Repeated Maternal Deprivation Alters Behavioral Pattern and Attenuates Prolactin Response to Mild Stressor in Adult Male Wistar Rats.

OBJECTIVE: To evaluate the impact of repeated neonatal mother deprivation (RMD) of male rats on the behavioral parameters and response of prolactin to mild stress stimuli in the adulthood. METHODS: Afer birth, the pups of Wistar Porton Olac rats were crossfostered and their number was adjusted to 8 per litter (4 males and 4 females). They were removed from the dam for 6 hours daily on postnatal day 6, 7, 8 and for 12 hours daily on postnatal day 12, 13, 15, 16 and placed to another cage lined with cotton wool at controlled temperature 37 øC.

Specificity of the effect of repeated handling on sympathetic-adrenomedullary and pituitary-adrenocortical activity in rats.

The response of the pituitary-adrenocortical and sympathetic-adrenomedullary system to single and repeated handling was studied in rats. After repeated handling (14 days, 3 x 1 min daily or 1 day, 6 x 1 min at 30 min intervals) a reduction of plasma epinephrine and ACTH level was observed, while norepinephrine levels increased to the same extent as after the first handling. When repeatedly handled rats were handled by a different person, hormonal responses were altered: The reduction in the ACTH and epinephrine response was no longer apparent, whereas the norepinephrine response was potentiated.

Do the circulating neurohypophysial hormones affect basal or stress induced prolactin (PRL) release in male rats?

The action of acute administration of oxytocin (OXY), vasopressin (AVP) or its analog 1-deamino-8-D-arginine-vasopressin (dDAVP) on basal and stress induced PRL release in normal male rats and the effect of chronic injection of AVP on PRL stress response in AVP deficient rats were studied. The hormones (OXY, 600 ng min-1 per rat; AVP 6, 12 or 24 ng min-1 per rat and dDAVP 24 ng min-1 per rat) were infused to conscious rats via the jugular vein for 10 min and then the rats were immobilized under continuing the infusion for further 20 min. In parallel experiments arterial blood pressure (BP) was measured.

[The effect of chronic stress on the activity of the sympathetic-adrenomedullary system].

Plasma levels of adrenaline (ADR) and noradrenaline (NA) belong to the best parameters of activity of the sympatho-adrenomedullary system (SAS). Introduction of a sensitive radioenzymatic method for the determination of catecholamines in small volumes of plasma (0.05 ml) and observing conditions of stressless blood collection by means of an indwelling catheter made in possible to determine basal plasma catecholamine levels and their dynamics during stress.

Prolactin response to immobilization stress and hemorrhage: the effect of hypothalamic deafferentations and posterior pituitary denervation.

The roles of posterior and anterolateral connections to the mediobasal hypothalamus (MBH) as well as innervation of the posterior pituitary in the PRL response to immobilization (IMO) and hemorrhage (HEM) were studied by means of surgical isolation, performed 6-9 days before stress exposure. Male rats bearing indwelling tail artery cannulae subjected to 120-min IMO reached peak PRL secretion in 5-20 min. HEM of 25% elicited a significant rise of PRL levels.

[Immobilization stress-induced changes in catecholamine levels in the individual cerebral nuclei in rats of different zoosocial ranks].

Immobilization stress induced catecholamines level changes were studied in brain nuclei, taking part in blood pressure central regulation in rats with different zoosocial position. The significant differences in catecholamines level between the zoosocial groups of rats were shown in dopamine synthesized hypothalamic nuclei-n. arcuatus, n.

Prior immobilization stress alters adrenal hormone responses to hemorrhage in rats.

The effect of prior immobilization stress (IMO) on the plasma epinephrine (EPI), norepinephrine (NE), adrenocorticotropic hormone (ACTH), and corticosterone (CS) responses to acute hemorrhage was studied in conscious male rats with chronic catheters in tail artery, using two combinations of IMO and hemorrhage. IMO per se led to significant increases of EPI, NE, ACTH, and CS in all animals. Hemorrhage of 25% of estimated blood volume (EBV) performed immediately after 150 min IMO caused exaggerated release of EPI and NE, whereas CS remained unchanged at the level previously elevated by IMO.

Stressfree administration of drugs by intraperitoneal cannulation in small laboratory animals.

A simple technique of chronic intraperitoneal cannulation in small laboratory animals has been described. It can be used for repeated i.p.

[Open-field behavior of rats following bilateral coagulation of the locus coeruleus].

A modified open-field test was used in the experiments on rats. It was shown that animals 6 days after bilateral coagulation of locus coeruleus displayed weight changes and some behavioural parameters distinct from those of sham-operated and control animals. The most pronounced differences observed in animals after locus coeruleus coagulation, as compared to the control, were inversion and adaptive responses to a sudden brief stimulus, locomotor dysfunction and absence of response to handling.

