Edward H. Mougey

Comparison of stress response in male and female rats: pituitary cyclic AMP and plasma prolactin, growth hormone and corticosterone.

Three potent stressors (forced running, immobilization, and footshock) were found to increase levels of cyclic AMP in the pituitaries of both female and male rats. The pituitary cyclic AMP response in females was generally similar to that observed in males. The tested stressors elevated both plasma corticosterone and prolactin and decreased plasma growth hormone. Plasma corticosterone rose more rapidly in females than in males following stress. Control growth hormone levels were higher in male rats. There was no clear cause and effect relationship between elevations of pituitary cyclic AMP and changes in plasma levels of prolactin, corticosterone, and growth hormone.

Acute and repeated exposure to social conflict in male golden hamsters : increases in plasma POMC-peptides and cortisol and decreases in plasma testosterone

The purpose of the present study was to characterize the hormonal response of dominant and submissive male hamsters to acute and repeated exposure to social conflict. We found that submissive, but not dominant, males exhibited elevated plasma levels of adrenocorticotropin (ACTH), cortisol, and beta-endorphin (beta-EP) following one exposure to an agonistic encounter. After five exposures to a dominant opponent, submissive males showed smaller, but still significant, elevations in these plasma hormones. After nine exposures, submissive hamsters showed significant elevations only in plasma ACTH and beta-EP. Plasma testosterone was significantly suppressed in submissive males that fought nine times. We conclude that hamsters are a useful species with which to study the neuroendocrine correlates of social behavior.

Psychologic stress increases plasma levels of prolactin, cortisol, and POMC-derived peptides in man.

&NA; Stressful social interactions have been shown to elicit increases in heart rate as well as in plasma levels of epinephrine, norepinephrine, and cortisol in humans. We sought to determine whether a competitive oral examination would affect plasma levels of the pituitary hormones ACTH, beta‐endorphin, beta‐lipotrophic hormone, and prolactin in a group of healthy young males. Seven min after beginning the examination, heart rate increased 27% and plasma levels of ACTH, beta‐endorphin, beta‐lipotropic hormone and prolactin rose 59%, 79%, 42%, and 46%, respectively, compared to values shortly before the examination. These hormone values returned to initial levels after the subjects returned to the waiting room. Plasma cortisol changes were similar in direction to those of ACTH but occurred about 15 min later. The present study demonstrates that a stressful social interaction can elicit rapid increases in plasma levels of the proopiomelanocortin derived peptide hormones and prolactin in man.

Diurnal Variation in Neuroendocrine Response to Stress in Rats: Plasma ACTH, β-Endorphin, β-LPH, Corticosterone, Prolactin and Pituitary Cyclic AMP Responses

The effects of restraint stress applied at different times of the day on levels of five stress-responsive plasma hormones (ACTH, β-endorphin, β-LPH, corticosterone and prolactin) and pituitary cyclic AMP levels were assessed. Different groups of rats were subjected to 15 min of restraint stress at 2-hour intervals over a 24-hour period. Rats were sacrificed immediately upon removal from their home cage (controls) or immediately following restraint (stressed). The time of day of stress exposure markedly affected the stress responses measured. Generally, responses to stress applied at the beginning of the dark cycle (18.00) were less than those seen following stress applied at the beginning of the light cycle (06.00). Stress at 06.00 increased levels of pituitary cyclic AMP 10-fold, while stress applied at 18.00 did not significantly increase pituitary cyclic AMP levels. In stressed rats, high correlations were seen among levels of hormones derived from the common precursor, proopiomelanocortin (ACTH, β-endorphin, β-LPH) and between these hormones and levels of pituitary cyclic AMP. These findings support the hypothesis that pituitary cyclic AMP is involved in the stress-induced release or synthesis of the pituitary hormones ACTH, β-endorphin, and β-LPH.

Effects of repeated stress on pituitary cyclic AMP, and plasma prolactin, corticosterone and growth hormone in male rats

The effects of five putative stressors (saline injection, cold exposure, forced running, immobilization, and footshock) on levels of pituitary cyclic AMP, plasma prolactin, corticosterone and growth hormone were examined. In naive rats exposed to 15 min of these stressors for the first time, running, immobilization and footshock increased levels of pituitary cyclic AMP, plasma corticosterone and prolactin and decreased growth hormone, typical of stress response in the rat. Cold exposure only increased corticosterone and saline injection did not affect any measured parameter. In rats chronically exposed to the same stressor (once a day for 15 min) for 10 days immediately prior to the experiment, an attenuated pituitary cyclic AMP and plasma prolactin response was seen upon application of 15 min of that stressor on the day of the experiment, compared to the responses observed in the naive rats.

