Context-drug learning produces structural and functional synaptic changes in the circuitry of the basolateral nucleus of the amygdala (BLA). However, how the synaptic changes translated to the neuronal targets was not established. Thus, in the present study, immunohistochemistry with a cell-specific marker and the stereological quantification of synapses was used to determine if context-drug learning increases the number of excitatory and inhibitory/modulatory synapses contacting the gamma-aminobutyric acid (GABA) interneurons and/or the pyramidal neurons in the BLA circuitry. Amphetamine-conditioned place preference increased the number of asymmetric (excitatory) synapses contacting the spines and dendrites of pyramidal neurons and the number of multisynaptic boutons contacting pyramidal neurons and GABA interneurons. Context-drug learning increased asymmetric (excitatory) synapses onto dendrites of GABA interneurons and increased symmetric (inhibitory or modulatory) synapses onto dendrites but not perikarya of these same interneurons. The formation of context–drug associations alters the synaptic connectivity in the BLA circuitry, findings that have important implications for drug-seeking behavior.
Amphetamine conditioned place preference increased excitatory synapses contacting the spines and dendrites of pyramidal neurons and increased excitatory synapses onto dendrites of gamma-aminobutyric (GABA) interneurons. Context-drug learning increased inhibitory or modulatory synapses onto dendrites of these same interneurons. Context-drug learning alters the synaptic connectivity in the basolateral amygdala circuitry, findings that are important for drug-seeking behavior.