Effects of DOCA pretreatment on neuronal sensitivity and cell responsiveness to angiotensin II, in the bed nucleus of the stria terminalis in the rat.

ABSTRACT

A previous study has shown that DOCA pretreatment altered the responsiveness of neurons to microiontophoretic administration of angiotensin II (AII) and aldosterone (Aldo). This result coincided with an increase in activity in the septo-preoptic region and a decrease in activity of the central nucleus of the amygdala. The latter region is anatomically linked to the bed nucleus of the stria terminalis (BNST). Single unit activity was recorded in the BNST in response to iontophoretic application of AII, non-peptide AII-receptor antagonists or Aldo in DOCA-pretreated and in non-pretreated rats. DOCA-pretreatment significantly decreased the responsiveness to AII (28 cells (18.5%) vs. 8 cells (14.0%) u = 0.018 for excitation and 3 cells (8.6%) vs. 0 cells 0%, u = 0.011 for inhibition, P < 0.05) and to Aldo (24 cells (21.4%) vs. 4 cells (10.2%), u = 0.026 for excitation, and 3 cells (2.6%) vs. 0 cells, u = 0.009 for inhibition, P < 0.05) of the neurons localised in the BNST. A significant decrease was found in the inhibitory responses to iontophoretic application of losartan, an AII type-1 receptor (AT-1) antagonist (u = 0.042, P < 0.05). No significant differences were recorded with iontophoretic application of PD 123319, a specific AII-type-2 (AT-2) receptor antagonist. Therefore AT-1 receptors are likely responsible for the decreased responsiveness of the BNST correlated with the decrease in the activity within the amygdala.