Control Of Parathyroid Function By Dopamine
M.D. Francesco Amenta in Peripheral Dopamine Pathophysiology, 2019
This chapter reviews the pharmacology of beta-adrenergic receptor, its coupling to intracellular second messengers and parathyroid hormone (PTH) secretion, and its direct identification by radioligand binding studies. It compares the mechanisms by which dopamine (DA) and divalent cations regulate PTH release and examines the interrelationships between the secretagogues. The chapter also reviews the evidence relating to the physiological relevance of this dopamine receptor and its presence in other species in addition to the bovine. The parathyroid gland has been of particular interest to investigators studying the control of hormonal secretion because of the unusual, inverse relationship between the extracellular and intracellular Ca++ concentrations, on the one hand, and PTH release, on the other. Agents which raise cAMP content also activate adenylate cyclase in osmotically lysed bovine parathyroid cells. DA and other dopaminergic agonists are potent secretagoues for PTH in the bovine species in vivo and in vitro .
Miscellaneous Drugs
Sarah Armstrong, Barry Clifton, Lionel Davis in Primary FRCA in a Box, 2019
This chapter explains that cyclizine is histamine-1 receptor antagonist used as an antiemetic. It has mild antimuscarinic action which leads to its side effects of dry mouth, tachycardia and blurred vision. Drugs acting on the uterus are Oxytocin (e.g. syntocinon/carbetocin), Syntocinon 5 IU IV, Carbetocin 100 µg, and Vasodilatation. Drugs that inhibit uterine contractions and relax the uterus are β-adrenergic receptor agonists (ritodrine, salbutamol, terbutaline), Calcium channel blockers (e.g. nifedipine), and Oxytocin antagonists (e.g. atosiban). Neostigmine forms a carbamylated enzyme complex with cholinesterases. This slows the rate of hydrolysis of acetylcholine by acetylcholinesterase, so that more acetylcholine is available at the neuromuscular junction.
The Discovery of Adrenaline and the Concept of Autoreceptors at Synapses
Max R. Bennett in History of the Synapse, 2001
In 1931 Cannon and Bacq reported an increase in the sympathin in the blood stream, as determined by its effects on the heart, following stimulation of the sympathetic nerves to the colon or to the hind quarters (Cannon & Bacq, 1931). Subsequently Jang showed that the responses of several organs to sympathetic nerve stimulation could be potentiated by appropriate concentrations of the adrenergic receptor blocking drugs 933F, yohimbine and ergotoxine (Jang, 1940). That such blocking drugs may enhance the effects of sympathetic nerve stimulation was further elaborated by Holzbauer and Vogt in 1954, who showed that the responses of the dibenzyline pretreated uterus to exogenous adrenaline were greatly enhanced over control untreated preparations (Holzbauer & Vogt, 1956). However, it was not until 1957 that a thorough analysis was made of this phenomenon whereby alpha adrenergic blocking drugs potentiate the overflow of noradrenaline and the contractile response of organs to sympathetic nerve stimulation. Brown and Gillespie stimulated the sympathetic nerves to the spleen of the cat and determined the amount of noradrenaline in the venous blood during different frequencies of stimulation and in the presence of different alpha adrenergic blocking drugs (Brown & Gillespie, 1957). Following 200 impulses, noradrenaline output could just be detected at 10 Hz, with maximum output occurring at 30 Hz (Fig. 4.3A). They showed that the low level of output of noradrenaline at 10 Hz was not due to the breakdown of the catecholamine by monoamine oxidase. Furthermore the level at 10 Hz could be increased to the high level found at 30 Hz if adrenergic blocking drugs such as dibenamine were present in the perfusion fluid (Fig. 4.3A). This led them naturally to the conclusion that: The constancy of the output at frequencies between 1 and 30/sec after dibenamine would be explicable on the ground that the dibenamine had prevented the destruction of the transmitter. The known effect of dibenamine is to block the tissue receptors for noradrenaline, and we must conclude therefore that combination with the receptors is a necessary prelude to the destruction and removal of liberated noradrenaline.
