Effects of lysine-vasopressin and 1-deamino-8-D-arginine-vasopressin on memory in healthy individuals and diabetes insipidus patients

Potential clinical applications of current and future oral forms of desmopressin (Review)

Desmopressin is a synthetic analogue of vasopressin and a selective vasopressin receptor 2 agonist. It was first synthesised in 1967 and utilised for its antidiuretic properties. It is also used in bleeding disorders to enhance clotting. Other potential uses of the drug have been reported. The present review aims to provide a broad overview of the literature on potential further uses of oral forms of desmopressin. Key therapeutic areas of interest were identified based on known physiological activities/targets of desmopressin or reports of an effect of desmopressin in the literature. The feasibility of adequate dosing with oral forms of the drug was also considered. Systematic literature searches were carried out using the silvi.ai software for the identified areas, and summaries of available papers were included in tables and discussed. The results of the searches showed that desmopressin has been investigated for its efficacy in a number of areas, including bleeding control, renal colic, the central nervous system and oncology. Evidence suggests that oral desmopressin may have the potential to be of clinical benefit for renal colic and bleeding control in particular. However, further research is needed to clarify its effect in these areas, including randomised controlled studies and studies specifically of oral formulations (and doses). Further research may also yield findings for cancer, cognition and overactive bladder.

Leveraging a translational research approach to drive diagnostic and treatment advances for autism

Autism spectrum disorder (ASD) is a prevalent and poorly understood neurodevelopmental disorder. There are currently no laboratory-based diagnostic tests to detect ASD, nor are there any disease-modifying medications that effectively treat ASD's core behavioral symptoms. Scientific progress has been impeded, in part, by overreliance on model organisms that fundamentally lack the sophisticated social and cognitive abilities essential for modeling ASD. We therefore saw significant value in studying naturally low-social rhesus monkeys to model human social impairment, taking advantage of a large outdoor-housed colony for behavioral screening and biomarker identification. Careful development and validation of our animal model, combined with a strong commitment to evaluating the translational utility of our preclinical findings directly in patients with ASD, yielded a robust neurochemical marker (cerebrospinal fluid vasopressin concentration) of trans-primate social impairment and a first-in-class medication (intranasal vasopressin) shown in a small phase 2a pilot trial to improve social abilities in children with ASD. This translational research approach stands to advance our understanding of ASD in a manner not readily achievable with existing animal models, and can be adapted to investigate a variety of other human brain disorders which currently lack valid preclinical options, thereby streamlining translation and amplifying clinical impact more broadly.

A randomized placebo-controlled pilot trial shows that intranasal vasopressin improves social deficits in children with autism

The social impairments of autism spectrum disorder (ASD) have a major impact on quality of life, yet there are no medications that effectively treat these core social behavior deficits. Preclinical research suggests that arginine vasopressin (AVP), a neuropeptide involved in promoting mammalian social behaviors, may be a possible treatment for ASD. Using a double-blind, randomized, placebo-controlled, parallel study design, we tested the efficacy and tolerability of a 4-week intranasal AVP daily treatment in 30 children with ASD. AVP-treated participants aged 6 to 9.5 years received the maximum daily target dose of 24 International Units (IU); participants aged 9.6 to 12.9 years received the maximum daily target dose of 32 IU. Intranasal AVP treatment compared to placebo enhanced social abilities as assessed by change from baseline in this phase 2 trial's primary outcome measure, the Social Responsiveness Scale, 2nd Edition total score (SRS-2 T score; F _1,20 = 9.853; P = 0.0052; η_p ² = 33.0%; Cohen's d = 1.40). AVP treatment also diminished anxiety symptoms and some repetitive behaviors. Most of these findings were more pronounced when we accounted for pretreatment AVP concentrations in blood. AVP was well tolerated with minimal side effects. No AVP-treated participants dropped out of the trial, and there were no differences in the rate of adverse events reported between treatment conditions. Last, no changes from baseline were observed in vital signs, electrocardiogram tracings, height and body weight, or clinical chemistry measurements after 4 weeks of AVP treatment. These preliminary findings suggest that AVP has potential for treating social impairments in children with ASD.

