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  • 1
    Electronic Resource
    Electronic Resource
    In vivo release patterns and cardiovascular properties of inhibitory and excitatory amino acids in the hypothalamus (1995)
    Springer
    Amino acids 8 (1995), S. 47-58 
    Details
    ISSN: 1438-2199
    Keywords: Amino acids ; Taurine ; GABA ; Glutamate ; Arginine ; Blood pressure ; Push-pull cannula
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The posterior hypothalamus of conscious, freely moving rats was superfused with artificial cerebrospinal fluid through a push-pull cannula and the release of amino acids was determined in the superfusate. Under basal conditions, the release rates of taurine, GABA and glutamate fluctuated according to ultradian rhythms with different frequencies. Hypothalamic superfusion with veratridine or high concentrations of potassium choride enhanced the release rates of taurine, GABA and glutamate in a concentration-dependent way. Tetrodotoxin decreased the basal release rates of the three amino acids. The release of arginine was not influenced significantly by these compounds. A fall of blood pressure elicited by intravenous infusion of nitroprusside decreased the release rates of GABA and taurine and enhanced the release of glutamate. Infusion of noradrenaline increased blood pressure and release rates of GABA and taurine, while the release of glutamate was not influenced. Neither the pressor, nor the depressor responses to drugs influenced the release of arginine in the hypothalamus. It is concluded that the inhibitory amino acids taurine and GABA released from hypothalamic neurons possess a tonic hypotensive function. The excitatory amino acid glutamate, released from glutamatergic neurons of the hypothalamus, seems to possess a hypertensive function in counteracting a fall of blood pressure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00806543
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  • 2
    Electronic Resource
    Electronic Resource
    Pattern of in vivo release of endogenous histamine in the mamillary body and the amygdala (1988)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 337 (1988), S. 53-57 
    Details
    ISSN: 1432-1912
    Keywords: Endogenous histamine release ; Mamillary body ; Medial amygdaloid nucleus ; Ultradian rhythm ; Suprachiasmatic nucleus ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The mamillary body and the medial amygdaloid nucleus of cats anaesthetized with sodium pentobarbital were bilaterally and simultaneously superfused through push-pull cannulae with CSF and the release of endogenous histamine was determined in the superfusates. Collection of the superfusates in 10 min time periods revealed that histamine was rhythmically released in the two areas with frequencies of one cycle/90 min (mamillary body) or one cycle/135 min (medial amygdaloid nucleus). Collection of the superfusates in time periods of 2 min revealed the existence of an additional ultradian rhythm with a frequency of approximately one cycle/19 min in both areas. Bilateral lesions of the suprachiasmatic nucleus did not seem to influence the pattern of histamine release in the mamillary body and the medial amygdaloid nucleus, but the rate of histamine release was decreased in the mamillary body. It is concluded that the ultradian rhythms of histamine release in the mamillary body and the medial amygdaloid nucleus are not dependent on the integrity of the suprachiasmatic nucleus. The rate of histamine release in the mamillary body seems to be under the influence of excitatory neurons which originate from the suprachiasmatic nucleus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00169476
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  • 3
    Electronic Resource
    Electronic Resource
    Release of endogenous histamine in the hypothalamus of anaesthetized cats and conscious, freely moving rabbits (1982)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 321 (1982), S. 282-286 
    Details
    ISSN: 1432-1912
    Keywords: Release of endogenous histamine ; Hypothalamus ; Cat ; Freely moving rabbit ; Electrical stimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The hypothalamus of anaesthetized cats and conscious, freely moving rabbits was superfused with CSF through double-walled, push-pull cannulae and the release of endogenous histamine was determined in the superfusates by a radioenzymatic assay. In the posterior hypothalamic area of the anaesthetized cat, the rate of release of endogenous histamine varied rhythmically; phases of high rate of release appeared at 60 min cycles. The release of histamine was increased by electrical stimulation of the superfused area, as well as by hypothalamic superfusion with potassium-rich CSF. In the conscious rabbit, the anterior hypothalamic area and the posterior hypothalamic nucleus were superfused simultaneously. In both regions, the resting release of histamine varied rhythmically at approximately 70 min cycles. Phases of high or low-rate of release in the anterior hypothalamic area coincided with the corresponding phases in the posterior hypothalamic nucleus. The rhythmic release of endogenous histamine in the hypothalamus, as well as the ability of depolarizing stimuli to enhance the release of the amine support the idea that histamine acts as a neurotransmitter in the central nervous system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00498514
