Effect of perioperative lidocaine on metastasis after sevoflurane or ketamine-xylazine anaesthesia for breast tumour resection in a murine model.

BACKGROUND: Breast cancer accounts for 7% of female cancer deaths, usually attributable to metastasis. While surgery is a mainstay of treatment, perioperative interventions may influence risk of metastasis during breast tumour resection. Amide local anaesthetics influence cancer cell biology via numerous mechanisms in vitro, but in vivo data is lacking. We aimed to test the hypothesis that perioperative lidocaine reduces pulmonary metastasis after inhalation and i.v. anaesthesia in the 4T1 murine breast cancer model. METHODS: 4T1 Cancer cells were injected into the mammary fat-pad of immunocompetent BALB/c female mice. After 7 days, the resultant tumour was excised under either sevoflurane or ketamine/xylazine anaesthesia with or without perioperative i.v. lidocaine (1.5 mg kg-1 bolus followed by 25 min infusion 2 mg kg-1 h-1). Fourteen days post-surgery, posthumous lung and liver specimens were examined for metastasis. Pro-inflammatory and pro-metastatic cytokines were profiled in post-mortem serum from a small number of the mice. RESULTS: Primary tumour diameter was similar between groups. Lidocaine reduced lung metastatic colony count vs sevoflurane alone; median (inter-quartile range) 0 (0-2) compared with 22.5 (0-481), P=0.02 and reduced the proportion of animals with pulmonary metastasis (28.5% compared with 52.5%, P=0.04). In mice receiving ketamine-xylazine, lidocaine did not decrease the overall colony count: 60 (26-123) compared with 23.5 (0-225), P=0.43, but increased the proportion of animals with pulmonary metastasis (100% compared with 50%, P<0.01). Post-mortem serum analysis demonstrated reduced pro-inflammatory and angiogenic cytokine expression in animals without metastasis which received lidocaine with sevoflurane. CONCLUSIONS: In this 4T1 murine model of breast cancer, lidocaine decreased pulmonary metastasis when combined with sevoflurane anaesthesia, perhaps via anti-inflammatory and anti-angiogenic effects. It had no such effect in mice given ketamine anaesthesia.

The selective 5-HT6 receptor antagonist SLV has putative cognitive- and social interaction enhancing properties in rodent models of cognitive impairment.

In the present study, our aim was to investigate whether the novel highly selective 5-hydroxytryptamine6 (5-HT6) receptor antagonist SLV can ameliorate impairments in cognition and social interaction with potential relevance for both schizophrenia and Alzheimer's disease (AD). SLV sub-chronically - treated Wistar rats reared in isolation showed significantly enhanced prepulse inhibition (PPI) and object recognition performance when compared to vehicle - treated rats. In the isolated rats, also a significant reduction in expression of hippocampal neural cell adhesion molecule polysialylation (NCAM-PSA) was found which was ameliorated following treatment with SLV (30mg/kg). The social engagement deficit in rats exposed in utero (on gestational day 12.5) to valproic acid (VPA) was reversed by treatment with SLV (30mg/kg). SLV (20 and 30mg/kg, p.o.) fully reversed MK-801 - induced deficits in the ORT and also scopolamine - induced deficits in both the Object Recognition Task (ORT) and Object Location Task (OLT) in Wistar rats. In addition, a combination of sub-optimal doses of SLV and donepezil attenuated scopolamine-induced ORT deficits. Furthermore, SLV (10mg/kg, p.o.) reversed spontaneous alternation deficits in the T-maze induced by MK-801 administration in Swiss mice and in aged C57Bl/6J mice. SLV additionally improved T-Maze spatial learning and passive avoidance learning in Sprague-Dawley rats with amyoid-beta (Aß) injections into the hippocampus. In contrast, no benefits were found with SLV or the tested reference compounds (donepezil and RVT-101) on cognitive performance of 12months old Tg2576 mice. Also, in the social recognition task, an absence of cognitive enhancing properties was observed with SLV on "normal forgetting" in Wistar rats. Finally, analysis of spontaneous inhibitory postsynaptic currents (sIPSCs) frequency recorded from pyramidal cells revealed a reduction in the presence of 1µM of SLV. In conclusion, SLV was investigated in several rodent animal models and found to be effective at a least effective dose (LED) of 20mg/kg and 10mg/kg (p.o.) in the rat and the mouse, respectively.

Intraventricular infusions of anti-NCAM PSA impair the process of consolidation of both avoidance conditioning and spatial learning paradigms in Wistar rats.

