Increased synapses in the medial prefrontal cortex are associated with repeated amphetamine administration

Area of Science:

• Neuroscience
• Psychopharmacology
• Cellular Biology

Background:

• Psychostimulant drugs, such as amphetamine (AMPH), induce lasting behavioral changes and alter neuronal structure and function in the medial prefrontal cortex (mPFC).
• Previous research indicates increased neuronal activity in the lateral hypothalamus following repeated AMPH treatment.

Purpose of the Study:

• To investigate if repeated amphetamine (AMPH) treatment alters synaptic patterns and types in the medial prefrontal cortex (mPFC).
• Specifically, to examine synaptic changes on mPFC neurons projecting to the lateral hypothalamus.

Main Methods:

• Rats received a behaviorally sensitizing regimen of amphetamine (AMPH).
• Synapses in the infralimbic and prelimbic cortices of the mPFC were analyzed using unbiased stereology, including physical disector and electron microscopy.
• Synapses were counted, and their targets identified.

Main Results:

• Repeated AMPH administration significantly increased the number of asymmetric axospinous synapses in the mPFC.
• No significant changes were observed in axodendritic or axosomatic contacts.
• The total number of synapses on corticolateral hypothalamic pyramidal neurons remained unchanged compared to controls.

Conclusions:

• Behavioral sensitization induced by repeated amphetamine (AMPH) exposure is associated with an increased formation of spine synapses.
• These synaptic modifications occur specifically on pyramidal neurons in the medial prefrontal cortex (mPFC), not on dendritic or somatic elements.