Angiotensin II receptors in the arcuate nucleus mediate stress-induced reduction of prolactin secretion in steroid-primed ovariectomized and lactating rats.
Angiotensin II (Ang II) is a peptide that exerts an inhibitory effect upon pituitary prolactin (PRL) release through the hypothalamic arcuate nucleus (ARC). Since both PRL and Ang II are known to be affected by stress, the experiments reported here were conducted to investigate the possible participation of Ang II in the stress-induced response of PRL in situations in which pre-stress PRL levels are high, as during the PRL surge induced by estradiol (E(2)) and progesterone (P) in ovariectomized rats (OVXE(2)P) and lactating females on day 7 post-partum. Adult female rats were stereotactically implanted with bilateral guide-cannulae in the ARC; 3 days later, they were microinjected with saline or losartan and, after a 15-min interval, they were submitted to stress by ether inhalation during 1 min. Five minutes after stress, trunk blood samples were collected. Plasma PRL was measured by radioimmunoassay (RIA). In OVXE(2)P and lactating rats, a significant reduction in PRL levels was detected after stress compared to non-stressed animals. The microinjection of losartan in the ARC before stress blocked the reduction of PRL in both OVXE(2)P and lactating females. In conclusion, the stress-induced reduction of plasma PRL in OVXE(2)P and lactating rats is mediated by Ang II through AT(1) receptors in the ARC.
Donadio
Márcio Vinícius Fagundes
MV
Departamento de Fisiologia, Instituto de Ciências Básicas da Saúde (ICBS), Universidade Federal do Rio Grande do Sul (UFRGS), Sarmento Leite 500, Porto Alegre, RS 90050-170, Brazil.
Sagae
Sara Cristina
SC
Franci
Celso Rodrigues
CR
Anselmo-Franci
Janete A
JA
Lucion
Aldo Bolten
AB
Sanvitto
Gilberto Luiz
GL
D000704:Analysis of Variance; D057911:Angiotensin Receptor Antagonists; D000818:Animals; D001111:Arcuate Nucleus of Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D007774:Lactation / Q000187:drug effects*; D019808:Losartan / Q000494:pharmacology; D008297:Male; D008845:Microinjections / Q000379:methods; D010052:Ovariectomy / Q000379:methods; D011247:Pregnancy; D011388:Prolactin / Q000097:blood / Q000378:metabolism*; D011863:Radioimmunoassay / Q000379:methods; D051381:Rats; D017208:Rats, Wistar; D011945:Receptors, Angiotensin / Q000378:metabolism*; D013238:Stereotaxic Techniques / Q000009:adverse effects; D013256:Steroids / Q000494:pharmacology*; D013312:Stress, Physiological / Q000378:metabolism*
D057911:Angiotensin Receptor Antagonists; D011945:Receptors, Angiotensin; D013256:Steroids; D011388:Prolactin; D019808:Losartan