Diurnal and seasonal changes in sympathetic signal transduction in cardiac ventricles of European hamsters

1996 ◽  
Vol 270 (1) ◽  
pp. R304-R309 ◽  
Author(s):  
K. Pleschka ◽  
A. Heinrich ◽  
K. Witte ◽  
B. Lemmer
Keyword(s):  
Adenylyl Cyclase ◽  
Rank Order ◽  
Constant Darkness ◽  
Receptor Subtypes ◽  
Dark Phase ◽  
Light Cycle ◽  
Dark Light ◽  
Cardiac Ventricles ◽  
Beta 2 ◽  
The Relationship

This investigation of the relationship between cardiac beta-adrenoceptors and adenosine 3',5'-cyclic monophosphate (cAMP) formation in cardiac ventricles of the nocturnally active European hamster both during euthermia under a 12:12-h dark-light cycle and during hibernation under constant-darkness conditions showed that neither the densities, affinities, nor distribution of the beta 1- and beta 2-receptor subtypes differed between the dark phase, light phase, and hibernation. Basal formation of cAMP by the cardiac adenylyl cyclase of euthermic hamsters was higher in ventricles obtained at night [core temperature (Tcore) = 37.8 degrees C] than in ventricles obtained during the day (Tcore = 36.4 degrees C). Basal formation of cAMP was also significantly lower in hibernating hamsters (Tcore = 7.0 degrees C) than in euthermic hamsters. When adenylyl cyclase activity was stimulated by isoprenaline, guanylylimidodiphosphate [Gpp(NH)p], or forskolin, the rank order of potency was the same in euthermic hamsters and hibernating hamsters: isoprenaline < Gpp(NH)p < forskolin. Functional competition curves indicated that in the euthermic hamsters beta 1-receptors were responsible for 67% of the response to isoprenaline at night and 62% of the response during the day. In hibernating hamsters, in contrast, most of the response to isoprenaline (58%) was mediated via beta 2-receptors. This shift in the relative importance of the receptor subtypes may facilitate arousal from hibernation by making the heart more sensitive to circulating epinephrine.

Pharmacological Characterization of an Adenylyl Cyclase-Coupled 5-HT Receptor in Aplysia: Comparison With Mammalian 5-HT Receptors

2003 ◽  
Vol 89 (3) ◽  
pp. 1440-1455 ◽  
Author(s):  
Jonathan E. Cohen ◽  
Chiadi U. Onyike ◽  
Virginia L. McElroy ◽  
Allison H. Lin ◽  
Thomas W. Abrams
Keyword(s):  
Adenylyl Cyclase ◽  
Rank Order ◽  
Physiological Saline ◽  
Receptor Subtypes ◽  
Pharmacological Profile ◽  
Pharmacological Characterization ◽  
Firing Properties ◽  
Stimulation Of

We attempted to identify compounds that are effective in blocking the serotonin (5-hydroxytryptamine, 5-HT) receptor(s) that activate adenylyl cyclase (AC) in Aplysia CNS. We call this class of receptor 5-HTapAC. Eight of the 14 antagonists tested were effective against 5-HTapAC in CNS membranes with the following rank order of potency: methiothepin > metergoline ∼ fluphenazine > clozapine > cyproheptadine ∼ risperidone ∼ ritanserin > NAN-190. GR-113808, olanzapine, Ro-04-6790, RS-102221, SB-204070, and spiperone were inactive. Methiothepin completely blocked 5-HT stimulation of AC with a K b of 18 nM. Comparison of the pharmacological profile of the 5-HTapAC receptor with those of mammalian 5-HT receptor subtypes suggested it most closely resembles the 5-HT6 receptor. AC stimulation in Aplysia sensory neuron (SN) membranes was also blocked by methiothepin. Methiothepin substantially inhibited two effects of 5-HT on SN firing properties that are mediated by a cAMP-dependent reduction in S-K+ current: spike broadening in tetraethylammonium/nifedipine and increased excitability. Consistent with cyproheptadine blocking 5-HT stimulation of AC, cyproheptadine also blocked the 5-HT-induced increase in SN excitability. Methiothepin was less effective in blocking AC-mediated modulatory effects of 5-HT in electrophysiological experiments on SNs than in blocking AC stimulation in CNS or SN membranes. This reduction in potency appears to be due to effects of the high ionic strength of physiological saline on the binding of this antagonist to the receptor. Methiothepin also antagonized AC-coupled dopamine receptors but not AC-coupled small cardioactive peptide receptors. In conjunction with other pharmacological probes, this antagonist should be useful in analyzing the role of 5-HT in various forms of neuromodulation in Aplysia.

