A positive inotropic response of guinea pig isolated atria to histamine not mediated via H1 or H2 receptors

1980 ◽  
Vol 58 (2) ◽  
pp. 167-173 ◽  
Author(s):  
Campbell Wilson ◽  
Kenneth J. Broadley
Keyword(s):  
Guinea Pig ◽  
Adrenergic Receptors ◽  
Inotropic Response ◽  
Positive Component ◽  
Response Curves ◽  
H2 Receptors ◽  
Isolated Atria ◽  
Inotropic Responses ◽  
Β Adrenergic Receptors ◽  
Right Atria

The positive chronotropic responses of guinea pig isolated right atria to histamine were antagonized by metiamide (pA2, 5.95) thus confirming their H2 receptor classification. The positive inotropic responses of paced left atria were antagonized to some extent by mepyramine to give a pA2 value of 7.87, indicating the involvement of H1 receptors. A limit to the shift of cumulative dose–response curves for the inotropic response suggested an H1 receptor resistant component. The inotropic response to sequentially administered histamine was biphasic. On lowering the temperature to 25 °C, the two components became more demarcated and separated by a negative phase. Only the primary positive component and the negative component were antagonized by mepyramine. At 38 °C, the response was similarly converted to a monophasic one. The residual responses were resistant to metiamide and propranolol antagonism and therefore not mediated via H1, H2, or β-adrenergic receptors.

The Inotropic and Chronotropic Responses of the Guinea Pig and Dog Myocardium to Isoprenaline and Salbutamol

1975 ◽  
Vol 53 (2) ◽  
pp. 231-238 ◽  
Author(s):  
R. L. Hughson ◽  
J. R. Ledsome
Keyword(s):  
Guinea Pig ◽  
Adrenergic Receptors ◽  
Response Pattern ◽  
Inotropic Response ◽  
Dog Heart ◽  
Relative Response ◽  
Guinea Pig Atrium ◽  
Inotropic Responses

The relative effects of isoprenaline and salbutamol on the inotropic and chronotropic responses of the denervated myocardium of the chloralose anesthetized dog and of the isolated guinea pig atrium, and the inotropic response of the isolated dog papillary muscle were studied. Both the in vivo dog heart and the in vitro guinea pig atrium displayed a similar relative response pattern to isoprenaline and salbutamol with regard to their inotropic and chronotropic responses. However, a comparison of the relative inotropic responses of the dog heart in vivo and in vitro showed that in vitro, salbutamol has a much lower affinity and efficacy for the adrenergic receptors than isoprenaline.

Interaction of clonidine with chronotropic agents on isolated right atria

1980 ◽  
Vol 58 (1) ◽  
pp. 28-33 ◽  
Author(s):  
Robert L. Rodgers ◽  
Thomas E. Tenner Jr. ◽  
Ismail E. Laher ◽  
John H. McNeill
Keyword(s):  
Guinea Pig ◽  
Adrenergic Receptors ◽  
Direct Interaction ◽  
Atrial Rate ◽  
Chronotropic Effects ◽  
Β Adrenergic Receptors ◽  
Right Atria

Clonidine was administered to isolated guinea pig right atria in order to characterize its chronotropic activity and its interaction with other chronotropic agents at the postjunctional level. Clonidine either had no significant effect (10−7–10−4 M) or decreased (10−3 M) atrial rate. Pretreatment of the atria with clonidine noncompetitively antagonized (10−6–10−4 M) the positive chronotropic actions of isoproterenol, and competitively antagonized (10−4 M) the negative chronotropic actions of pilocarpine. At doses of 10−6 or 3 × 10−6 M, clonidine also noncompetitively antagonized the positive chronotropic effects of 4-methylhistamine and glucagon. The results show that clonidine antagonizes both adrenergic and cholinergic influences on atrial rate at the postjunctional level and suggest that the antagonism of adrenergic influences does not involve a direct interaction with β-adrenergic receptors.

