Dopamine-enabled anti-Hebbian timing-dependent plasticity in prefrontal circuitry

Area of Science:

• Neuroscience
• Synaptic Plasticity
• Learning and Memory

Background:

• Spike-timing-dependent plasticity (STDP) is crucial for learning, with specific spike orders inducing potentiation (t-LTP) or depression (t-LTD).
• Dopamine (DA), a key reward signal, modulates synaptic plasticity, but its role in negative timing-induced plasticity is unclear.
• Previous work showed DA extends the temporal window for Hebbian t-LTP in the prefrontal cortex (PFC).

Purpose of the Study:

• To investigate dopamine's modulation of synaptic plasticity induced by negative spike timing (post-pre pairings) in mouse medial PFC.
• To elucidate the receptor mechanisms underlying DA's influence on anti-Hebbian plasticity.

Main Methods:

• Electrophysiological recordings from layer V pyramidal neurons in mouse medial PFC slices.
• Application of a negative timing STDP protocol (post-pre pairings at δt = -30 ms).
• Pharmacological manipulation of dopamine receptors (D1Rs, D2Rs) and intracellular signaling pathways (cAMP/PKA).

Main Results:

• DA application during negative timing STDP induced robust long-term potentiation (LTP), not depression.
• This DA-enabled anti-Hebbian LTP was dependent on GluN2B-containing NMDA receptors.
• Postsynaptic D1 receptor activation and subsequent cAMP/PKA signaling were essential for this plasticity, unlike DA-gated Hebbian t-LTP.

Conclusions:

• Dopamine acts as a potent modulator of coincidence detection in associative synaptic plasticity.
• DA enables anti-Hebbian LTP via postsynaptic D1R-cAMP/PKA signaling, distinct from its effects on Hebbian t-LTP.
• This mechanism may facilitate input-target associations crucial for reward learning and top-down control in the PFC.