INVOLVEMENT OF SWIMMING-INDUCED ACUTE STRESS IN THE SENSITIVITY OF RAT VAS-DEFERENS TO NOREPINEPHRINE

1. The effects of swimming-induced stress on rat sensitivity to norepinephrine were studied.2. Through microscopic analysis of the stomach from swimming stressed rats significant ulceration was observed, confirming that the stress situation was really present.3. Sensitivity to norepinephrine either in the presence or in the absence of cocaine and propranolol in acutely swimming stressed rats was not altered significantly.4. Bilateral adrenalectomy was performed in rats 2 days before swimming and acute stress resulted in a supersensitivity to norepinephrine, indicating that adrenal glands may, at least, partially mediate the sensitivity to this drug in vasa deferentia isolated from these animals.

Influence of the estrous cycle on the sensitivity to catecholamines in right atria from rats submitted to foot-shock stress

We investigated the mechanisms of the alterations in sensitivity to catecholamines in right atria from female rats exhibiting regular 4-day estrous cycles after three foot-shock sessions at estrus, metestrus, and diestrus or at diestrus, proestrus, and estrus. Right atria from stressed rats sacrificed at diestrus showed subsensitivity to noradrenaline and adrenaline. After in vitro sympathetic denervation (38 μM 6-hydroxydopamine) plus inhibition of neuronal reuptake (0.1 μM desipramine) subsensitivity to noradrenaline was abolished, but it was again evident when extraneuronal uptake was also inhibited (10 μM phenoxybenzamine and 30 μM corticosterone). The same pretreatment abolished the subsensitivity to adrenaline. After addition of 1 μM butoxamine, a β2-adrenoceptor antagonist, the tissues from stressed rats were subsensitive to adrenaline. Right atria from stressed rats sacrificed at estrus did not show any alteration in sensitivity to catecholamines. We conclude that after foot-shock stress, right atria from female rats sacrificed at diestrus showed subsensitivity of the chronotropic response to catecholamines as a result of a conformational alteration of β1-adrenoceptors, simultaneously with an increase in β2-adrenoceptor-mediated response. The mechanisms seem to be similar to those which underlie stress-induced alterations in catecholamine sensitivity in right atria from male rats. However, during estrus there are some protective factors that prevent the effects of stress on right atria.

Different stress biomarkers sensitivity during acute treadmill running exercise in rats

The level of stress during acute or chronic exercise is important since higher levels of stress may impair homeostasis. The adrenal gland is an essential stress-responsive organ involved in the hypothalamic-pituitary-adrenal axis. The aim of the study was to analyze the sensitivity of different stress biomarkers of the adrenal gland during acute treadmill running at different intensities. Adult rats performed three 25 min running tests at velocities of 15, 20 and 25 m/min, for determination of maximum lactate steady state (MLSS). After obtaining individual MLSS animals were assigned to two groups: M, sacrificed after 25 minutes of exercise at MLSS, and AM, sacrificed after exercise at 25% above MLSS. For comparison, a control group C was sacrificed at rest. Blood corticosterone concentrations, as well, adrenal gland cholesterol and ascorbic acid concentrations were used as biomarkers. Serum corticosterone concentrations were higher after exercise in both M (1802,74±700,42) and AM (2027,96±724,94) groups when compared C group (467,11±262,12), but were not different as a function of exercise intensity. No difference in adrenal ascorbic acid (M=2,37±0,66; AM=2,11±0,50 and C=2,54±0,53) and cholesterol (M=1,04±0,12; AM=0,91±0,31 and C=1,15±0,40) levels were observed when the three groups were compared. Serum corticosterone concentrations showed to be sensitive to acute treadmill exercise intensity. On the other hand, ascorbic acid and cholesterol concentrations in adrenal were biomarkers not adequate to evaluate exercise stress in rats.

Incubation and rearing temperature effects on Hsp70 levels and heat stress response in broilers

Incubation temperature (IT) was changed to evaluate if 6-wk-old birds become more tolerant to heat stress. After 13 d of incubation, 470 eggs were submitted to low (36.8degreesC), normal (37.8degreesC) and high (38.8degreesC) temperatures. At day 7 post-hatching, 144 birds were allocated to three rearing temperatures (48 birds/treatment): control/thermoneutral (35-24degreesC), high (33-30degreesC) or low (27-18degreesC) according to the age of the birds. Hsp70 levels in tissues of birds (1 d and 42 d), stress response (42 d) and performance were evaluated. High IT decreased brain (P < 0.01) and liver (P < 0.01) Hsp70 levels, whereas low IT decreased brain (P < 0.01) but increased heart (P < 0.01) Hsp70 levels in 1-d-old chicks. Birds incubated at a low temperature had higher (P < 0.05) feed intake (1-42d). High rearing temperature decreased feed intake (P<0.01) and liveweight (P<0.01). Colonic temperature was lower in birds incubated at a low temperature (P < 0.05) and higher in birds reared in a high temperature (P < 0.05) before heat stress. Birds reared in low temperature had higher increase in colonic temperature after heat stress (P < 0.05). Tissue Hsp70 levels were differently affected by rearing temperature, which affected broiler performance more than IT. Lower IT seemed to increase the sensitivity of birds to heat stress at market age.