Processing of information for long-term storage requires specific patterns of activity that lead to modification of synapse structure and eventual change in neural connectivity pattern. Morphological change associated with memory consolidation is reliant on neural cell adhesion molecule (NCAM) function and that of its polysialylated variant (NCAM PSA). Across species and paradigms, a transient frequency increase of polysialylated neurons in the hippocampal dentate has been found necessary for memory consolidation, however, recent studies suggest that NCAM PSA may serve to suppress memory formation in certain paradigms. As intraventricular infusions of NCAM blocking antibodies have been used successfully to demonstrate its time-dependent role at the 6 h post-training period of memory consolidation, we employed the same procedure to demonstrate a functional requirement for NCAM PSA in the consolidation of two commonly used behavioral paradigms: avoidance conditioning and spatial learning in Wistar rats. Anti-PSA was found to significantly induce amnesia of the passive avoidance response when infused at the 10 h post-training time, a period coincident with the learning-associated increase in dentate polysialylated cell frequency. Moreover, the amnesia became apparent at the 48 h recall time and was not apparent at the 24 h post-training time, suggesting a possible role in memory reconsolidation. A similar anti-PSA action was observed following water maze training in aged animals but was not apparent in young animals, an effect suggested to be due to inadequate antibody saturation of the polysialylated cell population. These studies confirm the requirement for NCAM PSA in memory consolidation and separate it from that of NCAM.

Protein kinase C delta regulates neural cell adhesion molecule polysialylation state in the rat brain.

Polysialylation of neural cell adhesion molecule (NCAM PSA) modulates cell-cell homophilic binding and signalling during brain development and the remodelling of discrete brain regions in the adult. Following learning, a transient increase in the frequency of polysialylated neurones occurs in the dentate gyrus of the hippocampal formation, and this has been correlated with the selective retention and/or elimination of synapses that are transiently overproduced during memory consolidation. We now demonstrate that protein kinase C delta (PKCdelta) negatively regulates polysialyltransferase activity in the rat brain during development and also in the hippocampus during memory consolidation, where its down-regulation in the Golgi membrane fraction coincides with the transient increase in NCAM PSA expression. Decreased expression of PKCdelta was also observed in the hippocampus of rats reared in a complex environment and this directly contrasted the significant increase in frequency of hippocampal polysialylated neurones observed in these animals. These effects were isoform-specific as no change in total PKC enzyme activity was detected during memory consolidation and complex environment rearing had no effect on the hippocampal expression of PKCalpha, beta, gamma or epsilon. By sequential immunoprecipitation and immunoblot analysis, phosphorylation of polysialyltransferase protein(s) was (were) demonstrated to occur on both serine and tyrosine residues and this was associated with decreased enzyme activity. Moreover, a similar experimental approach revealed the degree of PKCdelta co-precipitation with polysialyltransferase protein(s) to be inversely correlated with polysialyltransferase activity. These findings support in vitro evidence indicating PKCdelta to regulate polysialyltransferase activity and NCAM polysialylation state.

Pentyl-4-yn-valproic acid enhances both spatial and avoidance learning, and attenuates age-related NCAM-mediated neuroplastic decline within the rat medial temporal lobe.

2-N-Pentyl-4-pentynoic acid [pentyl-4-yn-valproic acid (VPA)] is an analogue of valproic acid that induces neuritogenesis and increases neural cell adhesion molecule (NCAM) prevalence in cultured neural cells. As memory consolidation involves synapse growth, aided by cell adhesion molecule function, we determined whether or not pentyl-4-yn-VPA had cognition-enhancing properties. Pentyl-4-yn-VPA (16-85 mg/kg) significantly improved water maze learning and task retention when given prior to each training session. Acute administration of pentyl-4-yn-VPA also influenced memory consolidation processes as, when given at 3 h post-passive avoidance training, the amnesia induced by scopolamine given 6 h post-training was prevented in a dose-dependent manner. Chronic administration of pentyl-4-yn-VPA (16.8 or 50.4 mg/kg) also significantly reduced escape latencies in the water maze task, 24 h following the last drug administration. This improved spatial learning was accompanied by enhanced neuroplasticity as the expression of NCAM polysialylated neurons in the infragranular zone of the dentate gyrus and in layer II of the perirhinal and piriform cortex was increased significantly following chronic drug treatment. The cognition-enhancing qualities of pentyl-4-yn-VPA, combined with its ability to attenuate the age-related loss of the NCAM polysialylation state, suggest that it may effectively slow the onset of cognitive decline.

Spatial learning activates neural cell adhesion molecule polysialylation in a corticohippocampal pathway within the medial temporal lobe.

