The effect of fornix transection on the diurnal fluctuation in plasma corticosterone levels was investigated in adult male rats. Using the stereotaxic approach, the fornix was cut by means of a small piece of a razor blade. Plasma corticosterone levels at 8 a.m. and 6 p.m. were measured 1 week or 3 weeks after surgery. There was no diurnal variation in the plasma corticosteroneconcentration 1 week after fornix transection. At 3 weeks post-operatively, however, significant diurnal variations were present. The data suggest that, contrary to the assumption of other authors, the fornix is not the key structure in the mediation of extrahypothalamic influences to the medial basal hypothalamus that are essential for the diurnal rhythm in plasma corticosterone levels.
- ACTH rhythm
- Biological rhythms
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism
- Endocrine and Autonomic Systems
- Cellular and Molecular Neuroscience