Activity wheel running reduces escape latency and alters brain monoamine levels after footshock

We examined the effects of chronic activity wheel running on brain monoamines and latency to escape foot shock after prior exposure to uncontrollable, inescapable foot shock. Individually housed young (approximately 50 day) female Sprague-Dawley rats were randomly assigned to standard cages (sedentary) or cages with activity wheels. After 9-12 weeks, animals were matched in pairs on body mass. Activity wheel animals were also matched on running distance. An animal from each matched pair was randomly assigned to controllable or uncontrollable inescapable foot shock followed the next day by a foot shock escape test in a shuttle box. Brain concentrations of norepinephrine (NE), dopamine (DA), dihydroxyphenylacetic acid (DOPAC), 5-hydroxytryptamine (5-HT), and 5-hydroxyindole acetic acid (5-HIAA) were assayed in the locus coeruleus (LC), dorsal raphe (DR), central amygdala (AC), hippocampus (CA1), arcuate nucleus, paraventricular nucleus (PVN), and midbrain central gray. After prior exposure to uncontrollable foot shock, escape latency was reduced by 34% for wheel runners compared with sedentary controls. The shortened escape latency for wheel runners was associated with 61% higher NE concentrations in LC and 44% higher NE concentrations in DR compared with sedentary controls. Sedentary controls, compared with wheel runners, had 31% higher 5-HIAA concentrations in CA1 and 30% higher 5-HIAA concentrations in AC after uncontrollable foot shock and had 28% higher 5-HT and 33% higher 5-HIAA concentrations in AC averaged across both foot shock conditions. There were no group differences in monoamines in the central gray or in plasma prolactin or ACTH concentrations, despite 52% higher DA concentrations in the arcuate nucleus after uncontrollable foot shock and 50% higher DOPAC/DA and 17% higher 5-HIAA/5-HT concentrations in the PVN averaged across both foot shock conditions for sedentary compared with activity wheel animals. The present results extend understanding of the escape-deficit by indicating an attenuating role for circadian physical activity. The altered monoamine levels suggest brain regions for more direct probes of neural activity after wheel running and foot shock.

Graded footshock stress elevates pituitary cyclic AMP and plasma β-endorphin, β-LPH, corticosterone and prolactin

Abstract Male rats were subjected to 15 min of various intensities of footshock current (0.0, 0.2, 0.4, 0.8, 1.6, 2.4, 3.2mA) on a variable interval schedule with an average intershock interval of 30 sec (30 shocks/15 min session). Each shock lasted 5 sec. Animals were sacrificed immediately after being removed from the shock box. Two similar studies were conducted. In the first experiment, rats were sacrificed by microwave irradiation and pituitary cyclic AMP levels were determined. In the second study, rats were decapitated and plasma hormones (prolactin, corticosterone, β-endorphin, β-LPH) were measured by radioimmunoassay. Although all biochemical indices of stress measured increased as shock intensity increased, some differences among the substances measured were observed with respect to threshold intensity, range of proportional response and maximal response.

Specific Hormonal and Neurochemical Responses to Different Stressors

The neuroendocrine and neurochemical responses of rats to 5 min of cold exposure versus 5 min of forced immobilization were determined and compared. We found that plasma hormones and brain neurochemical systems responded differently to the two different stressors. Plasma prolactin levels were elevated over 10-fold in the immolilized group, while rising only 2-fold in the cold stress group. Levels of corticosterone were significantly increased and growth hormone levels were decreased in both stressed groups as compared to controls. Levels of cyclic GMP were markedly elevated in 11 brain regions following cold exposure. Surprisingly, no elevation of cyclic GMP was found after forced immobilization. Cyclic AMP, norepinephrine, and dopamine levels throughout the 17 regions of brain examined showed no significant response to 5 min of either stressor. Lesions of the ventral medial tegmental area did not affect the cyclic GMP or neuroendocrine responses to cold stress. Lesion of the nucleus locus ceruleus did not affect the cyclic GMP response but significantly reduced growth hormone levels in the cold-stressed rats.

Androgen responses to stress. II. Excretion of testosterone, epitestosterone, androsterone and etiocholanolone during basic combat training and under threat of attack.

&NA; Recruits in the first month of basic training at Fort Dix, NJ and special forces personnel anticipating imminent combat in Vietnam showed lowered excretion of testosterone, epitestosterone, androsterone, and etiocholanolone. This suggests that men responded to the potential threat of these situations with an inhibition of testosterone secretion. The wide range of values, similar to that observed for 17‐OHCS excretion, reflects the importance of individual differences in response and adaptation. The relative decrease in sexual activity experienced by men in these environments may have contributed to the lowered excretion of the androgen metabolites. The parallel fall in the excretion of 17‐OHCS and C19O2 and C19O3 metabolites in the Vietnam group provides evidence of psychological adaptation rather than a shift in adrenal secretory or metabolic pathways in response to exposure to more chronic stress.

Hormonal responses to fighting in hamsters: Separation of physical and psychological causes

Male Syrian hamsters were paired and allowed to interact with a conspecific for 15 min a day for 4 days. On the fifth day, the animals were again paired, but they were kept physically separated by a mesh partition that allowed visual, olfactory, and auditory contact between the animals. Controls were placed with conspecifics on each of the 5 testing days, but the partition between them was never removed. Hamsters that were submissive on days 1-4 exhibited elevated plasma adrenocorticotropin-like immunoreactivity (ACTH-LI), beta-endorphin-like immunoreactivity (B-EP-LI), and cortisol on day 5 even though no fighting occurred on that day. Dominant hamsters did not differ from controls. These data support the hypothesis that there is an important psychological component to the pituitary-adrenocortical response in defeated hamsters.