Effect of propylthiouracil-induced hypothyroidism on cerebral cortex of young and aged rats: Lipid composition of synaptosomes, muscarinic receptor sites, and acetylcholinesterase activity

Abstract

The effect of hypothyroidism on the lipid composition of synaptosomes, density and affinity of muscarinic receptor sites, and acetylcholinesterase activity in the cerebral cortex of young and aged rats was investigated. The animals were made hypothyroid by adding 0.05% propyl-2-thiouracil to their drinking water for four weeks. This pathological state induced an increase in the relative percentage of sphingomyelin in young rats. In aged rats hypothyroidism induced a decrease of sphingomyelin and glycerophosphocholine and an increase of cholesterol. The effect of hypothyroid state on cerebral cortex resulted in an increase of acethylcholinesterase activity both in young and aged rats and was also reflected in an increase of density of M1-AChRs but only in the former.

Maintenance of brain thyroid hormone level during peripheral hypothyroid condition in adult rat

“…Mental depression may arise when the homeostasis is lost as it is known that hypoactivity of cholinergic neurotransmission results in depression (Dilsaver, 1986). However, AChE patterns still remain ambiguous as reports on both unchanged enzyme activity in thyroidectomized and increased activity in PTU-induced hypothyroid or T3-treated rats are available (Salvati et al, 1994;Owasoyo et al, 1981).…”

“…psychobehavioural changes in human (Dilsaver, 1986). Although a complex relationship has been shown to exist between THs and cholinergic function during developmental stages and in adulthood (Salvati et al, 1994), the definite role of TH on cholinergic function of adult brain cerebral cortex is still far from clear. Hypothyroidism has been reported in adult patients with senile dementia of the Alzheimer type (SDAT) where choline acetyltransferase (ChAT) and AChE activities are affected most (Fylkesnes and Nygaard, 2000).…”

“…The present study is aimed at evaluating the chronology of this central thyroid hormone homeostatic mechanism evoked by injecting propylthiouracil (PTU, an antithyroid drug) and its relationship with the activities of Na + -K + -ATPase and AChE. Thyroid dysfunction has been shown to influence the AChE activity both in developing and adult rats (Salvati et al, 1994). The synaptosomal membrane Na + -K + -ATPase has also been identified as a thyroid hormone responsive physiological parameter in adult rat cerebral cortex Ray, 1993, 1998).…”

Maintenance of Homeostasis for Thyroid Hormone in the Adult Rat Brain: Possible Involvement of a Nuclear-Mediated Phenomenon

“…Therefore, the activity of AChE represents the status of the cholinergic neurotransmission. Although a complex relationship has been shown to exist between THs and cholinergic function [36], the definite role of TH in the cholinergic function of the adult brain cerebral cortex is still far from clear. In our study, the synaptosomal AChE activity decreased on the 2nd (day of onset) and 20th (day of termination) days of PTU injection [4].…”

Thyroid Hormone Effects on Sensory Perception, Mental Speed, Neuronal Excitability and Ion Channel Regulation

“…(156)). Although smaller and more localized effects are reported in adults, several lines of evidence suggest that acetylcholine -release may be enhanced by thyroid hormone and decreased in hypothyroidism in the adult nervous system as well (157,158). A decrease of cholinergic activity could perhaps also explain the occurrence of slow EEG waves (159) as well as the cognitive impairments frequently seen in hypothyroid subjects.…”