Calcitonin-Immunoreactive Neurons in the Brain of the Bullfrog, Rana Catesbeiana With Special Reference to Their Liquor-Contacting and Neurosecretory Nature. An Immunochemical and Immunohistochemical Study

The occurrence of calcitonin-immunoreactive neurons in the brain is first demonstrated using anti-human calcitonin antiserum.Immunoassay of the brain extracts of the bullfrog, Rana catesbeiana indicates the occurrence of a calcitonin-like immunoreactivity contained in two neuronal system: 1) in neurons dispersed in the parvicellular preoptic nucleus whose beaded axons are traced towards the tuber cinereum, and 2) in neurons in nucleus infundibularis ventralis, most of which are bipolar in structure.These bipolar neurons extend a process to reach the cerebrospinal fluid in the third ventricle and an axon either to the median eminence or to the preoptic area.The axons reaching the median eminence are beaded in shape containing the calcitonin-immunoreactive substance and apparently release it into the hypophyseal portal vessels.It is unknown whether the process to the cerebrospinal fluid of these bipolar neurosecretory neurons might be sensory or secretory in nature.Immunochemical and immunohistochemical examinations support the view that the calcitonin-like immunoreactivity in the bullfrog hypothalamus is authentic calcitonin or related peptide and not a part of the precursor molecule of ACTH-B-LPH. KEY WORDS bullfrog brain / Rana caresbeiana /