ACTH and attention in humans: a review

Oxytocin Release Increases With Age and Is Associated With Life Satisfaction and Prosocial Behaviors

Helping behaviors and life satisfaction generally increase after middle-age. Identifying the neural substrates of prosocial behaviors in older adults may offer additional insights into these changes over the lifespan. The present study examines the endogenous release of the neuromodulator oxytocin (OT) in participants aged 18-99 and its relationship to prosocial behaviors. OT has been shown to influence trust, altruism, charity, and generosity, yet the effect of age on OT release has not been well-established. Blood samples before and after a video stimulus were obtained from 103 participants in order to examine the impact of OT on prosocial behaviors. We found that OT release following a social prime increased with age (r = 0.49, p = 0.001) and that OT moderated the relationship between age and donations to charity. We tested for robustness by examining three additional prosocial behaviors, money and goods donated to charity during the past year and social-sector volunteering. OT moderated the impact of age on all three prosocial behaviors (ps < 0.05). The analysis also showed that participants' change in OT was positively associated with satisfaction with life (p = 0.04), empathic concern (p = 0.015), dispositional gratitude (p = 0.019), and religious commitment (p = 0.001). Our findings indicate that the neural chemistry that helps sustain social relationships and live a fulfilled life appear to strengthen with age.

The effects of acute stress and stress hormones on social cognition and behavior: Current state of research and future directions

Stress encompasses profound psychological and physiological changes that are observable on all levels, from cellular mechanisms, humoral changes, and brain activation to subjective experience and behavior. While the impact of stress on health has already been studied for decades, a more recent field of research has revealed effects of stress on human social cognition and behavior. Initial studies have attempted to elucidate the underlying biological mechanisms of these stress-induced effects by measuring physiological responses or by using pharmacological approaches. We provide an overview of the current state of research on the effects of acute stress induction or pharmacological manipulations of stress-related neuro circuitry on social cognition and behavior. Additionally, we discuss the methodological challenges that need to be addressed in order to gain further insight into this important research topic and facilitate replicability of results. Future directions may help to disentangle the complex interplay of psychological and biological stress variables and their effects on social cognition and behavior on health and in disorders with social deficits.

Elevated Cortisol at Retrieval Suppresses False Memories in Parallel with Correct Memories

Retrieving a memory is a reconstructive process in which encoded representations can be changed and distorted. This process sometimes leads to the generation of “false memories,” that is, when people remember events that, in fact, never happened. Such false memories typically represent a kind of “gist” being extracted from single encountered events. The stress hormone cortisol is known to substantially impair memory retrieval. Here, in a double-blind, placebo-controlled crossover design, we tested the effect of an intravenous cortisol infusion before retrieval testing on the occurrence of false memories and on recall of correct memories using a modified Deese–Roediger–McDermott paradigm. Subjects studied sets of abstract shapes, with each set being derived from one prototype that was not presented during learning. At retrieval taking place 9 hr after learning, subjects were presented with studied shapes, nonstudied shapes, and the prototypes, and had to indicate whether or not each shape had been presented at learning. Cortisol administration distinctly reduced susceptibility to false memories (i.e., false recognition of prototypes) and, in parallel, impaired retrieval of correct memories (i.e., correct recognition of studied shapes). Response bias as well as confidence ratings and remember/know/guess judgments were not affected. Our results support gist-based theories of false memory generation, assuming a simultaneous storage of the gist and specific details of an event. Cortisol, by a general impairing influence on retrieval operations, decreases, in parallel, retrieval of false (i.e., gist) and correct (i.e., specific) memories for the event.

Effects of cortisol suppression on sleep-associated consolidation of neutral and emotional memory

BACKGROUND

Previous research indicates that hippocampus-dependent declarative memory benefits from early nocturnal sleep, when slow-wave sleep (SWS) prevails and cortisol release is minimal, whereas amygdala-dependent emotional memory is enhanced through late sleep, when rapid eye movement (REM) sleep predominates. The role of the strong cortisol rise accompanying late sleep for emotional memory consolidation has not yet been investigated.

