Regional rat brain noradrenaline turnover in response to restraint stress

Acute cold-restraint stress affects alpha 2-adrenoceptors in specific brain regions of the rat

The effect of acute cold-restraint stress on binding of [3H]rauwolscine to alpha 2-adrenoceptors was investigated in 10 regions of rat brain. Acute stress: significantly decreased the density but had no significant effect on the affinity of binding sites in the hippocampus; decreased density and increased affinity in the amygdala; and increased density and decreased the affinity in the midbrain. Seven other brain regions showed no significant changes in binding parameters in response to stress. These results, together with previous findings in this laboratory showed that alteration by restraint stress of noradrenaline levels in amygdala and hippocampus, but not other regions, indicate an association between neurotransmitter turnover and receptor function.

Role of stress in the exacerbation of chronic illness: effects of clonidine administration on blood pressure and plasma norepinephrine, cortisol, growth hormone and prolactin concentrations

Systolic blood pressure (SBP), diastolic blood pressure (DBP), and plasma norepinephrine (NE), cortisol (CRT), growth hormone (GH) and prolactin (PRL) were studied before and after clonidine (2.5 micrograms/kg i.m.) administration in 193 chronic severely ill patients and 193 normal subjects matched by age and sex. During exacerbation periods (positive manifestations of impairment and progressive disease), the patients showed higher NE, CRT and DBP than the normals or when they were investigated during non-exacerbation periods (92 of the 193). Clonidine induced sharp, marked reductions of NE, CRT and DBP, plus a sudden increase of GH, in all the patients during exacerbation periods. Non-significant reductions of NE, CRT and DBP were observed in normals and in patients during non-exacerbation periods. On the other hand, the GH increase registered during exacerbation periods was of an order of magnitude higher than that registered in normals and in patients during non-exacerbation periods. Significant reduction of SBP was registered both in normals and patients (exacerbation and non-exacerbation periods). Some tendency to PRL lowering was observed during exacerbation periods only. A high positive correlation between NE and DBP (pre- and post-clonidine values) was obtained during exacerbation periods in patients, but not in normals or during non-exacerbation periods in the patients. Similarly, a close negative correlation was obtained between CRT and GH (postclonidine values) during exacerbation periods, but not in normals or during non-exacerbation periods. No significant correlation was found between NE and SBP in any group of subjects. The clonidine-induced changes in GH and CRT observed in the patients during exacerbation periods were in striking contrast to the absence of these changes in depressed patients. This finding is consistent with the low rate of depression (6.7%) registered among our patients during exacerbation periods. The high plasma NE and CRT levels registered in chronic severely ill patients during exacerbation periods reflect a central and peripheral sympathetic hyperactivity, accompanied by an overactivity of the pituitary--adrenocortical axis. The strong reduction of DBP, NE and CRT, along with the sharp and great increase of GH, might be useful as indicators in assessing the exacerbation and progression of severe chronic illnesses.

Restraint stress in biomedical research: a review

The use of restraint or immobilization for investigations of animal physiology, pathology and pharmacology has an extensive history. The major use of this technique has been as a "stressor" for the induction of stress response syndromes in animals. Many such syndromes have been characterized from the behavioral level to the neurochemical concomitants of stress. As a consequence of this particular use of the restraint procedure, much information concerning drug effects on stress response syndromes has been obtained. Indeed, many researchers in the area of gastrointestinal drugs routinely screen their new compounds in a restraint model of gastric stress ulcer. The purpose of this review is to present for researchers, a summary of the methods for, the parameters of, and known drug effects on, restraint-induced pathology. In our experience, this technique has proven to be a very useful one for the examination of both central and peripheral mechanisms of stress-related disorders, as well as for studying drug effects upon these disorders.

Automated method to estimate catecholamine and indoleamine content and turnover rates

A double-label isotopic method for estimation of the rate of formation of serotonin (5-HT) and dopamine (DA) in mouse striatum, hippocampus and cortex was standardized. Mice received an intravenous pulse injection of [3H]tryptophan (TRP) and [3H]tyrosine (TYR) at 2.5, 5, 10 or 20 min before sacrifice by microwave irradiation. Compounds of interest were separated by automated high-performance liquid chromatography and their contents were determined by electrochemical detection. Programmed collection of the TYR, DA, 5-HT and TRP peaks allowed determination of their radioactivity by liquid scintillation. Conversion of [3H]TYR to [3H]DA was nearly ten times greater in striatum than cortex, whereas the formation of [3H]5-HT from [3H]TRP was similar in striatum, cortex and hippocampus.

