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  • 1
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    Circulating relaxin acts on subfornical organ neurons to stimulate water drinking in the rat (2002)
    National Academy of Sciences
    Details
    Publication Date: 2002-02-05
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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    PAPER CURRENT
  • 2
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    Multiple receptor subtypes mediate the effects of serotonin on rat subfornical organ neurons (1998)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The subfornical organ (SFO) receives significant serotonergic innervation. However, few reports have examined the functional effects of serotonin on SFO neurons. This study characterized the effects of serotonin on spontaneously firing SFO neurons in the rat brain slice. Of 31 neurons tested, 80% responded to serotonin (1-100 microM) with either an increase (n = 15) or decrease (n = 10) in spontaneous activity. Responses to serotonin were dose dependent and persisted after synaptic blockade. Excitatory responses could also be mimicked by the 5-hydroxytryptamine (5-HT)2A/2C receptor agonist 2,5-dimethoxy-4-iodoamphetamine (DOI; 1-10 microM) and could be blocked by the 5-HT2A/2C-receptor antagonist LY-53,857 (10 microM). LY-53,857 unmasked inhibitory responses to serotonin in 56% of serotonin-excited cells tested. Serotonin-inhibited cells were also inhibited by the 5-HT1A-receptor agonist 8-hydroxy-2(di-n-propylamino)tetralin (8-OH-DPAT; 1-10 microM; n = 7). The data indicate that SFO neurons are responsive to serotonin via postsynaptic activation of multiple receptor subtypes. The results suggest that excitatory responses to serotonin are mediated by 5-HT2A or 5-HT2C receptors and that inhibitory responses may be mediated by 5-HT1A receptors. In addition, similar percentages of serotonin-excited and -inhibited cells were also sensitive to ANG II. As such the functional relationship between serotonin and ANG II in the SFO remains unclear.
    Keywords: Life Sciences (General)
    Type: The American journal of physiology (ISSN 0002-9513); 275; 6 Pt 2; R2035-42
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
    Electronic Resource
    Electronic Resource
    Excitatory and inhibitory responses caused by norepinephrine in duck subfornical organ neurons are mediated by β- and α 2-adrenoceptor activation (1995)
    Springer
    Journal of comparative physiology 176 (1995), S. 149-158 
    Details
    ISSN: 1432-1351
    Keywords: Osmoregulation ; Duck ; Angiotensin II Isoproterenol ; Clonidine ; Phenylephrine Noradrenaline ; (SFO) Drinking ; Thirst ; Water intake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The responsiveness of spontaneously active neurons in the subfornical organ (SFO) of adult ducks to angiotensin II (ANGII), norepinephrine (NE), isoproterenol (Iso, β-agonist), phenylephrine (Phe, α 1-agonist) and clonidine (Clo, α 2-agonist) was investigated in brain slices with extracellular recording technique. 64% (n=90) of the neurons increased their activity after superfusion with ANGII, the rest were unresponsive. Application of NE activated 10 and inhibited 8 neurons (n=22); the excitation being correlated with an excitatory ANGII responsiveness of the same neurons and the inhibition with the absence of an ANGII responsiveness. Iso activated 74% (n=58) and Clo inhibited 88% (n=16) of the investigated neurons. Phe did not have an effect on the majority (60%) of the neurons and produced both excitatory and inhibitory actions on the remaining cells. These results offer a plausible explanation for the dose dependent dipsogenic effect of Iso and the failure of NE to elicit dose dependent drinking, which can be explained by its dual, excitatory and inhibitory effect on SFO neurons. It is further concluded, that peripherally applied Iso exerts its dipsogenic action in high concentration by a direct excitatory effect on SFO neurons via the open blood brain barrier. Under physiological conditions, afferent neuronal input of still unknown origin might specifically modulate the activity of SFO neurons, because plasma concentrations of NE are probably not high enough to activate SFO neurons from the blood side of the blood brain barrier.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239918
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Excitatory action of the bird antidiuretic hormone vasotocin on neurons in the subfornical organ (1995)
    Springer
    Journal of comparative physiology 176 (1995), S. 653-660 
    Details
    ISSN: 1432-1351
    Keywords: Osmoregulation ; Duck ; Antidiuretic hormone ; Vasotocin ; Subfornical organ ; Drinking ; Thrist ; Vasopressin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The responsiveness of spontaneously active neurons in the subfornical organ (SFO) of adult ducks to angiotensin II (ANGII) and the bird specific anti-diuretic hormone, arginine vasotocin (AVT), the analog of the mammalian arginine vasopressin (AVP), were investigated in brain slices with extracellular recording technique. 65% (n = 66) of the neurons increased their activity after superfusion with ANGII, the rest were unresponsive. Application of AVT activated 52% (n = 68) of the investigated neurons and like ANGII never caused an inhibition of the spontaneously active SFO neurons. A close correlation exists between the ANGII and AVT sensitivity of duck SFO neurons, because 29 out of 33 neurons were excited by AVT as well as ANGII. The relatively weak antagonistic effect of the V1-type receptor antagonist Pmp-Tyr (Me)-Arg8-vasopressin on the AVT induced excitation suggests a different pharmacology of the bird AVT receptor as compared to the mammalian AVP receptor. The excitatory response of ANGII and AVT on the very same neurons suggest a similar function of both peptides on SFO mediated effects in vivo, such as an increase in water intake. However, peripheral AVT concentrations, unlike ANGII concentrations in the blood are not high enough to activate SFO neurons from the blood side of the blood brain barrier. Therefore AVT is presumably released from synapses of neurons originating within or projecting to the SFO. The identity of the ANGII and AVT reactive neurons suggests that synaptically released AVT should facilitate SFO mediated drinking.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01021585
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  • 5