Alcohol-induced changes in methylation status of individual CpG sites, and serum levels of vasopressin and atrial natriuretic peptide in alcohol-dependent patients during detoxification treatment

Disturbances of volume-regulating peptides like vasopressin (AVP) and atrial natriuretic peptide (ANP) have been described in early abstinent alcohol-dependent patients. In a longitudinal approach, we investigated whether changes in AVP and ANP serum levels correlated to cytosine-phosphatidyl-guanine (CpG) methylation of the respective gene promoters on days 1, 7 and 14 of alcohol withdrawal. We analyzed the blood samples of 99 patients suffering from alcohol dependence alongside age- and BMI-matched controls. Concerning AVP promoter methylation, we observed an interaction between time of measurement and CpG loci with CpG 2 showing a significant increase in methylation from day 1 to 14. Serum levels of AVP were significantly decreased in the patient group. Compared to healthy controls, promoter-related DNA methylation of the ANP promoter was significantly reduced on days 7 and 14. Moreover, we detected a significant interaction between CpG position and group. In both cases the difference was mainly observed at CpG 1. The present study shows significant changes in the methylation status of individual CpG sites of AVP and ANP. Observing respective alterations of AVP serum protein levels in alcohol-dependent patients during detoxification treatment, we consider methylation as a possible mode of regulation for these proteins during alcohol detoxification.

Epigenetic regulation and gene expression of vasopressin and atrial natriuretic peptide in alcohol withdrawal

Disturbances of volume regulating peptides like vasopressin and atrial natriuretic peptide (ANP) have been described in early abstinent patients. Aim of the present study was to evaluate possible alterations of the promoter-related DNA methylation of the ANP and vasopressin precursor genes and the related mRNA-expression of these genes in early alcohol withdrawal. We analyzed blood samples of 57 healthy controls and of 111 patients suffering from alcohol dependence that were admitted for detoxification treatment. Promoter-related DNA methylation and mRNA-expression of vasopressin and ANP genes were assessed using real-time PCR. Vasopressin mRNA-expression was not statistically different between patients and controls. However, we found a significantly elevated promoter-related DNA methylation of the vasopressin gene in patients with alcohol dependence (Mann-Whitney U-test: Z=-2.178, p=0.029). ANP mRNA-expression was significantly elevated in alcoholic patients (Z=-6.240, p<0.001) while promoter-related DNA methylation of ANP was significantly decreased (Z=-2.282, p=0.023). Furthermore, promoter-related DNA methylation of ANP was significantly correlated to the extent of craving measured with the OCDS (r=-0.197, p=0.040). The findings of the present study show significant alterations of the mRNA-expression and promoter-related DNA methylation of vasopressin and especially ANP precursor genes in patients with alcohol dependence. Further studies focusing on longitudinal changes of epigenetic regulation and gene expression of both peptides are needed to clarify the pathophysiological role of these findings.

Effects of desmopressin (DDAVP) on memory impairment following electroconvulsive therapy (ECT)

BACKGROUND

Memory impairment is a common adverse effect of electroconvulsive therapy (ECT). Studies on animals and humans suggest that vasopressin improves the cognitive function, and positive effects of desmopressin on memory and learning have been reported. This research was performed for evaluation of the effects of desmopressin in the prevention of memory impairment following ECT.

METHODS

This randomized, double-blind controlled clinical trial with placebo administration was performed on 50 patients with psychiatric disorders who were candidates for ECT. Subjects in the case group received 60 µm of intranasal desmopressin daily (in three doses of 20 µm). For the control group 0.9% saline solution was administered in the same way. Memory function was evaluated using Wechsler's Memory Scale three times a week (the first time before the start of ECT and the second and third times after the third and sixth sessions, respectively). Results were analyzed by t-test and Paired t-test.

