Further studies on the effects of intravenously administered 6-hydroxydopamine on the median eminence of the rat.

6-Hydroxydopamine (6-OHDA) given i.v. in a dose of 150 mg/kg to adult male Sprague-Dawley rats produces at 24 h a complete depletion of median eminence (ME) and neurointermediate lobe (NIL) catecholamines (CA), as judged by Falck-Hillarp fluorescence histochemistry, leaving the remainder of the hypothalamus substantially unaltered. Restoration of a normal fluorescence histochemical appearance took place over 35 days, apparently due to regeneration of CA-containing terminals. Administration of desipramine prior to 6-OHDA injection modified its effect; depletion was largely confined to the midline region of the external layer of the ME and to the NIL, suggesting that these regions contain dopaminergic terminals. Microspectrofluorometric methods were used in an attempt to verify this conclusion. It is suggested that this technique provides a model for establishing the role of ME and NIL CA-containing structures in control of pituitary gland function.