Psycho-physiologic correlates of MSH activity in man

Concepts for biologically active peptides

Here we review a unique aspect of CNS research on biologically active peptides that started against a background of prevalent dogmas but ended by exerting considerable influence on the field. During the course of refuting some doctrines, we introduced several concepts that were unconventional and paradigm-shifting at the time. We showed that (1) hypothalamic peptides can act 'up' on the brain as well as 'down' on the pituitary, (2) peripheral peptides can affect the brain, (3) peptides can cross the blood-brain barrier, (4) the actions of peptides can persist longer than their half-lives in blood, (5) perinatal administration of peptides can exert actions persisting into adulthood, (6) a single peptide can have more than one action, (7) dose-response relationships of peptides need not be linear, (8) the brain produces antiopiate as well as opiate peptides, (9) there is a selective high affinity endogenous peptide ligand for the mu-opiate receptor, (10) a peptide's name does not restrict its effects, and (11) astrocytes assume an active role in response to metabolic disturbance and hyperleptinemia. The evolving questions in our laboratories reflect the diligent effort of the neuropeptide community to identify the roles of peptides in the CNS. The next decade is expected to see greater progress in the following areas: (a) interactions of peptides with other molecules in the CNS; (b) peptide involvement in cell-cell interactions; and (c) peptides in neuropsychiatric, autoimmune, and neurodegenerative diseases. The development of peptidomics and gene silencing approaches will expedite the formation of many new concepts in a new era.

Immediate recovery of cognitive functions and resolution of fatigue by treatment with weak electromagnetic fields in a patient with multiple sclerosis

Cognitive deficits are common among patients with multiple sclerosis (MS). The pathogenetic mechanisms underlying the cognitive impairment in MS are unknown and there is presently no effective therapeutic modality which has shown efficacy in improving cognitive deficits in MS. A 53 year old college professor with a long history of secondary progressive MS experienced, over the preceding year, noticeable deterioration in cognitive functions with difficulties in short and long term memory, word finding in spontaneous speech, attention and concentration span. Unable to pursue his academic activities, he was considering early retirement. Mental examination disclosed features of subcortical and cortical dementia involving frontal lobe, left hemispheric and right hemispheric dysfunction. Almost immediately following the extracerebral application of AC pulsed electromagnetic fields (EMFs) of 7.5 picotesla intensity and a 4-Hz sinusoidal wave, the patient experienced a heightend sense of well being, which he defined as enhancement of cognitive functions with a feeling "like a cloud lifted off my head." He reported heightend clarity of thinking and during the application of EMFs he felt that words were formed faster and he experienced no difficulty finding the appropriate words. His speech was stronger and well modulated and he felt "energized" with resolution of his fatigue. There was improvement in manual dexterity and handwriting and testing of constructional praxis demonstrated improvement in visuospatial, visuoperceptive and visuomotor functions. It is suggested that some of the cognitive deficits associated with MS, which are caused by synaptic disruption of neurotransmitter functions, may be reversed through pulsed applications of picotesla range EMFs.

Reversal of alexia in multiple sclerosis by weak electromagnetic fields

The occurrence of cognitive deficits in patients with multiple sclerosis (MS) has been recognized since 1877 when Charcot first observed "enfeeblement of memory" in his patients. Cognitive deficits have been reported in almost 50% of patients with a relapsing-remitting course and in a significantly higher percentage of patients with a chronic progressive course leading to intellectual disability which is often severe enough to preclude employment. MS is considered a form of subcortical dementia and the occurrence of classical cortical disorders such as aphasia, agnosia and apraxia is reported to be rare in the disease. However, in my experience alexia, a reading impairment unrelated to visual acuity or visual field defects, is common in patients with MS. Recently, I reported that treatment with picotesla range electromagnetic fields (EMFs) is an efficacious modality in the management of both the motor and cognitive symptoms of MS. Three patients with MS who developed alexia as a manifestation of the disease are presented. In all patients the alexia was reversed several months after they began treatment with EMFs. Since alexia usually reflects a disconnection syndrome whereby lesions involving the left visual cortex and the splenium of the corpus callosum disconnect language association areas from visual association areas, it is suggested that reversal of the alexia in these patients by EMFs was related to improved interhemispheric transcallosal transmission of visual information. In addition, it is conceivable that changes in the metabolism of monoamines, which are involved in visual information processing and reading comprehension, may have been important in causing reversal of the alexia. This report further supports the unique efficacy of this treatment modality in reversing specific cognitive deficits in MS.

