STUDIES ON CHOLINERGIC FUNCTION AND MEMORY IN MICE (CHOLINOTOXINS, WORKING, REFERENCE MEMORY, RADIAL ARM MAZE)

Considerable evidence suggests that central cholinergic neurons participate in either acquisition, storage or retrieval of information. Experiments were designed to evaluate information processing in mice following either reversible or irreversible impairment in central cholinergic activity. The cholinergic receptor antagonists, atropine and methylatropine were used to reversibly inhibit cholinergic transmission. Irreversible impairment in central cholinergic function was achieved by central administration of the cholinergic-specific neurotoxins, N-ethyl-choline aziridinium (ECA) and N-ethyl-acetylcholine aziridinium (EACA). ECA and EACA appear to act by irreversible inhibition of high affinity choline uptake (proposed rate-limiting step in acetylcholine synthesis). Intraventricular administration of ECA or EACA produced persistent reduction in hippocampal choline acetyltransferase activity. Other neuronal systems and brain regions showed no evidence of toxicity. Mice treated with either ECA or EACA showed behavioral deficits associated with cholinergic dysfunction. Passive avoidance behavior was significantly impaired by cholinotoxin treatment. Radial arm maze performance was also significantly impaired in cholinotoxin-treated animals. Deficits in radial arm maze performance were transient, however, such that rapid and apparent complete behavioral recovery was seen during retention testing. The centrally active cholinergic receptor antagonist atropine also caused significant impairment in radial arm maze behavior, while equivalent doses of methylatropine were without effect. The relative effects of cholinotoxin and receptor antagonist treatment on short-term (working) memory and long-term (reference) memory in radial arm maze behavior were examined. Maze rotation studies indicated that there were at least two different response strategies which could result in accurate maze performance. One strategy involved the use of response algorithms and was considered to be a function of reference memory. Another strategy appeared to be primarily dependent on spatial working memory. However, all behavioral paradigms with multiple trails have reference memory requirements (i.e. information useful over all trials). Performance was similarly affected following either cholinotoxin or anticholinergic treatment, regardless of the response strategy utilized. In addition, rates of behavioral recovery following cholinotoxin treatment were similar between response groups. It was concluded that both cholinotoxin and anticholinergic treatment primarily resulted in impaired reference memory processes

Determinants of International Insurers' Participation in Foreign Non-Life Markets

Mirroring the trend in the broader marketplace, the global insurance industry is steadily moving toward increased liberalization and deregulation. This study seeks to develop the first empirical model that examines the importance of foreign market characteristics as they relate to the participation of international insurers in the non-life business of those countries. The analysis reveals that market structure is an important factor in determining whether international insurers participate in a given foreign market. In addition, for markets that are not competitive, removing trade barriers would significantly improve the desirability of those countries as host markets. The results also suggest that countries with higher gross domestic product tend to attract more involvement from international insurers. While this research focuses on the markets of industrialized countries, the findings will provide significant implications for those emerging markets that have not yet collected relevant data on a number of the variables included in this study. Copyright 2003 The Journal of Risk and Insurance.

Market Deregulation and Insurer Pricing Strategies: The Japanese Experience

In 1998, rate regulation in the Japanese auto insurance industry shifted from a tightly controlled tariff regime to that of a less regulated (theoretically) prior approval system. While actual rate regulation is generally not directly observable, Danzon (1983) contends that the “true” character of regulation is indirectly observable in the pricing strategies of insurers. This paper applies Danzon's hypothesis to the Japanese auto insurance market. The empirical analysis employs a two-way random-effects panel data methodology that includes data from the domestic competitors in the Japanese auto insurance market over the 1991–2000 period. Even though an increased dispersion of pricing strategies corresponding to insurer size is observed after deregulation, our analysis reveals that the Japanese auto insurance market still operates much like a cartel. The implication is that despite formal deregulation, Japan's regulatory body still maintains significant control. The Geneva Papers (2005) 30, 312–326. doi:10.1057/palgrave.gpp.2510028