Interference with the GABAergic system in the dorsolateral telencephalon and modulation of the electric organ discharge frequency in the weakly electric fish Gymnotus carapo.

The functional role of the dorsal portions of dorsolateral telencephalon in modulating the stable electric organ discharge was determined by microinjection of an agonist or antagonist GABAergic drug in the awake weak electric fish, Gymnotus carapo. The dorsolateral telencephalon, which is interconnected with the preglomerular complex and the dorsocentral telencephalic area was microinjected through a guide cannula previously implanted, with different doses of bicuculline, muscimol and saline. Microinjection of bicuculline into the dorsolateral telencephalon induced a complex response consisting of increase, decrease and abrupt interruptions in the frequency of electric organ discharges and an increase in motor activity. Motor activity and modulations in the electric organ discharge are dose dependent. The somatic, but not the electric, effect is abolished under anesthesia by urethane, suggesting that the two responses are parallel but unrelated in terms of occurrence. These data, together with former neuroanatomical findings by this laboratory, suggest two parallel pathways by which the blockage of GABAA receptors in the dorsolateral telencephalon causes modulations in the firing of the medullary pacemaker nucleus. A possible route for the motor effect through reticular projection from the torus semicircularis dorsalis is discussed.

Anxiety-like behavior in rats: a computational model.

This work describes a neural network model of the rat exploratory behavior in the elevated plus-maze, a test used to study anxiety. It involves three parameters: drive to explore; drive to avoid aversive stimuli; and spontaneous locomotor activity. Each network unit corresponds to a specific location in the maze and the connections, only between closest neighbors, represent the possible adjacent places to which a virtual rat can navigate. Competitive learning is used to generate a sequence of network states that correspond to the virtual rat successive locations in the maze. To evaluate the generality of the model it was also tested for two modifications of the elevated plus-maze: one with totally closed arms and the other with totally open arms. The results are compared with data obtained with rats. The simulations are consistent with experimental evidence and may provide an efficient way of describing the anxiety-like rat behavior in the elevated plus-maze. This could be useful for researching the emotional parameters involved in this anxiety animal model.