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Biomedical subjects

J W Guzek

Publications and source records attributed to J W Guzek.

At least 19 recordsLinked to original sources
PubMed1992

Thyrotropin-releasing hormone (TRH) and vasopressin and oxytocin release: in vitro as well as in vivo studies.

Rats euhydrated and dehydrated for two or four days were given intracerebroventricularly (i.c.v.) thyrotropin-releasing hormone (TRH) in a daily dose of 200 ng dissolved in 10 microliters of 0.9% sodium chloride.) A single dose of TRH administered to euhydrated animals was followed by a significant increase of the vasopressin content in the neurohypophysis and hypothalamus as well as of the hypothalamic oxytocin content. On the contrary, a single dose of TRH decreased the oxytocin content in the neurohypophysis. Under conditions of dehydration TRH distinctly restrained the decrease of vasopressin and oxytocin in the hypothalamus. In animals dehydrated for two or four days the decrease of oxytocin in the neurohypophysis, brought about by stimulation of osmoreceptors, was distinctly more marked under treatment with TRH. On the contrary, the depletion of neurohypophysial vasopressin was significantly less apparent under such conditions. 28 nmol/L TRH markedly increased vasopressin release but inhibited that of oxytocin from the neurointermediate lobes incubated in vitro both under basal conditions as well as during stimulation with excess (56 mmol) potassium.

Animals↗
PubMed1992

Melatonin, pinealectomy, and release of neurohypophysial hormones: in vitro studies.

The effect of melatonin as well as pinealectomy on the basal and K(+)-evoked release of vasopressin and oxytocin from the neurointermediate lobes in vitro was determined. Pineal removal resulted in a diminution of vasopressin and oxytocin release from the neurointermediate lobes in vitro. Melatonin (10(-3) or 10(-6) M/l) increased vasopressin and oxytocin release from neurointermediate lobes of sham-operated rats. Nevertheless, when pinealectomized rats served as donors of the neurointermediate lobes, melatonin (10(-3) or 10(-6) M/l) increased vasopressin release under basal conditions. For the same tissue, melatonin did not affect the oxytocin release either under basal conditions or during depolarization due to excess potassium. When 10(-7) M/l melatonin was used, no changes in either vasopressin or oxytocin release were observed in vitro.

Animals↗
PubMed1992

Neurohypophysial vasopressin and oxytocin as influenced by (6R)-5,6,7,8-tetrahydro-alpha-biopterin in euhydrated and dehydrated rats.

Experiments were performed to test a possible role of (6R)-5,6,7,8-tetrahydro-alpha-biopterin dihydrochloride (BH4) in the neurohypophysial vasopressin and oxytocin content in euhydrated and dehydrated rats. Chronic treatment with BH4, administered to not dehydrated animals, was followed by a significant decrease of neurohypophysial vasopressin, but not of neurohypophysial oxytocin. In dehydrated animals the neurohypophysial vasopressin content decreased progressively; this process was not affected significantly by BH4. In rats dehydrated and treated simultaneously with BH4 the decrease of neurohypophysial oxytocin content was distinctly less marked.

Animals↗
PubMed1992

Daily rhythms in the hormone content of the neurohypophysial system and release of oxytocin and vasopressin in the male rat: effect of constant light.

Patterns of neurohypophysial hormone secretion and changes in the hormone content of the hypothalamus and posterior pituitary lobe were monitored in the male rat for cycles of 24 h in association with changes in food and water intake and fluid excretion. Plasma oxytocin and vasopressin concentrations were seen to rise significantly over the hours of daylight, decreasing during the night. Parallel changes were seen in the immunoreactive material in the hypothalamus, whilst the content of the neurohypophysis was inversely related to plasma concentrations. The ratio of plasma oxytocin:vasopressin reached a significant peak at about 02.00 h which might be related to the feeding activity of the rats, food and water intake being largely confined to the night, as was fluid excretion. On exposure to constant light, despite initial disruption hormonal rhythms were still seen but showed a phase shift. The relationships between plasma and tissue levels were maintained. Patterns of food and water intake and urinary excretion were little affected by exposure to constant light, remaining largely confined to the former night phase. The hormonal rhythms appeared to be more closely related to the activity of the rats, which also showed a phase shift during constant light.

Animals↗
PubMed1992

The vasopressin and oxytocin neurohypophysial content as influenced by bleeding or dehydration: effect of cholecystokinin octapeptide.

The effect of CCK-8 (50 ng, i.c.v.) on the neurohypophysial vasopressin and oxytocin storage was estimated in haemorrhaged (1 ml per 100 g b.w.) male Wistar rats. In another experimental series rats dehydrated for three days were given CCK-8 in a daily i.c.v. dose of 50 ng. The neurohypophysial vasopressin and oxytocin content was bioassayed by pressor effect following Dekański or milk-ejection activity in vitro following van Dongen and Hays, respectively. The decrease of neurohypophysial vasopressin and oxytocin content, brought about by dehydration, was significantly less marked in animals treated with CCK-8. The depletion of neurohypophysial vasopressin and oxytocin content in haemorrhaged animals could be completely inhibited by earlier i.c.v. administration of CCK-8. It is suggested that hypothalamic cholecystokinin may serve as a modulator of neurohypophysial function.

Animals↗
PubMed1992

Atrial natriuretic peptide inhibits neurohypophysial hormones' release in the rat (in vitro and in vivo studies).