METHODS

Effects of the cortisol synthesis inhibitor metyrapone on sleep-associated consolidation of memory for neutral and emotional texts were investigated in a randomized, double-blind, placebo-controlled study in 14 healthy men. Learning took place immediately before treatment, which was followed by 8 hours of sleep. Retrieval was tested at 11 am the next morning.

RESULTS

Metyrapone suppressed cortisol during sleep and blocked particularly the late-night rise in cortisol. It reduced SWS and concomitantly impaired the consolidation of neutral texts. Emotional texts were spared from this impairing influence, however. Metyrapone even amplified emotional enhancement in text recall indicating amygdala-dependent memory.

CONCLUSIONS

Cortisol blockade during sleep impairs hippocampus-dependent declarative memory formation but enhances amygdala-dependent emotional memory formation. The natural cortisol rise during late sleep may thus protect from overshooting emotional memory formation, a mechanism possibly pertinent to the development of posttraumatic stress disorder.

Gedächtnisleistung im Alter:

Zusammenfassung. Das höhere Lebensalter ist durch zahlreiche Veränderungen des Hormonsystems charakterisiert. Besonders markant ist die Abnahme der Sexualsteroidhormone (Östradiol, Progesteron, Testosteron, DHEA), während die basalen Spiegel des “Stresshormons“ Cortisol stabil bleiben oder leicht ansteigen. Die vorliegende Übersichtsarbeit diskutiert die Relevanz dieser hormonellen Veränderungen für Funktion und Struktur des Gehirns am Beispiel der Gedächtnisleistung im höheren Lebensalter. Bei älteren Frauen wurden wiederholt gedächtnisverbessernde und neuroprotektive Effekte von Östradiol berichtet. Inwieweit und in welche Richtung Progesteron die Östrogeneffekte moduliert, ist noch unklar, da sowohl synergistische als auch antagonistische Effekte berichtet wurden. Die Rolle des Testosterons für die Gedächtnisleistung des alternden Mannes ist bisher kaum untersucht. Mehrere Studien haben hingegen gezeigt, dass DHEA bei gesunden älteren Männern und Frauen keine positiven Effekte auf die Gedächtnisleistung ausübt. Das Nebennierenrindenhormon Cortisol verschlechtert akut Leistungen des Arbeitsgedächtnisses und des deklarativen Gedächtnisses. Darüber hinaus gibt es vermehrt Hinweise darauf, dass erhöhte basale Cortisolspiegel im Alter sowohl zu einer Verschlechterung der Gedächtnisleistung als auch zu einer Verringerung des Hippocampusvolumens führen. Zusammengenommen verdeutlichen diese Befunde, dass Steroidhormone die Struktur und Funktion des menschlichen zentralen Nervensystems nachhaltig beeinflussen.

HPA axis and memory

The hormones of the hypothalamus-pituitary-adrenal (HPA) axis influence memory in situations of acute and chronic stress. The present review tries to summarize the current state of knowledge by describing the enhancing as well as the impairing effects of stress or glucocorticoid (GC) treatment documented in animals and humans. GCs secreted during the acquisition of a stressful task facilitate consolidation. However, acute stress (or GC treatment) unrelated to the task impairs performance. The effects of acute stress are additionally modulated by gender, age and the emotional valence of the learning material. Chronic stress in rodents has mostly impairing effects on memory and hippocampal integrity. However, other regions of the brain, such as the prefrontal cortex, are also sensitive to stress. In humans, similar observations have been reported in several patient populations as well as in older subjects. The potential to reverse these effects using behavioural or pharmacological approaches needs to be explored.

