Neuronal Histamine Systems and Behavior

Re: Histamine-Yanai

Kazuhiko Yanai

On Mon Dec 14, Ruediger Hasenoehrl wrote
>Dear Kazuhiko,
>Hope you enjoy our meeting! I have the following questions: there is evidence that fear-parameters are increased by excessive 5-HT and decreased by a reduction of 5-HT activity. From your findings one would expect that mutant mice should be more anxious than the wild type - did you compare wild and mutants in anxiety-tests like the elevated plus-maze or the social interaction test? Furthermore, you report that, in the wild-type, d-chlorpheniramine can enhance 5-HT release. This seems contrary (to the statement above and) to our behavioral findings showing that the H1 antagonist (intra-NBM injection in rats) exerts anxiolytic-like effects. Any ideas about this? Yours
>Ruediger Hasenoehrl  

Dear Ruediger:
Thank you very much for your attention to our works. We examined aggressive behaviors and nociception in H1 receptor knockout mice several time. They showed marked reduction in aggressiveness and response to nociception. We could not observe any change in the apparent distribution of light-dark room and elevated plus-maze. Reduced aggressiveness and antinociception could be partly explained by the increased release of 5-HT in H1KO. I think that the increased 5-HT activity in the amygdala may be anxiety-promoting. However, we did not examine the release of 5-HT in the small regions. The forebrains were used in this study. As you pointed out, the release of neurotransmitters in the small regions will be the next target for investigation.

Kazuhiko Yanai

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