A recent U.S. study has found morphine blocks the brain's ability to strengthen inhibitory synapse connections thus affecting its ability to retain memory. The study, which was conducted by a team of researchers led by Brown University Professor Julie Kauer, is also an important finding for addiction therapy.

After a series of tests on rats, it was found that a single dose of morphine blocks long-term potentiation, or LTP even 24 hours later, long after the drug was out of the animal's system.

The information is stored in the brain with the help of LTP where connections between neurons, called synapses, the major spot of information exchange in the brain, become stronger after recurring stimulation.

This whole process involving the improved synaptic power is believed to be the cellular foundation for memory. The researchers also found that the affected synapses occurred between inhibitory neurons and dopamine neurons.

The inhibitory cells in a healthy brain bound the release of dopamine, the "pleasure chemical" as it gets released by naturally rewarding experiences. However, when a man takes alcohol or cocaine, there was a similar increase seen in dopamine release.

Hence the researchers concluded that the net effect of morphine and other opioids is that they enhance the brain's reward response. The study appears in the journal Nature.