Download Identification of Neuronal Populations in the Locomotor Central

Identification of Neuronal Populations in the Central Pattern Generator
Circuit
Saraswoti Neupane
The nervous system is divided into the central nervous system (CNS) and the peripheral
nervous system (PNS). The central nervous system consists of the brain and the spinal cord
where as the peripheral nervous system consists of the nerves that connect the sensory organs
and the muscles to the CNS. The neurons are the basic functional unit of the nervous system.
They are organized into circuits, called neuronal circuits, to process a specific function. The
arrangement of neuronal circuits varies depending on their functions. Generally they have
sensory neurons (that carry the information from sensory receptors to the CNS), motor
neurons (that transmit information from the CNS to the muscle) and interneurons (that
connect neurons to other neurons). These circuits allow the brain to react to the external and
internal environment and to generate the correct response to control the body.
Signals from the higher centres of the brain can activate the neurons in the circuits and
generate rhythmic motor output in appropriate sequence and intensity. Once initiated,
rhythmic motor activity is self-sustained. Such local neuronal circuits are called central
pattern generators. Some fundamental behaviour of organism such as breathing, chewing and
walking are controlled by this type of neuronal circuits.
Locomotion in vertebrates is controlled by central pattern generator circuits located in the
spinal cord. They generate basic rhythmic motor patterns that enable the organisms to walk or
swim. Locomotor central pattern generator circuits are the ideal systems for determining how
neuronal systems generate simple physical output (motor output) in limbs. Identification of
neuronal groups involved in the locomotor central pattern generator circuit is still challenging
because of millions of neurons are present in the spinal cord.
In this project I used a labelling method to identify the neurons in the hindlimb locomotor
central pattern generator circuits in mouse. The labelling method enabled me to detect what
genes were expressed in what part of spinal cord sections.
The results from my analyses showed that 4% of the genes that were active in cells close to
the middle part of the spinal cord sections were expressed only in those cells. Those specific
genes were active in neuronal cells that might participate in the hindlimb locomotor central
pattern generator circuits. In a broad perspective, identification of neurons in the locomotor
central pattern generator circuits will enable understanding of the function and diseases of the
nervous system that control locomotion.
Degree project in biology
Examensarbete i biologi, 20p, 2007
Biology Education Centre and Department of Neuroscience, Developmental Genetics,
Uppsala University
Supervisior: Klas Kullander and Nadine Rabe