RESULTS

The mean age of patients was 29 years (range 20-40). During the course of ECT, patients in the control group demonstrated a meaningful decrease in memory scores (from a base score of 80.15-75.45 in the second test and 72.60 in the third test). Despite this, a meaningful increase in memory scores was observed during the treatment with desmopressin in the case group (from a base score of 73.27-75.70 and 79.13 in the second and the third tests, respectively). There was a meaningful difference between the two groups (P < 0.0001).

CONCLUSION

This study confirms the protective effect of desmopressin against memory impairment. The results confirm that memory impairment is a common side-effect of ECT and suggest that desmopressin may prevent ECT-induced memory impairment by its effects on memory and the learning process.

Neuropsychological effects of vasopressin in healthy humans

Animal research indicated that vasopressin (VP) exerts its principle behavioral influence, the improvement of memory formation, through an action on septo-hippocampal and connected limbic structures. Here human research is reviewed with the notion of a comparable effect of VP in healthy humans. Although the human studies yielded less consistent results than those in rats, they indicate that VP is able to improve declarative memory formation which is the type of memory essentially relying on hippocampal function. The effect appears to center on the encoding process for memory. In examinations of event-related brain potentials (ERPs) VP was consistently found to increase the 'mismatch negativity' (MMN) and the P3 components which are ERP potentials closely linked to the hippocampal processing of novel, unexpected and salient events. Enhanced processing of these stimulus aspects is considered to precipitate memory encoding. The regulation of voluntary selective attention and arousal do not appear to be primary targets of VP effects in humans. A mediation of effects by peripheral changes can be excluded since the central nervous effects were observed in studies using intranasal VP administration providing a direct access to brain functions.

Effect of acute and chronic treatment with desglycinamide-[Arg8]vasopressin in young male and female volunteers

A single dose of DGAVP (2 mg) and a chronic treatment of 2 weeks (1 mg/day) were given to male and female volunteers by the intranasal route. Memory, mood, vigilance, and attention were tested starting 60 min after treatment. Initial storage of abstract words was improved in the males but not in the females after chronic treatment with DGAVP. This effect persisted after discontinuation of treatment. Initial storage and learning of concrete words were not affected by treatment with DGAVP. Chronic, but not acute, treatment with DGAVP reduced the reaction time for scanning of digits in a memory comparison task (Sternberg paradigm) in both sexes. No treatment effects were found for visual memory, vigilance, attention, mood, or blood pressure. The present study indicates a sexual dimorphism in the effect of DGAVP on certain memory processes.

Effect of a single dose of des-glycinamide-[Arg8]vasopressin or oxytocin on cognitive processes in young healthy subjects

A single dose of des-glycinamide-[Arg8]vasopressin (DGAVP, 2 mg intranasal) or oxytocin (OXT, 20 IU intranasal) was given to female and male volunteers, respectively, in a placebo-controlled double-blind trial. Memory, vigilance, attention, and mood were tested starting 10 minutes after treatment. The DGAVP dose improved delayed recognition of abstract words when measured 1 week after treatment and reduced the intercept of a memory comparison task (Sternberg paradigm). A trend was present for DGAVP and OXT to affect learning, i.e., storage processes of verbal memory in an opposite way; DGAVP improved, while OXT attenuated initial storage and the rate of storage. No treatment effects on visual memory and vigilance were found. Of the mood measures, vigor was reduced immediately after treatment with OXT.

Behavioral effects of neurohypophyseal peptides in healthy volunteers: 10 years of research

A short summary of behavioral studies on the effects of vasopressin and oxytocin published during the past decade is provided. Only studies using healthy volunteers as subjects were included. Among the studies reviewed, large differences exist with respect to design, procedure, treatment schedule and dose used. Results from the majority of the studies support that vasopressin and oxytocin affect central nervous functions in man after systemic administration. Since the hormonal influences do not appear to be consistently restricted to certain stages of stimulus processing but nonspecifically concern a great variety of cognitive functions, it is suggested that the influence of hypophyseal peptides on stimulus processing is mediated through an action on basic mechanisms involved in the general regulation of central nervous activation, i.e., on arousal systems that could also alter affective aspects of stimulus processing. The altogether moderate number of studies, so far, does not provide a sufficient data base justifying a clinical application of these peptides as nootropic treatments.