Molecular analysis of beta-adrenergic receptor subtypes in rat collecting duct: effects on cell cAMP and Ca2+ levels

1995 ◽  
Vol 268 (6) ◽  
pp. F1070-F1080 ◽  
Author(s):  
B. Mandon ◽  
E. Siga ◽  
A. Champigneulle ◽  
M. Imbert-Teboul ◽  
J. M. Elalouf
Keyword(s):  
Rank Order ◽  
Collecting Duct ◽  
Receptor Subtypes ◽  
Thick Ascending Limb ◽  
Camp Accumulation ◽  
Beta Adrenergic ◽  
Beta Agonists ◽  
Fluorescence Measurements ◽  
Beta 2 ◽  
Collecting Tubules

Expression and functional properties of beta-adrenergic receptors (beta-ARs) were studied in rat collecting tubules isolated by microdissection. Reverse transcription-polymerase chain reaction experiments demonstrated that the beta 1- and beta 2-AR mRNAs, but not the beta 3-subtype, are expressed in the cortical collecting duct (CCD). Quantitation of mRNAs, carried out using mutant RNAs as internal standards, further showed that beta 1- and beta 2-ARs transcripts are present at comparable amounts in CCD (3,000–4,000 copies/mm of tubular length), but reach 6–8 times lower levels in the outer medullary collecting duct (OMCD: beta 1, 480 +/- 180; beta 2, 590 +/- 110 copies/mm of tubular length). Functional studies, carried out in CCD, corroborated the expression of these two receptor subtypes. The rank order of potency of beta-agonists for stimulating adenosine 3',5'-cyclic monophosphate (cAMP) accumulation was isoproterenol > norepinephrine = epinephrine, and similar efficiencies were found for a beta 1- and a beta 2-antagonist to inhibit isoproterenol-dependent cAMP formation. Fura 2 fluorescence measurements revealed that isoproterenol (10 microM) induces a biphasic rise of intracellular free Ca2+ concentration ([Ca2+]i), consisting of an initial fast increase (delta [Ca2+]i = 122 nM) followed by a plateau phase (delta [Ca2+]i = 58 nM). In the absence of basolateral Ca2+, the initial peak was still observed, suggesting intracellular Ca2+ release. Norepinephrine and epinephrine, as well as selective beta 1- and beta 2-agonists, also increased [Ca2+]i in CCD. Only slight [Ca2+]i variations were produced by isoproterenol in the OMCD (delta [Ca2+]i = 21 nM) and the cortical thick ascending limb (delta [Ca2+]i = 25 nM). These results show that both beta 1- and beta 2-ARs are expressed in the collecting tubule and that they predominate in the CCD. The two receptor subtypes contribute to cAMP accumulation induced by beta-agonists. They also trigger [Ca2+]i variations, indicating their possible coupling to several transduction pathways in the rat CCD.

scholarly journals The Relationship Between the Diurnal Light Cycle and the Time of Ovulation in Mice

1957 ◽  
Vol 34 (2) ◽  
pp. 177-188
Author(s):  
A. W. H. BRADEN
Keyword(s):  
Probit Analysis ◽  
Genetic Constitution ◽  
Dark Phase ◽  
Light Cycle ◽  
C Stocks ◽  
C Stock ◽  
The Mean ◽  
Mixed Origin ◽  
Time Required ◽  
The Relationship

