α-Adrenoceptor responsiveness in the aged rat

Docherty, James R.; Hyland, Lisa

doi:10.1016/0014-2999(86)90740-5

Cited by 37 publications

(19 citation statements)

References 13 publications

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“…Recently, Docherty and Hyland (27) have also examined the effects of aging on vascular alphas and alpha2-adrenoceptor activity in the pithed young (3-7 months) and senescent (21-24 months) Sprague Dawley rats utilizing amidephrine and xylazine as an alpha, and alpha2 agonist, respectively. They found that the pressor effects of the alpha, -adrenoceptor agonist amidephrine were not significantly altered between 3 and 24 months, an observation which agrees well with our present results, although we examined pithed rats between 2 and 12 months of age using phenylephrine as an alpha, -selective agonist.…”

Section: Discussionmentioning

confidence: 99%

Effects of triiodo-L-thyronine(T3)-induced hyperthyroidism on the cardiovascular alpha-adrenoceptor system in young and older rats.

Tsujimoto

Hashimoto

1987

Jpn.J.Pharmacol

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Abstract-We have compared the vasopressor response of alpha-adrenoceptor agonists in young (2 month-old) and older (12 month-old) pithed rats both in the presence and absence of triiodo-L-thyronine (T3)-induced hyperthyroidism. There was no age-related changes in the pressor response to either the alpha, selective agonist phenylephrine or the alpha2-selective agonists clonidine and UK 14,304. However, T3-induced hyperthyroidism caused a selective reduction in postjunctional alpha2-adrenoceptor-mediated pressor responses but not alpha, adrenoceptor-mediated ones in both age groups. In contrast to vascular alpha adrenoceptors, there was an age-related decrease in the number of myocardial alpha, -adrenoceptor sites measured by specific binding of [3H] prazosin. With thyroid hormone treatment, the density of ventricular alpha, receptors was found to be further reduced even in the older rats. These results suggest that thyroid hormone and aging have different influences on the cardiovascular alpha-adre noceptor system and that these two physiological variables are independently

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Section: Discussionmentioning

confidence: 99%

Effects of triiodo-L-thyronine(T3)-induced hyperthyroidism on the cardiovascular alpha-adrenoceptor system in young and older rats.

Tsujimoto

Hashimoto

1987

Jpn.J.Pharmacol

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“…The finding that in 549 1 young rats, yohimbine alone given into the NTS produced a pressor response suggests that a reduced sensitivity of a2-adrenoceptors at this level is of physiological importance. Several results suggest that in old animals, and probably in man, there is an impairment of the basic mechanisms underlying neurotransmission both at the pre-and post-synaptic level in several areas of the brain (see Agnoli et al, 1983;Docherty & Hyland, 1986). It has been suggested that a common feature of the impairment of neurotransmission in old age is attributable to a decrease in neuronal membrane fluidity at presynaptic nerve terminals as well as at postsynaptic membranes (Nagy et al, 1983;Schroeder, 1985;Toffano, 1985).…”

Section: Discussionmentioning

confidence: 99%

“…It has been suggested that a common feature of the impairment of neurotransmission in old age is attributable to a decrease in neuronal membrane fluidity at presynaptic nerve terminals as well as at postsynaptic membranes (Nagy et al, 1983;Schroeder, 1985;Toffano, 1985). As far as the noradrenergic mechanisms in the brain are concerned, evidence exists for a decreased number of ac-and a2-adrenoceptor in rabbit brain (Hamilton et al, 1984) and in the periphery (Docherty & Hyland, 1986).…”

Section: Discussionmentioning

confidence: 99%

The effects of phosphatidylserine on the decreased cardiovascular response to clonidine microinfused into the nucleus tractus solitarii of old rats

Mollace¹,

Masuda

Pelaggi³

et al. 1990

British J Pharmacology

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1 The cardiovascular effects of direct microinfusions of clonidine into the nucleus tractus solitarii (NTS) in rats of different ages were studied. 2 Clonidine microinfused into the NTS produced a dose-dependent hypotensive and bradycardic response, which was reduced by previous microinfusion of yohimbine but not of propranolol or prazosin. 3 Unilateral microinfusion of clonidine into the NTS produced a significantly smaller hypotensive and bradycardic response in 16 month old rats than in 3 month old rats, whereas in older animals (24 month old) the same doses of clonidine were ineffective. In 16 month old rats, yohimbine given into the NTS produced a smaller pressor and tachycardic response than in 3 month old rats whereas in 24 month old animals yohimbine, at the same doses, was unable to change blood pressure and heart rate.4 Oral administration of phosphatidylserine (50mg kg 1 dayf 1 for 30 consecutive days) enhanced the hypotensive and bradycardic response to clonidine microinfused into the NTS in 16 month old rats. The same schedule of treatment with phosphatidylserine did not affect the cardiovascular response to clonidine in young (3 month old) rats and did not restore responsiveness to clonidine in older rats (24 month old). 5 Methoxamine and phentolamine, given intravenously, produced similar pressor and depressor responses, respectively in 3, 16 and 24 month old rats, suggesting that the decreased sensitivity to clonidine in old rats was not due to peripheral cardiovascular changes. 6 In conclusion, the present results indicate that, during aging, there is a decreased sensitivity of a2-adrenoceptors in the brain. Such an alteration can be reversed by chronic treatment with phosphatidylserine during the initial but not the later stages of aging.

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“…There are a number of studies aimed at measuring changes in the feedback function of prejunctional  2 -adrenoceptors. Measurements of NA overflow have shown an age-related decline in the effect of prejunctional 2 -adrenoceptor antagonists in pithed rats, rat vas deferens, heart, and tail artery (Hyland & Docherty, 1985;Docherty & Hyland, 1986;Daly et al, 1989;Buchholz & Duckles, 1990). On the surface these studies seem to offer support for the idea of a general age-related decline in the function of prejunctional 2 -adrenoceptors.…”

Section: Transmitter Uptake and Function Of Inhibitory Prejunctional mentioning

confidence: 99%

Calcium Regulation in Neuronal Function with Advancing Age: Limits of Homeostasis

Buchholz¹,

Pottorf²,

Vanterpool³

et al. 2012

Senescence

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α-Adrenoceptor responsiveness in the aged rat

Cited by 37 publications

References 13 publications

Effects of triiodo-L-thyronine(T3)-induced hyperthyroidism on the cardiovascular alpha-adrenoceptor system in young and older rats.

Effects of triiodo-L-thyronine(T3)-induced hyperthyroidism on the cardiovascular alpha-adrenoceptor system in young and older rats.

The effects of phosphatidylserine on the decreased cardiovascular response to clonidine microinfused into the nucleus tractus solitarii of old rats

Calcium Regulation in Neuronal Function with Advancing Age: Limits of Homeostasis

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