Multiple sclerosis: improvement of visuoperceptive functions by picoTesla range magnetic fields

The occurrence of cognitive deficits in multiple sclerosis (MS) has been recognized since 1877 when Charcot first observed "enfeeblement of memory" in his patients. Recent studies employing standardized neuropsychological tests have confirmed the high incidence of cognitive deficits in MS patients particularly those with a chronic progressive course of the disease. Visuoperceptive and visuomotor deficits commonly occur in MS patients and are thought to reflect damage to attentional systems due to interruption by demyelinating plaques of nerve conduction along the ascending projections from the brainstem reticular formation to the cortex. Impairment of synaptic conductivity due to serotoninergic depletion (5-HT) may contribute to the emergence of cognitive deficits in MS. The present communication concerns a 36 year old patient with MS in whom external application of picoTesla range magnetic fields (MF) resulted in rapid improvement of symptoms including visuoperceptive functions as demonstrated on various drawing tasks. The report confirms the efficacy of picoTesla range MF in the treatment of MS and demonstrates beneficial effects on cognitive functions as well.

Effect of chronic electrical stimulation of the centromedian thalamic nuclei on various intractable seizure patterns: II. Psychological performance and background EEG activity

We studied the effect of electrical stimulation of centromedian thalamic nuclei (ESCM) on seizure control and paroxysmal EEG activity in 23 patients. We report the effect of chronic ESCM on psychological performance and background EEG activity of patients with various intractable seizure patterns. In each patient, a simple specifically designed neuropsychological scales (one for adults and one for children) was administered at the end of the baseline (BL), ESCM, and poststimulation (Post) periods; and 14 consecutive EEG recordings during these periods were performed to determine the degree of neuropsychological improvement and the temporal course of EEG changes. A significant increase in psychological scores and the number of background EEG waves per 10 s was noted in groups A (generalized tonic-clonic seizures, GTC), C (complex partial seizures, CPS), and D (generalized tonic seizures) and the total group of patients from BL to ESCM and from BL to Post periods. Group B patients showed a substantial increase (partial motor seizures) during the same periods. Improvement on psychological performance correlated better with age and baseline degree of deterioration than with the nature of the particular psychological improvement in any given subtest. The improvement in EEG background rhythm was most noticeable at the end of ESCM and at the beginning of the Post periods. Complete normalization of neuropsychologic scores and EEG rhythms was rare, but improvement was significant for both. Psychological scores increased from BL 14 +/- 2 to ESCM 21 +/- 2 and Post 23 +/- 2 (normal expected 26), and EEG background rhythm increased from BL 42 +/- 2 to ESCM 62 +/- 2 and Post 54 +/- 2 EEG waves/10 s. (normal expected > 80).

Reversal of visual neglect in Parkinson's disease by treatment with picoTesla range magnetic fields

Visual neglect and impairment in perceptual motor or visuospatial tasks are among the most frequently encountered abnormalities in neuropsychological testing of patients with Parkinson's disease, being present in up to 90% of patients. It has been proposed that neglect reflects an attentional-arousal deficit induced by lesions that interrupt a cortical-limbic-reticular loop. Recently, we have reported that application of extracranial magnetic fields (MF) in the picoTesla range was efficacious in reducing the severity of the motor disability of Parkinsonism as well as improving some of the cognitive abnormalities associated with the disease such as visuoperceptive deficits. We now present a 61 year old fully medicated Parkinsonian patient in whom rapid reversal of left visual neglect as well as improvement in visuoconstructional (drawing) performance was noted immediately after a single external application of MF. We propose that this effect was related to enhancement of directed attention through a mechanism involving an interaction between the pineal gland, which is considered a "magnetosensor," and the reticular formation which mediates arousal and attention. This report demonstrates the efficacy of extremely weak MF in reversing some of the cognitive abnormalities in Parkinsonism, notably neglect and visuoperceptive deficits, which contribute significantly to impairment of the patient's daily living activities.