The period required for the completion of ovulation in groups of mated females has been studied in 615 mice from three random-bred stocks (L, C and PCT) and in 137 mice of mixed origin. The mice were examined after having been kept for some time under one of four different diurnal light cycles, viz. the natural diurnal light cycle in Edinburgh in December (1) and in June (2) and artificial, reversed, light cycles of 10 hr. darkness/14 hr. light (3) and 4 hr. darkness/20 hr. light (4). The variation between mice in any one group was greatest when they were maintained under the cycles that had a relatively long dark phase: a period of 12-14 hr. was required for ovulation in groups of L and C stock mice under cycles with a dark phase of 10-15 hr. whereas groups of similar females maintained under cycles with a 4-6 hr. dark phase required only 8-9 hr. for ovulation. Probit analysis indicated that this difference was statistically significant. In changing the length of the dark phase of the diurnal cycle the beginning of each phase was altered by 3-4½ hr.; the mid-points of each phase were altered by less than 1 hr. The results suggest that the mid-point of the ovulation period was determined more by the mid-point of the dark phase than by its onset or completion. Differences noted between stocks of mice in the mid-point of the ovulation period and in the ability to adjust quickly to an altered light cycle gave indication that the neural mechanisms involved in the control of the time of ovulation in mice are modified according to the genetic constitution of the animal. The mean interval between coitus and ovulation in females of L and C stocks under natural light cycles was found to be approximately 5 hr. The average time required for the ovulation of three-quarters of the total number of eggs shed in any one mouse (mean 11-12 eggs) was estimated as 0.5 hr.

1606-P: Effect of Changes in Dark/Light Cycle on Physiological Homeostasis as a Confounding Prelude to Diabetes in Fischer 334 Animal Model

Diabetes ◽  
2020 ◽  
Vol 69 (Supplement 1) ◽  
pp. 1606-P
Author(s):  
BALANEHRU SUBRAMANIAN ◽  
GANAPATHY RAMAKRISHNAN ◽  
PANNERSELVAM TAMILMARAN ◽  
BALAKRISHNAN SUNDARAKRISHNAN ◽  
KRISHNA SESHADRI
Keyword(s):  
Animal Model ◽  
Light Cycle ◽  
Dark Light ◽  
Physiological Homeostasis

Vigilance States: Central Neural Pathways, Neurotransmitters and Neurohormones

2019 ◽  
Vol 19 (1) ◽  
pp. 26-37 ◽  
Author(s):  
Michele Iovino ◽  
Tullio Messana ◽  
Giovanni De Pergola ◽  
Emanuela Iovino ◽  
Edoardo Guastamacchia ◽  
...  
Keyword(s):  
Circadian Rhythm ◽  
Neural Pathways ◽  
Light Cycle ◽  
Behavioral State ◽  
State Control ◽  
Dark Light ◽  
Concentration Of Ions ◽  
Brainstem Nuclei ◽  
Reticular Activating System ◽  
Plasmatic Concentration

Background and Objective: The sleep-wake cycle is characterized by a circadian rhythm involving neurotransmitters and neurohormones that are released from brainstem nuclei and hypothalamus. The aim of this review is to analyze the role played by central neural pathways, neurotransmitters and neurohormones in the regulation of vigilance states.Method:We analyzed the literature identifying relevant articles dealing with central neural pathways, neurotransmitters and neurohormones involved in the control of wakefulness and sleep.Results:The reticular activating system is the key center in the control of the states of wakefulness and sleep via alertness and hypnogenic centers. Neurotransmitters and neurohormones interplay during the dark-light cycle in order to maintain a normal plasmatic concentration of ions, proteins and peripheral hormones, and behavioral state control.Conclusion:An updated description of pathways, neurotransmitters and neurohormones involved in the regulation of vigilance states has been depicted.

scholarly journals Melatonin MT1 and MT2 Receptors Exhibit Distinct Effects in the Modulation of Body Temperature across the Light/Dark Cycle

2019 ◽  
Vol 20 (10) ◽  
pp. 2452 ◽  
Author(s):  
Martha López-Canul ◽  
Seung Hyun Min ◽  
Luca Posa ◽  
Danilo De Gregorio ◽  
Annalida Bedini ◽  
...  
Keyword(s):  
Body Temperature ◽  
Receptor Antagonist ◽  
Partial Agonist ◽  
Receptor Subtypes ◽  
Dark Phase ◽  
Light Phase ◽  
Dark Cycle ◽  
Simultaneous Activation ◽  
Type 3 ◽  
G Protein Coupled

