Antischizophrenic activity independent of dopamine D2 blockade

Regulation of pituitary adenylyl cyclase-activating polypeptide (PACAP, ADCYAP1: adenylyl cyclase-activating polypeptide 1) in the treatment of schizophrenia

BACKGROUND

Deficiency of pituitary adenylyl cyclase-activating polypeptide (PACAP) and its specific receptor, PAC1, causes a schizophrenia-like phenotype in mice. In addition, the relation of the PACAP and PAC1 genes to schizophrenia has been shown by single-nucleotide polymorphism association studies. Furthermore, PACAP is reported to be involved in the function of disrupted-in-schizophrenia 1.

OBJECTIVE

To summarize briefly the recent evidence relating the PACAP system and schizophrenia and discuss the application of PACAP to the treatment of schizophrenia.

RESULTS/CONCLUSION

The regulation of PACAPergic signals is an interesting potential treatment for schizophrenia. Further studies of PACAP signals and the association of PACAP signals with schizophrenia should shed the light on the utility of this approach in the treatment of schizophrenia.

Effect of gabapentin on oculomotor control and parkinsonism in patients with progressive supranuclear palsy

The efficacy of gabapentin on motor, oculomotor and frontal lobe symptoms was evaluated in patients with progressive supranuclear palsy (PSP) in a pilot study. Fourteen patients were included and seven of them received gabapentin. Clinical evaluation and horizontal eye movement recordings were performed at inclusion and 5-weeks later. Motor score and saccade latency in the visually guided saccade (VGS) task were identical in the two groups. However, the error rate in the antisaccade task was significantly decreased in the gabapentin group. This preliminary study shows that gabapentin improves reflexive saccade inhibition in patients with PSP but does not improve the latency of VGSs.

Association of the C677T and A1298C polymorphisms of methylenetetrahydrofolate reductase gene with schizophrenia: association is significant in men but not in women

Schizophrenia is a complex and common psychiatric disorder with a polygenic inheritance. In our previous report, we showed an association between the methylenetetrahydrofolate reductase (MTHFR) gene C677T and A1298C polymorphisms and schizophrenia in patients from Bakirkoy in Istanbul, Turkey [Sazci, A., Ergul, E., Guzelhan, Y., Kaya, G., Kara, I., 2003. Methylenetetrahydrofolate reductase gene polymorphisms in patients with schizophrenia. Mol. Brain Res. 117, 104-107]. We wanted also independently to confirm this study in a gender-specific manner with schizophrenic patients from Erenkoy in Istanbul, Turkey. To investigate the role of the C677T and A1298C polymorphisms of methylenetetrahydrofolate reductase gene in schizophrenia in a gender-specific manner, we analyzed the genotypes of MTHFR677 and MTHFR1298 of 297 schizophrenic patients and 341 healthy controls, using a polymerase chain reaction restriction fragment length polymorphism method. The MTHFR 677T allele was significantly distributed (chi2=7.312; P=0.026), between schizophrenic patients and healthy controls. The T677T genotype was overrepresented in the total schizophrenic patients (OR=1.938; 95%CI=1.133-3.315; chi2=5.996; P=0.014). Similarly, the T677T/A1298A compound genotype was the most significant one in the total schizophrenic patients (OR=2.397; 95% CI=1.327-4.330; chi2=8.821; P=0.003). The C1298C genotype was overrepresented in the total schizophrenic patients (OR=1.706; 95%CI=1.014-2.870; chi2=4.126; P=0.042). Likewise, the C677C/C1298C compound genotype was significant in the total schizophrenic patients (OR=1.689; 95%CI=0.985-2.894; chi2=3.695; P=0.055). When schizophrenic patients and healthy controls were stratified according to gender difference, the T677T genotype and T677T/A1298A compound genotype were significantly overrepresented (OR=2.184; 95% CI=1.069-4.462; chi2=4.767; P=0.029; OR=2.748; 95% CI=1.215-6.214; chi2=6.301; P=0.012, respectively) in men schizophrenic patients. However, neither the MTHFR C677T nor the A1298C polymorphisms are associated with schizophrenia in women. In conclusion, the MTHFR 677T allele and T677T, C1298C genotypes, and T677T/A1298A, C677C/C1298C compound genotypes are genetic risk factors for schizophrenia in men but not in women in a gender-specific manner.

Ketamine-induced distractibility: An oculomotor study in monkeys

BACKGROUND

Administration of subanesthetic doses of ketamine, a noncompetitive N-methyl-D-aspartate receptor antagonist, induces a spectrum of behavioral disorders that are commonly observed in patients with schizophrenia. Although it has been demonstrated that poor antisaccade performance is a core dysfunction in schizophrenia, the ability of ketamine to induce an increased distractibility has not been demonstrated. The present study aimed to determine whether ketamine administration would reproduce the same antisaccade deficit as that observed in schizophrenic subjects.

METHODS

We studied the effect of acute ketamine or saline administration on the performance of two monkeys trained on a reflexive visually guided saccade task and an antisaccade task.

RESULTS

The main result is that ketamine administration induced a markedly increased antisaccade error rate and increased antisaccade latency, similar to that seen in schizophrenic subjects. Other impairments consisted of increased reflexive saccade latency and the presence of a gaze-evoked nystagmus.

CONCLUSIONS

This study supports the validity of ketamine as a pharmacological model of schizophrenia. Based on the known pharmacological effects of ketamine, further studies should allow the investigation of the pharmacological basis of distractibility.

L-homocysteine sulfinic acid and other acidic homocysteine derivatives are potent and selective metabotropic glutamate receptor agonists

Moderate hyperhomocysteinemia is associated with several diseases, including coronary artery disease, stroke, Alzheimer's disease, schizophrenia, and spina bifida. However, the mechanisms for their pathogenesis are unknown but could involve the interaction of homocysteine or its metabolites with molecular targets such as neurotransmitter receptors, channels, or transporters. We discovered that L-homocysteine sulfinic acid (L-HCSA), L-homocysteic acid, L-cysteine sulfinic acid, and L-cysteic acid are potent and effective agonists at several rat metabotropic glutamate receptors (mGluRs). These acidic homocysteine derivatives 1) stimulated phosphoinositide hydrolysis in the cells stably expressing the mGluR1, mGluR5, or mGluR8 (plus Galpha(qi9)) and 2) inhibited the forskolin-induced cAMP accumulation in the cells stably expressing mGluR2, mGluR4, or mGluR6, with different potencies and efficacies depending on receptor subtypes. Of the four compounds, L-HCSA is the most potent agonist at mGluR1, mGluR2, mGluR4, mGluR5, mGluR6, and mGluR8. The effects of the four agonists were selective for mGluRs because activity was not discovered when L-HCSA and several other homocysteine derivatives were screened against a large panel of cloned neurotransmitter receptors, channels, and transporters. These findings imply that mGluRs are candidate G-protein-coupled receptors for mediating the intracellular signaling events induced by acidic homocysteine derivatives. The relevance of these findings for the role of mGluRs in the pathogenesis of homocysteine-mediated phenomena is discussed.