Bipolar manic depressive illness and the fragile X syndrome

Some of the effects of the selective sigma ligand (+)pentazocine are mediated via a naloxone-sensitive receptor

Recently, in an attempt to isolate the nonopioid sigma receptor, Su and colleagues purified a protein from rat liver and brain which appeared to resemble the original sigma opioid receptor as proposed by Martin in 1976, and for which the nonopiate sigma-1 ligand (+)pentazocine presents a high affinity. Previous in vivo electrophysiological studies from our laboratory have demonstrated that several selective sigma-1 ligands potentiate the neuronal response to NMDA. The goal of the present series of experiments was to assess the effects of some selective sigma-1 ligands on the potentiation of the NMDA response and to determine if this potentiation was mediated by the naloxone-sensitive sigma receptor. Extracellular unitary recordings from pyramidal neurons of the CA3 region of the rat dorsal hippocampus were obtained. The sigma-1 ligands BD 737, L 687-384, and JO-1784 (igmesine), administered intravenously at low doses, potentiated the NMDA response but the opiate antagonist naloxone failed to reverse this potentiation. However, the potentiation of the NMDA response induced by the sigma-1 ligand (+)pentazocine was suppressed by naloxone but not by the mu antagonist cyprodime hydrobomide, the kappa antagonist DIPPA nor by the delta antagonist naltrindole. (+/-) Cyclazocine, which presents a high affinity for the above-mentioned sigma-opiate receptor acted as an antagonist by suppressing the potentiation of the NMDA response induced by both JO-1784 and (+)pentazocine. These results suggest that the effects induced by some sigma-1 ligands may, in fact, be sensitive to naloxone while others may not. The original classification of sigma receptors as opiates might have been partly accurate.

Chromosomal aberrations and bipolar affective disorder

Chromosomal abnormalities associated with bipolar disorder may help in the localisation of susceptibility genes for bipolar illness by pinpointing 'candidate' regions of the genome for further study using molecular genetic methods. We review descriptions of chromosomal abnormalities in association with bipolar and related affective disorders and evaluate their relevance for localising susceptibility genes for bipolar disorder, using standardised criteria. We found 28 reports. We identified four genomic regions of potential interest: 11q21-25; 15q11-13; chromosome 21;Xq28. It is important that clinicians are able to recognise patients who may have chromosome abnormalities which could help in the localisation of susceptibility genes for psychiatric disorders. We suggest referral for specialist investigation and karyotyping, to a psychiatric genetics research group, of any patient with functional psychosis and one or more of the following: (a) a strong family history of functional psychosis; (b) mental retardation; (c) another disease known to be caused by a single gene; or (d) congenital abnormalities.