Cognitive function in congenital adrenal hyperplasia

Cognition in patients with CAH has not been as well studied as other aspects of psychologic function. Nevertheless, it is possible to make some conclusions and to offer a number of hypotheses for further study (Table 1). First, patients with CAH do not seem to have an overall intellectual advantage as a direct consequence of the disease. The high IQs reported in some groups of patients with CAH are also reported in their siblings and probably reflect sampling bias. Second, it is possible that, on average, patients with salt-wasting CAH have lower overall ability than patients with the simple-virilizing form, but both groups are well within the normal range, and there is considerable variability among both groups. Third, the evidence to date does not confirm that patients with CAH are more likely to have diagnosable learning disabilities when compared with their unaffected relatives, but this issue has not been well studied with the appropriate psychoeducational assessments. It is unlikely that patients with CAH are at substantially increased risk for frank learning disabilities, but they may be likely to have problems in specific areas. Fourth, females with CAH seem to have enhanced spatial ability as a result of exposure to high levels of androgens early in development. The neural substrate of this advantage is unknown but a subject of active research. It is unclear whether when compared with their unaffected siblings, females with CAH are better in other abilities that are typically performed best by males or worse in abilities typically performed best by females. Fifth, it is likely that patients with CAH have other cognitive changes as a consequence of disease characteristics (besides androgens) and of the treatment of the disease. Some evidence suggests that patients with CAH are more likely to have white-matter brain changes produced by the disease and its treatment. This has not been well studied but should be because of the potential clinical implications. It is reasonable to hypothesize that there will be cognitive changes that reflect effects of undertreatment (e.g., ACTH effects on attention) and other changes that reflect effects of overtreatment (e.g., glucocorticoid effects on memory). Some of these effects may be transient, reflecting acute brain changes, whereas others may become chronic as a result of permanent brain changes with repeated exposure. There is need for continuing study of cognition in patients with CAH. Such studies will provide basic information about hormonal effects on cognition and the neural mechanisms that mediate those effects. They will also provide important clinical information to guide psychologic and medical treatment of patients.

Manipulating neuropeptidergic pathways in humans: a novel approach to neuropharmacology?

Given the tremendous number of neuropeptides, which are synthesized in the central nervous system, the brain can be viewed as one of the most prominent endocrine organs. Elucidation of the functions of these peptides is hampered by the facts that after intravenous administration access to brain receptors is prevented or impaired by the blood-brain barrier. Here, we provide evidence that intranasal administration can be a way to circumvent the blood-brain barrier. Selected experiments will be reported indicating that peptides after intranasal administration in humans can specifically alter a great variety of brain functions. For vasopressin, we demonstrated improving effects of long-term intranasal treatment on sleep in elderly people. Insulin showed improving effects of short-term memory functions. For adrenocorticotropin/melanocyte stimulating hormone, ACTH/MSH-(4-10), a twofold action was isolated: The melanocortin fragment diminished selective attention and, with subchronic administration, reduced body fat. These results could provide the basis for developing a new, specific, and "soft" neuropharmacology.

Event-related brain potentials and working memory function in healthy humans after single-dose and prolonged intranasal administration of adrenocorticotropin 4-10 and desacetyl-alpha-melanocyte stimulating hormone

Neuropeptides of the adrenocorticotropin/melanocorticotropin (ACTH/MSH) family are most potent modulators of cognitive function. Their neurobehavioral activity is principally encoded in the 4-10 fragment of the ACTH/MSH molecule; in humans, it has been shown to pertain primarily to functions of attentive stimulus/response processing. The aims of this study were (1) to examine the effects of ACTH 4-10 on event-related brain potentials (ERPs) and behavioral indicators of stimulus encoding within the working memory; (2) to compare the effects after a single dose and after prolonged treatment with ACTH 4-10; and (3) to compare the effects of ACTH 4-10 with those of desacetyl-alpha-MSH (i.e., ACTH 1-13 amide), which, like ACTH 4-10, binds to the known brain melanocortin receptors (MC-Rs) but with distinctly higher affinity. Double-blind, placebo-controlled experiments were performed in 60 healthy control subjects. The authors monitored ERPs and reaction times while these subjects performed an auditory vigilance task ("oddball"). Recall was tested on a verbal short-term memory task including different word categories (neutral, rare, food, sex). After a single (1 mg) as well as prolonged intranasal administration (1 mg/day over a period of 6 weeks), ACTH 4-10 enhanced the positive slow wave in ERPs to target stimuli of the vigilance task (p < 0.05), but left classic P3 unaffected. Moreover, single-dose and prolonged administration of ACTH 4-10 increased the rate of false responses during vigilance (p < 0.01). In the short term, ACTH 4-10 also impaired recall of neutral words (p < 0.05). Equimolar doses of desacetyl-alpha-MSH did not influence ERPs, neither after a single dose nor after prolonged treatment. Similar to ACTH 4-10, desacetyl-alpha-MSH increased the error rate during vigilance and acutely impaired the recall of neutral words. The increase in ERP slow-wave positivity, in conjunction with behavioral impairments after treatment with ACTH 4-10, complemented previous results of inferior focusing of attention and a less concise structure of thought after administration of ACTH 4-10. The changes indicated an impairment in differential processing of relevant versus irrelevant contents within the working memory, and, in this regard, might mimic aspects of psychopathologic disturbances of attention and thought processes. Their persistence after prolonged treatment with ACTH 4-10 suggests an activation of mechanisms subserving the consolidation of the peptide's effects. The poor efficacy of desacetyl-alpha-MSH suggests that the known MC-Rs may be irrelevant for mediating cognitive effects of this neuropeptide family.

