Transient postnatal NMDA receptor blockade by phencyclidine (PCP), ketamine, or MK-801 induces developmental neuroapoptosis and adult behavioral deficits, which resemble abnormal human behaviors typically present in schizophrenia. This study tested the hypothesis that PCP-induced developmental apoptosis causes a specific deficit of GABAergic interneurons containing parvalbumin (PV), calretinin (CR), or calbindin (CB). Young adult (PND56) rats that were given a single dose of PCP (10 mg/kg) on PND7 exhibited no densitometric change of either CR or CB neurons in any brain region studied, but demonstrated a selective deficit of PV-containing neurons in the superficial layers (II-IV) of the primary somatosensory (S1), motor (M), and retrosplenial cortices, but not in the striatum (CPu) or hippocampus. Further, CR and CB neurons, which were expressed at the time of PCP administration, showed no colocalization with cellular markers of apoptosis (terminal dUTP nick-end labeling (TUNEL) of broken DNA or cleaved caspase-3), indicating that CR- and CB-containing neurons were protected from the toxic effect of PCP and survived into adulthood. This suggests that the deletion of PV neurons occurred during development, but cleaved caspase-3 showed no colocalization with BrdU, a specific marker of S-phase proliferation. These data suggest that the loss of PV-containing neurons was not due to an effect of PCP on proliferating neurons, but rather an effect on post-mitotic neurons. The developmental dependence and neuronal specificity of this effect of PCP provides further evidence that this model may be valuable in exploring the pathophysiology of schizophrenia.

This study determined the role of caspase-3 in phencyclidine (PCP)-induced neurodegeneration in postnatal rats. PCP administration to postnatal day 7 rats induced a dose-dependent increase in caspase-3 enzymatic activity in frontal cortex, striatum, and hippocampus. Enzymatic activation was present at 4 h, peaked between 6 and 12 h, and disappeared by 24 h. Further, cleaved caspase-3-immunoreactive neurons were detected as early as 2 h in the cortex, and were found throughout the brain, including, in addition, the thalamus and striatum. Within the cingulate, frontal, parietal, and retrosplenial cortices, immunoreactivity was specific for layers II-IV (especially layer II). Neurons positive for both silver staining and terminal deoxynucleotidyl transferase biotin-d-UTP nick-end labeling (TUNEL) were found in the same brain regions and subregions. Double labeling experiments confirmed that cleaved caspase-3 and TUNEL were coexpressed in many neurons in all brain regions and subregions studied. Temporal studies revealed that procaspase-3 cleavage preceded TUNEL staining by about 3 h, with many neurons being positive for both caspase-3 and TUNEL 9 h after PCP treatment. In organotypic corticostriatal slices, PCP caused a concentration-and time-dependent cleavage of procaspase-3 that was also colocalized with TUNEL staining in layers II-IV of the parietal cortex. Caspase-3 activation again preceded PCP-induced DNA damage assessed by TUNEL. PCP-induced neuronal death in vitro as measured by TUNEL staining was blocked 85% by Ac-AAVALLPAVLLALLAPDEVD-CHO, a cell-permeable selective caspase-3 inhibitor. These data demonstrate that caspase-3 activation plays a necessary role in the regionally selective neuronal death induced by PCP in the developing rat brain.

Oxidative stress may be involved in the cellular damage and tissue destruction as burn wounds continues to progress after abatement of the initial insult. Since iron and calcium ions play key roles in oxidative stress, this study tested whether topical application of Livionex formulation (LF) lotion, that contains disodium EDTA as a metal chelator and methyl sulfonyl methane (MSM) as a permeability enhancer, would prevent or reduce burn injury. Methods We used an established brass comb burn model with some modifications. Topical application of LF lotion was started 5 minutes post-burn, and repeated every 8 hours for 3 consecutive days. Rats were euthanized and skin harvested for histochemistry and immunohistochemistry. Formation of protein adducts of 4-hydroxynonenal (HNE), malonadialdehyde (MDA) and acrolein (ACR) and expression of aldehyde dehydrogenase (ALDH) isozymes, ALDH1 and ALDH2 were assessed. Results LF lotion-treated burn sites and interspaces showed mild morphological improvement compared to untreated burn sites. Furthermore, the lotion significantly decreased the immunostaining of lipid aldehyde-protein adducts including protein -HNE, -MDA and -ACR adducts, and restored the expression of aldehyde dehydrogenase isozymes in the unburned interspaces. Conclusion This data, for the first time, demonstrates that a topically applied EDTA-containing lotion protects burn injury progression with a concomitant decrease in the accumulation of reactive lipid aldehydes and protection of aldehyde dehydrogenase isozymes. Present studies are suggestive of therapeutic intervention of burn injury by this novel lotion.

Chemical modulation of the monoamine neurotransmitter systems involving dopamine (DA), serotonin (5-HT), and norepinephrine (NE) provides an important means to control certain neurological disorders such as depression, 1 anxiety, 2 alcoholism, 3 chronic pain, 4 eating disorders, 5 and obsessive compulsive disorders. 6 For example, a major pharmaceutical approach to the treatment of depression has come about through the development of agents that interfere with the primary mechanism of removal of 5-HT or NE from the synapse. 7 As the result, the selective 5-HT reuptake inhibitors (SSRIs) such as fluoxetine (Prozac) 8 and paroxetine (Paxil), 9 among others, have been developed for the treatment of depression and related psychological disorders. Despite these recent clinical developments, a detailed understanding of the structural factors that govern the potency and selectivity of ligands at the specific monoamine transporters is still evolving. During our efforts to discover ligands of possible use as medications, 10 we discovered a rather interesting aspect of the 5-HT transporter (SERT) structure activity relationships (SAR), namely that significant selectivity and potency can be achieved through the use of a bivalent ligand approach (Figure 1).The rationale for employing the bivalent ligand approach stems from the possibility that dimeric structures may be capable of bridging independent recognition sites on the transporters resulting in a thermodynamically more favorable binding interaction than the monovalent binding of two molecules. 11 As such proximal binding sites are likely to differ in their location for the three monoaminergic transporters the length of the linker connecting the two binding moieties could thus provide a means to finetune transporter selectivity profiles. Empirical support for such a possibility stems from the enhanced potency and selectivity reported for both bivalent narcotic antagonists containing the naltrexamine pharmacophore 12 and for serotonin-based bivalent 5-HT 1B/1D agonists. 13 We have recently reported on the chemistry and pharmacology of some 3,4-disubstituted piperidine-based ligands that show reasonable potency at the dopamine transporter (DAT). 14 On the basis of these and other studies 15 it had become apparent to us that 3,4-disubstituted piperidines are structurally related to drugs such as femoxetine and paroxetine that exhibit high potency and selectivity for the SERT. 16 One of these piperidines was therefore chosen as the starting monomer for the assembly of bivalent ligands that were postulated to exhibit potent and selective SERT activity.Briefly, piperidine-based ligands 4-16 were prepared in optically pure form from arecoline (1) 14 (Scheme 1) and were evaluated for their ability to inhibit high affinity uptake of DA, 5-HT, and NE using rat synaptosomal nerve endings. 17 The uptake data expressed as K i values and the selectivity profile (ratio of K i values) for these compounds are provided in Table 1. In general, all dimers (7-16) exhibit substantially ...