Amitriptyline, clovoxamine and cognitive function: a placebo-controlled comparison in depressed outpatients

Ropanicant (SUVN-911), an α4β2 nicotinic acetylcholine receptor antagonist intended for the treatment of depressive disorders: pharmacological, behavioral, and neurochemical characterization

RATIONALE

Ropanicant (SUVN-911) (3-(6-Chloropyridine-3-yloxymethyl)-2-azabicyclo (3.1.0) hexane hydrochloride) is a novel α4β2 nicotinic acetylcholine receptor (nAChR) antagonist being developed for the treatment of depressive disorders.

OBJECTIVES

Pharmacological and neurochemical characterization of Ropanicant to support a potential molecule for the treatment of depressive disorders.

METHODS

Ropanicant was assessed for antidepressant-like activity using the rat forced swimming test (FST) and differential reinforcement of low rate -72 s (DRL-72 s). Alleviation of anhedonia was assessed in chronic mild stress model using sucrose preference test. To understand the mechanism of action, serotonin levels, ionized calcium-binding adaptor molecule 1 (Iba1), and brain-derived neurotrophic factor (BDNF) were determined. The onset of antidepressant-like activity was determined using the reduction in submissive behavior assay. The effects on cognition and sexual functions were assessed using the object recognition task and sexual dysfunction assay respectively. Interaction of Ropanicant, TC-5214, and methyllycaconitine (MLA) with citalopram was investigated individually in mice FST.

RESULTS

Ropanicant exhibited antidepressant like properties in the FST and DRL-72 s. A significant reduction in anhedonia was observed in the sucrose preference test. Oral administration of Ropanicant produced a significant increase in serotonin and BDNF levels, with a reduction in the Iba1 activity. The onset of antidepressant like effect with Ropanicant was within a week of treatment, and was devoid of cognitive dulling and sexual dysfunction. While Ropanicant potentiated the effect of citalopram in FST, such an effect was not observed with MLA or TC-5214.

CONCLUSIONS

Preclinical studies with Ropanicant support the likelihood of its therapeutic utility in the treatment of depressive disorders.

[Cognitive impairments in patients with depression]

Cognitive impairments are frequent in patients suffering from major depressive disorders. They are among the first symptoms, often persist independently of improvement even after remission of the affective symptoms and are an important predictor of psychosocial functioning. In the clinical practice it is mandatory to ask about subjective complaints of the patient as well as to assess the cognitive abilities with the help of a standardized neuropsychological test battery. Cognitive remediation, selective serotonin reuptake inhibitors (SSRI) and vortioxetine as well as repetitive transcranial magnetic stimulation have proven their effectiveness as treatment options.

Optimizing Cognitive Function in Persons With Chronic Pain

OBJECTIVES

Cognitive functioning is commonly disrupted in people living with chronic pain, yet it is an aspect of pain that is often not routinely assessed in pain management settings, and there is a paucity of research on treatments or strategies to alleviate the problem. The purpose of this review is to outline recent research on cognitive deficits seen in chronic pain, to give an overview of the mechanisms involved, advocate cognitive functioning as an important target for treatment in pain populations, and discuss ways in which it may be assessed and potentially remediated.

METHODS

A narrative review.

RESULTS

There are several options for remediation, including compensatory, restorative, and neuromodulatory approaches to directly modify cognitive functioning, as well as physical, psychological, and medication optimization methods to target secondary factors (mood, sleep, and medications) that may interfere with cognition.

DISCUSSION

We highlight the potential to enhance cognitive functions and identify the major gaps in the research literature.

Cognitive Impairment in Patients with Chronic Neuropathic or Radicular Pain: An Interaction of Pain and Age