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of short-lasting and long-lasting blood pressure changes on the release of endogenous catecholamines in the hypothalamus of the conscious, freely moving rabbit (1983)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 322 (1983), S. 203-209 
    Details
    ISSN: 1432-1912
    Keywords: Endogenous catecholamines ; Push-pull cannula ; Rhythmic release ; Blood pressure ; Hypothalamus ; Conscious rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In anaesthetized rabbits guide cannulae were stereotaxically inserted into the anterior hypothalamic area and into the posterior hypothalamic nucleus. Additionally, catheters were inserted into the carotid artery and the jugular vein. Some days after the operation push-pull cannulae were inserted through the guide cannulae into the hypothalamic regions of the conscious, freely moving animal. The areas were superfused with artificial CSF and the release of the endogenous catecholamines dopamine, noradrenaline and adrenaline was determined in the superfusates. In the two hypothalamic regions the resting release of the catecholamines rhythmically varied with time at approximately 70 min cycles. A rise in blood pressure induced by the intravenous injection of noradrenaline or tramazoline enhanced the rates of release of the catecholamines in the anterior hypothalamic area. A fall of blood pressure elicited by the intravenous injection of nitroprusside or chlorisondamine decreased the release of the catecholamines in this hypothalamic area. The changes in blood pressure coincided with the changes in the rates of release of the catecholamines in the anterior hypothalamic area. These and previous results concerning changes in the release of endogenous catecholamines in the posterior hypothalamic nucleus also indicate that in the conscious, freely moving rabbit changes in blood pressure lead to counteracting alterations in the release of catecholamines in the two hypothalamic regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00500766
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  • 5
    Electronic Resource
    Electronic Resource
    Does brain histamine contribute to the development of hypertension in spontaneously hypertensive rats? (1991)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 343 (1991), S. 307-310 
    Details
    ISSN: 1432-1912
    Keywords: Histamine ; Brain ; Histidine decarboxylase ; Blood pressure ; α-Fluoromethylhistidine ; Spontaneously hypertensive rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Histaminergic neurons of the brain have been implicated in genetic hypertension. We investigated the effect of inhibition of histamine synthesis by α-fluoromethylhistidine (α-FMH), the irreversible inhibitor of histidine decarboxylase, on the development and maintenance of hypertension in spontaneously hypertensive rats. Young (3-week-old) and adult (7-week-old) rats were treated with α-fluoromethylhistidine for 29 and 13 days, respectively. Treatment of spontaneously hypertensive rats and normotensive Wistar-Kyoto rats with α-fluoromethylhistidine led to a pronounced decrease in the histidine decarboxylase activity and in the histamine concentration in the brain (hypothalamus, brainstem, cortex —midbrain). In adult spontaneously hypertensive rats, the development of hypertension was not influenced by α-fluoromethylhistidine. In young spontaneously hypertensive rats, α-fluoromethylhistidine led to a transient delay in the development of hypertension which was followed by a transient tendency to increased blood pressure. It is concluded that histaminergic neurons of the brain play only a subordinate role, if any at all, in the development of hypertension in spontaneously hypertensive rats.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00251131
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  • 6
    Electronic Resource
    Electronic Resource
    Release of endogenous GABA in the posterior hypothalamus of the conscious rat; effects of drugs and experimentally induced blood pressure changes (1993)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 347 (1993), S. 402-406 
    Details
    ISSN: 1432-1912
    Keywords: GABA release ; Hypothalamus ; Blood pressure ; Veratridine ; Tetrodotoxin ; Push-pull cannula
