Effects of estrogen on intracellular signaling pathways linked to activation of muscarinic acetylcholine receptors and on acetylcholinesterase activity in rat hippocampus

• Published in: Biochemical pharmacology Vol. 75; no. 9; pp. 1827 - 1834
• Main Authors: Pereira, Renato Tavares dos Santos, Porto, Catarina Segreti, Godinho, Rosely Oliveira, Abdalla, Fernando Maurício Francis
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01-05-2008; Elsevier Science
• Subjects: Acetylcholinesterase; Acetylcholinesterase - metabolism; Animals; Biological and medical sciences; Estradiol - administration & dosage; Estradiol - deficiency; Estradiol - pharmacology; Estrogen; Estrogen Replacement Therapy; Estrogens - administration & dosage; Estrogens - deficiency; Estrogens - pharmacology; Female; Hippocampus; Hippocampus - drug effects; Hippocampus - enzymology; Hippocampus - metabolism; Inositol phosphate; Inositol Phosphates - metabolism; Medical sciences; Muscarinic acetylcholine receptors; Ovariectomy; Pharmacology. Drug treatments; Rats; Rats, Wistar; Receptors, Muscarinic - metabolism; Signal Transduction; Inositol phosphate; Ovariectomy; Acetylcholinesterase; Muscarinic acetylcholine receptors; Hippocampus; Estrogen; Rat; Central nervous system; Esterases; Encephalon; Signal transduction; Cholinergic receptor; Signaling pathway; Surgery; Enzyme; Rodentia; Ovarian hormone; Biological activity; Carboxylic ester hydrolases; Vertebrata; Mammalia; Treatment; Animal; Hydrolases; Muscarinic receptor; Sex steroid hormone
• ISSN: 0006-2952; 1873-2968
• DOI: 10.1016/j.bcp.2008.01.016

The aim of the present study was to investigate the effects of estrogen lack and estrogen replacement on the production of total [
3H]inositol phosphate ([
3H]IP) induced by the activation of muscarinic acetylcholine receptors (mAChRs) and on the mechanisms for inactivation of acetylcholine. Hippocampi were obtained from rats in proestrus (PE), ovariectomized for 15 days (C15), ovariectomized for 15 days and then treated with 17β-estradiol for 7 days (E7) and ovariectomized and immediately treated with 17β-estradiol for 21 days (E21). Ovariectomy did not change the basal level of total [
3H]IP in the hippocampus. 17β-Estradiol replacement (E7 and E21) reduced the basal level of total [
3H]IP. In all experimental groups, carbachol (CCh) caused a concentration-dependent rise in total [
3H]IP. The maximum effect was reached with 10
−4
M CCh. The response to 10
−4
M CCh in the hippocampi from C15 and E7 rats was twofold higher than in hippocampi from PE and E21 animals and was blocked by pirenzepine, but not by methoctramine. Ovariectomy or 17β-estradiol treatment for 7 days did not change neither the total acetylcholinesterase (AChE) activity nor the relative amount of mono- and dimeric G
1/G
2 and tetrameric G
4 globular forms. Conversely, hormonal treatment for 21 days induced an increase in AChE activity of G
1/G
2 and G
4 forms, indicating that 17β-estradiol stimulates both synthesis and assembly of AChE molecular forms. The present results suggest that the duration and/or a critical period with regard to the initiation of estrogen therapy are important to regulate the function of mAChRs and AChE activity in female rat hippocampus.