A growing body of empirical research has confirmed an association between chronic pain and cognitive dysfunction. The aim of the present study was to determine whether cognitive function is affected in patients with a diagnosis of chronic neuropathic or radicular pain relative to healthy control participants matched by age, gender, and years of education. We also examined the interaction of pain with age in terms of cognitive performance. Some limitations of previous clinical research investigating the effects of chronic pain on cognitive function include differences in the pain and cognitive scale materials used, and the heterogeneity of patient participants, both in terms of their demographics and pathological conditions. To address these potential confounds, we have used a relatively homogenous patient group and included both experimental and statistical controls. We have also specifically investigated the interaction effect of pain and age on cognitive performance. Patients (n = 38) and controls (n = 38) were administered a battery of cognitive tests measuring IQ, spatial and verbal memory, attention, and executive function. Educational level, depressive symptoms, and state anxiety were assessed as were medication usage, caffeine, and nicotine consumption to control for possible confounding effects. Both the level of depressive symptoms and the state anxiety score were higher in chronic pain patients than in matched control participants. Chronic pain patients had a lower estimated IQ than controls, and showed impairments on measures of spatial and verbal memory. Attentional responding was altered in the patient group, possibly indicative of impaired inhibitory control. There were significant interactions between chronic pain condition and age on a number of cognitive outcome variables, such that older patients with chronic pain were more impaired than both age-matched controls and younger patients with chronic pain. Chronic pain did not appear to predict performance on the Wisconsin Card Sorting Task, which was used a measure of executive function. This study supports and extends previous research indicating that chronic pain is associated with impaired memory and attention.

Perspective: Compared to healthy control participants, patients with chronic neuropathic or radicular pain showed cognitive deficits which were most pronounced in older pain patients.

Differential effectiveness of tianeptine, clonidine and amitriptyline in blocking traumatic memory expression, anxiety and hypertension in an animal model of PTSD

Individuals exposed to life-threatening trauma are at risk for developing post-traumatic stress disorder (PTSD), a debilitating condition that involves persistent anxiety, intrusive memories and several physiological disturbances. Current pharmacotherapies for PTSD manage only a subset of these symptoms and typically have adverse side effects which limit their overall effectiveness. We evaluated the effectiveness of three different pharmacological agents to ameliorate a broad range of PTSD-like symptoms in our established predator-based animal model of PTSD. Adult male Sprague-Dawley rats were given 1-h cat exposures on two occasions that were separated by 10 days, in conjunction with chronic social instability. Beginning 24 h after the first cat exposure, rats received daily injections of amitriptyline, clonidine, tianeptine or vehicle. Three weeks after the second cat exposure, all rats underwent a battery of behavioral and physiological tests. The vehicle-treated, psychosocially stressed rats demonstrated a robust fear memory for the two cat exposures, as well as increased anxiety expressed on the elevated plus maze, an exaggerated startle response, elevated heart rate and blood pressure, reduced growth rate and increased adrenal gland weight, relative to the vehicle-treated, non-stressed (control) rats. Neither amitriptyline nor clonidine was effective at blocking the entire cluster of stress-induced sequelae, and each agent produced adverse side effects in control subjects. Only the antidepressant tianeptine completely blocked the effects of psychosocial stress on all of the physiological and behavioral measures that were examined. These findings illustrate the differential effectiveness of these three treatments to block components of PTSD-like symptoms in rats, and in particular, reveal the profile of tianeptine as the most effective of all three agents.

Amitriptyline versus placebo for major depressive disorder

BACKGROUND

Amitriptyline is a tricyclic antidepressant that was synthesised in 1960 and introduced as early as 1961 in the USA, but is still regularly used. It has also been frequently used as an active comparator in trials on newer antidepressants and can therefore be called a 'benchmark' antidepressant. However, its efficacy and safety compared to placebo in the treatment of major depression has not been assessed in a systematic review and meta-analysis.

OBJECTIVES

To assess the effects of amitriptyline compared to placebo or no treatment for major depressive disorder in adults.

SEARCH METHODS

We searched the Cochrane Depression, Anxiety and Neurosis Group's Specialised Register (CCDANCTR-Studies and CCDANCTR-References) to August 2012. This register contains relevant randomised controlled trials from: The Cochrane Library (all years), EMBASE (1974 to date), MEDLINE (1950 to date) and PsycINFO (1967 to date). The reference lists of reports of all included studies were screened and manufacturers of amitriptyline contacted for details of additional studies.

SELECTION CRITERIA

All randomised controlled trials (RCTs) comparing amitriptyline with placebo or no treatment in patients with major depressive disorder as diagnosed by operationalised criteria.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data. For dichotomous data, we calculated the odds ratio (OR) with 95% confidence intervals (CI). We analysed continuous data using standardised mean differences (with 95% CI). We used a random-effects model throughout.

