New pharmacotherapeutic modalities for negative symptoms in psychosis

Negative symptoms in schizophrenia comprise a psychopathologic and pathophysiologic syndrome which is absent from normal mental function. Renewed interest in negative symptoms has led to the development of better measuring instruments, among which is the Positive And Negative Syndrome Scale (PANSS), which provides a way of measuring and reporting positive and negative symptoms in a balanced and convenient form. A number of strategies are being investigated for treating negative symptoms. Dopamine agonists such as levodopa, amphetamines and bromocriptine have been shown to produce improvements in negative symptoms, although good, well-controlled clinical trials are lacking. Partial dopamine agonists, such as MAR 327, are also currently under investigation and results are expected soon. Tricyclic, selective serotonin reuptake inhibitors and monoamine oxidase antidepressants appear to be able to modify negative symptoms in schizophrenia, although, once again, carefully designed trials are needed. Modification of GABAergic transmission has shown little promise, but the use of glycine to augment transmission at N-methyl-D-aspartate (NMDA) synapses suggests that the strategy may be beneficial. These results also imply that altered glutamate receptor function may be partly responsible for negative symptoms. One strategy that has been shown to have a beneficial effect against negative symptoms is combined serotonin/dopamine antagonism. Clozapine was found to have this profile after its introduction, and the recently introduced antipsychotic, risperidone was developed intentionally to be a combined 5-HT2/D2 antagonist. Both risperidone and clozapine have been shown to be effective against negative symptoms. One problem associated with the assessment of drug effects on negative symptoms, however, is that drugs can act on both primary and secondary negative symptoms.(ABSTRACT TRUNCATED AT 250 WORDS)

Efficacy of risperidone for behavioral disorders in the elderly: a clinical observation

Standard antipsychotics are ineffective in some geriatric patients. In addition, they are not helpful for apathy and withdrawal. Studies have demonstrated that 5HT2 antagonists improve affective symptoms and anxiety; therefore, the efficacy of risperidone on agitation and withdrawal was considered. The literature on risperidone was reviewed, and the efficacy and limitations of risperidone observed in two geriatric patients, one with agitation and another with apathy and withdrawal. Risperidone proved to be effective in controlling disruptive behavior in geriatric patients. Combined antagonism of D2 and 5HT2 receptors might be effective in improving agitation and withdrawal. Risperidone, with both D2 and 5HT2 antagonistic properties, seems to have potential as an alternative agent in controlling agitation and withdrawal in geriatric patients. Caution and need for further observation is recommended.

Psychopharmacologic treatment of negative schizophrenic symptoms

Diverse pharmacologic agents have been reported to be effective in treating negative schizophrenic symptoms (NSS). In light of this large and growing literature, as well as of reconceptualizations of the underlying pathophysiology of NSS, the time may have come to reject models that assume "irreversibility" of NSS. However, flaws in existing studies prevent closure regarding the reversibility of, and by inference the treatability of, NSS. Guidelines for future studies are articulated, e.g., the need to distinguish primary from secondary NSS, to include drug-free subjects with a predominance of NSS in clinical trials, and to use well-validated and psychometrically sound instruments for assessing NSS.

Homovanillic acid in the cerebrospinal fluid: patterns of response after four weeks of neuroleptic treatment

Lumbar cerebrospinal fluid (CSF) homovanillic acid (HVA) concentrations were measured before and after 4 weeks of neuroleptic treatment in schizophrenic (n = 15) and schizoaffective (n = 4) patients. Neuroleptic treatment induced a nonsignificant (17%) increase in CSF HVA group mean levels. For the total group, no correlations were found between pretreatment CSF HVA and clinical measures, or between changes in HVA and clinical response. An alternative interpretation was attempted by defining "tolerant" and "nontolerant" subgroups. A "tolerant" response was defined as a reduction in posttreatment HVA values below pretreatment levels, whereas a "nontolerant" response was characterized by posttreatment values above pretreatment levels. When thus defined, nontolerant patients had a significantly inferior clinical response to neuroleptics, in contrast to their tolerant counterparts. Further, although there was no difference in pretreatment CSF HVA values between these two groups, pretreatment clinical profiles did differ significantly. Also, in a retrospective analysis, nontolerant patients were found to have a significantly earlier age of illness onset, a greater number of prior psychiatric hospitalizations, and more time spent in psychiatric hospitals.

BMY-14802, a sigma ligand and potential antipsychotic drug, reverses amphetamine-induced changes in neostriatal single-unit activity in freely moving rats

The effects of BMY-14802 (5, 10, or 20 mg/kg), a sigma-receptor ligand showing preclinical evidence of antipsychotic efficacy, were tested on single-unit activity in the neostriatum of freely moving rats with or without pretreatment with 1.0 mg/kg D-amphetamine. Relative to resting baseline, amphetamine activated the large majority of neurons that changed firing rate in close temporal association with movement. All doses of BMY-14802 reversed this neuronal response, but the effect was most pronounced at 20 mg/kg. This dose, however, was equally likely to reverse or to induce a haloperidol-like potentiation of those neurons inhibited by amphetamine. In contrast, 10 mg/kg BMY-14802 consistently reversed amphetamine-induced neuronal inhibitions. All doses of BMY-14802 attenuated the locomotor effects of amphetamine, but only the higher doses also blocked other aspects of the amphetamine behavioral response. By itself, BMY-14802 dose dependently inhibited motor-related neurons, but elicited less behavioral activation than amphetamine. BMY-14802 (20 mg/kg) also induced hindlimb ataxia and occasional backwards locomotion. Haloperidol (1.0 mg/kg) reliably suppressed both behavior and neuronal activity when injected 30 min after BMY-14802, whether or not amphetamine pretreatment was given. Thus, BMY-14802 shares with other neuroleptics the capacity to reverse amphetamine-induced excitations of neostriatal motor-related neurons, whereas other effects of BMY-14802 reveal some haloperidol-like actions at 20 mg/kg that do not occur at lower doses.

Effect of amperozide on rat cortical 5-HT2 and striatal and limbic dopamine D2 receptor occupancy: implications for antipsychotic action

Amperozide (FG 5606, N-ethyl-4-[4',4'-bis(p-fluorophenyl)butyl]-1-piperazine-carboxamide) is an atypical antipsychotic drug which has relatively weak in vitro affinity for striatal dopamine2 (D2) receptors and strong affinity for cortical 5-HT2 receptors. The in vivo affinity for 5-HT2 binding sites in rat cortex was 1.1 mg/kg. In striatum or olfactory tubercle, doses of amperozide up to 40 mg/kg did not displace radioligand binding to D2 receptors. Amperozide, haloperidol and ritanserin had similar in vivo potency in blocking the 5-HT2 binding site, but only haloperidol displaced D2 receptor binding. Based on the clinically effective dose of amperozide (0.14-0.28 mg/kg per day), it is suggested that the antipsychotic effect of amperozide is related, in part, to its in vivo interaction with the 5-HT2 receptor and that amperozide cannot be expected to exert its antipsychotic action by blockade of D2 receptors in the striatum or limbic regions.