Application of optogenetic and pharmacogenetic tools to study the neural circuits underlying emotional valence, feeding, arousal and motivated behaviors has provided crucial insights into brain function. Expression of light sensitive proteins into specific neurons and subsequent stimulation by light (optogenetics) to control neuronal activity or expression of designer receptors exclusively activated by designer drugs (DREADD) in specific neuronal populations with subsequent activation or suppression of neuronal activity by an otherwise inert ligand (pharmacogenetics) provides control over defined elements of neural circuits. These novel tools have provided a more in depth understanding into several questions about brain function. These include:
• Regulation of sleep-wake transition by the interaction of hypocretin neurons of lateral hypothalamus and nor adrenergic neurons of the locus coruleaus
• Regulation of feeding by AGRP and POMC neurons in arcuate nucleus of the hypothalamus
• Place preference and positive reinforcement by activation of DA neuron of VTA
• Place aversion by activation of VTA GABA and lateral habenula neurons
• Opposing influences on reinforcement by activation of D1 and D2 expressing medium spiny neurons of dorsal striatum and nucleus accumbens
The list still grows...