Calcitonin binding site distribution in the cat central nervous system: a wider insight of the peptide involvement in brain functions

Calcitonin (CT) binding site distribution has been studied in the cat CNS. The autoradiographic analyses of [125I]-eelCT (ECT) binding showed high density of silver grains in the mesencephalic PAG, in the raphe nuclei and in the dorsal horns, laminae I, IV, V, and VI, where ECT may act to inhibit nociceptive transmission. Other binding-rich areas included the caudatus, the amygdala, the hypothalamus, the substantia nigra, the locus coeruleus and the formatio reticularis mesencephalica. Medium to low density was seen, amongst other areas in the cortex piriformis, the hippocampus, the medial and intralaminar thalamus and the tractus spino-thalamicus. ECT binding site distribution revealed essentially homologous locations in the cat and rat CNS. At difference, the presence of binding in the piriform cortex and in discrete thalamic nuclei suggests a widespread involvement of ECT in a variety of central functions in addition to what already demonstrated.