Diferenças de sexo e escolaridade na manifestação de Stress em adultos jovens

Este estudo pesquisou sintomas de stress em adultos jovens, relacionando-os com o sexo e ano escolar em curso. Investigou também o tipo e a freqüência de sintomas. Participaram 295 estudantes de 15 a 28 anos, sendo 150 mulheres e 145 homens, que cursavam o primeiro e terceiro anos do ensino médio, curso pré-vestibular e primeiro e quarto anos de ensino superior. A avaliação do stress foi realizada através do Inventário de Sintomas de Stress de Lipp. Os resultados acusaram correlação significativa entre sexo e nível de stress (p<0,0001) sendo que as mulheres apresentaram maior nível de stress em todos os grupos avaliados. Maior índice de stress surgiu em estudantes do curso Pré-Vestibular, seguidos do terceiro ano do ensino médio. A sintomatologia apresentada foi predominantemente psicológica e os sintomas mais prevalentes foram sensibilidade emotiva excessiva, para as mulheres e, para os homens, pensamento recorrente.

Adrenergic response patterns in vas deferens isolated from rats under diurnal rhythms - Influence of stress

The aim of this study was to verify, by means of functional methods, whether the circadian rhythm changes adrenergic response patterns in the epididymal half of the vas deferens isolated from control rats as well as from rats submitted to acute stress. The experiments were performed at 9:00 a.m., 3:00 p.m., 9:00 p.m., and 3:00 a.m. The results showed a light-dark dependent variation of the adrenergic response pattern on organs isolated from control as well as from stressed rats. In the control group, only the phenylephrine sensitivity was changed throughout the circadian rhythm. Under the stress condition, both norepinephrine and phenylephrine response patterns were changed, mainly during darkness. The maximal contractile response to both alpha- and beta-agonist and alpha(1)-agonist was increased in the dark phase, corresponding to high plasmatic concentrations of endogenous melatonin. The vas deferens isolated from stressed rats during the light phase simultaneously incubated with exogenous melatonin showed the same pattern of response obtained in the dark phase, thus indicating a peripheric action of melatonin on this organ. Therefore, the circadian rhythms are important to the adrenergic response pattern in rat vas deferens from both control and stressed rats. In conclusion, we suggest a melatonin modulation on alpha(1)-postsynaptic adrenergic response in the rat vas deferens. (c) 2005 Elsevier B.V. All rights reserved.

Caution for using ventilatory frequency as an indicator of stress in fish

This study tested the use of ventilatory frequency (VF) as an indicator of stress in the Nile tilapia, Oreochromis niloticus (L.). Firstly, we tested the relationship between VF and plasma cortisol after confinement. Confined fish showed higher VF and plasma cortisol levels, but the latter continued to increase significantly for longer time than VF. Secondly, we conducted another experiment to test the use of VF as indicator of fish stress. In four out of six treatment, we confined the fish for different intervals (30 s, 5, 15 or 30 min). The others were used as control. In one, no handling was imposed. The other control consisted of introducing the partition (the same used to perform the confinement) into the aquarium for less than 4 s, without confinement and immediately removing the partition (partition control). Ventilatory frequency was increased for the partition control as much as for the longer duration of confinement. This clearly indicates that VF is a very sensitivity response to disturbance, but of limited use because this parameter does not reflect the severity of the stimulus. Thus, although VF is a non-invasive technique that does not require sophisticated recording equipment, its usefulness is limited. (C) 2004 Elsevier B.V. All rights reserved.

Germination of Jacaranda mimosifolia (D. Don - Bignoniaceae) seeds: effects of light, temperature and water stress

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Stress-induced subsensitivity to catecholamines depends on the estrous cycle

In this article we compare how sensitivity to the chronotropic effect of noradrenaline and adrenaline of right atria isolated from female rats is modified after repeated swimming or foot-shock stress, under the influence of the estrous cycle. Right atria from stressed female rats sacrificed at diestrus were subsensitive to both catecholamines, irrespective of the stressor agent. However, although subsensitivity to noradrenaline was of similar intensity, subsensitivity to adrenaline was more pronounced in right atria from foot shock stressed rats as opposed to swimming-stressed rats. Identical stress protocols did not induce any alteration in atrial sensitivity to catecholamines when the stressed female rats were sacrificed at estrus. We conclude that the stress reaction concerning the mediation of cardiac chronotropism by catecholamines is related to the severity of the stressor agent and is strongly influenced by the estrous cycle.

