Effect of desmopressin on normal and impaired memory

The physiological and pathophysiological functions of renal and extrarenal vasopressin V2 receptors

The arginine vasopressin (AVP) type 2 receptor (V2R) is unique among AVP receptor subtypes in signaling through cAMP. Its key function is in the kidneys, facilitating the urine concentrating mechanism through the AVP/V2 type receptor/aquaporin 2 system in the medullary and cortical collecting ducts. Recent clinical and research observations strongly support the existence of an extrarenal V2R. The clinical importance of the extrarenal V2R spans widely from stimulation of coagulation factor in the endothelium to as yet untested potential therapeutic targets. These include V2R-regulated membranous fluid turnover in the inner ear, V2R-regulated mitogensis and apoptosis in certain tumor tissues, and numerous other cell types where the physiological role of V2Rs still requires further research. Here, we review current evidence on the physiological and pathophysiological functions of renal and extrarenal V2Rs. These functions of V2R are important, not only in rare diseases with loss or gain of function of V2R but also in relation to the recent use of nonpeptide V2R antagonists to treat hyponatremia and possibly retard the growth of cysts and development of renal failure in autosomal dominant polycystic kidney disease. The main functions of V2R in principal cells of the collecting duct are water, salt, and urea transport by modifying the trafficking of aquaporin 2, epithelial Na(+) channels, and urea transporters and vasodilation and stimulation of coagulation factor properties, mainly seen with pharmacological doses of 1-desamino-8-D-AVP. The AVPR2 gene is located on the X chromosome, in a region with high probability of escape from inactivation; this may lead to phenotypic sex differences, with females expressing higher levels of transcript than males.

Post-trial administration of vasopressin in humans does not enhance memory formation (vasopressin and memory consolidation)

Many animal studies show an enhancing effect of vasopressin (VP) on memory, but not all human studies could confirm this finding. This study examined the influence of post-learning administration of VP (40 IU, intranasally) on the consolidation of declarative memories in healthy humans during different intervals of sleep and waking. We could not find any effect of VP on memory consolidation, but EEG activity indicated a significant arousing influence of VP. Results suggest that if VP affects memory function it might do so primarily at the stage of encoding of the materials to be learned but it leaves unaffected processes of consolidation.

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.

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 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.

A placebo-controlled evaluation of vasopressin for ECT-induced memory impairment

Vasopressin may be involved in normal memory functions and may alleviate certain memory impairments. In this study, the usefulness of vasopressin to relieve electroconvulsive therapy (ECT)-induced memory impairment was evaluated using a placebo-controlled, random assignment, double-blind design. Patients were 33 depressives receiving bilateral ECT. Vasopressin, in a nasal spray, was administered q.i.d. from the first through the fifth ECT. Extensive memory testing evaluated both retrograde and anterograde amnesia; ratings of depression and patient ratings of subjective memory complaints were also obtained. Results did not show statistically significant evidence of benefit from vasopressin, though a number of comparisons were in the predicted direction. The role of vasopressin in reducing memory impairment of various types remains to be elucidated.

Treatment of chronic organic mental disorders associated with alcoholism

Considering the magnitude of the problem, the treatment of alcoholism-associated chronic organic mental disorders has not been extensively studied. Alcoholic organic brain disease is heuristically viewed as the admixture of clinical syndromes of impairment [alcoholic amnestic disorder or Korsakoff's psychosis (KP) and dementia associated with alcoholism (DAA)], each with its distinguishing cognitive, neuropathological, and neurochemical characteristics. Differences between KP and DAA are highlighted by studies that compare KP patients with those having Alzheimer's disease or depression. Furthermore, treatment of cognitive deficits in KP and DAA may be modeled after strategies that have proved effective for these other neuropsychiatric disorders. Although abstinence and proper nutrition remain the cornerstones of treatment, pharmacological modification of neurotransmitter function and/or enhancement of cerebral metabolism combined with behavioral methods may also be beneficial. Serotonergic approaches to improve memory in detoxified alcoholics may also reduce alcohol intake, and this has implication for treatment of less impaired alcoholics.

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.

Cognitive enhancing agents: current status in the treatment of Alzheimer's disease

Extensive recent literature on drugs used to enhance cognitive functioning, reflects the growing social problem of dementia. Many clinical trials have been undertaken with variable success. In most cases the disorder studied has been Alzheimer's disease. The pharmacological approach has been designed to rectify the presumed pathophysiological processes characteristic of the condition. Agents tested include cerebral vasodilators, cerebral metabolic enhancers, nootropics, psychostimulants, neuropeptides and neurotransmitters with a special emphasis on drugs used to enhance cholinergic function. Ethical and practical issues concerning clinical drug trials in dementia will be discussed.

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.

Penetration of DGAVP (Org 5667) across the blood-brain barrier in human subjects

To assess the penetration of desglycinamide-arginine-vasopressin (DGAVP, Org 5667) to the central nervous system, levels of DGAVP were measured in the lumbar CSF after peripheral administration. DGAVP (2 mg) was administered intranasally to 37 patients and CSF samples were collected from these patients 5 to 240 minutes later. Detectable levels of DGAVP in CSF could be found 5 minutes after administration, but levels declined rapidly during the next 90 minutes. The DGAVP levels in CSF correlated with plasma levels of DGAVP (r=0.586, p less than 0.001). According to these results, DGAVP may gain access to the central nervous system and may induce central effects.

Vasopressin has general rate-decreasing effects on schedules maintaining either high or low response rates

Male and female Wistar rats were treated with different doses of vasopressin (0.05, 0.25, 1.25, 3.75 and 6.25 micrograms/kg) after responding had stabilized on either a differential reinforcement of low rate 15 s (DRL 15 s) or a differential reinforcement of high rate 0.75 s (DRH 0.75 s) schedule of reinforcement. Low to moderate doses of vasopressin did not affect response rates, response efficiency or the number of reinforcers obtained during vasopressin sessions on both the DRL and DRH schedules. Administration of 6.25 micrograms/kg vasopressin reduced low response rates and the number of reinforcers obtained during vasopressin sessions, but increased response efficiency. High response rates and response efficiency were reduced after administration of 3.75 and 6.25 micrograms/kg vasopressin, while the number of reinforcers obtained during vasopressin sessions was reduced at 6.25 micrograms/kg. Sex differences in the effects of vasopressin were not observed on either schedule.

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.

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)

A clinical trial with desglycinamide arginine vasopressin for the treatment of memory disorders in man

In a double-blind cross-over trial the memory effect of the neuropeptide desglycinamide arginine vasopressin (DGAVP) was selected because of its well-documented facilitatory effects on memory components in rodents. Patients with stabilized or progressive amnesic disorders (Korsakoff disease, early stages of Alzheimer dementia, head injuries and other central nervous system diseases) did not respond to the drug. Factors possibly explaining the discrepancy with animal research are discussed.

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.