Freund's complete adjuvant induces ornithine decarboxylase activity in the central nervous system of male rats and triggers the release of pituitary hormones

In male rats, inoculation of Freund's complete adjuvant (FCA, 0.5 mg/rat of Mycobacterium butyricium in paraffin oil) induced high levels of ornithine decarboxylase (ODC) in the hypothalamus and pituitary gland (285% and 245% of controls, respectively, within 12 h to 2 days). ODC activity also altered in the cerebellum and left neocortex, but not in the right neocortex. This activity reflected a dynamic equilibrium which is influenced by ODC synthesis, degradation, activation, etc. The circadian rhtyhms of pituitary ODC activity and plasma prolactin level, 3-4 days after FCA, showed that enhancement of enzymatic activity during the dark phase correlated with a marked of prolactin (Prl). Durign this early period after FCA, changes in plasma levels and other pituitary hormones were not significant or were less important. Pretreatment with bromocriptine microcapsules inhibited both basal and FCA-induced hormone and adrenocorticotropic hormone were noted from days 4 and 8, respectively, amd onwards. Finally, a phase of reduced corticosterone secretion occurred and latency period. This study shows that FCA influences central nervous system pathways and supports the idea that endogenous Prl is involved in some early evets which lead to the development of adjuvant arthritis.