Effect of the type of environmental stress on the emergence of sunflower (Helianthus annus L.), soybean (Glycine max (L.) Merril) and maize (Zea mays L.) seeds with different levels of vigor

Sowing is a critical time in the cycle of a crop and the seeds are frequently exposed to adverse conditions that may compromise the establishment of seedlings in the field. on this basis, the objective of the present study was to determine the effect of types of environmental stress on the emergence of sunflower, maize and soybean seeds with different levels of vigor. High vigor seeds were artificially aged in order to obtain medium and low vigor seeds and then they were sown in clay soil in plastic boxes and submitted to the following types of environmental stress during the germination process : 1) high temperature (35degreesC), 2) low temperature (15 or 18degreesC), 3) water excess (Psi > -0.0001 MPa), 4) water deficiency (Psi approximately equal to -1.1; -1.2 and -0.6 MPa for sunflower, maize and soybean, respectively), 5) sowing at a depth of 7 cm and 6) pathogenic infection of sunflower seeds with Alternaria helianthi, of maize seeds with Fusarium moniliforme and of soybean seeds with Colletotrichum dematium, var. truncata. The results were compared to those obtained with controls sown under optimal condition. It was concluded that: 1) the effect of seed vigor on emergence depends on the type of enviromental stress to which the seeds are exposed, 2) the stress to which the the seeds demonstrated highest sensitivity varied with species and 3) high temperature stress was the one that most impaired the emergence of the three species.

Acute swimming stress induces changes in noradrenergic mechanisms in order to maintain the response pattern of the rat vas deferens to norepinephrine

This study investigated mechanisms involved in the maintenance of the functional response pattern of the postjunctional alpha(1)-adrenoceptor in vas deferens isolated from rats submitted to acute swimming stress. The plasma corticosterone levels increased approximately three times after the swimming stress in the nontreated rats as well as after swimming stress in the rats pretreated with desipramine (DMI), yohimbine (YO), or DMI with YO. No alteration was detected in the sensitivity to norepinephrine (NE) in the vasa deferentia from the stressed rats or stressed rats treated with DMI or DMI with YO, in relation to their respective control. However, when the vasa deferentia were previously incubated with DMI, a reduction in sensitivity to NE in organs from stressed rats was observed. Vasa deferentia excised from rats pretreated with YO before the swimming stress showed an increase in postjunctional alpha(1)-response that was abolished by prazosin (PZ). Thus, the neuronal uptake, the prejunctional alpha(2)-adrenoceptors (mediating prejunctional inhibition), the occupancy and functional response of the postjunctional alpha(1)-adrenoceptors, and the emotional stress component were very important for the determination of the noradrenergic response pattern in vas deferens from rats submitted to acute swimming stress. (C) 2002 Elsevier B.V. Ltd. All rights reserved.

Noradrenergic response in vas deferens from rats submitted to acute and repeated stress

1. This work investigated the effects of androgens on the norepinephrine sensitivity of vasa deferentia from rats submitted to acute or repeated stress, as well as the participation of alpha(1)-adrenoceptors in the response of intact and bisected vasa deferentia from adult normal rats submitted to acute or repeated stress.2. The acute stress produced subsensitivity to norepinephrine only in intact vasa deferentia from adult normal rats, which was prevented by lack of androgens, suggesting that the sensitivity may be dependent on the physiological level of androgen,3. No change was observed in intact vas deferens sensitivity to norepinephrine in repeated stress, suggesting the occurrence of adaptation to elevated norepinephrine levels or a mild decrease in androgen levers or both.4. The changes in sensitivity observed in acute and repeated stress may also be due to alterations in alpha(1)-adrenergic receptors that are located in the prostatic portion of the vas deferens. (C) 1998 Elsevier B.V.

Catecholaminergic responses in vas deferens isolated from rats submitted to acute swimming stress

The study was performed to examine the responses to catecholamines in vas deferens isolated from rats submitted to acute swimming-induced stress. It was demonstrated that acute stress induces a significant subsensitivity of rat vas deferens to norepinephrine. This subsensitivity was inhibited when the experiment was carried out in the presence of either cocaine (10(-5) M) or timolol (10(-5) M). on the other hand, the rat vas deferens sensitivity to methoxamine was significantly increased by acute swimming-induced stress. Thus, despite acute swimming stress inducing a reduction in response to norepinephrine, the alpha(1)-adrenoceptor-mediated contractile response was increased. Additionally there were increases in neuronal uptake and beta(2)-adrenoceptor activity that opposes the alpha(1)-adrenoceptor activity. Integrated, these phenomena are responsible for the rat vas deferens subsensitivity to norepinephrine which may be involved in body homeostasis in stressogenic situations. (C) 1995 the Italian Pharmacological Society

Role of androgenic deprivation on the contractile response to norepinephrine in vas deferens isolated from rats submitted to swimming-stress

The effects of androgenic deprivation induced by castration on the norepinephrine contractile response of vas deferens from rats, which have been submitted to acute swimming-stress were determined. Acute swimming-stress led to subsensitivity to norepinephrine in vas deferens excised from intact rats. Similarly, castration also induced subsensitivity to norepinephrine, but no further subsensitivity occurred in organs from castrated rats submitted to acute stress. The results indicate a different response to norepinephrine in terms of relative responsiveness ratio, when vas deferens was excised from castrated rats or castrated rats submitted to acute stress. It is suggested that androgenic steroids modulate the recovery of homeostasis in rat vas deferens during acute stress, and that this effect may involve mechanisms that affect both the sensitivity of adrenergic receptors and the system of neuronal uptake of catecholamines.