Effects of phencyclidine and analog drugs on acetylcholine receptor of cultured muscle cells

Perinatal administration of phencyclidine alters expression of Lingo-1 signaling pathway proteins in the prefrontal cortex of juvenile and adult rats

Postnatal administration of phencyclidine (PCP) in rodents causes major brain dysfunction leading to severe disturbances in behavior lasting into adulthood. This model is routinely employed to model psychiatric disorders such as schizophrenia, as it reflects schizophrenia-related brain disturbances including increased apoptosis, and disruptions to myelin and plasticity processes. Leucine-rich repeat and Immunoglobin-like domain-containing protein 1 (Lingo-1) is a potent negative regulator of both axonal myelination and neurite extension. The Nogo receptor (NgR)/tumor necrosis factor (TNF) receptor orphan Y (TROY) and/or p75 neurotrophin receptor (p75) complex, with no lysine (K) (WNK1) and myelin transcription factor 1 (Myt1) are co-receptors or cofactors in Lingo-1 signaling pathways in the brain. We have examined the developmental trajectory of these proteins in a neurodevelopmental model of schizophrenia using PCP to determine if Lingo-1 pathways are altered in the prefrontal cortex throughout different stages of life. Sprague-Dawley rats were injected with PCP (10 mg/kg) or saline on postnatal days (PN)7, 9, and 11 and killed at PN12, 5 or 14 weeks for measurement of Lingo-1 signaling proteins in the prefrontal cortex. Myt1 was decreased by PCP at PN12 (P=0.045), and at 14 weeks PCP increased Lingo-1 (P=0.037), TROY (P=0.017), and WNK1 (P=0.003) expression. This is the first study reporting an alteration in Lingo-1 signaling proteins in the rat prefrontal cortex both directly after PCP treatment in early development and in adulthood. We propose that Lingo-1 pathways may be negatively regulating myelination and neurite outgrowth following the administration of PCP, and that this may have implications for the cortical dysfunction observed in schizophrenia.

Alterations of p75 neurotrophin receptor and Myelin transcription factor 1 in the hippocampus of perinatal phencyclidine treated rats

Postnatal administration of phencyclidine (PCP) in rodents causes major disturbances to neurological processes resulting in severe modifications to normal behavioral traits into adulthood. It is routinely used to model psychiatric disorders such as schizophrenia, producing many of the dysfunctional processes in the brain that are present in this devastating disorder, including elevated levels of apoptosis during neurodevelopment and disruptions to myelin and plasticity processes. Lingo-1 (or Leucine-rich repeat and immunoglobulin domain-containing protein) is responsible for negatively regulating neurite outgrowth and the myelination of axons. Recent findings using a postmortem human brain cohort showed that Lingo-1 signaling partners in the Nogo receptor (NgR)/p75/TNF receptor orphan Y (TROY) signaling complex, and downstream signaling partners With No Lysine (K) (WNK1) and Myelin transcription factor 1 (Myt1), play a significant part in schizophrenia pathophysiology. Here we have examined the implication of Lingo-1 and its signaling partners in a neurodevelopmental model of schizophrenia using PCP to determine if these pathways are altered in the hippocampus throughout different stages of neurodevelopment. Male Sprague-Dawley rats were injected subcutaneously with PCP (10mg/kg) or saline solution on postnatal days (PN) 7, 9, and 11. Rats (n=6/group) were sacrificed at PN12, 5weeks, or 14weeks. Relative expression levels of Lingo-1 signaling proteins were examined in the hippocampus of the treated rats. p75 and Myt1 were decreased (0.001≤p≤0.011) in the PCP treated rats at PN12. There were no significant changes in any of the tested proteins at 5weeks (p>0.05). At 14weeks, p75, TROY, and Myt1 were increased in the PCP treated rats (0.014≤p≤0.022). This is the first report of an alteration in Lingo-1 signaling proteins in the rat hippocampus, both directly after PCP treatment in early development and in adulthood. Based on our results, we propose that components of the Lingo-1 signaling pathways may be involved in the acute neurotoxicity induced by perinatal administration of PCP in rats early in development and suggest that this may have implications for the hippocampal deficits seen in schizophrenia.

Morphological alterations in cultured neuromuscular tissue induced by two anesthetic agents

A diversity of pathogenic effects was observed in two complementary culture systems following their exposure to the anesthetic agents. Thiopental sodium and ketamine hydrochloride. The cytotoxic effects of both agents in these two culture types were reversible and dose-related. In organotypic spinal cord slice cultures, thiopental sodium caused general toxicity but no demyelination, while ketamine hydrochloride induced, to a varied extent, damage of the myelin sheath and degeneration of mitochondria into multilamellar bodies. In autologous nerve-muscle co-cultures both anaesthetic agents caused the arrest of muscle contractions. However, when added to skeletal muscle cultures, the drugs differed in their effect. Thiopental sodium did not inhibit spontaneous muscle contractions indicating, as in the case of Tubocurarine, a direct effect of the drug on the neuromuscular junction. Ketamine hydrochloride, in contrast, arrested spontaneous muscle contractions, implying that it did not directly affect the neuromuscular synapse.

Stimulating effects of prednisolone on acetylcholine receptor expression and myogenesis in primary culture of newborn rat muscle cells

Prednisolone at concentrations of 10(-5) to 10(-8) mol/l, added to 3-day (day D + 2) tissue cultures of newborn rat myogenic cells at the time myoblasts are beginning to fuse, increases the level of myotube acetylcholine receptor expression at the 8th day (day D + 7) of culture. This effect is associated with increases in the number and size of the formed myotubes, not with a changed affinity of the receptor for its ligand, and is very probably mediated by one or more extracellular proteins the synthesis of which is induced early by the presence of prednisolone.

Synergistic inhibition by trifluoperazine and phencyclidine of carbamylcholine-induced cation influx in muscle cultures

The effect of trifluoperazine (TFP) and phencyclidine (PCP) on acetylcholine receptor (AChR) function was studied in rat myotubes differentiated in vitro. While both drugs exerted an inhibitory effect on carbamylcholine (CCh)-induced Na+ or Ca2+ flux (I50 = 5-9 microM), alpha-bungarotoxin (alpha-Bgt) binding was not affected. The inhibitory effect of both drugs was independent of CCh concentration. The mutual inhibitory effect of TFP and PCP on Ca2+ influx was analyzed using three alternative models of interaction between the two drugs: competitive, additive and synergistic inhibition models. Our results are in accord with a synergistic interaction between the drugs probably not through desensitization. This synergistic interaction between the drugs provides a biochemical rationale to the phenothiazine contraindication in the treatment of PCP psychosis.