Influence of anterodorsal thalami nuclei on ACTH release under basal and stressful conditions.

Experiments were carried out to evaluate the effect of anterodorsal thalami nuclei (ADTN) lesions on plasma ACTH and corticosterone (C), in unstressed and stressed rats. Thirty days after lesion, basal values of plasma ACTH, plasma and adrenal C were significantly higher than those in sham lesioned rats (p < 0.05: p < 0.05; p < 0.01, respectively). Chronic stress (forced immobilization, 15 min/day, during 12 days) in sham-operated animals produced a significat increase in ACTH (p < 0.05) and plasma C (p < 0.05), and a slight decrease in adrenal C, as compared to unstressed rats. In lesioned stressed rats, plasma ACTH was below that found in unstressed lesioned and in sham-lesioned stressed rats (p < 0.05). Variations of plasma C concentrations of stressed lesioned rats were not significant. The adrenal glands of stressed lesioned rats showed a significantly lower content of C than that in unstressed lesioned rats (p < 0.005). It is concluded that ADTN in rats may play a significant role in regulating the hipophyso-adrenal system.