Adrenocorticotropin widens the focus of attention in humans. A nonliner electroencephalographic analysis

OBJECTIVE

This study examined the effects of ACTH 4-10, a fragment of adrenocorticotropin (ACTH) with known central nervous system (CNS) activity, on the dimensional complexity of the ongoing electroencephalographic (EEG) activity. Stressful stimuli cause ACTH to be released from the pituitary, and as a neuropeptide ACTH may concurrently exert adaptive influences on the brain's processing of these stimuli. Previous studies have indicated an impairing influence of ACTH on selective attention.

METHODS

Dimensional complexity of the EEG, which indexes the brain's way of stimulus processing, was evaluated while subjects performed tasks with different attention demands. Sixteen healthy men (23 to 33 years) were tested once after placebo and another time after administration of ACTH 4-10 (1.25 mg intravenously (i.v.), 30 minutes before testing). The EEG was recorded while subjects were presented with a dichotic listening task (consisting of the concurrent presentation of tone pips to the left and right ear). Subjects either a) listened to pips in both ears (divided attention), or b) listened selectively to pips in one ear (selective attention), or c) ignored all pips.

RESULTS

Dimensional complexity of the EEG was higher during divided than selective attention. ACTH significantly increased the EEG complexity during selective attention, in particular over the midfrontal cortex (Fz, Cz).

CONCLUSIONS

The effects support the view of a de-focusing action of ACTH during selective attention that could serve to improve the organism's adaptation to stress stimuli.

Chronic administration of ORG 2766 for 6 months produces a subtle impairment in strategic learning by rats

Rats were administered saline or 10 micrograms of the ACTH4-9 analog ORG 2766 on alternate days for 160 days (i.e. 80 injections total). Behavioral assessments began 1 week later. Locomotor competence was assessed by examining the number of slips and falls made by the animals on a rotating rod. The rats were also trained on a position task and 10 subsequent position reversals in a 'T' shaped water maze. Exposure to ORG 2766 failed to affect either locomotor competence or the overall number of errors committed while learning the original position habit and 10 reversals. However, the response accuracy of the ORG 2766-treated animals on trial 2 of the reversals was equivalent to that expected by chance (58% correct choices), whereas saline-treated animals effectively altered their behavior after experiencing nonreinforcement on the initial trial of a reversal (77% correct choices). This result is consistent with other observations revealing that ORG 2766 can influence attention and, therefore, some cognitive functions.

Effects of ORG-2766 on brain event-related potentials of autistic children

A double-blind, placebo-controlled study examined the effects of 6 weeks of treatment with the adrenocorticotropin4-9 analogue ORG-2766 (40 mg/day) on brain event-related potentials (ERPs) of autistic children. In visual and auditory oddball paradigms (with task and nontask conditions), standard (80%), target (10%), and unexpected novel stimuli (10%) were presented. ORG-2766 (a) increased the occipital P3 component of the ERP to visual targets, (b) decreased the occipital P3 component of the ERP to auditory targets, (c) did not affect visual and auditory parietal target P3 components, and (d) also did not affect the A/Pcz/300 to auditory novel stimuli. In addition, ORG-2766 treatment increased the N1 component of the ERP to task-irrelevant auditory stimuli.

