Ultrasonic vocalization ratios reflect the influence of motivational state and amygdala lesions on different types of taste avoidance learning.

Consumption of a sweet solution (the CS) and ultrasonic vocalizations (USVs) emitted by rats were recorded in a conditioned taste avoidance paradigm. The rats' affective states were inferred from a ratio of high to low-frequency ultrasonic calls, which have been associated with positive and negative affect, respectively. The interacting effects of deprivation state and lesions of the basolateral amygdala (BLA) on CS consumption and affective state were examined.

Prolonged rewarding stimulation of the rat medial forebrain bundle: neurochemical and behavioral consequences.

Extracellular dopamine levels were measured in the rat nucleus accumbens by means of in vivo microdialysis. Delivery of rewarding medial forebrain bundle stimulation at a low rate (5 trains/min) produced a sustained elevation of dopamine levels, regardless of whether train onset was predictable. When the rate of train delivery was increased to 40 trains/min, dopamine levels rose rapidly during the first 40 min but then declined toward the baseline range.

Learning the morphine conditioned cue preference: cue configuration determines effects of lesions.

The morphine conditioned cue preference was investigated using two different apparatus configurations. In one configuration, with a clear Plexiglas partition separating the drug-paired and unpaired compartments, rats could see the cues in both compartments while in either one. In the other configuration, with an opaque wood partition separating the two compartments, rats could see the cues in only one compartment at a time.