MAIN RESULTS

The review includes 39 trials with a total of 3509 participants. Study duration ranged between three and 12 weeks. Amitriptyline was significantly more effective than placebo in achieving acute response (18 RCTs, n = 1987, OR 2.67, 95% CI 2.21 to 3.23). Significantly fewer participants allocated to amitriptyline than to placebo withdrew from trials due to inefficacy of treatment (19 RCTs, n = 2017, OR 0.20, 95% CI 0.14 to 0.28), but more amitriptyline-treated participants withdrew due to side effects (19 RCTs, n = 2174, OR 4.15, 95% CI 2.71 to 6.35). Amitriptyline also caused more anticholinergic side effects, tachycardia, dizziness, nervousness, sedation, tremor, dyspepsia, sedation, sexual dysfunction and weight gain. In subgroup and meta-regression analyses the results of the primary outcome were robust towards publication year (1971 to 1997), mean participant age at baseline, mean amitriptyline dose, study duration in weeks, pharmaceutical sponsor, inpatient versus outpatient setting and two-arm versus three-arm design. However, higher severity at baseline was associated with higher superiority of amitriptyline (P = 0.02), while higher responder rates in the placebo groups were associated with lower superiority of amitriptyline (P = 0.05). The results of the primary outcome were rather homogeneous, reflecting comparability of the trials. However, methods of randomisation, allocation concealment and blinding were usually poorly reported. Not all studies used intention-to-treat analyses and in many of them standard deviations were not reported and often had to be imputed. Funnel plots suggested a possible publication bias, but the trim and fill method did not change the overall effect size much (seven adjusted studies, OR 2.64, 95% CI 2.24 to 3.10).

AUTHORS' CONCLUSIONS

Amitriptyline is an efficacious antidepressant drug. It is, however, also associated with a number of side effects. Degree of placebo response and severity of depression at baseline may moderate drug-placebo efficacy differences.

Cognition and depression: the effects of fluvoxamine, a sigma-1 receptor agonist, reconsidered

Cognitive impairment is a primary feature of patients with major depressive disorder (MDD) and is characterised by stress-induced neural atrophy. Via alpha-adrenergic, anti-cholinergic and anti-histaminic activities, several antidepressants can cause significant counter-therapeutic cognitive impairment. Evidence is emerging of the involvement of sigma-1 receptor agonism in the mechanism of action of some antidepressants, notably fluvoxamine. Sigma-1 receptors are abundant in areas affected by depression/stress-induced cerebral atrophy and their ligands have a unique pharmacological profile; they may promote neurogenesis and initiate adaptive neural plasticity as a protection/reaction to stress. Fluvoxamine, as a potent sigma-1 receptor agonist, has shown ameliorating effects in animal models of psychosis, depression, stress, anxiety, obsessive-compulsive disorder (OCD) and aggression and has been shown to improve cognitive impairments. In humans, fluvoxamine may repair central nervous system (CNS) atrophy and restore cognitive function. The current review explores the mechanisms through which sigma-1 receptors can modulate cognitive function and examines how antidepressant therapy with fluvoxamine may help improve cognitive outcomes in patients with depression.

Effect of fluoxetine on some cognitive functions of patients of depression

BACKGROUND

This study was carried out to evaluate the effect of long-term administration of a commonly prescribed antidepressant, fluoxetine from different group on memory and psychomotor functions in patients of various psychiatric disorders using a battery of simple tests that can be conveniently applied to the Indian population.

MATERIALS AND METHODS

Memory was evaluated using the PGI memory scale and psychomotor functions were evaluated using six letter cancellation test. Statistical analysis was carried out using Wilcoxon signed-rank test.

RESULTS AND CONCLUSION

The results of the study reveal that there was significant improvement in some cognitive function. Cognitive functions are improved at first follow-up and they improved continuously up to last follow-up that is at one month. It is observed that there was improvement in the primary disease. So, final score of the cognitive parameters is because of the resultant activity of direct drug action and improvement in the underlying disease.

Effect of open-label lamotrigine as monotherapy and adjunctive therapy on the self-assessed cognitive function scores of patients with bipolar I disorder