Chronic and intra-amygdala administrations of the ACTH(4-9) analog ORG 2766 modulate behavioral changes after manipulation of NMDA-receptor activity

Microinjection of N-methyl-D-aspartic acid (NMDA, 300 ng/3 microliters) into the left lateral ventricle causes a substantial increase in locomotor activity which can be significantly reduced by a chronic pretreatment with the ACTH(4-9) analogue ORG 2766(1 microgram/0.5 ml saline, subcutaneous (s.c.) every day for 7 days, last injection 24 h before the NMDA-injection). A single dose of ORG 2766 (1 ng/1 microliter) injected into the left central amygdaloid nucleus 30 min before the NMDA-injection was equally effective in reducing the increase in locomotion. Furthermore it counteracted the predominance of contralateral turning induced by the NMDA-injection. The data give support for the idea that ORG 2766 excerts its effects on behavior and neural recovery by modulating NMDA receptor activity in the brain.

The ACTH(4-9) analog ORG 2766 and recovery after brain damage in animal models--a review

Treatment with adrenocorticotrophic hormone (ACTH), as well as with ACTH fragments and analogues, can influence behaviour of animals and humans. Furthermore it facilitates recovery of damaged peripheral nervous tissue. The question whether ACTH/MSH peptides affect recovery processes after injury to the central nervous system as well is addressed in the present review. The effects of administration of the ACTH(4-9) analog ORG 2766 after brain lesions has been studied frequently. However, the interpretation of the available data is confused by the variability of the results. Several factors can be identified which influence the efficacy of the peptide: (i) not all behavioural tests are equally suitable to reveal a peptide effect on behavioural recovery; (ii) the affected brain area; (iii) whether cell bodies or terminals are affected; (iv) the post-operative housing conditions; and (v) the onset and duration of peptide administration. Two possible explanations of peptide efficacy on functional recovery are considered: first, the peptide may accelerate spontaneously occurring recovery processes and second, the peptide may induce compensatory mechanisms underlying functional recovery without recuperation of the damaged neurons. These compensatory mechanisms seem to rely mainly on enhanced non-selective attention by activation of limbic structures. It is as yet unknown to which receptor system ORG 2766 binds; the analog lacks affinity for the known melanocortin (MC) receptors in brain, yet ORG 2766 is able to modulate the activity of endogenous opioids and the NMDA-receptor. A modulating influence of the peptide on NMDA-receptor activity might indirectly account for both enhanced attention--with ensuing behavioural recovery--and the acceleration of spontaneous recovery.

General intelligence and cognitive profile in women with congenital adrenal hyperplasia (CAH)

To investigate possible effects of prenatal androgen exposure on cognitive functions, general intelligence and cognitive profile were studied in 22 women, 17-34 years old, with prenatal virilization due to congenital adrenal hyperplasia (CAH) (21-hydroxylase deficiency) and 22 healthy controls matched for region and date of birth. The tests were selected to measure abilities where gender differences repeatedly had been observed or that had earlier shown differences between CAH subjects and controls. The following cognitive functions were tested: Verbal, Visuo-Spatial, Visuo-Motor, Arithmetical, Logical Inductive abilities, and Field Dependence. Contrary to earlier reports, the mean general intelligence level of the CAH (22) group was significantly lower than the controls' and the earlier observed inferiority for calculation abilities in female CAH subjects was not supported by the results of the present study. A possible verbal disadvantage with significantly inferior results was noted for the two verbal tests for the CAH (22) group. For the 13 CAH/control pairs with equal general intelligence levels, the discrepancy between the inferior verbal vs. visual, arithmetic, and logical category scores was significantly larger for the CAH group than the controls. These results may suggest that CAH women develop a more masculine cognitive pattern under the influence of increased prenatal androgen exposure.