Melatonin (MLT) is a neurohormone that regulates many physiological functions including sleep, pain, thermoregulation, and circadian rhythms. MLT acts mainly through two G-protein-coupled receptors named MT1 and MT2, but also through an MLT type-3 receptor (MT3). However, the role of MLT receptor subtypes in thermoregulation is still unknown. We have thus investigated the effects of selective and non-selective MLT receptor agonists/antagonists on body temperature (Tb) in rats across the 12/12-h light–dark cycle. Rectal temperature was measured every 15 min from 4:00 a.m. to 9:30 a.m. and from 4:00 p.m. to 9:30 p.m., following subcutaneous injection of each compound at either 5:00 a.m. or 5:00 p.m. MLT (40 mg/kg) had no effect when injected at 5 a.m., whereas it decreased Tb during the light phase only when injected at 5:00 p.m. This effect was blocked by the selective MT2 receptor antagonist 4P-PDOT and the non-selective MT1/MT2 receptor antagonist, luzindole, but not by the α1/MT3 receptors antagonist prazosin. However, unlike MLT, neither the selective MT1 receptor partial agonist UCM871 (14 mg/kg) nor the selective MT2 partial agonist UCM924 (40 mg/kg) altered Tb during the light phase. In contrast, UCM871 injected at 5:00 p.m. increased Tb at the beginning of the dark phase, whereas UCM924 injected at 5:00 a.m. decreased Tb at the end of the dark phase. These effects were blocked by luzindole and 4P-PDOT, respectively. The MT3 receptor agonist GR135531 (10 mg/kg) did not affect Tb. These data suggest that the simultaneous activation of both MT1 and MT2 receptors is necessary to regulate Tb during the light phase, whereas in a complex but yet unknown manner, they regulate Tb differently during the dark phase. Overall, MT1 and MT2 receptors display complementary but also distinct roles in modulating circadian fluctuations of Tb.

Disrupted circadian rhythms in VIP- and PHI-deficient mice

2003 ◽  
Vol 285 (5) ◽  
pp. R939-R949 ◽  
Author(s):  
Christopher S. Colwell ◽  
Stephan Michel ◽  
Jason Itri ◽  
Williams Rodriguez ◽  
J. Tam ◽  
...  
Keyword(s):  
Circadian Rhythms ◽  
Wheel Running ◽  
Activity Rhythm ◽  
Activity Patterns ◽  
Circadian System ◽  
Diurnal Rhythms ◽  
Constant Darkness ◽  
Light Cycle ◽  
Wild Type ◽  
Deficient Mice

The related neuropeptides vasoactive intestinal peptide (VIP) and peptide histidine isoleucine (PHI) are expressed at high levels in the neurons of the suprachiasmatic nucleus (SCN), but their function in the regulation of circadian rhythms is unknown. To study the role of these peptides on the circadian system in vivo, a new mouse model was developed in which both VIP and PHI genes were disrupted by homologous recombination. In a light-dark cycle, these mice exhibited diurnal rhythms in activity which were largely indistinguishable from wild-type controls. In constant darkness, the VIP/PHI-deficient mice exhibited pronounced abnormalities in their circadian system. The activity patterns started ∼8 h earlier than predicted by the previous light cycle. In addition, lack of VIP/PHI led to a shortened free-running period and a loss of the coherence and precision of the circadian locomotor activity rhythm. In about one-quarter of VIP/PHI mice examined, the wheel-running rhythm became arrhythmic after several weeks in constant darkness. Another striking example of these deficits is seen in the split-activity patterns expressed by the mutant mice when they were exposed to a skeleton photoperiod. In addition, the VIP/PHI-deficient mice exhibited deficits in the response of their circadian system to light. Electrophysiological analysis indicates that VIP enhances inhibitory synaptic transmission within the SCN of wild-type and VIP/PHI-deficient mice. Together, the observations suggest that VIP/PHI peptides are critically involved in both the generation of circadian oscillations as well as the normal synchronization of these rhythms to light.

scholarly journals Circadian Rhythm and Stress Response in Droppings ofSerinus canaria

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Maura Turriani ◽  
Nicola Bernabò ◽  
Barbara Barboni ◽  
Gianluca Todisco ◽  
Luigi Montini ◽  
...  
Keyword(s):  
Circadian Rhythm ◽  
Stress Response ◽  
Enzyme Immunoassay ◽  
Light Period ◽  
Daily Rhythm ◽  
Fecal Excretion ◽  
Dark Phase ◽  
Light Cycle ◽  
Serinus Canaria ◽  
Commercial Enzyme Immunoassay

