Androstenedione modulation of monoamine levels and turnover in hypothalamic and vocal control nuclei in the male zebra finch: steroid effects on brain monoamines

Abstract

Levels of norepinephrine (NE), dopamine (DA), serotonin and the latter's primary metabolite, 5-hydroxyindoleacetic acid, were measured in two hypothalamic and 6 vocal control areas in the brains of male zebra finches. NE and DA turnover in these areas were also estimated using α-methylparatyrosine. Males were castrated for at least 3 weeks and then received an implant of androstenedione (AE) or a control implant of cholesterol. Each male was then housed with a female for at least one week. Significant quantities of the 4 monoamines were found in all brain areas examined; steady-state levels varied significantly across brain areas. Hormone treatment affected steady-state monoamine levels in the preoptic area (POA), the magnocellular paraventricular nucleus and the vocal control area, area X. Hormone treatment altered both NE and DA turnover in the POA, area X and a second vocal control area, nucleus robustus archistriatalis. NE turnover was altered by hormone treatment in a third vocal area, the dorsomedial portion of the intercollicular nucleus. These data suggest that monoaminergic neurotransmitters may be involved in the mediation of steroid-dependent changes in singing behavior in passerine birds.