Heroin and Morphine are common versions of drugs known as opiates.
They are better known as narcotics.
These drugs are based on opium which is an extract from the opium poppy.
These drugs are highly addictive, and this addiction has been a serious health problem for centuries.
Morphine is used medically as a pain reliever though heroin is only used recreationally.
The story of the discovery of how heroin, morphine and other opiates work is a fascinating story
and leads to the discovery of a new class of neurotransmitters, sometimes called endorphins
It turns out that all opiates act to mimic these natural neurotransmitters.
Opiates bind to the to the endorphin receptors and have the same effect on the post-synaptic neuron.
The effects are found both in the central and peripheral nervous system
but two regions are very important, the ventral tegmental area and nucleus accumbens.
Both the ventral tegmental area and nucleus accumbens are important parts of the brains natural reward circuitry.