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The traveling salesman problem (TSP) is used to measure the efficiency of spatial route selection. Among researchers in cognitive psychology and neuroscience, it has been utilized to examine the mechanisms of decision making, planning, and spatial navigation. While both human and non-human animals produce good solutions to the TSP, the solution strategies engaged by non-human species are not well understood. We conducted two experiments on the TSP using Long-Evans laboratory rats as subjects. The first experiment examined the role of arena walls in route selection. Rats tend to display thigmotaxis in testing conditions comparable to the TSP, which could produce results similar to a convex hull type strategy suggested for humans. The second experiment examined the role of turn angle between targets along the optimal route, to determine whether rats exhibit a preferential turning bias. Our results indicated that both thigmotaxis and preferential turn angles do affect performance in the TSP, but neither is sufficient as a predictor of route choice in this task. [ABSTRACT FROM AUTHOR]

The human CHP100 neuroblastoma cell line has been shown to provide an useful in vitro model to elucidate the mechanisms underlying HIV-1 gp120 neurotoxicity. Here we report western blotting evidence demonstrating that exposure to a cytotoxic concentration of the viral coat protein up-regulates expression of the inducible isoform of cyclooxygenase (COX-2) in neuroblastoma cells and this seems to be due to the previously observed increase in secreted IL-1β. In fact, here we show that acetyl-Tyr-Val-Ala-Asp-chloromethylketone (Ac-YVAD-CMK) and t-butoxycarbonyl-l-aspartic acid benzyl ester-chloromethylketone (Boc-Asp-(OBzl)-CMK), two inhibitors of Interleukin-1 Converting Enzyme (ICE; also referred to as caspase-1), abolish COX-2 expression enhanced by gp120 and consequent cell death. In addition, NS-398, a selective inhibitor of COX-2 activity, affords neuroprotection strengthening the role of COX-2 in the mechanisms of death. In conclusion, the present data support the notion that IL-1β is the signal through which gp120 elevates COX-2 expression and the latter is strongly implicated in the mechanisms underlying cytotoxicity. [Copyright &y& Elsevier]