Postsynaptic Mechanisms Render Syn I/II/III Mice Highly Responsive to Psychostimulants

Area of Science:

• Neuroscience
• Molecular Biology
• Behavioral Pharmacology

Background:

• Synapsins (SYN I, SYN II, SYN III) are crucial proteins regulating neurotransmitter release by maintaining synaptic vesicle reserves.
• Understanding synapsin function is key to deciphering neural circuit regulation of behavior.

Purpose of the Study:

• To investigate the role of synapsins in dopamine-mediated behaviors, particularly responses to cocaine and dopamine receptor agonists.
• To differentiate between presynaptic and postsynaptic contributions to psychostimulant-induced behaviors in the absence of synapsins.

Main Methods:

• Utilized SynI/SynII/SynIII triple knockout mice to examine presynaptic dopamine release via microdialysis.
• Assessed postsynaptic responses to dopamine receptor agonists and cocaine in an open field arena.
• Manipulated medial frontal cortex activity using GABA agonists to probe circuit-specific effects.

Main Results:

• Triple knockout mice displayed enhanced spontaneous locomotion and hypersensitivity to D1 and D2 dopamine agonists.
• Cocaine-induced hyperlocomotion and sensitization were altered by novelty exposure in knockout mice.
• Presynaptic dopamine release and vesicle pools were comparable to wild-type, indicating postsynaptic involvement.

Conclusions:

• Presynaptic dopamine release does not directly correlate with hyperlocomotion in synapsin-deficient mice.
• The heightened response to novelty and psychostimulants in these mice is primarily mediated by postsynaptic mechanisms and network alterations.