Early antipsychotic intervention and schizophrenia

Importance of intervention timing in the effectiveness of antipsychotics

The use of early pharmacological intervention in treating young patients with schizophrenia is a debating issue for psychiatrists. However, on the basis of developmental theory, early antipsychotic intervention can be beneficial in terms of protecting neurons from further deterioration. This study investigated whether the initiation of second-generation antipsychotic (SGA) treatment at a younger age can effectively reverse schizophrenia-relevant behavioral and neurochemical features, namely acoustic prepulse inhibition (PPI) and accumbal dopamine (DA) efflux, respectively. Risperidone (RIS, 1mg/kg/day) or olanzapine (OLA, 2.5mg/kg/day) was administered for 6weeks in rats subjected to isolation rearing (IR) in adolescence or young adulthood. Behavioral testing was performed at 3 and 5 (for locomotor activity) and 2 and 4 (for PPI) weeks after the initiation of the pharmacological regimen. An additional PPI test was performed 6weeks after the initiation of the pharmacological regimen to assess the acute add-on effect of RIS or OLA. Dopamine (DA) efflux of the nucleus accumbens was evaluated through in vivo microdialysis at the end of the study, for measuring both the baseline levels after the chronic regimen and the responsiveness to acute add-on RIS or OLA treatment. Our results demonstrated that the effects of SGAs on PPI and accumbal DA efflux were dissociated. Specifically, RIS intervention was more beneficial for adolescent than young adult IR rats in restoring their PPI deficit, whereas OLA was age-independently effective in stimulating the accumbal DA efflux. Both PPI and accumbal DA could be employed to reflect IR-induced abnormalities, in which accumbal DA appeared to be more suitable in depicting the long-term effect of IR, whereas PPI might be a more accurate biological index for revealing the advantages of early RIS intervention.

Effects of 5HT1A Activation on Gating Profile Following 5HT Depletion in Rats Lacking Social Attachment Since Weanling

OBJECTIVE

Central 5-HT1A receptor is involved in the modulation of sensorimotor gating function. However, its precise role is not clearly defined in developmentally social deprived (isolation rearing, IR) rats featured with impaired sensorimotor gating ability. We therefore aimed to examine the effects of 5HT1A activation on acoustic startle response (ASR) and prepulse inhibition (PPI) in IR rats in a condition of compromised presynaptic 5-HT functions.

METHODS

Social control (SOC) and IR rats received an intracerebraoventricular (ICV) injection of 5-HT depletor, 5,7-DHT. Seven days later rats entered a protocol of 8-OH-DPAT, a 5-HT1A agonist, in which locomotor activity, ASR and PPI and their tissue levels of 5-HT were measured.

RESULTS

Our results found that both IR and 5,7-DHT decreased the tissue concentration of 5-HT. IR-induced hyperactivity and gating impairment were unaffected by 5-HT depletion. 8-OH-DPAT strengthened the ASR in IR but not SOC rats and the drug-reduced PPI could be adjusted by 5,7-DHT pretreatment. 8-OH-DPAT at 100 μg/kg enhanced PPI in 5-HT-depleted SOC rats. However for IR rats, 8-OH-DPAT strengthened PPI in sham rats but downgraded it in depletion condition.

CONCLUSION

The integrity of central 5-HT system is important to 5-HT1A-modulated sensorimotor gating in isolation-reared rats.

True alignment of preclinical and clinical research to enhance success in CNS drug development: a review of the current evidence

Central nervous system pharmacological research and development has reached a critical turning point. Patients suffering from disorders afflicting the central nervous system are numerous and command significant attention from the pharmaceutical industry. However, given the numerous failures of promising drugs, many companies are no longer investing in or, indeed, are divesting from this therapeutic area. Central nervous system drug development must change in order to develop effective therapies to treat these patients. Preclinical research is a cornerstone of drug development; however, it is frequently criticised for its lack of predictive validity. Animal models and assays can be shown to be more predictive than reported and, on many occasions, the lack of thorough preclinical testing is potentially to blame for some of the clinical failures. Important factors such as translational aspects, nature of animal models, variances in acute versus chronic dosing, development of add-on therapies and understanding of the full dose-response relationship are too often neglected. Reducing the attrition rate in central nervous system drug development could be achieved by addressing these important questions before novel compounds enter the clinical phase. This review illustrates the relevance of employing these criteria to translational central nervous system research, better to ensure success in developing new drugs in this therapeutic area.