cord and replaced the SCG with a different one, the SCG was still innervated the same portion of the spinal cord as before. When he replaced the SCG with a T5 ganglion, the ganglion tended to be innervated by the posterior portion of the spinal cord (T4–T8). The replacement of the original SCG with either a different one or a T5 ganglion supported Langley's theory of topographic specificity of the SCG. Research Ganglia of the peripheral autonomic nervous system are commonly used to study synaptic connections. These ganglia are studied as synaptic connections show many similarities to the central nervous system (CNS) and are also relatively accessible. They are easier to study than the CNS since they have the ability to regrow, which neurons in the CNS do not have. The SCG is frequently used in these studies being one of the larger ganglia. Today, neuroscientists are studying topics on the SCG such as survival and neurite outgrowth of SCG neurons, neuroendocrine aspects of the SCG, and structure and pathways of the SCG. These studies are usually performed on rats, guinea-pigs, and rabbits. Historical contributions E. Rubin studied the development of the SCG in fetal rats. Research on the development of nerves in the SCG has implications for the general development of the nervous system. The effects of age on dendritic arborisation of sympathetic neurons has been studied in the SCG of rats. Findings have shown that there is significant dendritic growth in the SCG of young rats but none in aged rats. In aged rats, it was found, that there was a reduction in the number of dendrites. SCG cells were used to study nerve growth factor (NGF) and its ability to direct growth of neurons. Results showed that NGF did have this directing, or tropic, effect on neurons, guiding the direction of their growth. Additional images References External links Sympathetic ganglia