Pituitary-adrenal responses to repeated small hemorrhage in conscious dogs

Lilly, M. P.; Engeland, William C.; Gann, D. S.

doi:10.1152/ajpregu.1986.251.6.r1200

Cited by 16 publications

(10 citation statements)

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“…However, if either of the stimuli are sufficiently intense, facilitation will override the feedback inhibition (56). Importantly, potentiation of HPA responses to repeated stressors appear to mediated at least in part by post-stress increases in ACTH release or enhanced adrenal sensitivity (101, 102, 130, 162). …”

Section: Chronic Stressmentioning

confidence: 99%

Regulation of the Hypothalamic‐Pituitary‐Adrenocortical Stress Response

Herman

McKlveen

Ghosal

et al. 2016

Comprehensive Physiology

1,293

946

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The hypothalamo-pituitary-adrenocortical (HPA axis) is required for stress adaptation. Activation of the HPA axis causes secretion of glucocorticoids, which act on multiple organ systems to redirect energy resources to meet real or anticipated demand. The HPA stress response is driven primarily by neural mechanisms, invoking corticotrophin releasing hormone (CRH) release from hypothalamic paraventricular nucleus (PVN) neurons. Pathways activating CRH release are stressor dependent: reactive responses to homeostatic disruption frequently involve direct noradrenergic or peptidergic drive of PVN neurons by sensory relays, whereas anticipatory responses use oligosynaptic pathways originating in upstream limbic structures. Anticipatory responses are driven largely by disinhibition, mediated by trans-synaptic silencing of tonic PVN inhibition via GABAergic neurons in the amygdala. Stress responses are inhibited by negative feedback mechanisms, whereby glucocorticoids act to diminish drive (brainstem), promote trans-synaptic inhibition by limbic structures (e.g, hippocampus). Glucocorticoids also act at the PVN to rapidly inhibit CRH neuronal activity via membrane glucocorticoid receptors. Chronic stress-induced activation of the HPA axis takes many forms (chronic basal hypersecretion, sensitized stress responses, even adrenal exhaustion), with manifestation dependent upon factors such as stressor chronicity, intensity, frequency and modality. Neural mechanisms driving chronic stress responses can be distinct from those controlling acute reactions, including recruitment of novel limbic, hypothalamic and brainstem circuits. Importantly, an individual’s response to acute or chronic stress is determined by numerous factors, including genetics, early life experience, environmental conditions, sex and age. The context in which stressors occur will determine whether an individual’s acute or chronic stress responses are adaptive or maladaptive (pathological).

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Section: Chronic Stressmentioning

confidence: 99%

Regulation of the Hypothalamic‐Pituitary‐Adrenocortical Stress Response

Herman

McKlveen

Ghosal

et al. 2016

Comprehensive Physiology

1,293

946

View full text Add to dashboard Cite

show abstract

“…We have demonstrated increased adrenal sensitivity to ACTH in dogs prepared for direct measurement of adrenal corticosteroid secretion after either hemorrhage (Lilly et al 1983(Lilly et al , 1986 or surgery (Lilly & Gann 1982). There is evidence in rats that this effect of surgery may be mediated by modulation of ultradian rhythms in splanchnic nerve activity (Jasper & Engeland 1994).…”

Section: Discussionmentioning

confidence: 99%

Post-surgical recovery and time-of-day mask potentiated responses of ACTH to repeated moderate hemorrhage in conscious rats