Cognitive deficits in patients with bipolar disorder are likely to impair occupational and social functioning. In a post hoc analysis of data from a prospective, open-label study of lamotrigine in 1175 patients 13 years or older with bipolar I disorder, changes in the self-rated cognitive function scores of patients receiving lamotrigine as monotherapy or as adjunctive therapy were evaluated. Lamotrigine was given for 12 weeks, with a target dosage of 200 mg/d. Cognitive function was assessed at baseline and week 12 with the self-rated Medical Outcomes Study Cognitive (MOS-Cog) Scale. Mean MOS-Cog scores improved significantly from baseline in the overall group (+8.4 +/- 22.55 points, P < 0.0001) and in subgroups of patients receiving and not receiving concomitant valproate, antidepressants, or antipsychotics. Patients receiving lamotrigine and not receiving concomitant antipsychotics, however, exhibited a small but significantly greater degree of improvement than patients who were receiving concomitant antipsychotics (adjusted mean difference = 4.05; 95% confidence interval, 1.30-6.81; P = 0.0039). Statistically significant improvement was seen in patient subgroups with a depressive (mean change from baseline, 8.8 +/- 21.97; P < 0.0001) or a manic (mean change from baseline, 7.5 +/- 22.62; P = 0.0007) index episode. Improvements in MOS-Cog scores significantly correlated with improvement in both depressive (correlation coefficient, -0.339; P < 0.0001) and manic (correlation coefficient, -0.151; P < 0.0001) symptoms. Overall, self-rated cognitive function scores improved during open-label lamotrigine therapy in patients with bipolar I disorder whether or not they were receiving concomitant valproate, antidepressants, or antipsychotics. Additional research is needed to explore the clinical relevance of these findings.

Memory consolidation in sleep; dream or reality

We discuss several lines of evidence refuting the hypothesis that procedural or declarative memories are processed/consolidated in sleep. One of the strongest arguments against a role for sleep in declarative memory involves the demonstration that the marked suppression or elimination of REM sleep in subjects on antidepressant drugs or with brainstem lesions produces no detrimental effects on cognition. Procedural memory, like declarative memory, undergoes a slow, time-dependent period of consolidation. A process has recently been described wherein performance on some procedural tasks improves with the mere passage of time and has been termed "enhancement." Some studies, but not others, have reported that the consolidation/enhancement of perceptual and motor skills is dependent on sleep. We suggest that consolidation or enhancement, initiated in waking with task acquisition, could in some instances extend to sleep, but sleep would serve no unique role in these processes. In sum, there is no compelling evidence to support a relationship between sleep and memory consolidation.

Clinical and neurobiological effects of tianeptine and paroxetine in major depression

Selective serotonin reuptake inhibitors (SSRIs) are widely used as effective pharmacological agents to treat depressive disorders. In contrast to the SSRIs, which block the presynaptic serotonin (5-HT) transporter and by this route increase the concentration of serotonin in the synaptic cleft, the antidepressant tianeptine enhances the presynaptic neuronal reuptake of 5-HT and thus decreases serotonergic neurotransmission. Both SSRIs and tianeptine are clinically effective; however, their opposite modes of action challenge the prevailing concepts on the need of enhancement of serotonergic neurotransmission. To better understand the differences between these two opposite pharmacological modes of action, we compared the changes induced by tianeptine and paroxetine on psychopathology, the hypothalamic-pituitary-adrenocortical (HPA) system, and cognitive functions in a double-blind, randomized, controlled trial including 44 depressed inpatients over a period of 42 days. Depressive symptomatology significantly improved in all efficacy measures, with no significant differences between tianeptine and paroxetine. There was a trend toward better response to the SSRI among women. Assessment of the HPA system showed marked hyperactivity before the beginning of treatment, which then normalized in most of the patients, without significant differences between the two antidepressants. Cognitive assessments showed no significant differences between the two drugs investigated. The results of the current study suggest that the initial effect, i.e., enhancement or decrease of 5-HT release, is only indirectly responsible for antidepressant efficacy, and they support the notion that downstream adaptations within and between nerve cells are crucial. The normalization of the HPA system as a common mode of action of different antidepressants seems to be of special interest.

Persistence of cognitive impairment in geriatric patients following antidepressant treatment: a randomized, double-blind clinical trial with nortriptyline and paroxetine

Cognitive dysfunction is common in older persons suffering from a major depression. However, the degree to which this dysfunction is reversible with successful treatment of the depression remains uncertain. The present study examined the effects that treatment (randomized double-blind design) with either an SSRI (paroxetine) or a tricyclic antidepressant (nortriptyline) had on cognition in older depressed patients. The patients' performance was compared to that of a group of normal controls of similar age and education. Patients and controls were administered measures of working memory, information-processing speed, episodic memory and attention five times over the course of a 12 week trial. At baseline, the patients performed more poorly than the elderly controls on all cognitive measures. While the patients' performance did improve over the course of their treatment, the magnitude of this improvement did not exceed that produced in the elderly controls by practice alone. The same pattern of results was evident in both intent-to-treat and responder analyses. Thus, there was no evidence that the depressed patients' cognitive performance normalized after response to antidepressant therapy. Neither the patients' age at onset nor their baseline level of cognitive functioning influenced the amount by which their performance improved over the 12 week trial. There was no difference between paroxetine and nortriptyline in the amount of cognitive change associated with treatment. The present results suggest that cognitive dysfunction persists in older depressed patients even after their mood disorder has responded to antidepressant medications.