Sympathoadrenal activity facilitates beta-endorphin and alpha-MSH secretion but does not potentiate ACTH secretion during immobilization stress.

The potential involvement of the sympathoadrenal system in stress-induced secretion of peptides from the intermediate lobe of the pituitary gland and the activation of the pituitary-adrenal axis was studied. Male Wistar rats were subjected to control procedures, to sympathectomy by chronic administration (8 weeks) of guanethidine and/or to medullectomy by adrenal enucleation 9 weeks prior to exposure to forced immobilization stress for various periods of time. In intact or sham-operated rats, immobilization caused a prompt increase of circulating norepinephrine, epinephrine (EPI), corticosterone and of immunoreactive adrenocorticotropic hormone (ACTHi), alpha-melanocyte-stimulating hormone (alpha-MSHi) and beta-endorphin (beta-ENDi).

[Catecholamines in nuclei of the brains of the August strain rat during immobilization stress].

Changes in epinephrine, norepinephrine and dopamine levels in different brain nuclei of the August rats were studied after 6.5-hr immobilization. The linkage between the BP dynamics under emotional stress and changes of catecholamines content was observed in epinephrinsynthetizing area A1, norepinephrinsynthetizing area A6 (locus Coeruleus) and dopaminsynthetizing area A9 (substantia nigra).

[Emotional stress-induced changes in catecholamines in the nuclei of the brains of rats differing in "open-field" behavior].

The open-field test was used to study the role of initial emotionality in participation of brain catecholamines (CAs) in the BP control under emotional stress. The rats different in emotionality differed from each other in the level of CAs in single brain nuclei under normal conditions. Under stress, opposite CAs changes occurred in rats differing by their initial emotionality, in noradrenaline-synthetizing brain nuclei only.

Hypertension induced by repeated stress: possible participation of sympathetic-adrenomedullary catecholamines.

Several groups of male Wistar rats weighing 250-300 g were subjected to immobilization stress (IMO) for various intervals (2.5 h to 19 h daily omitting weekends for a total of 2 to 15 weeks). Blood pressure (BP) was measured with the aid of indirect cuff pressure method under routine conditions once weekly during the whole period of immobilization and in some groups also for 10 weeks after the end of this period.

Effects of rewarding hypothalamic stimulation on plasma catecholamine levels in rats.

Plasma catecholamines were measured before, during and after exposure to lick-contingent rewarding hypothalamic stimulation, clock-triggered neutral hypothalamic stimulation, and licking maintained by water. Rewarding hypothalamic stimulation elicited a marked rise in plasma epinephrine levels which returned to baseline levels 3 min after the self-stimulation session. No changes in plasma epinephrine were observed under the latter two conditions.

Corticosterone and prolactin responses to repeated handling and transfer of male rats.

The changes of plasma corticosterone and prolactin levels have been studied in rats after single, repeated or cross exposition to the moderate stressors: handling and transfer. The diminution of corticosterone and prolactin response has been found after repeated handling, but not after repeated transfer. The corticosterone level was significantly elevated in both cross-transfer and cross-handling groups and plasma prolactin level was significantly higher in the cross-handling animals.

Changes of plasma and adrenal catecholamines and corticosterone in stressed rats with septal lesions.

The effect of septal lesions on plasma catecholamine and corticosterone (B) levels has been studied in rats during single and 7 times repeated immobilization stress (IMO). Blood samples were obtained via a catheter in the tail artery or by decapitation. The increased circulating epinephrine (EPI) and norepinephrine (NE) levels observed in the initial phase of acute stress as well as the elevated baseline EPI level after six times repeated IMO are indicative of an enhanced response of the sympathetic adrenomedullary system after lesions of the septum.

[Changes in the level of catecholamines in norepinephrine-producing structures of the brain of rats subjected to immobilization].

Radioenzymatic assay was used to determine the catecholamine content in locus ceruleus and n. subceruleus in Wistar rats after 6.5-hour immobilization.

[Catecholamines in the brain structures of rats responding differently to the "open field" test].

Wistar rats divided into groups according to the open-field test showed essential differences in the catecholamine level in 3 out of eight principal catecholamine-synthesizing brain nuclei. In rats with a sharp decrease in crossing and rearing seen throughout the experiment, the adrenaline and dopamine levels in A1 area were significantly higher and the dopamine level in locus ceruleus and n. arcuatus was lower as compared with rats which were not so emotional.

Participation of "emotionality" in activation of the adrenal cortex of rats in some stress situations.

The present work attempts to interpret the relation between humoral and behavioral manifestations in rats under conditions of stress. The index of the humoral reaction to stress was plasma corticosterone levels. Initially, behavioral manifestations which are commonly subsumed under the term "emotionality" were studied.