    Electronic Resource
    Electronic Resource
    Excitatory action of the bird antidiuretic hormone vasotocin on neurons in the subfornical organ (1995)
    Springer
    Journal of comparative physiology 176 (1995), S. 653-660 
    Details
    ISSN: 1432-1351
    Keywords: Osmoregulation ; Duck ; Antidiuretic hormone ; Vasotocin ; Subfornical organ ; Drinking ; Thrist ; Vasopressin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The responsiveness of spontaneously active neurons in the subfornical organ (SFO) of adult ducks to angiotensin II (ANGII) and the bird specific anti-diuretic hormone, arginine vasotocin (AVT), the analog of the mammalian arginine vasopressin (AVP), were investigated in brain slices with extracellular recording technique. 65% (n = 66) of the neurons increased their activity after superfusion with ANGII, the rest were unresponsive. Application of AVT activated 52% (n = 68) of the investigated neurons and like ANGII never caused an inhibition of the spontaneously active SFO neurons. A close correlation exists between the ANGII and AVT sensitivity of duck SFO neurons, because 29 out of 33 neurons were excited by AVT as well as ANGII. The relatively weak antagonistic effect of the V1-type receptor antagonist Pmp-Tyr (Me)-Arg8-vasopressin on the AVT induced excitation suggests a different pharmacology of the bird AVT receptor as compared to the mammalian AVP receptor. The excitatory response of ANGII and AVT on the very same neurons suggest a similar function of both peptides on SFO mediated effects in vivo, such as an increase in water intake. However, peripheral AVT concentrations, unlike ANGII concentrations in the blood are not high enough to activate SFO neurons from the blood side of the blood brain barrier. Therefore AVT is presumably released from synapses of neurons originating within or projecting to the SFO. The identity of the ANGII and AVT reactive neurons suggests that synaptically released AVT should facilitate SFO mediated drinking.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192494
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  • 6
    Electronic Resource
    Electronic Resource
    Vasotocin acts as a dipsogen in ducks at concentrations stimulating subfornical organ neurons in vitro (1996)
    Springer
    Journal of comparative physiology 165 (1996), S. 615-621 
    Details
    ISSN: 1432-136X
    Keywords: Subfornical organ ; Water intake ; Arginine vasotocin ; Angiotensin II ; Domestic duck
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The effects of systemic infusions of the avian antidiuretic hormone arginine vasotocin on water intake of domestic ducks were investigated under steady conditions of water balance in which angiotensin II was effective as a dipsogen. The study proceeded from the consistent stimulatory effect of arginine vasotocin on angiotensin II-responsive neurons found in the subfornical organ of ducks, suggesting brain-intrinsic vasotocinergic control of these neurons which are also accessible to circulating agents because of the lacking blood-brain barrier. Levels of circulating arginine vasotocin of about 2700 pg·ml-1 which were close to the threshold for activation of subfornical organ neurons in vitro, induced weak but significant drinking responses. Even at this high arginine vasotocin level circulatory effects were absent, thereby excluding their interference with water intake. Arginine vasotocin plasma levels of about 60 pg·ml-1 significantly attenuated the dipsogenic action of angiotensin. While drinking in response to high pharmacological levels of arginine vasotocin is assumed to mimic a stimulatory innervation of angiotensin-responsive subfornical organ neurons by brain-intrinsic vasotocinergic axons, attenuation of angiotensin-induced drinking by high physiological arginine vasotocin levels cannot be explained by its action on central neurons, but may be secondary to body fluid retention caused by the antidiuretic action of arginine vasotocin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00301129
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of angiotensin II and its blockers Sar1-lle8-angiotensin II and DuP 753 on drinking in ducks in relation to properties of subfornical organ neurons (1996)
    Springer
    Journal of comparative physiology 165 (1996), S. 607-614 
    Details
    ISSN: 1432-136X
    Keywords: Subfornical organ ; Water intake ; Angiotensin II ; Losartan ; Sar1-Ile8-angiotensin II ; Domestic duck
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Properties of systemically applied angiotensin II in stimulating water intake of normally hydrated ducks were studied and the results compared with properties of angiotensin II-responsive neurons of the subfornical organ which are considered as targets for circulating angiotensin, II acting as a dipsogen. Following intravenous infusion of hypertonic saline (2000 mosmol·kg-1 at 0.3 ml·min-1 for 1 h), intravenous infusion of 0.3 ml·min-1 isotonic saline with angiotensin II (200 ng·min-1), starting 1 h later, stimulated drinking in each case at an angiotensin II plasma level of about 1400 pg·ml-1. Without hypertonic priming, the same angiotensin II infusion did not stimulate drinking in each experiment; however, if effective, repeated infusions of ANGII induced stable dipsogenic responses. Angiotensin II infusions did not alter plasma levels of antidiuretic hormone. Sar1-Ile8-angiotensin II, a non-selective angiotensin II antagonist, acted weakly as a partial agonist when injused at a dose 200-fold higher than angiotensin II and effectively blocked the dipsogenic action of angiotensin II; this corresponds to the inhibition of angiotensin II-induced excitation by Sar1-Ile8-angiotensin II observed in duck subfornical organ neurons. DuP 753 (losartan), an angiotensin II antagonist specifically blocking AT1 receptors in mammals, had equivocal effects on angiotensin II-induced drinking in ducks at rates 50- and 200-fold higher than angiotensin II, which corresponds to the weak inhibitory action of this compound on angiotensin II-induced neuronal excitation in the duck SFO. Blood pressure was only marginally elevated by the applied angiotensin II dose and Sar1-Ile8-angiotensin II had no effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00301128
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    Paper (German National Licenses)
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