Mood-altering effects of biperiden in healthy volunteers

Normalization of impaired emotion inhibition in bipolar disorder mediated by cholinergic neurotransmission in the cingulate cortex

The muscarinic-cholinergic system is involved in the pathophysiology of bipolar disorder (BD), and contributes to attention and the top-down and bottom-up cognitive and affective mechanisms of emotional processing, functionally altered in BD. Emotion processing can be assessed by the ability to inhibit a response when the content of the image is emotional. Impaired regulatory capacity of cholinergic neurotransmission conferred by reduced M₂-autoreceptor availability is hypothesized to play a role in elevated salience of negative emotional distractors in euthymic BD relative to individuals with no history of mood instability. Thirty-three euthymic BD type-I (DSM-V-TR) and 50 psychiatrically-healthy controls underwent functional magnetic resonance imaging (fMRI) and an emotion-inhibition paradigm before and after intravenous cholinergic challenge using the acetylcholinesterase inhibitor, physostigmine (1 mg), or placebo. Mood, accuracy, and reaction time on either recognizing or inhibiting a response associated with an image involving emotion and regional functional activation were examined for effects of cholinergic challenge physostigmine relative to placebo, prioritizing any interaction with the diagnostic group. Analyses revealed that (1) at baseline, impaired behavioral performance was associated with lower activation in the anterior cingulate cortex in BD relative to controls during emotion processing; (2) physostigmine (vs. placebo) affected behavioral performance during the inhibition of negative emotions, without altering mood, and increased activation in the posterior cingulate cortex in BD (vs. controls); (3) In BD, lower accuracy observed during emotion inhibition of negative emotions was remediated by physostigmine and was associated with cingulate cortex overactivation. Our findings implicate abnormal regulation of cholinergic neurotransmission in the cingulate cortices in BD, which may mediate exaggerated emotional salience processing, a core feature of BD.

Trihexyphenidyl Misuse in Delusional Disorder

Trihexyphenidyl is an anticholinergic medication that is routinely used for the management of extrapyramidal symptoms in patients who receive antipsychotic medications. Trihexyphenidyl has been reported to be abused by some patients, who start to take it in increasing doses and tend to report a sensation of relaxation or pleasure with this medication. Hence, whether trihexyphenidyl should be considered a psychoactive substance and whether nonprescription misuse of this medication should be considered under the purview of substance use disorders need further clarity. We present here two cases of trihexyphenidyl misuse which developed in the context of persistent delusional disorders and highlight the challenges in diagnosis in such a situation.

Blockade of muscarinic acetylcholine receptors facilitates motivated behaviour and rescues a model of antipsychotic-induced amotivation

Disruptions to motivated behaviour are a highly prevalent and severe symptom in a number of neuropsychiatric and neurodegenerative disorders. Current treatment options for these disorders have little or no effect upon motivational impairments. We assessed the contribution of muscarinic acetylcholine receptors to motivated behaviour in mice, as a novel pharmacological target for motivational impairments. Touchscreen progressive ratio (PR) performance was facilitated by the nonselective muscarinic receptor antagonist scopolamine as well as the more subtype-selective antagonists biperiden (M1) and tropicamide (M4). However, scopolamine and tropicamide also produced increases in non-specific activity levels, whereas biperiden did not. A series of control tests suggests the effects of the mAChR antagonists were sensitive to changes in reward value and not driven by changes in satiety, motor fatigue, appetite or perseveration. Subsequently, a sub-effective dose of biperiden was able to facilitate the effects of amphetamine upon PR performance, suggesting an ability to enhance dopaminergic function. Both biperiden and scopolamine were also able to reverse a haloperidol-induced deficit in PR performance, however only biperiden was able to rescue the deficit in effort-related choice (ERC) performance. Taken together, these data suggest that the M1 mAChR may be a novel target for the pharmacological enhancement of effort exertion and consequent rescue of motivational impairments. Conversely, M4 receptors may inadvertently modulate effort exertion through regulation of general locomotor activity levels.