The influences of fragments and analogs of ACTH/MSH upon recovery from nervous system injury

Post-injury treatment with some fragments and analogs of the adrenocorticotropic hormone (ACTH) can influence recovery after nervous system injury. This review considers both the successful and unsuccessful attempts to facilitate neural and behavioral recovery from nervous system damage via post-injury administration of these compounds. To date no single unifying explanation for the mixed results observed in animals prepared with forebrain injuries has been achieved. Several possible explanations for the variety of observations reported and several potentially productive avenues for future research are suggested.

Degradation of ACTH/MSH(4-10) and its synthetic analog semax by rat serum enzymes: an inhibitor study

Degradation of the behaviorally active peptide ACTH/MSH(4-10) and its synthetic analog semax was studied in serum in the presence of several specific peptidase inhibitors. Bestatin and puromycin were used to inhibit aminopeptidase activity, lisinopril for angiotensin-converting enzyme, phosphoramidon for neutral endopeptidase 24.11, and Z-Pro-prolinal for prolyl endopeptidase. Bestatin inhibited up to 66%, puromycin about 33%, and lisinopril about 15% of total degrading activity against both ACTH/MSH(4-10) and semax. Involvement of neutral endopeptidase and prolyl endopeptidase in hydrolysis of the two peptides was less definitive. These studies showed that aminopeptidases and angiotensin-converting enzyme are responsible for the major part of the hydrolysis of ACTH/MSH(4-10) and semax in rat serum.

An ACTH/MSH(4-9) analog counteracts the behavioral effects of a mineralocorticoid receptor antagonist

The ACTH/MSH(4-9) analog Org2766 has been demonstrated to counteract age-related behavioral and morphological parameters especially those related to hippocampal functioning. Hippocampal mineralocorticoid receptors (MRs) are known to decline in the senescent rat. This decrease can be also counteracted by a chronic treatment with an ACTH(4-9) analog. The apparent effect of the peptide on hippocampal functioning prompted us to study a possible interaction between ACTH and MRs at a behavioral level. A chronic treatment with the ACTH(4-9) analog prevented the behavioral alteration induced by a specific MR antagonist (RU28318; 100 ng/microliters, ICV) in the Morris water maze and a step-through avoidance task. A possible role for neuronal excitation, involving MR activation, in peptide-facilitated behavioral recovery as seen in lesion studies and aging is discussed.

Event-related potential measures of attention in moderately depressed subjects

Prior research has inferred attentional changes related to depression from evidence concerning other cognitive processes. The present experiment investigated attentional changes related to depression in a more direct manner. Subjects were 32 young adults attending college. Depression was measured by self-report measures. In an auditory selective attention task similar to that of Hansen and Hillyard (1980), auditory event-related potentials (ERPs) were recorded from central (Cz) and frontal (Fz) scalp locations. Evidence for selective attention was manifest as the difference wave (Nd), which showed larger mean and peak amplitudes for the less difficult of two attention conditions. Nd was also shown to have an earlier peak latency at the Cz scalp location. However, there was no significant difference between the Depressed and Control groups as measured by the Nd wave. Significant differences were found between groups for the amplitude of the N1 peak of the ERP at the Fz scalp location. This suggests that the Depressed group differed in arousal level or sensory sensitivity from the Control group.

Personality characteristics and platelet MAO activity in women with congenital adrenal hyperplasia (CAH)

Personality traits and platelet monoamine oxidase (MAO) activity were studied in 22 women, 17-34 years old, with prenatal virilization due to congenital adrenal hyperplasia (CAH) (21-hydroxylase deficiency) and 22 healthy controls. The CAH group differed significantly on two of the eight scales of the Karolinska Scales of Personality (KSP), which have earlier shown significant gender differences. Both differences were in the masculine direction, with a high, male level, score for Detachment and a lower score for Indirect Aggression. The Detachment scale reflects distance in social relations, and has earlier been shown to be strongly gender differentiating. There was no significant difference in platelet MAO activity between the CAH group and the controls. Although an influence of psychosocial factors cannot be excluded, the results suggest a possible association between prenatal androgen exposure and the high Detachment score for the CAH group. Gender differences in empathy, affiliation motivation, intimacy and maternal behavior may be relevant parallels.