Rapid improvement of visuoperceptive functions by picoTesla range magnetic fields in patients with Parkinson's disease

Impairment in perceptual motor or visuospatial tasks is among the most frequently encountered abnormality in neuropsychological testing of patients with Parkinson's disease, being present in up to 90% of cases. Visuoperceptive deficits can result from cortical and subcortical lesions involving the right hemisphere, thalamus, and basal ganglia and are thought to reflect a defect in attentional-arousal mechanisms induced by lesions that interrupt a cortical-limbic-reticular activating loop. Clinically, the presence of visuoperceptive impairment may not be noted by Parkinsonian patients but may contribute to various disabilities including difficulty driving a vehicle and difficulties performing daily tasks which require intact visuospatial abilities (i.e., walking, dressing, drawing and copying designs). The present communication concerns two fully medicated Parkinsonian patients who responded to extracranial treatment with picoTesla range magnetic fields (MF), behaviorally and also demonstrated rapidly and dramatically enhanced visuoperceptive functions as demonstrated on various drawing tasks. These findings demonstrate the efficacy of extremely weak MF in enhancing cognitive functions in patients with Parkinson's disease.

Effects of central alpha-MSH injections on performance in a cued discrimination task

Alpha-MSH has been implicated in changing attention behavior following peripheral injections, but no brain sites were studied. In the present report, alpha-MSH was injected directly into specific sites in the medial anterior hypothalamic/preoptic area (MAHPOA) while measuring performance in a visually cued discrimination task. Alpha-MSH injections resulted in reduced errors, indicated by decreased responding during noncued intervals, but no change in responding to correct cues. The improved error rate was consistent with attentional changes in a variety of paradigms. Attentional and motivational parameters were differentiated. The injected alpha-MSH appears to act on an inhibitory component of an attentional mechanism.

Iris pigmentation and behavioral inhibition

Two independent investigations of the association between the temperamental dimensions of inhibition and lack of inhibition to the unfamiliar, on the one hand, and the degree of pigmentation of the iris, on the other, revealed a statistically significant relation in Caucasian children between behavioral inhibition to the unfamiliar and blue irises and uninhibited behavior and brown irises. Several biochemical interpretations of this association were discussed and it was suggested that these behavioral styles might be influenced by biological factors that are partially marked by eye color in Caucasian populations.

ACTH 4-9 effects on the human visual event-related potential

Three oral doses (5, 10 and 20 mg) of an analog of ACTH 4-9 were compared with a vehicle control and d-amphetamine (10 mg). In a double-blind procedure, five men and five women were tested at weekly intervals with each treatment. In each session, four visual event-related potentials (ERPs) were recorded at hourly intervals. Visual ERPs were averaged from the electroencephalogram recorded from the left and right hemisphere. Dosage, time after administration, hemisphere of the brain and sex of the subject influenced the ERP. The ACTH 4-9 analog decreased amplitude of P100 but increased integrated activity of the ERP. This effect peaked at 60 minutes then "recovered." The effects of the peptide were more pronounced with doses of 5 and 10 mg, in the right hemisphere of men and in the left hemisphere of women. The findings indicated that the ACTH 4-9 analog influenced components of ERP commonly related to the perceptual/attentional state of the organism in a sexually dimorphic manner.

An ACTH 4-9 analog impairs selective attention in man

Male adults were tested in a dichotic listening task, providing electrophysiological measures of selective attention. Subjects were tested twice, 60 min after oral administration of either 40 mg of ACTH 4-9 analog, or placebo. Averaged auditory evoked potentials (AEPs) to tone pips when attended and when unattended, EEG spectra, heart rate and blood pressure, and behavioral performance were measured during task performance. ACTH 4-9 analog treatment impaired selective attention as indicated a) by a diminished difference between evoked potential waveforms to attended and to unattended tone pips, b) by an impaired behavioral signal detection performance. Furthermore, frontal EEG theta activity slowed down after ACTH 4-9 analog. With time on task, however, there was no decay, but an improvement of selective attention after peptide administration. Differences in attention could not be due to concurrent changes in general cortical and autonomic arousal as indicated by EEG alpha activity, blood pressure and heart rate. Since separate analyses of the AEPs revealed an increased processing of the unattended tone pips in the ACTH 4-9 analog sessions the impaired selective attention under ACTH 4-9 analog may be described as an inability to suppress processing of irrelevant or distracting stimuli.