Vasopressin and cognitive processes: two event-related potential studies

Two experiments studied the influence of arginine-vasopressin (AVP) on cognitive processes by means of an electrophysiological measure, the late positive complex (LPC) of the event-related potential. The LPC varies systematically with cognitive processes. The classical oddball paradigm and an incidental memory task (structural encoding of emotional adjectives) were used. The two studies differed only in the dose of AVP (study 1: three time nasal application of 10 IU AVP; study 2: 20 IU). In study 1, AVP intake enhanced memory performance. The LPC elicited by oddball stimuli was not influenced by AVP, neither when compared before and after intake nor when compared to placebo treatment. However, specific influences of AVP on the LPC elicited during the structural encoding task were observed. In both studies, AVP intake resulted in a marked change of the scalp distribution of the P3 component, which is a prominent part of the LPC. Furthermore, subjects treated with the lower dose of AVP showed a more positive P3 component on emotional (negative and positive) adjectives, when compared to neutral ones. The results suggest that vasopressin influences the central nervous processing of the emotional content of stimuli.

Effects of vasopressin on the habituation of the orienting reaction in men

Effects of arginine-vasopressin (AVP) on the habituation of the orienting reaction and response to stimulus mismatch were investigated in a between-group design with 40 healthy male volunteers using skin conductance and heart rate responses as dependent measures. Twenty-one 1000 Hz tones of 90 dB(A) intensity and 2 s duration were presented with alternating intervals of 20 and 140 s. Stimulus mismatch responses were analyzed to the tones after the long intervals and to a change of the interval duration. The expected prevention of habituation as an indicator of a general stimulus-related increase of phasic arousal under AVP could not be confirmed. There were no differences between the AVP and the placebo group in the skin conductance and heart rate responses. The interval change did not provoke a dishabituation reaction, but responses to the tones after the long intervals were reliably enhanced. However, AVP did not increase the reaction to stimulus mismatch. It is concluded that autonomic indicators of the habituation of the OR remain unaffected by AVP.

Effects of DDAVP on movement planning and execution processes in the healthy elderly

Effects of DDAVP on speed and consistency of planning and executing simple and complex movements in healthy older adults were studied. A simple reaction time (SRT) task, a single-plane movement task, and two tasks involving multiplane movements of distal upper extremities were performed with and/or without a 0.6 ml intranasal dose (60 micrograms) of DDAVP or placebo. Results indicated that DDAVP had no significant effect on speed or consistency of SRT processes, or the speed with which simple or complex movements were planned or executed. There was also no effect on retention of motor responses.

Effects of DDAVP on movement planning and execution processes in healthy young adults

This study investigated the effects of an acute dose of DDAVP on speed and consistency of planning and execution of simple and complex movements in healthy young adults. A simple reaction time task (SRT), a simple movement task (SMT), and a complex movement task (CMT) were performed with and without a 0.6 ml intranasal dose (60 micrograms) of DDAVP. Results indicated DDAVP-treated individuals planned and executed CMT and SRT tasks faster and more consistently than did placebo-treated subjects. There were nonsignificant DDAVP effects on speed and variability of both RT and MT processes involved in the SMT.

Effects of DGAVP on verbal memory

Effects of DGAVP (desglycinamide-arginine-vasopressin, a synthetic vasopressin analog) on verbal memory were investigated in 13 healthy male volunteers. Ten word lists, each consisting of 15 words, were presented to the subjects who had to recall them according to a free recall paradigm. The total number of recalled words was not different between DGAVP and placebo treatment; but DGAVP had an effect on memory performance depending on the serial position of the words. It attenuated the primacy effect and enhanced the recency effect of memory performance. The pattern of changes after DGAVP may be consistent with an effect of the peptide on general arousal. Since the experiment was not designed to test influences of DGAVP on arousal, these considerations remain tentative.

