Effects of postpuberal castration on dopamine receptor sensitivity in the male rat brain

In order to study the effects of castration of brain dopamine (DA) receptor sensitivity, the effects of apomorphine on locomotor activity and striatal DA synthesis, as assessed by the dihydroxyphenylalanine (DOPA) accumulation after NSD-1015 treatment, were examined in normal and castrated male Sprague-Dawley rats pretreated with reserpine (5 mg/kg-18 hrs). There was an enhanced locomotor response to apomorphine (0.05-0.1 mg/kg) in castrated animals, as compared to sham operated controls. Furthermore, the increase in DOPA accumulation produced by the reserpine treatment was antagonized to a greater extent by apomorphine in the castrated animals. These results indicate an enhanced DA receptor sensitivity at both pre- and post-synaptic sites.