Effect of alpha-MSH 11-13 (lysine-proline-valine) on fever in the rabbit

In previous experiments, alpha-MSH (1-13) and ACTH (1-24), which contains the alpha-MSH 1-13 amino acid sequence, were found to reduce fever after central and peripheral administration of low, non-hypothermic doses. Shorter molecules, including alpha-MSH 1-10, had no effect. The idea that the 11-13 amino acid sequence is important to the effect of the parent molecule was tested by giving lysine-proline-valine both centrally and peripherally to rabbits made febrile by IV administration of leukocytic pyrogen. The tripeptide reduced fever after both central (0.5-2.0 mg) and peripheral (2-200 mg) administration. It appears that the 11-13 sequence is part of the message sequence of alpha-MSH with regard to antipyretic activity. However, the lower potency relative to that of the parent molecule suggests that other portions of the molecule are essential to full expression of the antipyretic effect.

ACTH 1-17 and short-term memory, anxiety, heart rate, blood pressure

The research investigated the effects of acute ACTH 1-17 administration on plasma cortisol, short-term memory, anxiety state, blood pressure and heart rate. In a double blind crossover design, healthy volunteers were serially evaluated at 5 min, 20 min, 40 min, 60 min after injection of ACTH 1-17 or placebo in separate sessions. Results show that ACTH 1-17 produced, in addition to an increase in plasma cortisol (5 min - 60 min), significant improvements in short-term memory (5 min), a reduction in anxiety (20 min and 40 min), and an increase in systolic (5 min and 20 min) and diastolic blood pressure (5 min). If confirmed by other studies, the short-term memory effect of ACTH 1-17 at 5 min after i.v. could suggest a central action of the peptide, and confirm the role of HPA axis as a modulator of performance and emotional arousal during acute environmental changes.

Misleading concepts in the field of brain peptides

Peptide research, like all of science, requires a careful balance between building upon previously accumulated knowledge and exploring perspectives that are in conflict with prevailing views. Many of the concepts discussed here originally stimulated certain lines of research. The downfall of most of these concepts, and thus their misleading nature, lies in the limitation of possible modes by which peptides are perceived to affect the functioning of the central nervous system (CNS).

Intracerebroventricular somatostatin attenuates electroconvulsive shock-induced amnesia in rats

In the present study the effect of intracerebroventricularly (ICV) administered somatostatin on electroconvulsive shock-(ECS) induced retrograde amnesia was investigated in rats. The ECS significantly decreased foot shock-induced avoidance latency. Somatostatin in a dose of 1 microgram/4 microliter (ICV) had no action on the ECS-induced retrograde amnesia, while in a dose of 4 micrograms/4 microliters it significantly increased the avoidance latency if the treatment was performed immediately, 4 hr, 20 hr or 23 hr after the ECS. The results suggest that ICV administered somatostatin has an antiamnesic effect.

alpha-MSH injected into the septal region reduces fever in rabbits

In previous research the concentration of alpha-MSH within the septal region of rabbits increased with fever. This finding raises the possibility that the septal concentration of this peptide, which reduces fever when given both peripherally and intracerebroventricularly, is important to limitation of fever. To test this idea, rabbits with cannulas in the septal region were made febrile by IV injections of leukocytic pyrogen (LP). Injection of alpha-MSH (1 microgram bilaterally) into the septal region did reduce fever, consistent with the idea that the increase in septal alpha-MSH concentration which occurs naturally in fever limits the febrile response. We also noted late rises in body temperature when experimental and control septal injections were given close together in time. These increases in temperature were similar to those known to occur after injections into the primary temperature control in the PO/AH region. This commonality further strengthens the possibility that septal neurons are important to central modulation of body temperature.