Vasopressin and vasopressin analogues for treatment of memory disorders in clinical practice

1. Beyond its antidiuretic and vasopressor effects, vasopressin has central nervous system effects, first described in rats by David de Wied in 1965. 2. Its first clinical use in humans, in 1978, confirmed its stimulant action in normal individuals, especially in middle-aged male subjects. 3. Its utility in mnemic problems is also worht considering when the pathology is relatively recent (less than 2 years prior) and unaccompanied by major neurological lesions. Behavioral modifications, such as improvement of "sociability", "mood" improvement, independent of its effects on memory have been described, and would justify complementary clinical investigation. 4. New synthetic vasopressin derivatives which would eliminate metabolic effects while maintaining behavioral effects intact, and the definition of clinical, neuroendocrine, and neurophysiological prognostic criteria, will be the two most important paths for investigation over the next years.

Inhibitory influence of oxytocin infusion on contingent negative variation and some memory tasks in normal men

A double-blind study combining electrophysiological and psychometrical approaches was carried out to investigate the central effects of an intravenous oxytocin (OT) infusion in normal men. Contingent negative variation (CNV) was selected as the measure of central cognitive evoked potential, and the psychometric tests measured mood, vigilance and memory. OT infusion induced a significant decrease of CNV amplitude and an increase of post-imperative positive potentials in vertex derivations. A similar effect was still evidenced one week after treatment in frontal derivations, suggesting a long time effect of OT on human brain. No significant influence of OT on mood or vigilance tests was apparent; only one item of a memory test revealed a significant impairment of some mnesic performances. These observations provide new electrophysiological arguments supporting a central action of peripheral OT administration in man.

Vasopressin and memory: improvement in normal short-term recall and reduction of alcohol-induced amnesia

The vasopressin analogue 1-desamino-8-D-arginine vasopressin (DDAVP) has been shown in healthy male volunteers to cause significant improvement in short-term memory and to reduce alcohol-induced amnesia. There was no significant effect upon semantic retrieval or simple reaction time. It was concluded that vasopressin benefited the initial processes of consolidation and learning, while the reduction of the amnesic effects of alcohol may support the contentions of other authors that the peptide improves memory in states of mild amnesia.

Time-related memory effects of vasopressin analogues in rats

The present study was designed to investigate critical time periods for the memory modulating effect of vasopressin and several analogues in rats using a passive avoidance test as the behavioral paradigm. AVP, AVP-(4-8) and AVP-(5-8) were more effective when given immediately after the learning trial (consolidation), while AVP-(1-8) (DGAVP) and AVP-(5-9) were more active when administered one hour prior to the retention test (retrieval). DDAVP and AVP-(4-9) were highly active both when given immediately after the learning trial or 1 hour before the retention test. The period between 12 and 18 hr after the learning trial appeared to be another sensitive period. Administration, in particular of DGAVP, and AVP-(5-9) at 12, 15, and 18 hr after the learning trial induced marked retention of the avoidance response at the 24 hr retention test. Injection at 6 and 21 hr after the learning trial was the least effective in facilitating passive avoidance latencies. The more stable analogue DDAVP facilitated avoidance latencies irrespective of the time of administration. Vasopressin and related peptides exert a long term effect on avoidance behavior. However, DGAVP and AVP-(5-9) facilitated passive avoidance behavior at the 24, 48, and 72 hr retention test if administered immediately after the learning trial. If injection was postponed till 15 hr after the learning trial, passive avoidance behavior was facilitated at the 24 hr retention test only.(ABSTRACT TRUNCATED AT 250 WORDS)

Porphyrin synthesis in primary nervous tissue cultures from 10(-3) M delta-aminolaevulinic acid in the presence of melatonin and neuropeptides

Of the primary neuronal tissue cultures (glia cell, neuronal cells, mixed and retina cultures), the neuronal cells of (cells + medium) display the highest total porphyrin production from 10(-3) M delta-aminolaevulinic acid (ALA). In the presence of 10(-3)-10(-6) M melatonin, the quantity of total porphyrins produced by the neuronal cultures decreases in inverse proportion to the concentration. Oxytocin, lysine-vasopressin, CCK-8 sulphate ester and des-Tyr-gamma-endorphin in concentrations of 10(-5) and 10(-6) M block the porphyrin synthesis of the glia cells and display different effects on that of the neuronal cells. They enhance the total porphyrin synthesis of the cell cultures, with the exception of 10(-5) M des-Tyr-gamma-endorphin, which exerts an inhibitory effect on the glia cells.

