A group of nerve cells in
the forebrain release the neurotransmitter dopamine when activated by
tactile or certain visual stimuli, discovered Prof. Dr. Wolfgang Driever and his team of neurobiologists at the
University of Freiburg.
These dopaminergic nerve cells send
connections to almost all parts of the brain and spinal cord, thereby
affecting the functions of many circuits. These new findings could play a
role in the future treatment of such illnesses as restless leg
syndrome, a condition in which patients have unpleasant sensations in
their limbs during sleep.
‘The type and intensity of stimuli control the activity of nerve cells that release the neurotransmitter dopamine.’
The researchers have published their research
results in the journal Current Biology
Regardless of whether we are sitting in a loud aeroplane or walking
through a quiet forest clearing, how humans perceive their environment
depends on the stimuli. This, in turn, affects our behavior - sometimes
consciously, sometimes subconsciously.
For their research, the scientists studied the four-millimeter-long
larvae of zebrafish, which are common aquarium fish. The scientists
observed the activity of individual dopaminergic nerve cells within the
brains of the larvae, which were alert and active, under a microscope.
The researchers were able to make their activity visible using
optogenetic calcium sensors, which emit light in active nerve cells.
Until now, studies of the dopaminergic nerve cells in vertebrates have
primarily focused on the midbrain, where the dopaminergic cells are
involved in the control of locomotion and reward behavior. These become
functionally impaired in patients with Parkinson's disease.
dopaminergic neurons of the forebrain, on the other hand, have been
little researched until now because they are located deep in the brain
and are therefore difficult to reach. In the forebrain, they are also
connected to parts of the hypothalamus, which controls the switch in
basic behavior, such as fight or flight and rest or sleep.
The findings of the team of researchers from the University of
Freiburg reveal that certain intense sensory stimuli may affect such
basic behavior through the activity of dopaminergic nerve cells.
Because there are also connections between these nerve cells and the
sensory organs, it is possible that dopaminergic nerve cells are
involved in adjusting the sensitivity of sensory organs' reactions to
stimuli. This function could be useful for treating diseases.
properties of dopaminergic nerve cells in the forebrain could thus be
used in the future to reduce the sensation of patients with restless
legs syndrome and hence to suppress the tingling in their extremities
that occurs when sleeping. Further research of these dopaminergic
neurons is expected to help scientists understand how these diseases
develop - and in general how humans adapt to quickly changing stimuli
and sensations in their environments.