Intracerebroventricular hANP (50 nmol) inhibits release of vasopressin and oxytocin following dehydration as well as after haemorrhage. 10 nmol/L hANP markedly inhibits vasopressin and oxytocin release in vitro from the neurointermediate lobes both under basal condition as well as during stimulation with excess (56 mM) potassium. It is suggested that ANP may serve as a modulator of vasopressin and oxytocin release. The respective processes are localized, at least in part, at the neurohypophysial level.

Animals↗
PubMed1991

Inhibition of prostaglandin synthesis and the release of vasopressin and oxytocin from the rat neurohypophysis: in vitro studies.

The basal and K(+)-evoked release of vasopressin (VP) and oxytocin (OT) from the neurointermediate lobes in vitro was determined under conditions of indomethacin-induced inhibition of prostaglandin (PG) synthesis. The in vivo treatment with indomethacin (IM), administered to donor animals, did not modify the release of VP during resting conditions as well as during the potassium stimulation; on the contrary, both base-line and K(+)-evoked release of OT was significantly inhibited under such conditions. Incubation of neurointermediate lobes in a solution containing indomethacin resulted in an inhibition of VP and OT release both during resting conditions and during depolarization due to excess potassium.

Animals↗
PubMed1990

(6R)-5,6,7,8-tetrahydro-alpha-biopterin affects vasopressin and oxytocin release from rat neurointermediate lobe in vitro.

Incubation of neurointermediate lobes in Locke's solution containing 0.13 mumol.l-1 (6R)-5,6,7,8-tetrahydro-alpha-biopterin dihydrochloride (THB4) resulted in an inhibition of bioassayed vasopressin secretion and in an increase of that of oxytocin both under resting conditions as well as during depolarization due to excess potassium. It is suggested that some events related to THB4 and localized in the neural lobe are involved in the mechanism of vasopressin and oxytocin release.

Animals↗
PubMed1990

The vasopressin and oxytocin content in the neurohypophysis under conditions of increased beta-adrenergic transmission in euhydrated and dehydrated rats.

In rats euhydrated or dehydrated for two or four days the neurohypophysial vasopressin and oxytocin content was estimated. Rats were given intracerebroventricularly (i.c.v.) isoprenaline in a daily dose of 10 micrograms dissolved in 10 microliters of 0.9% sodium chloride. The neurohypophysial vasopressor and oxytocic activity diminished progressively during deprivation of water. A single dose of isoprenaline diminished the neurohypophysial content of vasopressin in euhydrated rats. In animals dehydrated for two or four days the depletion of neurohypophysial vasopressin storage (as brought about by osmoreceptor stimulation) was distinctly less marked under treatment with isoprenaline. The neurohypophysial oxytocin storage was diminished by a single dose of isoprenaline; on the contrary, during dehydration isoprenaline distinctly intensified the oxytocin depletion in the neurohypophysis.

Adrenergic Fibers↗
PubMed1990

The effect of intracerebroventricular insulin on the hypothalamic and neurohypophysial oxytocin activity in euhydrated or dehydrated rats.

Rats dehydrated up to four days were given intracerebroventricularly insulin in a daily dose of 100 ng. Insulin decreased significantly the hypothalamic and neurohypophysial oxytocin content in euhydrated rats. In dehydrated animals the oxytocin activity in the hypothalamo-neurohypophysial system, markedly depleted after deprivation of water, could be further reduced by intracerebroventricular treatment with insulin. These results seem to suggest a possible regulatory role of brain insulin in the mechanisms of oxytocin release.

Animals↗
PubMed1988

Vasopressin and oxytocin neurohypophysial content under conditions of beta-adrenergic blockade in euhydrated and dehydrated rats: further studies.

Rats euhydrated and dehydrated for two days were given intracerebroventricularly (i.c.v.) propranolol hydrochloride in a daily dose of 10 micrograms. In euhydrated rats the single dose of propranolol diminished significantly the vasopressin and oxytocin content in the neurohypophysis. On the contrary, in animals dehydrated for two days the depletion of the vasopressin and oxytocin neurohypophysial storage was distinctly less marked during i.c.v. treatment with propranolol.

Animals↗
PubMed1988

Insulin and release of neurohypophysial hormones: in vivo and in vitro studies.

No significant effect of intracerebroventricular administration of insulin on the bioassayed neurohypophysial storage of vasopressin and oxytocin could be found. This finding, however, only indirectly reflects possible changes of vasopressin and oxytocin release. Incubation of neurointermediate lobes in Locke's solution containing 3.3 mumol/l insulin resulted in an inhibition of oxytocin release under resting conditions as well as in a decrease of both vasopressin and oxytocin release during depolarization due to excess potassium. These results seem to suggest a possible regulatory role of brain insulin in the mechanisms of release of neurohypophysial hormones.

Animals↗
PubMed1988

Hypothalamic and neurohypophysial vasopressin and oxytocin in melatonin-treated pinealectomized male rats.

The effect of melatonin on hypothalamic and neurohypophysial vasopressin and oxytocin was investigated in normal and pinealectomized rats. Pinealectomy was followed by a decrease of both vasopressin and oxytocin content in the hypothalamus and neurohypophysis. In unpinealectomized rats, melatonin decreased vasopressin and oxytocin storage in the hypothalamo-neurohypophysial system. Following pineal removal, melatonin did not augment the pinealectomy-induced decrease of vasopressin and oxytocin in the neurohypophysis; the hypothalamic storage of both neurohormones was even higher when compared with vehicle-treated animals.

Animals↗