Tissue distribution of calcitonin gene-related peptide administered via different routes in rats with subarachnoid hemorrhage

Abstract

Objective To investigate the tissue distribution of calcitonin gene-related peptide (CGRP) by nasal versus intravenous administrations in rats with subarachnoid hemorrhage (SAH). Methods The SAH rat model was established by injecting fresh autologous arterial blood into cisterna magna twice. Sixty-four rats were divided into 4 groups by random digit table: (1) group A (n=16) : the normal rats were treated with 125I marked CGRP (125I-CGRP) by nasal administration; (2) group B (n=16) : the SAH model rats were treated with 125I-CGRP by nasal administration; (3) group C (n=16) : the normal rats were treated with 125I-CGRP via femoral vein; (4) group D (n=16) : the SAH model rats were treated with 125I-CGRP via femoral vein. The tissue distribution of CGRP in rats of each group at 30 min after the treatment was compared by radioisotope tracing. Results The CGRP concentrations of brain regions, spinal cord, and cerebrospinal fluid (CSF) in normal rats and SAH model rats by nasal administration of 125I-CGRP were significantly higher than those by intravenous administration; whereas the CGRP concentrations of blood, thyroid, deep cervical lymph nodes, liver and lung tissues in normal rats and SAH model rats by nasal administration of 125I-CGRP were significantly lower than those by intravenous administration (all P<0.05). After nasal administration, the CGRP concentration in the olfactory bulb was the highest, followed by those in CSF and spinal cord. Conclusion Tissue distribution of CGRP differs between nasal administration and intravenous administration. Nasal administration of CGRP shows significant advantages in the medical treatment for disorders of the central nervous system. Key words: Calcitonin gene-related peptide; Central nervous system; Drug administration, intranasal; Subarachnoid hemorrhage; Rats