Alpha-melanocyte stimulating hormone facilitates learning of visual but not auditory discriminations

The neuropeptide alpha-MSH has been proposed to influence learning and memory by increasing visual attention. To test the possibility that MSH selectively affects visual learning, rats were tested in learning tasks in which the cues were either visual or auditory. Maze and bar-press tasks were used. MSH administration increased the rate of learning of the visual tasks, regardless of the task difficulty or the type of response required of the rat. MSH had no effect on the rate of learning of the auditory tasks. These results support the hypothesis that MSH facilitates learning by influencing some aspect of visual information processing.

Social and exploratory behaviour in the rat after septal administration of ORG 2766 and ACTH4-10

The time spent in active social interaction by pairs of male rats in a dimly-lit, familiar test arena, was decreased significantly after intraseptal injection of ACTH4-10 (250-500 ng). In contrast, the time spent in active social interaction was increased significantly after intraseptal injection of the tri-substituted ACTH4-9 analogue ORG 2766 (250-500 pg). Neither ACTH4-10 (250 ng) nor ORG 2766 (250 pg) affected exploration or locomotor activity measured in a holeboard, after intraseptal injection. Intraseptally administered ACTH4-10 (250 ng) increased aggression measured in a colony intruder model, but ORG 2766 (250 pg) was without effect.

Alpha-melanocyte-stimulating hormone and behavior

Melanocyte-stimulating hormone (MSH) has putative adaptive significance in all forms of species where it is present. In mammals the polypeptide chain influences learning, memory and attention. Chemically MSH shares the first 13 (alpha-MSH) or the first 18 or 22 (beta-MSH) amino acids with adrenocorticotropic hormone (ACTH), even though the mechanisms of secretion and behavioral effects are often quite different. The still shorter peptide chain MSH/ACH4-10 demonstrates significant melanotropic and behavioral actions of alpha-MSH without showing any steroidogenic effect. Behaviorally, alpha-MSH and MSH/ACTH analogues (MSH/ACTH4-9 and MSH/ACTH4-10 influence the parameters of learning, attention and memory in both human and infrahuman subjects. Alpha-MSH has also been reported to increase sensitivity and augment arousal mechanisms in the CNS. Alpha-MSH has been observed to increase and sustain novelty-induced defecation, and this behavior was found to be accompanied by a concomitant decrease in whole brain DA and NE levels in both intact and hypophysectomized rats exposed daily to a test box. The behavioral effects of alpha-MSH may be partially modulated by the enhanced cyclic-AMP activity in the CNS observed after MSH administration. MSH also seems to be working in conjunction with the hypothalamic tripeptide MIF-1 and the pineal hormone melatonin, both of which can affect the release of MSH from the pituitary. Recent evidence suggests that MSH is counterbalancing against and complementing with the effects of endorphins, specifically beta-endorphin (61-91 chain of beta-LPH), in maintaining learning and attentive behaviors.

Peripheral administration of alpha-MSH reduces fever in older and younger rabbits

In these experiments IV, ICV and intra-gastric administration of alpha-MSH reduced fever caused by injections of leukocytic pyrogen (LP). 2.5 micrograms alpha-MSH injected IV reduced fever caused by IV LP, more so in rabbits over 3 yrs old than in those under 2 yrs of age; 5 mg of acetaminophen given IV had no antipyretic effect in either age group. ICV administration of 25 ng alpha-MSH reduced fever caused by IV LP injection in the older but not in the younger rabbits, alpha-MSH given IV (2.5 micrograms) also lowered fever induced by ICV injection of LP in older but not in younger animals. Both older and younger rabbits showed reductions in fever evoked by IV LP after 2.5 mg alpha-MSH was given by gastric tube. The results indicate that this peptide which occurs naturally within the brain has potent antipyretic properties when given systemically, presumably as a result of a central antipyretic action. Greater sensitivity to central alpha-MSH in the older rabbits may account for the reduced febrile response seen in the aged. The findings support previous data which suggest that central alpha-MSH has a physiological role in the limitation of fever.

