Hypothalamic CRF neurons facilitate brain reward function.

Area of Science:

• Neuroscience
• Behavioral Neuroscience
• Neuroendocrinology

Background:

• Aversive stimuli activate hypothalamic paraventricular nucleus CRF neurons (PVN^CRF) for avoidance.
• The role of these neurons and brain stress systems in reward is less understood.

Purpose of the Study:

• Investigate the reinforcing properties of PVN^CRF neurons.
• Determine the neural pathways and mechanisms underlying PVN^CRF neuron-mediated reward.

Main Methods:

• Optogenetic activation of PVN^CRF neurons and their projections in mice.
• Behavioral assays (operant self-stimulation).
• Pharmacological manipulations (antagonists for CRF receptor 1, D1R, D2R; metyrapone).
• Neurochemical analysis (c-Fos expression, dopamine release in nucleus accumbens).

Main Results:

• Mice self-stimulated optical activation of PVN^CRF neurons, indicating reinforcement.
• PVN^CRF-VTA projections, not PVN^CRF cell bodies, mediated self-stimulation independently of the HPA axis.
• Self-stimulation was modulated by CRF receptor 1, dopamine D1 receptors, and corticosterone synthesis, but not D2 receptors.
• Activation of PVN^CRF-VTA projections increased dopamine neuron activity in the VTA and dopamine release in the NAc.

Conclusions:

• PVN^CRF neurons and their VTA projections play a significant role in reward-related behaviors.
• This reward pathway operates independently of the hypothalamic-pituitary-adrenal (HPA) axis.
• Suggests a novel mechanism where stress system activation can lead to positive reinforcement.