We previously reported that corticosterone (CORT) increased corticotropin-releasing
hormone (CRH) mRNA in the central nucleus of the amygdala (CEA), while reducing it
in the paraventricular nucleus (PVN) of the hypothalamus by using in situ hybridization
histochemistry. The bed nucleus of the stria terminalis (BNST) is closely related
to the amygdala, and it is also a source of extrahypothalamic CRH; therefore, we examined
CRH mRNA changes in the BNST following systemic treatment with CORT in adrenally-intact
rats. Effects of adrenalectomy on CRH mRNA in the BNST, PVN and CEA were also examined.
In addition, CRH content in these nuclei and in the median eminence (ME) were determined
by micropunch dissection technique combined with CRH radioimmunoassay in CORT pellet
implanted rats. Subcutaneous injections of high CORT (5 mg/day, over 14 days) increased
CRH mRNA in the dorsal part of the lateral BNST (BSTLD) at 2, 4 and 8 days, although
the low dose of CORT (1 mg/kg/day) had no significant effects. By contrast, in the
ventral part of the BNST (BSTV) neither the high nor low dose of CORT altered CRH
mRNA levels. In a second experiment, a slowly-releasing CORT pellet (200 mg, 60-day
release) produced an elevation of CRH mRNA at both 1 and 2 weeks or at 1 week in the
BSTLD or in the BSTV, respectively. These results show that glucocorticoids can facilitate
CRH mRNA expression in the BSTLD in the same manner as seen in the CEA, and that CRH
mRNA in the BSTLD can respond to CORT more than in the BSTV. In a third experiment,
bilateral adrenalectomy, however, did not affect CRH mRNA in the BNST although there
was a modest decrease in the CEA and a robust increase in the PVN. Finally, in CORT
pellet (200 mg, for 2 weeks) implanted rats, CRH content in the ME significantly decreased
and modestly increased in the CEA compared with control rats, whereas it did not change
in the PVN and BNST. Taken together, these results suggest that (1) CRH in the BNST
and the CEA may share some common functions in neuroendocrine and behavioral changes,
but that (2) mechanisms of CRH synthesis or its releasing sites may be different in
the BNST and CEA.