Central nervous system and peripheral effects of ACTH, MSH, and related neuropeptides

Adrenocorticotropic Hormone (ACTH), Melanocyte-Stimulating Hormone (MSH), and related peptides have been shown to have several neurogenic effects: alteration of cerebral protein synthesis, RNA synthesis, protein phosphorylation, and neurotransmitter turnover. Furthermore, there appears to be an ACTH containing circuit in the CNS which originates in the arcuate nucleus. Changes in concentration of the peptides in this family have been shown to alter electrophysiology, neuromuscular function, and behavior (e.g., grooming, learning) in infrahuman subjects. These findings suggest that the neuropeptides MSH and ACTH influence the capacity of an organism to efficiently evaluate information and influence the affective functioning of humans.

Analysis of behavioural responses to an ACTH analog in CXB/By recombinant inbred mice

Male mice of the C57BL/6By and BALB/cBy inbred strains, their reciprocal F1 hybrids, and 7 recombinant inbred strains, were tested for open-field activity, a shock-motivated successive reversal position discrimination problem in a T-maze, and a toggle box exploration task. The test battery was repeated one month later. Finally, mice were tested for the acquisition and extinction of a taste aversion conditioned by ethanol injection. Mice of each strain were tested after injection with saline or one of 3 doses of an ACTH analogue. Highly significant genotypic differences were found for all measures, an expected result. The strain distribution pattern seen in the toggle box suggested single gene mediation of exploratory activity after habituation. One aspect of avoidance responding and extinction of conditioned taste aversion also yielded strain distribution pattern consistent with single gene control. Peptide treatment reduced internal field crossings in the open field. This effect was not strain dependent. Peptide treatment had no effect on T-maze learning, conditioned taste aversion, or toggle-box exploration.

Inverse relationship between onset and duration of EEG effects of six peripherally administered peptides

Electrical activity in the rat brain after the peripheral injection of equimolar (0.1 mM) doses of Metenkephalin, Leu-enkephalin, beta-endorphin, gamma-endorphin, DSIP, and alpha-MSH was assessed by power spectral analysis. The mean onset of EEG activity for each peptide varied between 13.7 and 20.7 minutes and lasted between 27.8 and 40.8 minutes. The significant (p less than 0.001) interaction between duration and latency revealed that the longer the latency, the shorter the duration. Similar findings were observed after injection of the same peptides at a fixed dose of 80 microgram/kg body weight. Thus, the results demonstrate that peripherally injected peptides can exert EEG effects that last longer the sooner they start.

Cyclic AMP in female mouse brain is altered by the adrenocorticotropic hormone(4-9) analogue organon 2766

Cyclic AMP content was determined in 12 brain regions of young adult female mice at 30 min and at 24 h following an intraperitoneal injection of the tri-substituted adrenocorticotropic hormone(4-9) [ACTH(4-9)] analogue Organon 2766 [ORG 2766]. Animals were killed by focused 3.5 kW microwave radiation applied for 350 ms. Unlike previously reported responses in male mice, at 30 min post-injection there were no detectable differences in cyclic AMP content between the placebo and ORG 2766-treated animals. By contrast, 24 h after injection, the content of cyclic AMP was changed significantly in 8 of the 12 brain regions examined: medulla-pons, septal area, thalamus, hypothalamus, hippocampus, olfactory bulb, and parietal and occipital cortices. In most of the regions examined, differences consisted of 50% or greater reductions of tissue cyclic AMP content. The changes were unrelated to the estrus cycle of these animals.

Differential effects of neuropeptides on short-term memory in primates

In a within-subject design, six rhesus monkeys (3 males and 3 females) received a 100 micrograms/kg injection of one of seven neuropeptides or a diluent control solution and were then tested for activity level, learning (discrimination reversal), short-term memory (delayed response), and for responsiveness to noxious stimuli. One daily injection was made with a different peptide for 10 consecutive days, including pre- and post tests on th first and last days with the diluent control. DSIP and D-Phe4-Met enkephalin seemed to produce some interference with short-term memory, while alpha-MSH showed some facilitation of it, as indicated by interactions of the peptides with the delay periods of 0, 15, or 30 sec. Sex differences were found in the learning task and the responsiveness to a noxious stimulus, suggesting the possibility of interactions between the peptides and endogenous hormones.