Effects of preshock experience on enhancement of rat brain noradrenaline turnover induced by psychological stress

The present study examined alterations of brain noradrenaline (NA) turnover as a function of preshock and psychological stress treatments, by measuring contents of NA metabolite, 3-methoxy-4-hydroxyphenylethyleneglycol sulfate (MHPG-SO4), in discrete brain regions of male Wistar rats. Psychological stress induced by exposing to the sight, sound and odor of other rats being shocked produced higher levels of MHPG-SO4 in the hypothalamus, amygdala and locus coeruleus (LC) region, as well as higher levels of plasma corticosterone. Preshock experienced rats also showed marked increases of MHPG-SO4 levels in the same regions described above and elevated plasma corticosterone levels when placed but not shocked in the same environment in which the rats had previously received shocks. The effects of psychological stress on brain NA turnover were affected by the animal's shock history preferentially in the hypothalamus and amygdala. These results suggest that: a purely psychological stressor caused acutely enhanced NA turnover in specific brain regions; regional NA activity appeared to be reinstated simply by reexposure to the environment previously associated with shock; preshock experience further intensified the enhancement of amygdaloid NA turnover evoked by psychological stress. An additional experiment, studying the aftereffects of preshock experience, clearly showed that these findings result from sensitization or conditioning to the environment previously paired with shock, and not merely from the aftereffects of the shock per se.

Alteration of the turnover of dopamine and 5-hydroxytryptamine in rat brain associated with hypothermia

The alteration of monoamines and their metabolites in the brain in response to hypothermia was studied using rats subjected to a cold and immobilization stress. The experiments were designed to compare the responses in the "hypothermal" rats with those in the "normothermal" ones which received the same stress except for the change in body temperature. It has been found that the contents of norepinephrine (NE) and 5-hydroxytryptamine (5-HT) in various cerebral regions were significantly decreased during hypothermia. These decreases were readily reversed by the rewarming of animals. Moreover, the increase in the content of 5-hydroxyindole-3-acetic acid (5-HIAA), the metabolite of 5-HT, was also detected in some cerebral regions where the decrease of 5-HT was observed. Although the dopamine (DA) contents in all cerebral regions examined were found to be unaltered, its metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and/or homovanillic acid (HVA) contents in most regions in the brain showed a significant elevation during and/or after the occurrence of hypothermia. These results suggest that the metabolic turnovers of 5-HT and DA in various cerebral regions may be accelerated during hypothermia.

Early weaning predisposes rats to exacerbated activity-stress ulcer formation

Rats were weaned early (Day 15), normally (Day 21) or late (Day 27). When they reached 200 g (+/- 10) they were placed into the activity-stress paradigm. Half the rats in each weaning group were housed in activity-wheel cages and fed only 1 hr each day. The remaining rats served as food-yoked home cage controls and were fed only that amount of food eaten by their wheel-housed partners. Early weaned rats ran more than normally or late weaned animals. Early weaned rats also died at a faster rate and exhibited a significantly greater cumulative ulcer length than did normally or late weaned rats, although ulcer incidence did not differ between the groups. No ulcers occurred in home cage control rats. Early maternal deprivation may generally predispose rats to stress-induced gastrointestinal disease, whether or not such disease has an acid etiology.

Rat plasma levels of amino acids and related compounds during stress

Forty-one amino acids and related compounds were measured (using an HPLC physiological amino acid analysis procedure fully validated for plasma studies) in rat plasma obtained through an indwelling jugular catheter before, during and following a 30 min period of immobilization. Taurine, phosphoethanolamine, aspartic acid, glutamic acid, alanine, cystine, tyrosine, beta-alanine and ethanolamine were increased during the period of stress; whereas, valine, tryptophan and arginine were decreased. Most of these alterations were restored toward normal during the 30 min of rest following the stress period. However, cystine, ethanolamine and beta-alanine remained significantly elevated, and valine, tryptophan and arginine remained significantly reduced. Serine, isoleucine, leucine and glutamine were not significantly altered during the stress period, but became significantly reduced during the 30 min following the stress period. While the patterns of amino acid alterations were generally consistent from animal to animal, the magnitude of the responses were variable with some rats demonstrating much larger responses than others. These results may implicate amino acids as important markers for stress related pathologies. The individual differences noticed may explain why some individuals show more stress effects than others.

Stress and brain noradrenaline: a review

Noradrenergic neural systems have been expressly implicated in pathophysiological conditions induced by stress. The majority of experimental evidence supports a central role for brain noradrenaline in mediating the effects of stress and predisposing an organism to stress pathology as well as in producing a well-documented consequence of stress exposure-behavioral depression. This review briefly discusses the noradrenergic (NA) pathways involved, the functioning of NA synapses and their associated receptors and focuses directly upon the effects of stress on NA activity in the brain. These broad categories are discussed in terms of: 1. behavioral versus neurochemical explanations for the effects of stress; 2. the methods used to produce stress; 3. measurement of NA and its major metabolite ("turnover"); 4. regional brain effects of stress; 5. effects of pre-stress alterations in brain NA activity upon subsequent stress-induced brain NA changes; 6. correlation of stress-induced brain NA changes with peripheral manifestations of stress; and 7. predisposing factors in stress-induced neurochemical alterations.