No improvement in ethanol-induced memory deficits after administration of a vasopressin analog

Acute ingestion of ethanol impairs memory, an effect which might be related to ethanol-induced inhibition of vasopressin release. This was studied using tests of memory and cognitive function in 26 normal subjects before and after ethanol ingestion. Equal numbers of subjects received randomly, by double-blind intranasal administration, placebo or 1-desamino-8-D-arginine vasopressin prior to ethanol ingestion. Administration of the vasopressin analog did not reverse the ethanol-induced deficits in memory and cognitive function.

A mnemonic role for vasopressin: the evidence for and against

This review critically evaluates the animal and human research concerning vasopressin's putative mnemonic role. Weaknesses in the interpretations of the early animal experiments as well as the implications of the later inconsistent findings are discussed. It is concluded that both the initial enthusiasm and the subsequent skepticism concerning this hypothesized role were premature. This conclusion applies equally to the human research. A review of these studies reveals that almost all of the negative reports involved cognitively-impaired individuals. The relatively few studies that have been conducted concerning vasopressin's effects in unimpaired human subjects are consistent with the hypothesis that vasopressin does affect cognition, though both the mechanism of action and the specific cognitive processes which are altered have yet to be elucidated.

Vasopressin and vasotocin facilitate reversal of a brightness discrimination

Male albino rats received vasopressin, vasotocin, pressinoic acid or placebo and were tested on an aversively motivated brightness discrimination task. Treatment with both vasopressin and vasotocin had no effect on acquisition but facilitated the reversal of the discrimination. Pressinoic acid had an inconsistent effect. The results are interpreted to show that the C terminal of the peptides vasopressin and vasotocin influence potency of these peptides. Furthermore, the results are interpreted as showing that both vasotocin and vasopressin influence selective attention during aversively motivated tasks.

Hypothalamic neuropeptides and memory

Vasopressin and oxytocin exert pronounced effects on behavior by a direct action on the brain. A single injection of vasopressin results in a long-term inhibition of extinction of a conditioned avoidance response suggesting that vasopressin triggers a long-term effect on the maintenance of a learned response, probably by facilitation of memory processes. In addition vasopressin improves passive avoidance behavior, facilitates retention of sexually motivated T-maze choice behavior in male rats, delays extinction of an appetitive discrimination task, affects approach behavior to an imprinting stimulus in ducklings, delays the postcastration decline in copulatory behavior in male rats, prevents or reverses amnesia induced by electroconvulsive shock, CO2 inhalation, pentylenetetrazol or puromycin. The majority of these effects may be explained by stimulatory influences of vasopressin on memory processes. Generally oxytocin exerts effects which are opposite to those of vasopressin and it has been suggested that oxytocin may be an amnesic neuropeptide. Evidence has been obtained that endogenous vasopressin and oxytocin play a physiological role in brain processes related to memory. Various limbic system structures seem to act as the anatomical substrate for the behavioral effects of vasopressin and different neurotransmitter systems seem to be involved. It is postulated that in case vasopressin affects retrieval processes the site of action is located in the amygdala and the dentate gyrus of the hippocampal complex with dopamine and serotonin as the respective neurotransmitter systems involved.(ABSTRACT TRUNCATED AT 250 WORDS)

Vasopressin does not enhance memory processes: a study in human twins

Behavioral effects of lysin-vasopressin (LVP) were investigated applying two paradigms from human experimental psychology. The first task was designed to simulate amnesic symptoms in normals. The second task addressed the emotional value of the items to be processed. Additionally, EEG recordings were used as indicators of the central nervous system effectiveness of LVP. Blood pressure and heart rate measured peripheral arousal. The co-twin control method was employed to increase experimental power. Contrary to the prediction of the vasopressin memory hypothesis none of the specific memory parameters was improved by LVP treatment. Changes in the electrical activity of the brain, but not in blood pressure and heart rate indicated central nervous system actions of LVP. However, interpretation of LVP effects in terms of memory processing seems not to be justified.