Does endogenous adenosine have a role in the cardiac responses to isoprenaline and in the rapid fade of the inotropic response of perfused heart?

1994 ◽  
Vol 72 (2) ◽  
pp. 152-160 ◽  
Author(s):  
Kenneth J. Broadley ◽  
Andrew N. A. Wilson
Keyword(s):  
Guinea Pig ◽  
Adenosine Deaminase ◽  
Papillary Muscles ◽  
Inotropic Response ◽  
Force Of Contraction ◽  
Depressant Effect ◽  
Response Curves ◽  
Endogenous Adenosine ◽  
Left And Right ◽  
Right Atria

The role of endogenous adenosine during the β-adrenoceptor responses to isoprenaline of guinea-pig isolated cardiac preparations was examined. Insignificant effects of adenosine deaminase (0.3 U∙mL−1) on cumulative concentration–response curves for isoprenaline on isolated left and right atria and papillary muscles indicated a negligible depressant effect of endogenous adenosine during these responses. The increase in force of contraction to an infusion of isoprenaline (14 nM) in perfused spontaneously beating hearts rapidly waned while the infusion continued, whereas the increase in rate of contraction remained constant throughout the infusion. The degree of fade was less in paced preparations (5 Hz), indicating that it was only in part due to the rate increase exerting some mechanical constraint on the force of contraction. The P1-purinoceptor antagonist 8-phenyltheophylline (12 μM) and adenosine deaminase (0.3 U∙mL−1) did not enhance the peak responses to the isoprenaline infusion. The fade of the inotropic response in both spontaneous and paced hearts was also not attenuated by the presence of 8-phenyltheophylline or adenosine deaminase. The fade was not, therefore, due to release of endogenous adenosine exerting a depressant effect. Whether this declining inotropic response represents a form of rapid desensitization remains to be determined.Key words: guinea-pig perfused hearts, left and right atria, papillary muscles, β-adrenoceptor agonist, endogenous adenosine.

Up-regulation of guinea pig myometrial β-adrenergic receptors by intrauterine estradiol and progesterone pellets

1989 ◽  
Vol 160 (3) ◽  
pp. 751-757 ◽  
Author(s):  
Christos G. Hatjis ◽  
Donald R. Koritnik ◽  
David M. Grogan
Keyword(s):  
Guinea Pig ◽  
Adrenergic Receptors ◽  
Β Adrenergic Receptors

The characteristics of β-adrenergic binding sites on pancreatic islets of Langerhans

1986 ◽  
Vol 111 (2) ◽  
pp. 263-270 ◽  
Author(s):  
J. M. Fyles ◽  
M. A. Cawthorne ◽  
S. L. Howell
Keyword(s):  
Insulin Secretion ◽  
Adenylate Cyclase ◽  
Guinea Pig ◽  
Islets Of Langerhans ◽  
Binding Sites ◽  
Adrenergic Receptors ◽  
Islet Cells ◽  
Pancreatic Islets Of Langerhans ◽  
Β Adrenergic Receptors ◽  
Stimulation Of

ABSTRACT The sympathetic nervous system is believed to play a part in the control of insulin release from the pancreatic islets of Langerhans. Stimulation of α-adrenoceptors is thought to inhibit the release of insulin whereas stimulation of β-adrenoceptors enhances insulin release. The present experiments were conducted to establish the existence of β-adrenergic receptors on guinea-pig and rat islet cells and to quantify them using the selective β-adrenergic ligands [3H]dihydroalprenolol (DHA) and [125I]cyanoiodopindolol (CYP). Guinea-pig islets had 62 fmol β-adrenoceptors/mg protein using [3H]DHA, corresponding to 43 700 binding sites/cell and 25 fmol β-adrenoceptors/mg protein using [125I]CYP, corresponding to 17 400 sites/cell. Rat islet cells were found to have 4·6 fmol β-adrenoceptors/mg protein using [125I]CYP, corresponding to 7200 sites/cell. Adenylate cyclase activation exhibited a positive dose–response relationship when exposed to the β-adrenoceptor agonist isoprenaline, with a maximum response (190 ± 21% above basal) at 10 μmol isoprenaline/l. This response was abolished with 1 μmol/l of the β-adrenergic antagonist 1-alprenolol. Insulin secretion in the presence of 10 mmol glucose/l, but in the absence of the α-adrenoceptor blocker phentolamine, was not affected by 10 μmol isoprenaline/l. However, perifusion experiments showed that secretion of insulin from isolated rat islets in the presence of 10 mmol glucose/l was significantly increased (332%) by 10 μmol isoprenaline/l in the presence of 10 μmol phentolamine/l. These results suggest that binding of selective radio-labelled ligands occurs to β-adrenergic receptors on the B cell surface of the islets of Langerhans, and that these receptors are functionally coupled to insulin secretion through modulation of adenylate cyclase activity. J. Endocr. (1986) 111, 263–270

