Regulation of flunitrazepam binding in the dorsal horn of the spinal cord by adrenalectomy and corticosteroids

GONZÁLEZ S.L; FERRINI M; COIRINI H; GONZÁLEZ DENISELLE, M.C.; DE NICOLA A. F.

BRAIN RESEARCH

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 1992 vol. 589 p. 97 - 101

0006-8993

Adrenal corticostiroids and adrenalectomy have opposing effects on benzodiazepine binding sites in brain regions. These treatments were employed to study 3(H) flunitrazepam (FLU) binding in regions punched out from the rat spinal cord. We found that binding was higher in dorsal horn than ventral horn, and minimal in white matter. clonazepam and RO 15-1788 largely displaced 3(H) FLU binding, whereas RO 5-4864 was weakly active.Four days post-ADX, binding increased exclusively in the dorsal horn, and this effect was reversed by administration of corticosterone (CORT), but not dexamethasone (DEX) or aldosterone (ALDO) given over 4 days. When endogenous CORT was increased by administration of cold stress to adrenal intact rats, reduced benzodiazepine(BDZ) binding was also observed in the dorsal horn. When added in vitro, only ALDO and not CORT or DEX, inhibited 3(H) FLU binding. It is suggested that steroids with affinity for the type I corticosteroid receptor (CORT,ALDO) decrease 3(H) FLU binding to the neural type BDZ receptor in the dorsal horn. Reduction of the inhibitory BDZ system may be physiologically important, and can partly explain the enhancement of excitatory synaptic transmission produced by corticostiroids at the level of the spinal cord.