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Push-pull superfusion was used to investigate the release of endogenous GABA in the posterior hypothalamus of the conscious, freely moving rat at basal conditions and in response to centrally applied drugs or to peripherally induced blood pressure changes. After an initial, exponential decline, the release rate of GABA remained fairly constant for many hours. Fluctuations in the release rate of GABA point to the existence of an ultradian rhythm with an approximate frequency of 1 cycle/65 min. Hypothalamic superfusion with a potassium-rich (50 or 90 mmol/1) artificial cerebrospinal fluid led to a concentration-dependent increase in the GABA release. The release of GABA was also enhanced by veratridine (1 or 10 μmol/1) in a concentration-dependent way. Hypothalamic superfusion with the neutrotoxin tetrodotoxin (1 gmmol/1) led to a long-lasting decrease in the GABA release. The rise in blood pressure (45 mmHg) elicited by an intravenous infusion of noradrenaline was associated with an increased release rate of GABA in the hypothalamus. Hypotension produced by nitroprusside (25 mmHg) led to a counteracting decrease in hypothalamic GABA outflow. The findings suggest that approximately 4510 of the basal outflow of GABA found in the superfusate are released from GABA-ergic neurons of the posterior hypothalamus. The release rate of GABA fluctuates according to an ultradian rhythm. The modified release of GABA in response to experimentally induced blood pressure changes suggests that, in the posterior hypothalamus of the conscious rat, GABAergic neurons are involved in cardiovascular control and possess a hypotensive function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00165390
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  • 7
    Electronic Resource
    Electronic Resource
    In vivo release of catecholamines in the locus coeruleus (1994)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 350 (1994), S. 339-345 
    Details
    ISSN: 1432-1912
    Keywords: Locus coeruleus ; Dopamine ; Noradrenaline ; Adrenaline ; Veratridine ; Tetrodotoxin ; Push-pull cannula ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To investigate the release of endogenous dopamine, noradrenaline and adrenaline in the locus coeruleus, this brain area was superfused with artificial cerebrospinal fluid (CSF) through push-pull cannulae and the release of catecholamines was determined in the superfusate radioenzymatically. Collection of superfusates in time periods of 10 min revealed that release rates of the three catecholamines fluctuated, thus pointing to the existence of ultradian rhythms with following mean periods (minutes per cycle): noradrenaline 52±4, dopamine 37±2, adrenaline 36±2. The rhythm frequency of noradrenaline was significantly lower than the frequencies of dopamine and adrenaline. When the locus coeruleus was superfused with neuroactive drugs, superfusates were collected in time periods of 3 min. Superfusion with tetrodotoxin (1 μmol 1−1) for 12 min elicited a prompt and sustained decrease (−70%) in the release rates of dopamine and adrenaline. The release rate of noradrenaline was also reduced, although to a lesser extent (−40%). Superfusion with veratridine (50 μmol 1−1) led to an immediate and very pronounced enhancement in the release rates of dopamine, noradrenaline and adrenaline. The veratridine-induced increase in catecholamine outflow was decreased strongly by simultaneous superfusion with tetrodotoxin. The findings suggest that the release of endogenous catecholamines in the locus coeruleus fluctuates according to ultradian rhythms. Changes in the release on superfusion with veratridine and tetrodotoxin demonstrate the neuronal origin of the three catecholamines. The observed differences in the release characteristics between noradrenaline on the one hand and dopamine and adrenaline on the other might indicate that noradrenaline is partly released from somatodendritic sites of the noradrenergic cell bodies in the locus coeruleus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00178948
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  • 8
    Electronic Resource
    Electronic Resource
    Effects of blood pressure changes on the catecholamine release in the locus coeruleus of cats anaesthetized with pentobarbital or chloralose (1993)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 348 (1993), S. 242-248 
    Details
    ISSN: 1432-1912
    Keywords: Locus coeruleus ; Noradrenaline release ; Dopamine release ; Adrenaline release ; Blood pressure ; Baroreceptor reflex ; Push-pull cannula
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Effects of carotid occlusion and drugs applied intravenously on the release of endogenous catecholamines in the locus coeruleus of cats anaesthetized with pentobarbital or chloralose were investigated. The locus coeruleus was superfused bilaterally with artificial cerebrospinal fluid through push-pull cannulae inserted stereotaxically. Dopamine, noradrenaline and in some experiments also adrenaline were determined radioenzymatically in the superfusate. Under pentobarbital anaesthesia, a bilateral carotid occlusion increased the release rate of noradrenaline in the locus coeruleus, while the release of dopamine was decreased. These changes were due to the fall of blood pressure in the carotid sinus caused by the occlusion. Loading of baroreceptors by elevating blood