Lilly

Jones

Putney

et al. 2000

Journal of Endocrinology

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We determined how changes in the responsiveness of the hypothalamo-pituitary-adrenal (HPA) system that accompany experimentation affect facilitation of HPA responses to hemorrhage. Hemorrhage (10 ml/kg over 3 min) was performed in conscious, chronically prepared rats. Blood was sampled over 1 h followed by reinfusion of shed blood. Hemorrhage was performed either once or twice separated by 24 h in different groups of animals. To test the effect of the circadian variation in responsiveness, rats were hemorrhaged on days 4 and 5 after surgery either in the morning (AM) or in the afternoon (PM). The response of ACTH to hemorrhage on day 4 was greater in the PM than in the AM (P<0·01). The ACTH response to the second hemorrhage on day 5 was greater than that to hemorrhage on day 4 only in the AM group (P<0·01). Thus, facilitation of ACTH responses by prior hemorrhage was evident only in the AM. To determine the effects of surgical recovery, additional experiments were done in the AM either early (days 3 and 4) or later (days 6 and 7) after surgery. In these experiments, hemorrhage was performed in all rats on days 4 and 7 and either hemorrhage or blood sampling alone was performed on day 3 and 6. ACTH did not increase in rats with sampling and no hemorrhage. ACTH increased more after an initial hemorrhage on day 3 than on day 6 (P<0·01). ACTH response to hemorrhage on day 4 was greater when preceded by hemorrhage vs sampling on day 3 (P<0·01). ACTH response to hemorrhage in rats bled twice did not differ on day 3 and day 4. On day 7, the response of ACTH in rats that had hemorrhage on day 6 was greater than both their own response on day 6 and the response of a control group with sampling on day 6 (P<0·01). These results demonstrate potentiation of ACTH responses to hemorrhage by an earlier similar hemorrhage, but clearly indicate that enhanced sensitivity of the HPA to hemorrhage either by circadian factors or by surgery can mask this effect.

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“…Presumably, ail differences between treated and control pigs occurred in the 24-hour period subsequent to the 1-min stressor. For pigs [40], dogs [41,42], and rats [43. 44], previous stressor exposure altered functioning of the HPA axis measured 24 h later.…”

Section: Discussionmentioning

confidence: 99%

Functioning of the Porcine Pituitary-Adrenocortical Axis during Neonatal Development

Klemcke

Brown‐Borg²,

Borg³

1995

Neonatology

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A study was conducted with neonatal boars to measure age-related changes in functioning of the pituitary-adrenocortical axis. Pigs were randomly assigned to control (n = 7–10/age) or treated (1-min restraint, n = 9–11/age) groups to be sampled at either 12, 19, or 26 days of age. Blood samples were taken via catheter 10 min before and 3, 10, and 20 min after restraint or at similar time intervals in controls. One day later, pigs were killed and adrenal glands obtained for ACTH receptor measurements. Basal plasma ACTH concentrations were greatest (p = 0.035) on day 12 when compared with later ages, but basal plasma cortisol concentrations were comparable at the three ages. Compared with controls, restraint elevated incremental plasma ACTH and cortisol responses at each age (p < 0.004). On day 12, maximal plasma ACTH (p = 0.0006) and incremental cortisol (p < 0.006) responses to restraint were greater than at later ages. Binding to adrenal ACTH receptors was greatest (p < 0.05) at day 13, which may help explain the apparently increased in vivo response of the adrenal gland to ACTH at this time. Restrained pigs had increased growth rates with increasing age (p = 0.016) whereas growth rates for control pigs did not differ with age. At day 27, 24 h after the 1-min restraint, body weights of restrained pigs exceeded those of control pigs (p = 0.045). At day 20, adrenal DNA and protein in pigs restrained 24 h previously were greater than in control pigs (p < 0.05). These data suggest age-related changes in functioning of the pituitary-adrenal axis in neonatal boars, and an absence of a period during neonatal life when the porcine pituitary adrenocortical axis cannot respond to a stressor. The data also indicate both rapid and long-term responses of the adrenal to a very modest stressor and suggest an extreme sensitivity of neonatal pigs to environmental perturbations.

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Pituitary-adrenal responses to repeated small hemorrhage in conscious dogs

Cited by 16 publications

References 0 publications

Regulation of the Hypothalamic‐Pituitary‐Adrenocortical Stress Response

Regulation of the Hypothalamic‐Pituitary‐Adrenocortical Stress Response

Post-surgical recovery and time-of-day mask potentiated responses of ACTH to repeated moderate hemorrhage in conscious rats

Functioning of the Porcine Pituitary-Adrenocortical Axis during Neonatal Development

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