Vasopressin levels in the cerebrospinal fluid of rats with lesions of the paraventricular and suprachiasmatic nuclei

The circadian rhythm and dehydration-induced response of vasopressin (AVP) levels in rat cerebrospinal fluid (CSF) were studied after lesions had been made in the paraventricular (PVN) and suprachiasmatic (SCN) nuclei. The rhythmic fluctuation of AVP levels in CSF was abolished after SCN lesions, whereas lesions of the PVN had no effect. Dehydration seems to increase AVP levels in CSF of both sham-operated and lesioned animals. These data further suggest that the circadian rhythm of AVP in CSF is preferentially generated by SCN. In contrast, several areas of the brain may contribute to the overall AVP levels in CSF, both under normal physiological conditions and under osmotic stress.