Catecholamine reinnervation of supraoptic nucleus after deafferenting mechanical lesions and superior cervical ganglionectomy: histofluorescence and functional assessments in young adult and aged rats

Abstract

Catecholaminergic innervation of the hypothalamic vasopressin (VP)-secreting supraoptic nucleus (SON) was examined at selected intervals after deafferenting neurosurgical lesions, with respect to potential contribution of peripheral vascular sympathetic fibers. Young adult (3 months) and aged (20 months) male F344 rats were subjected to mechanical knife-cut lesion just caudal and medial to the SON, superior cervical ganglionectomy (SCGx), or both surgeries. SON and lesion sites were assessed at 4, 14, 30 or 45 days after surgery, by CA histofluorescence. Functional evaluation in rats subjected to chronic lesions consisted of monitoring water balance (water consumption and urine volumes, and urine osmolality and VP content) in individual rats for presurgical and postsurgical intervals. Histofluorescence evaluation showed that SCGx did not affect the overall SON fluorescence pattern, although a minor sympathetic contribution to that pattern was discerned by comparing SON in rats subjected to lesion alone vs SCGx + lesion. Morphological reinnervation of SON was accomplished at 30 days in young rats, and 45 days in aged rats, after both lesion and SCGx. In young rats, histofluorescence density 30 days after deafferentation was denser than the innervation pattern seen in intact (sham-lesioned) animals, while reinnervation at 45 days postsurgically in aged rats only approximated the presurgical pattern. Vasopressin excretion and corresponding water conservation measures were compromised by SON deafferentation at both ages; excreted VP levels and water balance did not rebound to presurgical values at chronic postsurgical intervals in either young or aged rats.(ABSTRACT TRUNCATED AT 250 WORDS)