Detailed gross anatomy and topography of the sympathetic cardiac nerves and related ganglia in Syrian hamsters (Mesocricetus auratus)

The detailed morphology and topography of the sympathetic cardiac nerves (SCNs) and ganglia with their surrounding structures in Syrian hamsters were examined to document the general topography and morphology and variations and to discuss the comparative anatomy between the SCNs and ganglia in Syrian hamsters and other rodents, as well as their comparative morphology and macroscopic evolutionary changes among rodents, rabbits, domestic animals (cats, dogs, sheep, goats, oxen, pigs and horses), primates, and humans. The composition of the cervical and thoracic parts of the sympathetic trunks and ganglia was bilaterally microdissected in twenty-eight sides of 14 adult male and female Syrian hamsters under a stereomicroscope. The general morphology of the SCNs and related ganglia in Syrian hamsters was obtained and noted as follows: (1) the absence of the vago-sympathetic trunk, (2) the absence of the middle cervical ganglion (MG), (3) constant presence of the cervicothoracic ganglion (CT) comprising generally from the caudal cervical ganglion and 1–2 thoracic ganglia and locating over the lateral surface of the longus colli muscle ventral to the heads of the first two ribs and communicating to the eight cervical and first two thoracic spinal nerves (C8-T2) in addition to the vertebral nerve, (4) extensive coverage of the lateral surface of the CT by branches of the subclavian artery, (5) the cranial and caudal limbs of the ansa subclavia (AS) joining the CT to the caudal end of the cervical sympathetic trunk, (6) the presence of an independent thoracic ganglion from the 2nd or 3rd to the 13th and connecting by single interganglionic branches, and communicating to each thoracic spinal nerve, (7) close relationship between the caudal portion of the thoracic sympathetic trunk and the psoas minor muscle, (8) the primary cardiac nerves (CNs) arising from the CT, and (9) the absence of CNs originating generally from the cervical sympathetic trunk, AS, MG, or independent thoracic ganglia or their interganglionic branches. Individual variations of the SCNs and ganglia in Syrian hamsters were noted, including the absence of the ansa subclavia on 5/28 sides (17.86%), the presence of the intermediate ganglia (IG) placed on the C7 on 3/28 sides (10.71%) or the C8 on 3/28 sides (10.71%), and no CNs arising from the IG as well as the presence of the double thoracic sympathetic trunk on 5/28 sides (17.86%). The anatomical characteristics of the SCNs and related ganglia wer