No abstract

The effects on freezing behavior elicited by contextual and phasic conditioned stimuli (CSs) were examined in rats with septal lesions. Two weeks after surgery, blocks of 2 conditioning trials consisting of a tone (10 kHz, 75 dB, 20 s) paired with a footshock (500 ms, 0.5 mA) were presented on 2 consecutive days. Tone-alone trials were presented each day thereafter until extinction criterion was met. Septal lesions were found to potentiate the freezing response elicited by contextual stimuli but had no effect on freezing elicited by the phasic CS. The septum thus appears to be involved in the acquisition and/or expression of defensive behaviors elicited by contextual stimuli.Recent studies have elucidated in great detail the neural system involved in the conditioning of fear responses to a discrete auditory or visual conditioned stimulus (CS;

These data implicate alterations in DRN 5-HT neurons in the potentiation of morphine reward produced by uncontrollable stress.

No abstract

No abstract