Opioids block long-term potentiation of inhibitory synapses

The response of excitatory synapses — nerve cell connections that push target neurons to fire more — gets stronger with continued use. This process, known as LTP (long-term potentiation), is involved in learning and memory. An in vitro study of rat brain shows that this excitatory potentiation is mirrored at the neighbouring inhibitory synapses in the ventral tegmental area of the brain, an area known to be involved in drug addiction. Morphine prevents long-term potentiation at the inhibitory synapses, suggesting that the disruption of the balance between neuronal excitation and inhibition may enhance the firing of dopaminergic neurons in the early stages of addiction. The targeting of GABAα receptors may therefore be a means of tackling the abuse-related effects of addictive drugs.