Increased central immunoreactive beta-endorphin content in patients with Wernicke-Korsakoff syndrome and in alcoholics

beta-endorphin, adrenocorticotrophin, and alpha-melanocyte stimulating hormone were measured by radioimmunoassay in three areas of human brain at necropsy in seven subjects with Wernicke-Korsakoff syndrome and in 52 controls. Thiamin concentration in six brain areas was also measured. Mamillary body beta-endorphin concentrations were significantly increased in those with the syndrome compared with controls, and those controls with high alcohol intake showed increased mamillary body beta-endorphin compared with controls with low alcohol intake. Brain thiamin concentration was similar in both groups, with the exception of the brainstem, where it was reduced in subjects with Wernicke-Korsakoff syndrome. Thalamic beta-endorphin in controls was inversely correlated with thiamin in frontal white matter, frontal cortex, parietal white matter and parietal cortex, while beta-endorphin in the hypothalamus of patients was inversely correlated with thiamin in frontal cortex, parietal white matter, thalamus and brainstem. These results suggest that there is a disturbance of the endorphinergic system in Wernicke-Korsakoff syndrome which may be related to alcohol intake.

Influences of peripheral adrenocorticotropin 1-39 (ACTH) and human corticotropin releasing hormone (h-CRH) on human auditory evoked potentials (AEP)

Hormones of the hypothalamus-pituitary-adrenal (HPA) axis have been considered to form part of an efferent humoral system modulating central nervous stimulus processing. The present experiments were designed to compare the effects of iv bolus administrations of placebo, porcine ACTH 1-39 (1.5 U) and h-CRH (25 micrograms) on auditory evoked potentials (AEPs) in healthy men. Also, cardiovascular parameters, cortisol and self-reported mood were assessed. ACTH significantly reduced the amplitude of the N1 component of the AEP; P1 and P2 remained unchanged. The selective reduction of N1 amplitude defies an interpretation of the changes in terms of a reduced stimulus-induced cortical arousal following ACTH; the ACTH-induced changes may rather indicate an influence on frontocortical functions of directing attention. The effect of ACTH on N1 cannot be attributed to its adrenocorticotropic action or to cardiovascular changes, but appears to represent an intrinsic extraadrenal influence of the hormone. The data do not provide evidence for effects of h-CRH on central nervous stimulus processing in humans, after peripheral administration.

ACTH 4-9 analog can retard spatial alternation learning in brain damaged and normal rats

Thirty adult male hooded rats (Long-Evans strain) were assigned randomly to one of three lesion groups (n = 10) and prepared with medial frontal, posterior parietal, or sham neocortical injuries. Following a recovery interval of 10-12 days, access to water was limited to 30 min per day and the rats were shaped to traverse a T-maze for a reward of sweetened water. After a pretraining criterion was attained, osmotic minipumps (Alzet 2002) were installed subcutaneously. The minipumps delivered chronically for the next 14 to 15 days either 0 or 1.2 micrograms of ACTH 4-9 dissolved in bacteriostatic saline per day while the rats were trained on a reinforced spatial alternation task. Analysis of the number of errors made to a criterion of at least 80% correct alternations in two consecutive training sessions, or a ceiling of 62 errors (attained by two rats with parietal lesions), revealed that learning was impaired in the rats with parietal injuries. Contrary to our hypothesis, animals receiving ACTH 4-9 committed more errors than their counterparts receiving only saline.

Fragments of ACTH affect electrophysiological signs of controlled stimulus processing in humans

It has been proposed that the systemic administration of the 4-10 fragment of ACTH in humans affects primarily attention. In the present study, influences of ACTH 4-10 on event-related potential (ERP) indicators of attention were evaluated in healthy men. The influences were compared with those of an analog of the ACTH 4-9 sequence (HOE 427) which was expected to have an increased potency. Following an adaptation session, each of 20 healthy men was tested on four occasions in a double-blind study designed according to a latin-square. On each occasion, subjects received (iv) one of the following treatments: placebo, ACTH 4-10 (1 mg), HOE 427 (60 micrograms) and HOE 427 (200 micrograms). Treatments were administered 40 min prior to recordings of ERPs. ERPs were recorded while the subjects performed on a dichotic listening task paradigm. The various tone pips presented in this task elicit ERPs providing measures of controlled stimulus processing (Nd reflecting selectivity of attention, and P3) and automatic processing of stimulus deviance (mismatch negativity). ACTH 4-10 as well as 200 micrograms HOE 427 reduced Nd and also P3 amplitudes following attended stimuli. Smaller (non-significant) changes in the same direction were observed following 60 micrograms HOE 427. The results suggest an impairing influence of ACTH 4-10 and of HOE 427 on signs of controlled stimulus processing, particularly on the Nd. The analog appeared to be more potent than the endogenous 4-10 fragment.

