Fig. 1.

Hormonal influences on 6-OHDA-induced lesions in the nigrostriatal dopaminergic pathway. Male and female rats underwent bilateral gonadectomy (GDX) or sham operation (controls). While still under anaesthesia, animals received a subcutaneous implant of slow release pellets containing estradiol (GDX + E2 to replicate proestrous levels), 5α-dihydrotestosterone (GDX + DHT to replicate physiological androgen levels) or a placebo pellet (GDX group). One week later all animals received a unilateral injection of 1 μg 6-OHDA into the left medial forebrain bundle and 2 weeks later tissue was collected for measurement of the lesion size in the striatum (dopamine, DA, levels in the lesioned side expressed as a percentage of levels in the contralateral, unlesioned side) or substantia nigra pars compacta, SNc (the number of tyrosine hydroxylase immunoreactive, TH-IR, cells in the the lesioned side expressed as a percentage of levels in the contralateral, unlesioned side), as described in Table 1. Females: (A) GDX enhanced striatal DA loss and this effect was reversed by E2, not DHT, whereas (B), the loss of TH-IR cells in the SNc was unaffected by hormonal manipulations. Males: (C) GDX reduced striatal DA loss and this effect was reversed by E2, not DHT, whereas (D), the loss of TH-IR cells in the SNc was unaffected by hormonal manipulations. Values represent the mean ± s.e.m. (n = 6). ^* P < 0.05 versus gonad intact controls; ^# p < 0.05 versus GDX. Full details in Murray et al. (2003) and McArthur et al. (2007).