pressure with phenylephrine (10 μg·kg−1·min−1, i.v. infusion) was accompanied by a decreased release of noradrenaline in the locus coeruleus. This decrease in noradrenaline release was not detected in the caudal aspect of the locus coeruleus. Under chloralose anaesthesia, phenylephrine diminished the release rate of noradrenaline to about the same extent as under pentobarbital anaesthesia. The release rate of adrenaline was also decreased. A prolonged infusion of phenylephrine led to a prolonged pressor response associated with a sustained decrease in the noradrenaline release rate. Intravenous injection of chlorisondamine (3 mg·kg−1) did not change the release of noradrenaline, while dopamine release was reduced. It is concluded that the release of catecholamines in the locus coeruleus is influenced by signals originating from peripheral baroreceptors. The influences are similar under pentobarbital and chloralose anaesthesia. Noradrenergic neurons responding to haemodynamic signals are not uniformly distributed within the locus coeruleus. It is suggested that noradrenergic and possibly dopaminergic and adrenergic neurons of the locus coeruleus are involved in the baroreceptor reflex, thus contributing to central homeostasis of blood pressure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00169151
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  • 9
    Electronic Resource
    Electronic Resource
    Changes in the arterial blood pressure increase the release of endogenous histamine in the hypothalamus of anaesthetized cats (1983)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 323 (1983), S. 162-167 
    Details
    ISSN: 1432-1912
    Keywords: Endogenous histamine ; Release ; Arterial blood pressure ; Hypothalamus ; Cat ; Push-pull cannula
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The posterior hypothalamus of anaesthetized cats was superfused with artificial CSF through a push-pull cannula and the arterial blood pressure was recorded in the femoral artery. The release of endogenous histamine was determined in the hypothalamic superfusate by a radioenzymatic assay. Intravenous injection of sodium nitroprusside elicited a fall of blood pressure which was accompanied by an increase in the rate of release of endogenous histamine in the posterior hypothalamus. Similary, a controlled bleeding lowered the arterial blood pressure and enhanced the release of histamine. The durations of depressor responses to nitroprusside or controlled bleeding coincided with the duration of the changes in the rate of release of histamine. Intravenous injection of chlorisondamine also lowered the arterial blood pressure and augmented the release of histamine. However, the hypotension lasted longer than the increased release of histamine in the hypothalamus. Intravenous injection of noradrenaline elicited a rise in the arterial blood pressure which was associated with an increase in the release of histamine in the posterior hypothalamus. Intravenous injection of tramazoline led to a long-lasting hypertension and to a short-lasting increase in the release of histamine. Transection of the spinal cord at C1/C2 elicited a pressor response which was followed by hypotension. Increase and decrease in the arterial blood pressure were associated with an increased rate of release of endogenous histamine. A second transection of the spinal cord at a higher level did not influence either blood pressure or rate of release of histamine. It is concluded that increases and decreases in the arterial blood pressure enhance the rate of release of endogenous histamine in the posterior hypothalamus of the anaesthetized cat. The alterations in the release of histamine seem to represent an immediate response of the hypothalamus to changes in peripheral blood pressure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00634265
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  • 10
    Electronic Resource
    Electronic Resource
    Carotid occlusion increases the release of endogenous GABA in the nucleus of the solitary tract (1989)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 340 (1989), S. 764-766 
    Details
    ISSN: 1432-1912
    Keywords: Nucleus of the solitary tract (NTS) ; GABA release ; Carotid occlusion ; Blood pressure ; Push-pull cannula ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In anaesthetized cats, the nucleus of the solitary tract was bilaterally superfused through push-pull cannulae with artificial cerebrospinal fluid (CSF) and the effect of carotid occlusion on the release of endogenous GABA was investigated. Bilateral carotid occlusion led to a rise in blood pressure which was associated with a very pronounced increase in the release rate of GABA in the nucleus of the solitary tract. The results demonstrate the hypertensive function of GABA in the nucleus of the solitary tract and the importance of GABAergic neurons of this nucleus for the central cardiovascular control.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00169687
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