Serinus canariais a widespread domestic ornamental songbird, whose limited knowledge of biology make compelling studies aimed to monitor stress. Here, a commercial enzyme immunoassay was adopted to measure immunoreactive corticosterone (CORT) in singleSerinus canariadropping sample, to monitor the daily fecal excretion of CORT in birds bred singly or in-group and to detect the effect promoted by aviary or small transport cage restraint. A robust daily rhythm of CORT was recorded in animals held on short-day light cycle, independent of bred conditions (single or group), which persisted when space availability was modified in single bred animal (transfer in aviary and transport cages). By contrast, a significant change in CORT excretion was recorded when group bred animals are restrained in a smaller cage. The daily rhythm in CORT excretion in response to manipulation showed the greatest response at the beginning of the light period, followed by the absence of the peak usually recorded at the end of the dark phase. These data indicated that EIA could be used as a reliable noninvasive approach to monitor the stress induced by restraint conditions inSerinus canaria.

Differential regulation of PI hydrolysis and adenylyl cyclase by muscarinic receptor subtypes

Nature ◽  
1988 ◽  
Vol 334 (6181) ◽  
pp. 434-437 ◽  
Author(s):  
Ernest G. Peralta ◽  
Avi Ashkenazi ◽  
John W. Winslow ◽  
J. Ramachandran ◽  
Daniel J. Capon
Keyword(s):  
Adenylyl Cyclase ◽  
Muscarinic Receptor ◽  
Differential Regulation ◽  
Receptor Subtypes ◽  
Muscarinic Receptor Subtypes ◽  
Pi Hydrolysis

scholarly journals Impact of Inorganic Carbon Availability on Microcystin Production by Microcystis aeruginosa PCC 7806

2007 ◽  
Vol 73 (21) ◽  
pp. 6994-7002 ◽  
Author(s):  
Sabine J�hnichen ◽  
Tilo Ihle ◽  
Thomas Petzoldt ◽  
J�rgen Benndorf
Keyword(s):  
Microcystis Aeruginosa ◽  
Type Strain ◽  
Inorganic Carbon ◽  
Wild Type Strain ◽  
Light Cycle ◽  
Variable Fluorescence ◽  
Wild Type ◽  
Dark Light ◽  
Sodium Dependent ◽  
The Impact

ABSTRACT Batch culture experiments with the cyanobacterium Microcystis aeruginosa PCC 7806 were performed in order to test the hypothesis that microcystins (MCYSTs) are produced in response to a relative deficiency of intracellular inorganic carbon (Ci,i). In the first experiment, MCYST production was studied under increased Ci,i deficiency conditions, achieved by restricting sodium-dependent bicarbonate uptake through replacement of sodium bicarbonate in the medium with its potassium analog. The same experimental approach was used in a second experiment to compare the response of the wild-type strain M. aeruginosa PCC 7806 with its mcyB mutant, which lacks the ability to produce MCYSTs. In a third experiment, the impact of varying the Ci,i status on MCYST production was examined without suppressing the sodium-dependent bicarbonate transporter; instead, a detailed investigation of a dark-light cycle was performed. In all experiments, a relative Ci,i deficiency was indicated by an elevated variable fluorescence signal and led to enhanced phycocyanin cell quotas. Higher MCYST cell quotas (in the first and third experiments) and increased total (intracellular plus extracellular) MCYST production (in the first experiment) were detected with increased Ci,i deficiency. Furthermore, the MCYST-producing wild-type strain and its mcyB mutant showed basically the same response to restrained inorganic carbon uptake, with elevated variable fluorescence and phycocyanin cell quotas with increased Ci,i deficiency. The response of the wild type, however, was distinctly stronger and also included elevated chlorophyll a cell quotas. These differences indicate the limited ability of the mutant to adapt to low-Ci,i conditions. We concluded that MCYSTs may be involved in enhancing the efficiency of the adaptation of the photosynthetic apparatus to fluctuating inorganic carbon conditions in cyanobacterial cells.

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