Mechanisms involved in glucagon-like peptide-1 (7-36) amide action on the rat hypothalamo-neurohypophysial system.
Glucagon-like peptide-1 (7-36) amide (tGLP-1) has been shown to modify the secretory function of the rat hypothalamo-neurohypophysial complex (HNC). However, mechanisms underlying this action are still unclear. Using explants containing the HNC obtained from euhydrated rats, possible interactions of tGLP-1 with angiotensin II (Ang II), forskolin-induced cAMP synthesis or calcium ions were investigated. In addition, explants taken from rats given 2% saline were used in order to examine whether chronic osmotic stimulation affects tGLP-1 action on vasopressin and oxytocin neurons. tGLP-1 did not modify Ang II- or forskolin-evoked hormone release. Incubation of the HNC in calcium-free medium inhibited the tGLP-1-dependent vasopressin/oxytocin secretion. Prolonged salt loading in vivo completely changed the neurohypophysial response to tGLP-1 in vitro; it did not only abolish the stimulatory effect of tGLP-1 on basal hormone release, but reduced K(+)-stimulated vasopressin/oxytocin secretion. Consequently, the neurohypophysial response to tGLP-1 may depend on the functional status of the HNC and on the presence of calcium ions, but not cAMP.
Bojanowska
Ewa
E
Department of Pathophysiology, Medical University of Lodz, Poland. ebojanow@mail.bg.am.lodz.pl
Stempniak
Bozena
B
D000704:Analysis of Variance; D000804:Angiotensin II / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D005576:Colforsin / Q000378:metabolism / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D005934:Glucagon; D052216:Glucagon-Like Peptide 1; D004763:Glucagon-Like Peptides; D007030:Hypothalamo-Hypophyseal System / Q000378:metabolism*; D008297:Male; D018377:Neurotransmitter Agents / Q000378:metabolism* / Q000494:pharmacology; D009924:Organ Culture Techniques; D010121:Oxytocin / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism* / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D015290:Second Messenger Systems / Q000502:physiology*; D014667:Vasopressins / Q000378:metabolism; D014882:Water-Electrolyte Balance / Q000502:physiology
D018377:Neurotransmitter Agents; D010446:Peptide Fragments; D014667:Vasopressins; D000804:Angiotensin II; C055453:glucagon-like peptide 1 (7-36)amide; D005576:Colforsin; D010121:Oxytocin; D004763:Glucagon-Like Peptides; D052216:Glucagon-Like Peptide 1; D005934:Glucagon; D000242:Cyclic AMP; D002118:Calcium