Effects of anticholinergic challenge on psychopathology and cognition in drug-free patients with schizophrenia and healthy volunteers

RATIONALE

Many aspects of the neurobiology of schizophrenia, especially the physiological basis of the negative symptoms and associated cognitive deficits, remain inadequately understood. Tandon and Greden (1989) postulated a central role of dopaminergic/cholinergic imbalance in schizophrenia.

OBJECTIVE/METHODS

In light of this hypothesis, we elected to investigate the effects of anticholinergic challenge on psychopathology, cognition and attention in 12 unmedicated patients with schizophrenia and 12 healthy controls. The first examination occurred before any pharmacological intervention; the second examination was carried out immediately following an intravenous infusion of 5 mg biperiden, a centrally acting antimuscarinergic agent.

RESULTS

The biperiden challenge provoked a considerable increase in PANSS scores in both groups which was significantly more pronounced in patients (repeated measures analysis of variance (ANOVA) (rmANOVA): F(df) = 6.4(1,22); p = 0.019). The increase in the PANSS scores showed a significant negative correlation with age in patients. Biperiden caused considerable cognitive impairments in both groups. A significant group difference (rmANOVA) could be observed for TMT-B (F(df) = 11.29(1,22); p = 0.003).

CONCLUSIONS

The anticholinergic intervention caused more pronounced psychopathological and cognitive deteriorating effects in patients suffering from schizophrenia than in healthy volunteers. This could be related to the disrupted cholinergic transmission in schizophrenia. Our findings speak on behalf of the need of a more restrictive use of anticholinergics in psychiatric patients. The age-related attenuation of PANSS score increases in patients could be related to the age-dependent changes in dopamine dynamics and also to the age-associated decline of the availability of muscarinic receptors. Our results emphasise the need for further investigation of cholinergic disturbances in schizophrenia.

Human electrophysiological correlates of learned irrelevance: effects of the muscarinic M1 antagonist biperiden

Learned irrelevance (LIrr) refers to a reduction in associative learning after pre-exposure of the conditioned and unconditioned stimulus in a non-contingent fashion. This paradigm might serve as a translational model for (pre)attentive information processing deficits in schizophrenia. This is the first study to investigate the event-related potentials (ERPs) of a within-subject LIrr paradigm in humans. Furthermore, the effects of the muscarinic M1 antagonist biperiden on LIrr were assessed. As expected, LIrr was found to be intact in young healthy volunteers after placebo. Furthermore, in the placebo condition P3b latency was decreased for target stimuli, which were pre-cued. This suggests that the predictability of the occurrence of these stimuli is mainly reflected by this ERP component. Biperiden had no effect on the behavioural LIrr measures, although prolonged reaction times were evident. Biperiden increased the N1 amplitude of the pre-exposed predictor letters, suggesting an effect of this drug on early perceptual processing. In conclusion, the within-subject paradigm used in the current study in combination with electroencephalography can reveal brain mechanisms involved in LIrr. M1 antagonism did not affect LIrr performance but seemed to influence early information processing.

The vigilance regulation model of affective disorders and ADHD

According to the recently proposed vigilance model of affective disorders (vigilance in the sense of "brain arousal"), manic behaviour is partly interpreted as an autoregulatory attempt to stabilise vigilance by creating a stimulating environment, and the sensation avoidance and withdrawal in Major Depressive Disorder (MDD) is seen as an autoregulatory reaction to tonically increased vigilance. Indeed, using a newly developed EEG-based algorithm, hyperstable vigilance was found in MDD, and the contrary, with rapid drops to sleep stages, in mania. Furthermore, destabilising vigilance (e.g. by sleep deprivation) triggers (hypo)mania and improves depression, whereas stabilising vigilance, e.g. by prolonged sleep, improves mania. ADHD and mania have common symptoms, and the unstable vigilance might be a common pathophysiology. There is even evidence that psychostimulants might ameliorate both ADHD and mania. Hyperactivity of the noradrenergic system could explain both the high vigilance level in MDD and, as recently argued, anhedonia and behavioural inhibition. Interestingly, antidepressants and electroconvulsions decrease the firing rate of neurons in the noradrenergic locus coeruleus, whereas many antimanic drugs have opposite effects.