Regulation of the β
Published in Experimental Lung Research, 1995
Dennis W. McGraw, Sandra E. Chai, F. Charles Hiller, Lawrence E. Cornett
Glucocorticoids increase β2-adrenergic responsiveness and receptor density in the lung, but the underlying mechanisms have not been clearly elucidated. To determine whether changes in β2-adrenergic receptor gene expression are involved in vivo, we measured β2-adrenergic receptor mRNA levels and β2-adrenergic receptor density in lungs from Sprague—Dawley rats treated with a daily injection of dexamethasone (1 mg/kg subcutaneously) for 1, 3, or 7 days. Animals were sacrificed either 2 or 24 h after receiving the last injection. β2-Adrenergic receptor mRNA levels were significantly (p < .05) elevated compared to saline-treated controls in the lungs of animals sacrificed 2 h after dexamethasone injection for 1 day (174 ± 12%), 3 days (236 ± 18%), and 7 days (220 ± 11%). Receptor mRNA levels measured 24 h after dexamethasone injection did not differ significantly from the control group. Induction of β2-adrenergic receptor mRNA by dexamethasone was transient, since no significant cumulative or sustained increase in receptor mRNA levels was observed during the study period. Treatment with dexamethasone increased β-adrenergic receptor density as expected, but no significant increase in receptor density was delected until 24 h after the third daily injection of dexamethasone, when levels reached 2045 ± 150 fmol/mg protein compared to 1292 ± 34 fmol/mg protein in the control group. Receptor density then remained at this elevated level through 7 days of treatment. These results show that dexamethasone up-regulates both the β2-adrenergic receptor and its mRNA in vivo in the lung. The induction of β-adrenergic receptor mRNA levels indicates that glucocorticoids may regulate receptor density in the lung through modulation of gene expression. However, the difference between the time course of induction for the β2-adrenergic receptor and its mRNA suggests that additional translational or post-translational mechanisms may also be involved.
The 5′ Flanking Region of the Rat β
Published in DNA Sequence, 1994
Julie A. Brown, Curtis A. Machida
β3-adrenergic receptor mRNAs exhibit species-specific expression (human vs. rodent) in distinct anatomical regions and appear to be expressed abundantly within rodent adipose tissue, but only at low levels within corresponding human tissues. In order to determine the genetic basis of the differential expression of the rat and human β3-adrenergic receptor genes, we cloned and sequenced the rat gene and compared the 5′ flanking regions of the two genes to identify potential discriminators in transcriptional regulation. We have found that the rat and human β3-adrenergic receptor 5′ flanking regions are only 67% similar, unlike the close sequence similarity observed between the coding blocks (> 90%) and also observed between species for the 5′ flanking regions of other β-adrenergic receptor subtype genes (> 90%). In addition, the rat β3-adrenergic receptor gene lacks the four potential cAMP responsive elements identified within the 5′ flanking region of the human receptor gene. The striking divergence in regulatory sequences between the rat and human β3-adrenergic receptor genes may potentially explain the differences in species-specific expression and tissue localization of the rat and human receptor mRNAs.
Non-Specific Binding of the Fluorescent B-Adrenergic Receptor Probe Alprenolol-NBD
Published in Journal of Receptor Research, 1985
Ben Rademaker, Klaas Kramer, Huub van Ingen, Michel Kranendonk, Henk Timmerman
The fluorescent ß-adrenergic receptor probe alprenolol-NBD was found to exhibit a high affinity (Kd 3.2 nM) and a low capacity (10 fmol/mg protein) for the ß2-adrenergic receptor on living Chang liver cells but also a high affinity (Kd 320 nM) for non-ß-adrenergic receptor binding sites with a very high capacity (28,000 fmol/mg protein). Calculations are presented which make clear that less than 3% of the binding of alprenolol-NBD during visualization experiments is ß-adrenergic receptor related. Furthermore, it is shown that besides the downregulation of ß-adrenergic receptors during incubation with isoproterenol, the high-affinity non-ß-receptor binding sites are also deminishing during incubation with isoproterenol. Based on our findings it is concluded that the results of Henis et al. (1) who claimed the visualization of the ß-adrenergic receptor population on Chang liver cells by alprenolol-NBD must be interpreted as an almost completely non-specific fluorescence.
Related Knowledge Centers
- Sympathetic Nervous System
- Epinephrine
- Catecholamine
- Norepinephrine
- G Protein-Coupled Receptor