Glucocorticoid modulation of muscarinic and β-adrenergic receptors in guinea pig lung

1997 ◽  
Vol 11 (2) ◽  
pp. 111-116 ◽  
Author(s):  
D. Scherrer ◽  
E. Lach ◽  
Y. Landry ◽  
JP Gies
Keyword(s):  
Guinea Pig ◽  
Adrenergic Receptors ◽  
Β Adrenergic Receptors

Dissociation constants (KA) and relative efficacies of sympathomimetic amines in isolated atria during hypothermia-induced supersensitivity

1983 ◽  
Vol 61 (6) ◽  
pp. 572-580 ◽  
Author(s):  
Kenneth J. Broadley ◽  
John H. McNeill
Keyword(s):  
Dose Response ◽  
Dissociation Constants ◽  
Response Curves ◽  
Isolated Atria ◽  
Adrenoceptor Agonists ◽  
Dose Response Curves ◽  
The Right ◽  
Tension Curves ◽  
Noradrenaline And Adrenaline ◽  
Right Atria

Hypothermia increases the sensitivity of isolated cardiac muscle to stimulation by β-adrenoceptor agonists. The purpose of this study was to determine pharmacologically whether this supersensitivity is associated with a change in the affinity of agonists for the receptor. The positive inotropic and chronotropic responses of guinea-pig paced left and spontaneously beating right atria were recorded. Cumulative dose–response curves to noradrenaline (or adrenaline) were compared with isoproterenol in each tissue. At 38 °C, the rate curves were to the left of the tension curves, with lower mean effective concentration (EC50) values. However, this difference was less for noradrenaline and adrenaline which were therefore tension selective relative to isoproterenol. Lowering the temperature to 25 °C induced supersensitivity, all dose–response curves being displaced to the left. In the presence of carbachol the curves were shifted to the right with depression of the maxima. Dissociation constants (KA) were calculated from plots of reciprocals of equiactive concentrations obtained before and in the presence of carbachol. KA values for rate and tension responses of each agonist were identical at 38 °C, indicating that the rate selectivity was not due to affinity differences. The efficacies (er) of noradrenaline and adrenaline were greater than isoproterenol for tension, but smaller for rate responses, which may explain their relative tension selectivity. At 25 °C the KA values of all agonists were reduced approximately 10-fold. Hypothermia-induced supersensitivity is therefore associated with an increase in affinity for the cardiac β-adrenoceptor.

scholarly journals Involvement of β adrenergic receptors in spasmolytic effect of caulerpine on guinea pig ileum

2016 ◽  
Vol 30 (22) ◽  
pp. 2605-2610 ◽  
Author(s):  
Luiz Henrique Agra Cavalcante-Silva ◽  
Ana Carolina de Carvalho Correia ◽  
Jéssica Celestino Ferreira Sousa ◽  
José Maria Barbosa-Filho ◽  
Bárbara Viviana de Oliveira Santos ◽  
...  
Keyword(s):  
Guinea Pig ◽  
Adrenergic Receptors ◽  
Guinea Pig Ileum ◽  
Β Adrenergic Receptors
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