Adrenoceptor mechanisms underlying imipramine-induced memory deficits in rats

The post-training administration of tricyclic antidepressant imipramine impairs memory consolidation in the passive avoidance task. The present study investigated the effects of intrahippocampal (i.h.) injection of adrenoceptor agents on imipramine-induced (2-8 microg/rat) amnesia. The administration of the alpha1-adrenoceptor agonist phenylephrine (0.05 microg/rat) and the alpha1-adrenceptor antagonist prazosin (0.5 microg/rat) did not alter the effect of imipramine. The lower doses of phenylephrine (0.005 and 0.015 microg/rat) impaired, while the higher dose of the drug (0.025 and 0.05 microg/rat) improved retention. The effect of phenylephrine was not altered by prazosin (0.5 and 1 microg/rat) pretreatment, although prazosin alone decreased retention latencies. The alpha2-adrenoceptor antagonist yohimbine (0.5 and 1 microg/rat) decreased the response induced by imipramine. However, the alpha2-adrenoceptor agonist clonidine (0.08 microg/rat) did not alter the effect of the drug. Clonidine (0.15 and 0.3 microg/rat) by itself decreased, while yohimbine (1 and 2 microg/rat) increased retention latencies. Yohimbine pretreatment attenuated the effect of clonidine. It is concluded that alpha2-adrenoceptor mechanism(s) may be involved in imipramine-induced impairment of memory.

Memory performance in panic disorder patients after chronic use of clomipramine

This study investigated the chronic use (6.3 +/- 0.5 years; mean +/- SEM) of therapeutic doses of clomipramine (57.0 +/- 8.0 mg/day) by outpatients with panic disorder/agoraphobia who were currently in remission to assess impairment of memory and psychomotor functions. In addition, the association between test performance and serum levels of clomipramine (CMI) and its active metabolite desmethylclomipramine (DCMI) was also assessed. Patients and healthy volunteers matched for sex, age and educational level were submitted to rating scales and to memory and psychomotor tests. There was no significant difference between groups regarding any variable, except for metamemory. Significant associations were found between (i) longer-term clomipramine treatment and poorer performance in the implicit test and (ii) higher serum levels of clomipramine or desmethylclomipramine, or both (CMI + DCMI) and lower performance in central executive tests and metamemory. The results showed that low doses of CMI chronically administered to panic patients are associated with diminished metamemory and impaired priming and working memory. Further investigations are needed to confirm these results and to determine whether the chronic use of higher therapeutic doses of tricyclic antidepressants is associated with more intense deleterious effects on memory and psychomotor functions.

Sleep states and memory processes in humans: procedural versus declarative memory systems

The present paper focuses on human studies attempting to relate sleep states to memory processes. These studies typically present learning material to participants and then examine their ability to recall this material after intervening post-training sleep or sleep deprivation. Most experiments utilize either sleep recording or sleep deprivation following task acquisition to reach their conclusions, although cueing and position emission tomography (PET) scan studies have also been done. Results strongly suggest that REM sleep is involved with the efficient memory processing of cognitive procedural material but not declarative material. Although there are some data to suggest that stage 3/4 or NREM sleep is necessary for declarative memory consolidation, NREM may in fact simply be occurring at the same time as another factor that is actually involved in the memory processing. Preliminary results suggest that the length of the NREM-REM sleep cycle may be important for declarative memory. Preliminary data also suggest that stage 2 sleep may be involved with the memory for motor procedural but not cognitive procedural tasks. Sleep researchers would do well to capitalize on the latest advancements in memory research by choosing tasks that represent special memory systems and examining their relationships to sleep states.

Cognitive performance in elderly subjects after a single dose of befloxatone, a new reversible selective monoamine oxidase A inhibitor

BACKGROUND

Patients with depression often have cognitive and psychomotor performance impairments. Antidepressive treatments can correct these deficits, provided sedative and anticholinergic adverse effects do not add to the preexisting condition, particularly in elderly patients. Newly developed antidepressants therefore should be without deleterious effects on cognitive functions, including memory. Befloxatone is a new antidepressant with a potent, selective, competitive, and reversible inhibitory activity on the A isoform of monoamine oxidase (MAO-A).

