Polyamines and the NMDA receptor: Modifying intrinsic activities with aromatic substituents

Pentamidine analogs as inhibitors of [(3)H]MK-801 and [(3)H]ifenprodil binding to rat brain NMDA receptors

The anti-protozoal drug pentamidine is active against opportunistic Pneumocystis pneumonia, but in addition has several other biological targets, including the NMDA receptor (NR). Here we describe the inhibitory potencies of 76 pentamidine analogs at 2 binding sites of the NR, the channel binding site labeled with [(3)H]MK-801 and the [(3)H]ifenprodil binding site. Most analogs acted weaker at the ifenprodil than at the channel site. The spermine-sensitivity of NR inhibition by the majority of the compounds was reminiscent of other long-chain dicationic NR blockers. The potency of the parent compound as NR blocker was increased by modifying the heteroatoms in the bridge connecting the 2 benzamidine moieties and also by integrating the bridge into a seven-membered ring. Docking of the 45 most spermine-sensitive bisbenzamidines to a recently described acidic interface between the N-terminal domains of GluN1 and GluN2B mediating polyamine stimulation of the NR revealed the domain contributed by GluN1 as the most relevant target.

The vascular extracellular calcium-sensing receptor: an update

The extracellular calcium-sensing receptor (CaR) was first described in the parathyroid gland. Recent studies have shown that the CaR is also expressed in blood vessels, especially in the endothelial and adventitial layers but its physiological function is still not clear. However, an understanding of its possible role(s) in the vasculature (perivascular-neurones, heart and blood vessels) is important because of the use of synthetic positive allosteric CaR modulators in hyperparathyroidism and the potential importance of negative modulators in the treatment of osteoporosis. In this review, the effects of CaR activation and inhibition are detailed and the possible role of the CaR as both an amplifier and attenuator of myo-endothelial coupling in the vasculature is described.

The involvement of the polyamines binding sites at the NMDA receptor in creatine-induced spatial learning enhancement

Achievements made over the last years have highlighted the important role of creatine in health and disease. However, studies of its effect on cognition function have been limited. In the present study, we investigated the effect of creatine on early consolidation of the spatial learning in rats. Statistical analysis showed that intrahippocampal administration of creatine (2.5 and 7.5 nmol/hippocampus) (post-training) decreased the latency for scape and mean number of errors in Barnes maze test. The involvement of polyamine binding site at NMDA receptor in creatine-induced spatial learning enhancement was investigated by co-administration of arcaine (0.02 nmol/hippocampus) or spermidine (0.02 nmol/hippocampus) with creatine (2.5 nmol/hippocampus) (post-training). Statistical analysis revealed that creatine-induced spatial learning enhancement was reverted by co-administration of arcaine (0.02 nmol/hippocampus) and intensified by spermidine (0.02 nmol/hippocampus). These results provide evidence that creatine not only seem to be involved in energy metabolism but may also play an important role in early consolidation of spatial learning in hippocampus which participation of polyamines binding site at the NMDA receptor.