Electrodermal activity in relation to cortisol dysregulation in depressive patients

Electrodermal activity (EDA), basal morning plasma cortisol, outcome of the dexamethasone suppression test (DST), and nocturnal urinary cortisol excretion were studied in a somewhat confined number of originally 59 depressive patients and 59 matched healthy subjects. The patients showed nocturnal hypercortisolism. According to the DST, EDA and cortisol dysregulation were unrelated. In the total patient group, the correlations between EDA and cortisol in plasma and in urine were small and insignificant. However, in suicide attempters, in nonsuicidal patients, and in the healthy subjects, complex patterns of correlations were found between tonic electrodermal activity, electrodermal responsivity, basal morning plasma cortisol, and nocturnal urinary cortisol. Some inconsistencies in the patterns may be explained by differences in the sampling of data. Future research should try to delineate possible relationships between EDA and hormones on all levels of the hypothalamic-pituitary-adrenocortical axis.

The behaviorally active peptide ACTH 4-10: measurement in plasma and pharmacokinetics in man

A specific radioimmunoassay for the quantitative measurement of ACTH 4-10 and a procedure for its extraction from plasma have been developed. Its pharmacokinetics was studied in eight healthy male volunteers given ACTH 4-10 125 micrograms/kg body weight as a bolus i.v. injection, by infusion and intranasally. Following the i.v. bolus, plasma levels rapidly declined biexponentially, with half-lives of 0.39 +/- 0.05 min for the alpha-phase and 3.84 +/- 1.5 min for the beta-phase (mean +/- SD). The constant rate i.v. infusion yielded steady-state levels between 0.74 and 5.06 ng/ml plasma. Administered as intranasal spray, absorption of intact ACTH 4-10 was low and variable (maximal bioavailability 7.6%). The results are discussed in relation to the dose-dependent effects of ACTH 4-10 on the auditory evoked potential.

Dose-dependent influences on electrophysiological signs of attention in humans after neuropeptide ACTH 4-10

The afferent humoral system exerts significant influences on brain activity. Central nervous actions of the adrenocorticotropic hormone (ACTH) are most likely to be mediated by information coded in a portion of this hormone structure corresponding to ACTH 4-10. Our previous research suggested an impairing effect of ACTH 4-10 on electrophysiological signs of selective attention in humans. The present experiments in 12 male subjects investigated the influences of ACTH 4-10 on different aspects of attention as indicated by auditory event-related potential (AERP) components. Furthermore, dose-response characteristics of these influences should be examined. Attention performance was tested in a dichotic listening paradigm, after 0, 0.1, 1.0, and 10 mg ACTH 4-10, administered intravenously 1 h prior to testing according to a double-blind latin-square design. Different aspects of attention were measured by brain electrical responses evoked either by frequent standard or rare target tone pips, which the subject had to attend to, or to ignore. The selective type of attention was reflected by the Nd determined as mean difference in amplitude between AERPs to tone pips when attended and when unattended, for a latency range between 0-460 ms post-stimulus. In addition, plasma cortisol, heart rate, blood pressure, and behavioral performance were measured. Results indicated a clear reduction of the Nd amplitude after all doses of ACTH 4-10. Other indicators of attention mechanisms such as mismatch processing were not affected by the peptide. The diminished Nd after ACTH 4-10 was due to an increased processing of unattended stimuli, but simultaneously attended tones were processed less intensively.(ABSTRACT TRUNCATED AT 250 WORDS)