A neuroheptapeptide influence on cognitive functioning in the elderly

The heptapeptide core common to melanocyte-stimulating hormone (MSH) and adrenocorticotropin (ACTH) was administered as a single subcutaneous dose of 30 mg to 13 elderly human subjects (9 men, 4 women) in a double-blind, cross-over design. Significant improvement was found in the Benton Visual Retention Test after MSH/ACTH 4--10 as compared with administration of saline. This appeared to be greater in men than women. No side effects or laboratory abnormalities were observed. The behavioral results are consistent with our earlier findings in men and rats of improved visual attention after administration of MSH and extend them to the elderly population.

Effects of ACTH4-10 on synaptic transmission in frog sympathetic ganglion

The influence of ACTH4-10, a behaviourally active fragment of adrenocorticotropic hormone (ACTH) devoid of endocrine activity, on synaptic transmission in the paravertebral sympathetic ganglion of the frog was investigated. Postsynaptic potentials evoked by electrical stimulation of pregnanglionic nerves were recorded using a sucrose gap method. Fast excitatory postsynaptic potentials (EPSPs), which are mediated via nicotinic cholinergic synapses, were not affected by 10(-6) M ACTH4-10. Application of ACTH4-10 in a concentration as low as 10(-8) M for 60 min caused a marked augmentation of the amplitude of slow inhibitory postsynaptic potentials (IPSPs) which are mediated via dopaminergic synapses. The increase in amplitude developed gradually after a latency of 60--90 min and outlasted the application of the peptide. In addition, ACTH4-10 at 10(-6) M increased the hyperpolarising response of the ganglion to exogenous dopamine, as studied by a micro-application method. There was no significant effect of ACTH4-10 on the muscarinic cholinergic depolarising response of the ganglion towards exogenous acetylcholine. The behaviourally active vasopressin fragment DG-LVP (10(-6) M) had no effect on slow IPSPs. The results demonstrate that ACTH4-10 specifically affects slow synaptic inhibition in frog sympathetic ganglion, probably by acting upon the postsynaptic membrane. The possibility is discussed that ACTH4-10 affects one of the intermediate steps between dopaminergic receptor interaction and generation of the slow IPSP.

ACTH 4-10 in the amelioration of neuropsychological symptomatology associated with senile organic brain syndrome

Eighteen male and female volunteers over the age of sixty who exhibited mild senile organic brain syndrome were administered ACTH 4-10 (Org OI 63) (30 mg, s.c.) or saline in a 2 X 2 Latin square design. Subjects experienced a reduction in depression and confusion and an increase in vigor. This evidence of an increase in vigor was supported behaviorally by a delay in the onset of increased latency in reaction time. Data also indicated that retrieval from memory may be enhanced by this compound. The electroencephalogram evinced a shift to lower frequencies under ACTH 4-10, but this effect was primarily noted in the females who received drug followed by placebo. These effects of ACTH 4-10 are intriguing and suggest that further work in this area should be encouraged.

Disapearance and excretion of labeled alpha-MSH in man

Despite the considerable evidence for the CNS actions of alpha-melanocyte-stimulating hormone (alpha-MSH) in man, little attention has been given to its half-time disappearance from plasma and urinary excretion in normal individuals. In the first experiment, a healthy man was given 15 muCi of tritiated (3H)-alpha-MSH as a rapid IV injection. A plot of the disappearance time in plasma was characteristic of a multiexponential curve, the linear components of which were resolved by the subtraction method and half-time disappearance calculated directly from the slope of the regression line. The half-time disappearance was 1 min for the first component and 25 min for the second component. After the IV adminisration of 50 muCi of 125I-alpha-MSH in the second experiment, the two components showed halftime disappearances of 1 min and 4.8 min respectively. These times were not changed by precipitation of the plasma with 10% trichloroacetic acid. Thirty-eight percent and 42% of the label appeared in the urine 4 hr after the injection of either 3H-alpha-MSH or 125I-alpha-MSH. The results suggest that the persistence of high levels of alpha-MSH in the blood after injection in man may be too short to fully explain the CNS effects of alpha-MSH.