Levels of dehydroepiandrosterone and dehydroepiandrosterone sulfate in the cerebrospinal fluid of healthy dogs and dogs affected by neurological disorders.

Aged dogs develop neuropathology and pattern of cognitive decline that mirrors that seen in both successfully aging humans and patients with senile cognitive dysfunctions. Although biomedical research has devoted much effort on neurobiological effects of steroids and neurosteroids on aging nervous system this aspect has never been investigated in the dog. The present research aims to explore the possible role of two neurosteroids, namely dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEAS), in the central nervous system of the dog. Animals included in the study underwent complete neurological evaluation in the clinical facilities of the Faculty of Veterinary Medicine of Padua (Italy). Thirty nine cerebrospinal fluid (CSF) samples were obtained from healthy dogs (N = 7) and dogs affected by various neurological disorders (compressive myelopathy, N = 8; degenerative myelopathy, N=5; other neurological disorders, N=19). The CSF samples were divided in 3 groups based on the age of the dogs and tested for DHEA and DHEAS concentrations by RIA. Mean CSF levels of DHEA and DHEAS were 74,8 pg/ml and 15,8 pg/ml respectively, and no significant differences were found between animal affected or not affected by neurological diseases. On the contrary, analysis of variance showed significant effect of age (P < 0,05) on steroid level ratio (DHEAS/DHEA) which resulted higher in young adult animals (Duncan test). In addition, DHEAS/DHEA ratio was significantly lower (Mann-Whitney test; P < 0,01) in dogs affected by degenerative myelopathy, while DHEAS concentration was higher in dogs affected by compressive myelopathy (Mann-Whitney test; P < 0,01). These data provide the first evidence of the presence of DHEA and its sulfate in the CSF of the dog. Moreover, the variation of their CFS levels related to aging and to neurological condition suggests a role of DHEA and DHEAS in the physiopathology of the canine central nervous system. The results deepen neuroendocrine aspects related to canine aging and provide compelling support for the aged dog as a model of human cognitive aging and disorders.