The emergence test: effects of psychotropic drugs on neophobic disposition in Wistar Kyoto (WKY) and Sprague Dawley rats

1. The Emergence Test (ET), a variation of the open field test in which the rat is not handled, and is purported to measure neophobia, was applied to Wistar Kyoto (WKY) and Sprague Dawley (S-D) rats.

2. While no-stress control WKY rats were less active in the ET, pre-treatment with shock stress exacerbated strain differences. WKY rats, previously exposed to shock, did not emerge from the home cage start box during repeated testing, whereas previously stressed S-D rats vacated the home cage quickly and revealed increasing behavioral agitation.

3. Diazepam reduced emergence latency only in S-D rats, whereas nomifensine significantly increased head poke responses in WKY rats.

4. WKY rats responded to the ET with characteristically depressive behavior, whereas S-D rats responded to the same ET with behavioral agitation and anxiety. The implications of these behavior patterns for discriminating between anxiety and depressive behavior are presented.

Author Keywords: anxiety; diazepam; depression; desipramine; fluoxetine; neophobia; nomifensine; open field test; stress; WKY rat