Similarity of clozapine's and olanzapine's acute effects on rats' lapping behavior

Quantitative behavioral models for high-resolution measurement and characterization of tremor in rodents

Tremor is an involuntary, rhythmic movement disorder. Despite its prevalence, the underlying pathophysiology remains poorly understood and effective treatment options are limited. Animal models are essential in enhancing our understanding of the mechanisms of tremorogenesis and developing new therapeutic interventions. Although tremor is amenable to measurement by automated systems, visual observation is still the most prevalent method for recording tremor in animal studies. This review gives a brief summary of two behavioral methods that enable quantitative measurement of forelimb tremor (the press-while-licking task) and whole-body tremor (the force-plate actometer) in rodents. These methods utilize force transducer and computing technologies to generate high-resolution force-time waveforms for automated detection and characterization of tremor. The focus will be on the sensitive, precise, and quantitative measurement of tremors induced in rodents by low-dose pharmacological agents, brain lesion, physical training, and genetic mutations. The methods reviewed here provide new tools that can facilitate preclinical assessment of treatment strategies for tremor.

Assays of Tongue Force, Timing, and Dynamics in Rat and Mouse Models

Communication and swallowing are highly complex sensorimotor events that are tightly linked to respiration and vital to health and well-being. The tongue is a complex organ, often described as a muscular hydrostat, that is crucial for maintaining airway patency, preparing and safely transporting food/liquid, and rapidly changing position and shape for speech. As with any complex behavior, tongue function can be compromised with aging, diseases/conditions, trauma, or as a pharmacologic side effect. As such, modeling lingual function and dysfunction for basic and translational research is paramount; understanding how the nervous system controls tongue function for complex behavior is foundational to this work. Non-invasive access to tongue tissues and kinematics during awake behavior has been historically challenging, creating a critical need to measure tongue function in model systems. Germane to this field of study are the instruments and assays of licking/lapping and drinking, including tongue force and timing measures, many of which were designed or modified by Dr. Stephen C. Fowler. The focus of this paper is to review some of the important contributions of measuring tongue behaviors in awake rats and mice and how these have been modified by other researchers to advance translational science.

Selection of sucrose concentration depends on the effort required to obtain it: studies using tetrabenazine, D1, D2, and D3 receptor antagonists

RATIONALE

Low doses of dopamine (DA) antagonists and accumbens DA depletions reduce food-reinforced instrumental behavior but do not impair primary food motivation, causing animals to reallocate behavior away from food-reinforced tasks with high response requirements and select less effortful alternatives. However, it is uncertain if this same pattern of effects would occur if sucrose was used as the reinforcer.

OBJECTIVES

These experiments studied the impact of DA depletion and antagonism on performance of an effort-related choice task using sucrose as the reinforcer, as well as sucrose consumption, preference, and taste reactivity tests.

METHODS

The effects of DA manipulations were assessed using a task in which rats chose between lever pressing on a fixed ratio 7 schedule for 5.0 % sucrose versus freely consuming a less concentrated solution (0.3 %).

RESULTS

The DA depleting agent tetrabenazine shifted effort-related choice, decreasing lever pressing for 5.0 % sucrose but increasing intake of the concurrently available 0.3 % sucrose. Tetrabenazine did not affect sucrose appetitive taste reactivity, or sucrose consumption or preference, in free consumption tests. The D1 antagonist ecopipam and the D2 antagonist haloperidol also shifted choice behavior at doses that did not alter sucrose consumption or preference. In contrast, sucrose pre-exposure reduced consumption across all conditions. D3 antagonism had no effects.

CONCLUSIONS

D1 and D2 receptor blockade and DA depletion reduce the tendency to work for sucrose under conditions that leave fundamental aspects of sucrose motivation (intake, preference, hedonic reactivity) intact. These findings have implications for studies employing sucrose intake or preference in animal models of depression.

Safety and efficacy of olanzapine monotherapy in treatment-resistant bipolar mania: a 12-week open-label study

OBJECTIVE

To examine the safety and efficacy of olanzapine monotherapy in treatment-resistant bipolar mania.

METHOD

Subjects (n = 18) who were acutely manic, did not respond to lithium, anticonvulsants, and neuroleptics, and/or had intolerable side effects to them in previous manic episodes were openly treated with olanzapine monotherapy (5-40 mg/d) for 12 weeks. The primary and secondary outcomes included the change from baseline to endpoint in Young Mania Rating Scale (YMRS) total score, Clinical Global Impression for Bipolar Disorder-Severity Scale (CGI-S), 17-item Hamilton Depression Rating Scale (HAM-D) and Positive and Negative Syndrome Scale (PANSS), and response and remission rate.

RESULTS

The mean change in YMRS total score from baseline to endpoint was -23.3 ± 8.4 (p < 0.001). Fifteen (88.5%) patients achieved response (≥50% reduction in YMRS total score) and 14 (77.8%) achieved remission (YMRS total score ≤9 at endpoint). Mean changes from baseline to endpoint in CGI-S for mania and PANSS total score were significant, but not the changes in HAM-D total score or CGI-S for depression. The most common adverse events were sedation, self-reported weight gain, ≥7% increase in body weight, dizziness, and akathisia.

