Glutamatergic neurons of the hippocampus influence selective behaviors related to exploratory preferential decisions in the rat.

ABREGO VA; RATTI SG; ALVAREZ EO

Mendoza, Argentina

Congreso; XXVII Reunión Científica Anual de la Sociedad de Biología de Cuyo; 2009

Sociedad de Biología de Cuyo

Previously our laboratory has shown that rats exhibit spontaneous lateralized behavioural patterns during exploration of novel environments, showing dependency on the activity of hippocampal neurons. The objective of the present work was to continue and to complete previous observations about the possible glutamatergic activity in the hippocampus on the lateralized exploratory behavior in the rat. Adult male rats were implanted bilaterally into the ventral hippocampus with guiding cannulae for in situ microinjections. 48 h later, animals were locally injected with monosodium glutamate (MSG, 1 nmol/ìl) into either right (n=16) left (n=16) or both hippocampus (n=15) with simultaneous injection of 2 ìg of lidocaine into the respective contralateral hippocampus. Saline-injected animals (n=22) were considered control. 5 min afterwards, all groups of animals were tested in the Multiple Double Choices labyrinth (MDC), and the Double Lateral Holeboard (DLHB) during 5 min as previously described. Results have shown that in the MDC, MSG did not change the behavioral exploratory patterns observed in control. However, in the DLHB, MSG administration into left/right hippocampus significantly increased Total Behavioral Activity in the corridor compared to Control (339±35 Counts/5 min Vs 224.5±18.9 Counts/5 min,  p<0.01). MSG administration into left or right hippocampus, significantly decreased proportion of animals choosing left exploration of corridor compared to Control (0% Vs 81.8%; MSG left, p <<0.001; 11.8% Vs 81.8%; MSG right, p<0.01). Results suggest that glutamatergic neurons regulate exploration but did not modulate the hippocampal lateralized exploratory behavior.