Transient and time-dependent modulations of neural cell adhesion molecule (NCAM) polysialylation in the dentate gyrus of the rodent hippocampus are a feature of spatial and nonspatial forms of learning. In the hippocampal formation, polysialic acid immunoreactivity was localized to granule-like cells and their mossy fibre axons. We now demonstrate the latter to extend to the CA3 region where apparent recurrent and Schaffer collaterals were labelled. The axons of the CA1 pyramidal cell layer were immunopositive, as was the subiculum that they innervate. Layers I and III of the entorhinal cortex stained intensely for polysialic acid; however, these were not visible in the more lateral aspect of this region and were replaced by a single band of immunopositive neurons that extended to include the perirhinal and piriform cortices. After Morris water maze training, the number of polysialylated neurons within the entorhinal cortex exhibited a two- to threefold increase at the 10-12-h posttraining time with respect to that observed immediately after training. This increase was task specific, as no change was observed in freely swimming animals or those required to locate a visible platform. These results suggest the presence of a corticohippocampal pathway involved in the eventual consolidation of memory.

A synthetic peptide ligand of neural cell adhesion molecule (NCAM) IgI domain prevents NCAM internalization and disrupts passive avoidance learning.

The neural cell adhesion molecule (NCAM) mediates cell adhesion and signal transduction through trans-homophilic- and/or cis-heterophilic-binding mechanisms. Intraventricular infusions of anti-NCAM have revealed a functional requirement of NCAM for the consolidation of memory in rats and chicks in a specific interval 6-8 h after training. We have now extended these studies to a synthetic peptide ligand of NCAM (C3) with an affinity for the IgI domain and the capability of inhibiting NCAM-mediated neurite outgrowth in vitro. Intraventricular administration of a single 5 microg bolus of C3 strongly inhibited recall of a passive avoidance response in adult rats, when given during training or in the 6-8-h posttraining period. The effect of C3 on memory consolidation was similar to that obtained with anti-NCAM as the amnesia was not observed until the 48-h recall time. The unique amnesic action of C3 during training could be related to disrupted NCAM internalization following training. In the 3-4-h posttraining period NCAM 180, the synapse-associated isoform, was down-regulated in the hippocampal dentate gyrus. This effect was mediated by ubiquitination and was prevented by C3 administration during training. These findings indicate NCAM to be involved in both the acquisition and consolidation of a passive avoidance response in the rat. Moreover, the study provides the first in vivo evidence for NCAM internalization in learning and identifies a synthetic NCAM ligand capable of modulating memory processes in vivo.

Syntheses of benzoquinolizidine and benzoindolizidine derivatives as anti-amnesic agents.

Tacrine, one of the drugs available for Alzheimer's disease based on the cholinergic approach, suffers from considerable toxicity. Many analogues of tacrine have been prepared which retain the pharmacologically rich aminopyridine or aminoquinoline motifs. The current research was undertaken to produce an acetylcholinesterase inhibitor by employing 11-aminobenzoquinolizidines (4) and 10-aminobenzoindolizidines (5) as templates. Thus, we aimed to achieve three goals relative to tacrine: eliminate the pyridine and quinoline moieties and render the molecule less flat. Overall, the compounds we prepared were poorer inhibitors of acetylcholinesterase compared to tacrine. The single exception was compound 6f which exhibited an effect comparable to that of tacrine, but only at a dose of the order of 10(-3) M. However, despite the poor acetylcholinesterase inhibition by 6b, this compound proved to be an effective anti-amnesic agent at 45 mg/kg dose.

Syntheses of 1,2-diamino and 1,2-aminoalcohol derivatives in the piperidine and pyrrolidine series as anti-amnesic agents.

Tacrine, one of the drugs available for Alzheimer's disease based on the cholinergic approach, suffers from considerable toxicity. Many analogues of tacrine has been prepared which retain the pharmacologically rich aminopyridine or aminoquinoline motifs. The current research is a continuation of our efforts in the area of 11-aminobenzoquinolizidines (4) and 10-aminobenzoindolizidines (5) (cf. ref9). A serendipitous discovery led us to the biologically active open chain analogue 9, and we proceeded to elaborate on this molecule. Overall, the compounds we prepared were poor inhibitors of acetylcholinesterase as compared to tacrine. The single exception was compound 20 which exhibited an effect comparable to that of tacrine, but only at a dose in the order of 10(-3) M. However, despite the poor acetylcholinesterase inhibition by 9, this compound was found to be an effective antiamnesic agent.