CONCLUSIONS

These preliminary results suggest that olanzapine monotherapy is effective and relatively safe in patients with treatment-resistant bipolar mania. Randomized, double-blind, placebo-controlled study is warranted.

Clozapine and prazosin slow the rhythm of head movements during focused stereotypy induced by d-amphetamine in rats

RATIONALE

Clozapine is an efficacious, symptom-ameliorating, atypical antipsychotic drug with few extrapyramidal side effects. Clozapine has been reported either not to affect or to increase d-amphetamine-induced stereotypy, a behavior that is blocked by typical antipsychotic drugs.

OBJECTIVES

This work used a high-resolution measurement system to reassess clozapine's effects on d-amphetamine-induced focused stereotypy (FS) in rats.

MATERIALS AND METHODS

A force-plate actometer permitted the quantitation of the rhythm and vigor of movements during FS. Eight rats received a sensitizing series of doses of 5.0 mg/kg d-amphetamine sulfate, and this dosing regimen induced head movements with a rhythm near 10 Hz. Thirty minutes after d-amphetamine treatment, rats received acute clozapine (2.5-10.0 mg/kg), followed by eight, daily clozapine injections (5.0 mg/kg) given with d-amphetamine on days 2, 5, and 8. Effects of acute doses of the alpha1-noradrenergic antagonist prazosin (0.5-2.0 mg/kg) on the d-amphetamine response were also examined.

RESULTS

Clozapine dose-dependently slowed the near 10-Hz rhythm and reduced the vigor of the d-amphetamine-induced FS. Clozapine significantly lengthened the duration of the FS phase, but the rhythm remained slowed. No evidence for tolerance to clozapine's rhythm-slowing effects was seen in the subchronic phase. Prazosin dose-dependently reduced the near 10-Hz rhythm induced by d-amphetamine, but prazosin did not lengthen the FS phase.

CONCLUSIONS

The results show that clozapine diminished the rhythm and vigor of d-amphetamine-induced stereotyped head movements but, at the same time, lengthened the duration of the expression of the stereotypy. alpha1 antagonism is a likely contributor to the rhythm-modulating effects of clozapine.

Clozapine-like motor effects of the atypical antipsychotic risperidone in rats

A behavioral preparation that affords concurrent measurement of forelimb force, lick rhythm, and forelimb tremor in rats was used to assess the effects of the atypical antipsychotic risperidone. Rats that were trained to press downward on an isometric force transducer while simultaneously licking water reinforcement were administered risperidone (0.08, 0.12, and 0.16 mg/kg). Risperidone suppressed task engagement and increased the duration of individual press-hold-release bouts, effects shared with both typical and atypical antipsychotic drugs in this task. Although risperidone did not significantly affect forelimb force output as clozapine does, it did significantly decrease tremor power in the high-frequency (10-25 Hz) band of the power spectrum. Risperidone dose-dependently decreased the dominant 6 Hz frequency of the power spectrum, a reflection of slowed lick rhythm which is an effect that is shared by other atypical antipsychotic drugs in this task. The results reported in the present study suggest that, although risperidone may not possess the exceptionally low extrapyramidal side-effect profile that clozapine does, its effects are more similar to clozapine than to the extrapyramidal side-effect-producing haloperidol in this task.

Olanzapine. A review of its pharmacological properties and therapeutic efficacy in the management of schizophrenia and related psychoses

Olanzapine is a thienobenzodiazepine derivative which displays efficacy in patients with schizophrenia and related psychoses. It has structural and pharmacological properties resembling those of the atypical antipsychotic clozapine and an improved tolerability profile compared with the classical antipsychotic haloperidol. In several large, well controlled trials in patients with schizophrenia or related psychoses, olanzapine generally 5 to 20 mg/day was at least as effective as haloperidol (5 to 20mg) and more so than placebo, as assessed by overall rating scales for psychoses. Olanzapine improved negative symptoms to a greater extent than haloperidol in 2 of 3 comparative trials, including the largest trial. Efficacy of olanzapine has a rapid onset (within 1 to 2 weeks). Its clinical benefits appear to be maintained for treatment periods of up to 1 year, as shown by analysis of the extension phase of several trials demonstrating decreased probability of hospitalisation over this period compared with haloperidol. Preliminary data suggest the drug may also improve quality of life. Olanzapine was associated with significantly fewer adverse movement disorders (e.g. akathisia, dystonia, hypertonia, extrapyramidal symptoms) than haloperidol. There have been no reports of agranulocytosis (as occurs with clozapine) or any other haemotoxicity attributed to olanzapine, and the drug has shown minimal effect on prolactin levels. Transient increases in levels of hepatic transaminases seem to be clinically important. The only events recorded more frequently during olanzapine than during haloperidol therapy were weight gain, dry mouth and increased appetite. Although the antipsychotic activity of olanzapine has been well demonstrated. Its efficacy in refractory schizophrenia and its place relative to other atypical antipsychotics remain to be determined. Nevertheless, if the long term tolerability profile of olanzapine is confirmed, the drug should provide a valuable therapeutic alternative in the management of schizophrenia and related psychoses.