Vasopressin: site of behavioral action and role in human mental performance

Diminishment of endogenous vasopressin in various brain areas (dorsal and ventral hippocampus, dorsal septum) by local application of diluted anti-vasopressin serum results in attenuation of passive avoidance behavior of rats. Both post-learning or pre-retention treatment results in impaired behavior when the anti-vasopressin serum was applied in the dorsal or ventral hippocampus, whereas only pre-retention but not post-learning application of the antiserum in the dorsal septum induced behavioral impairment. Only injection of less diluted antiserum into the lateral ventricle results in attenuation of passive avoidance behavior. These results suggest that endogenous vasopressin present in these brain sites plays a functional role in brain processes related to memory and in particular in processes involved in storage and/or retrieval of information. These findings are discussed and compared with observations of vasopressin treatment on memory functions in man. The observation that some patients with memory disorders do not respond to vasopressin treatment may be due to lesions in the anatomical sites of action of vasopressin.

Vasopressin impairs or enhances retention of learned submissive behavior in mice depending on the time of application

The effects of vasopressin on learning and memory were investigated in a paradigm using adaptive capabilities of interacting male mice. Test animals of the DBA/2 strain which were not submissive in a confrontation with a non-aggressive subordinate C57BL/6 mouse on day 1 (baseline), were defeated on day 2 (learning) by an aggressive dominant C57 mouse, and showed learned submissive behavior upon mere contact with a non-aggressive C57 mouse on day 3 (retest). Pretrial injections of lysine-vasopressin (0.01, 0.1 or 1.0 I.U., s.c.) 20 min before defeat on day 2 resulted in less submissive behavior on day 3 compared to controls, with 0.1 I.U. (equal to 370 ng) being the most effective dose. Post-trial injections of vasopressin (0.1 I.U.) immediately after defeat on day 2 significantly improved retention on day 3. Preretention injections of vasopressin (0.1 I.U.) 20 min before testing on day 3 significantly increased learned submissive behavior. The amnesic effect observed after pretrial injections of vasopressin was neither due to state dependency nor to an acquisition deficit, nor to antinociception. It is concluded that processing of the stressful experience of defeat is differently influenced by vasopressin given before or after training, resulting in an impaired or facilitated retention, respectively. Among the hypothetically discussed underlying mechanisms, one suggestion is that exogenous vasopressin interacts with an assumed discriminative stimulus function of endogenously released vasopressin. Another possibility might be that exogenous vasopressin interferes with the defeat-activated opioid peptide system.

Human memory and neurohypophyseal hormones: opposite effects of vasopressin and oxytocin

A classical task of experimental psychology, the retention of lists of words, was given twice to three groups of subjects treated with lysine vasopressin (LVP), oxytocin or saline. From a baseline session (no treatment) to a second session with treatment, the LVP and placebo groups showed an enhancement of the number of words remembered correctly, whereas the oxytocin group did not. Rather, oxytocin impaired memory performance. However, we cannot claim a memory enhancing effect of LVP, because placebo treatment enhanced memory performance to the same extent.

A major metabolite of arginine vasopressin in the brain is a highly potent neuropeptide

A peptide that accumulated as the major product during the proteolysis of arginine vasopressin by rat brain synaptic membranes was isolated and its structure was shown to be the hexapeptide pGlu-Asn-Cys(Cys)-Pro-Arg-Gly-NH2. When administered intracerebroventricularly in extremely low doses, this vasopressin fragment and its desglycinamide derivative facilitated memory consolidation in a passive avoidance situation. These vasopressin metabolites, which are devoid of pressor activity, constitute highly potent neuropeptides with selective effects on memory and related processes; they are activated via proteolytic processing of vasopressin by brain peptidases.