Effect of Metoprolol injected into the Nucleus Accumbens Septi in the Plus-Maze Test in rats.

MELONARI, P.; OLGUIN, M.; FRAILE, M.; LLANO, L.; TALEY, S.; TARRAZó, M.F.; CASTELLER, G.; LANDA, A.; GARGIULO, P.A.

Gottingen, Alemania.

Congreso; 30th Gottingen Neurobiology Conference and the 6th Meeting of the German Neuroscience Society. Communication 227B.; 2005

Sociedad Alemana de Neurociencias.

The Nucleus Accumbens Septi (Acc) has been extensively studied because of its role in several behavioral processes, like locomotion, stereotipies, reward and cognitive functions, such as learning, memory and visual discrimination. In previous reports we have communicated that glutamatergic transmission within Acc modulates anxiety. The aim of the present work is to study the behavioral action of â-adrenergic antagonist metoprolol in male rats  bilaterally cannulated into the Acc using the plus maze test. The rats were divided in three groups (n=15) that received either 1 ìl injections of saline or metoprolol (0.5 and 1.0 ìg). Time spent into the open arm was significantly increased by the lower (p<0.05) and the higher (p<0.001) doses when compared with saline controls. A dose-response curve was observed, with significant difference between 0.5 and 1.0 ìg (p<0.001). These results suggests a specific action on the behavioral display. Open arm entries and closed arm entries were not modified by the treatment. The quotient time spent in the open arm / number of entries to the open arm was significantly increased by the higher dose (p<0.05). Presents results show that metoprolol has an anxiolytic-like effect when injected into the Acc. We conclude that present results show a new and important evidence about the role of â-adrenergic mediation of anxiety levels in the Acc.