median: 1.4) were determined for psychiatric patients. For the controls, a mean B max of 1,590 fmole/mg protein (range: 870-2,570; median: 1,440) and a mean Kd of 1.4 nM (range 0.8-2.4; median 1.4) were determined. When patients were subdivided based on ICD-9 psychiatric diagnoses, no significant differences between distinct subgroups of psychiatric patients with respect to B max or Kd values for platelet 3H-imipramine binding could be established. Similarly, no significant difference between psychiatric patients and controls was obtained.

Adolescent↗