Biperiden dependence: case report and literature review

Anticholinergic drugs are frequently used in psychiatry for the prophylaxis and treatment of extrapiramidal symptoms caused by neuroleptics. Abuse of anticholinergic agents has been reported in patients with psychotic disorders, on treatment with neuroleptics, and polysubstance use disorders. We are reporting the case of a patient who presented with hypoactive delirium as a consequence of biperiden dependence. The clinician must pay special attention to detect anticholinergic misuse in patients presenting with delirium of unknown cause.

The safety and tolerability of atypical antipsychotics in bipolar disorder

Atypical antipsychotics (aAPs), have become a first-line treatment option, both in schizophrenia and bipolar disorders. Almost all aAPs now have proven efficacy in acute mania, some also in bipolar depression and in maintenance treatment. This provides reliable data on their safety and tolerability in this particular group of patients. This review focuses on the safety and tolerability of aAPs in the treatment of bipolar disorders. Both tolerability, for example, extrapyramidal symptoms, and safety issues, for example, occurrence of weight gain and hyperglycaemia, will be highlighted for olanzapine, quetiapine, risperidone, ziprasidone and aripiprazole.

The Bech-Rafaelsen Mania Scale in clinical trials of therapies for bipolar disorder: a 20-year review of its use as an outcome measure

Over the last two decades the Bech-Rafaelsen Mania Scale (MAS) has been used extensively in trials that have assessed the efficacy of treatments for bipolar disorder. The extent of its use makes it possible to evaluate the psychometric properties of the scale according to the principles of internal validity, reliability, and external validity. Studies of the internal validity of the MAS have demonstrated that the simple sum of the 11 items of the scale is a sufficient statistic for the assessment of the severity of manic states. Both factor analysis and latent structure analysis (the Rasch analysis) have been used to demonstrate this. The total score of the MAS has been standardised such that scores below 15 indicate hypomania, scores around 20 indicate moderate mania, and scores around 28 indicate severe mania. The inter-observer reliability has been found to be high in a number of studies conducted in various countries. The MAS has shown an acceptable external validity, in terms of both sensitivity and responsiveness. Thus, the MAS was found to be superior to the Clinical Global Impression scale with regard to responsiveness, and sensitivity has been found to be adequate, with the MAS able to demonstrate large drug-placebo differences. Based on pretreatment scores, trials of antimanic therapies can be classified into: (i) ultrashort (1 week) therapy of severe mania; (ii) short-term therapy (3 to 8 weeks) of moderate mania; (iii) short-term therapy of hypomanic or mixed bipolar states; and (iv) long-term (12 months) therapy of bipolar states. The responsiveness of MAS is such that the scale has been able to demonstrated that typical antipsychotics are effective as an ultrashort therapy of severe mania; that lithium and anticonvulsants are effective in the short-term therapy of moderate mania; and that atypical antipsychotics, electroconvulsive therapy (ECT) and transcranial magnetic stimulation seem to have promising effects in the short-term therapy of moderate mania. In contrast, the scale has been used to demonstrate that calcium antagonists (e.g. verapamil) are ineffective in the treatment of mania. MAS has also been used to add to the literature on the evidence-based effect of lithium as a short-term therapy for hypomania or mixed bipolar states and as a long-term therapy of bipolar states.

Anticholinergic effects in a depressed parkinsonian patient

Depression is commonly associated with idiopathic Parkinson's disease. Various antidepressants can be helpful in the treatment of this type of depression. Anticholinergic medications are at times used for treating the motor symptoms of parkinsonism. While some authors have reported euphorigenic effects from anticholinergics in other groups of patients, generally, they have not been used in the treatment of depression, with or without parkinsonism. In the case presented, a depressed patient with Parkinson's disease on levodopa/carbidopa and fluoxetine was given benztropine for his motor symptoms. The result was some improvement in his motor symptoms and a wide, dose-related spectrum of other central nervous system changes ranging from delirium to mania, hypomania, and euthymia from a "baseline" of residual depression. At a very low dose (0.25 mg per day), benztropine appeared to have an augmenting antidepressant effect that rendered the patient euthymic.