Nov 24, 1999

Induction of tyrosine hydroxylase and neuropeptide Y by carbachol: modulation with age

The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences
Nihal TümerP J Scarpace

Abstract

With aging, circulating catecholamines are elevated in both humans and animals. This may be related to the increased basal levels of dopamine beta-hydroxylase (DbetaH) and tyrosine hydroxylase (TH) mRNA levels and TH enzyme activity in the adrenal medulla of senescent compared with younger animals. Cold exposure induces TH and DbetaH mRNA, and the cholinergic pathway is believed to be involved in the cold-stimulated increase in TH expression in the adrenal medulla. However, TH gene expression in the senescent rat is resistant to stimulation by cold exposure, suggesting that the cholinergic pathway may be impaired with age in the adrenal medulla. To investigate this possibility, we administered carbachol (0.5 mg/kg i.p., every 12 hours for 3 consecutive days), a mixed nicotinic-muscarinic agonist, to young (4-month-old) and senescent (24-month-old) male F-344 rats. We examined the induction of TH mRNA, TH immunoreactivity, and TH enzyme activity in the adrenal medulla in young and old rats. In addition DbetaH and NPY mRNA levels were determined in the adrenal medulla with or without carbachol administration. Basal levels of TH mRNA, TH immunoreactivity, and TH activity as well as DbetaH and neuropeptide Y (NPY) mRNA were 1.5- to...Continue Reading

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Mentioned in this Paper

Biochemical Pathway
Immunoreactivity
Carboptic
Cold Temperature
Catecholamines Measurement
Immunocytochemistry
Senility
Dopamine-beta-monooxygenase
Rats, Inbred F344
Enzyme Activity

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