METHODS

The effects on cognition and psychomotor performance of single oral doses of befloxatone (10 mg) and amitriptyline (50 mg) were compared in a randomized, double-blind, placebo-controlled, three-way crossover design trial in 12 healthy elderly (65 to 85 years) volunteers. The performances of the subjects were evaluated by a comprehensive battery of validated psychometric tests that explored alertness, psychomotor performance, information processing, and memory. Subjective feelings on mood and sleep were rated on visual analog scales. MAO-A inhibition was estimated by multiple titrations of 3,4-dihydrophenylglycol (DHPG) in plasma.

RESULTS

Amitriptyline displayed the expected deleterious effects on performance tasks, critical flicker fusion threshold, digit symbol substitution, and body sway, and it deteriorated memory (immediate and delayed free recall of words). In contrast, befloxatone did not impair cognition or psychomotor performance but instead significantly improved the delayed free recall. Amitriptyline adversely affected subjective feelings of alertness and contentedness, but befloxatone permitted sustained alertness and did not alter other subjective feelings or sleep. Concurrently, a single dose of 10 mg befloxatone markedly decreased the DHPG concentration in plasma.

CONCLUSION

Contrary to tricyclic antidepressants, whose deleterious effects are greater in elderly subjects, this study demonstrated the safety of befloxatone on cognition and psychomotor performance in elderly subjects.

Antidepressant treatment of depression: a metaanalysis

OBJECTIVE

To carry out a metaanalysis of antidepressant studies to calculate the effect sizes for antidepressant effect in depressive disorder.

METHOD

A metaanalysis of all antidepressant studies that included an active comparison drug as well as placebo was used to calculate the effect size. Articles were selected from a MEDLINE search for the period January 1966 to June 1995. Forty-nine studies were included in the metaanalysis.

RESULTS

The effect sizes for antidepressant treatment are moderately larger than for placebo. A larger effect size was observed in studies where objective diagnostic criteria for depression were used.

CONCLUSIONS

We conclude that the superior efficacy of antidepressants over placebo can be demonstrated.

The role of serotonergic-cholinergic interactions in the mediation of cognitive behaviour

Cholinergic systems have been linked to cognitive processes such as attention, learning and mnemonic function. However, other neurotransmitter systems, such as the serotonergic one, which may have only minor effects on cognitive function on their own, interact with cholinergic function and their combined effects may have marked behavioural actions. Some studies have dealt with serotonergic-cholinergic interactions, but it is unclear whether both systems affect cognition directly or whether interactions at a behavioural level result from additional alterations in non-cognitive factors. This distinction is difficult, since it is possible that the diverse cholinergic and serotonergic systems serve different roles in the mediation of cognitive processes, both at the neuroanatomical and neurochemical level. Nevertheless, it is possible that cholinergic systems primarily alter accuracy in cognitive tasks, whereas serotonergic neurotransmission modulates behaviour by altering bias (motivation, motor processes). Whether serotonin alters accuracy or bias, however, may also depend on the cognitive process under investigation: it is suggested that attention, stimulus processing and/or arousal can be influenced by both cholinergic and serotonergic systems independently from each other. Cholinergic and serotonergic projections to cortex and thalamus may be of importance in the mediation of these cognitive processes. Serotonergic-cholinergic interactions could also be of importance in the mediation of learning processes and trial-by-trial working memory. The data available do not allow an unambiguous conclusion about the role of these interactive processes in the mediation of long-term reference memory. These processes may rely on serotonergic-cholinergic interactions at the hippocampal level. It is concluded that serotonergic-cholinergic interactions play an important role in the mediation of behavioural, including cognitive, performance, but that further studies are necessary in order to elucidate the exact nature of these interactions.

Effects of major depression on the cognitive function of younger and older subjects

The effects of age and depression on cognitive function were investigated in two groups of in-patient major depressives aged under and over 60 years who were tested when depressed and after recovery. The majority of the tests showed impaired performance during depression with improvement after recovery, and also differences between the two age-groups in both the depressed and recovered phases. However, the older subjects were not more severely affected by depression than the younger subjects. The pattern of impairment associated with depression was different to that associated with older age: depression affected performance on more 'complex tasks', whereas age was associated particularly with slowing on timed tests. This study did not suggest that the impairment from baseline due to the depression is greater in the elderly than in younger subjects.