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Biomedical subjects

M Palkovits

Publications and source records attributed to M Palkovits.

At least 199 records · Page 11Linked to original sources
PubMed1989

The asymmetry of 3H-imipramine binding may predict psychiatric illness.

The Bmax and Kd values for 3H-imipramine binding were measured in post-mortem human brains from drug-free selected psychiatric subject homicide victims (n = 15) and normal controls (n = 15). The two groups were comparable in age and gender. The number of imipramine binding sites (Bmax) in the frontal cortices of psychiatric subjects had significantly higher Bmax values in the left hemisphere than in the right hemisphere. Inversely, the number of imipramine binding sites (Bmax) in the frontal cortices of normal controls were significantly higher in the right brain than in the left brain. It was postulated that the inhibiting effect of central serotonin (5-HT) has weakened in psychiatric cases, therefore the change of presynaptic serotonergic activity might be associated with psychiatric illness in the left hemisphere of human brain.

Adolescent↗
PubMed1989

Activation of brainstem endorphinergic neurons causes cardiovascular depression and facilitates baroreflex bradycardia.

The effects of electrical stimulation of the arcuate nucleus on blood pressure, heart rate and baroreflex sensitivity were studied in urethane-anesthetized Sprague-Dawley rats. Stimulation of the mid-anterior parts of the arcuate nucleus at 80 Hz, 0.8 ms and 50-200 microA caused a biphasic, depressor/pressor, response and moderate bradycardia. Intravenous administration of a vasopressin V1-receptor antagonist eliminated the pressor component and unmasked a pure depressor response. This depressor response could be inhibited by naltrexone, 2 mg/kg i.v., by an antiserum against beta-endorphin, 100 nl injected directly into the ipsilateral nucleus tractus solitarii, or by deafferentation of the dorsal vagal complex (nucleus tractus solitarii and dorsal vagal nucleus) by an ipsilateral, dorsolateral knife-cut of the medulla oblongata. Stimulation of the arcuate nucleus at currents of 20-40 microA did not influence basal blood pressure or heart rate but potentiated the reflex bradycardia induced by phenylephrine, and this effect was completely blocked by naltrexone. It is concluded that a beta-endorphin-containing pathway projecting from the arcuate nucleus to the ipsilateral dorsal vagal complex is involved in depressor cardiovascular regulation and in the facilitation of baroreflex bradycardia.

Animals↗
PubMed1989

Atrial natriuretic factor content of brain nuclei in deoxycorticosterone acetate-salt hypertension in the rat.

1. The influence of deoxycorticosterone acetate (DOCA)-salt hypertension on brain atrial natriuretic factor (ANF) in rats was investigated to elucidate the role of central ANF in a renin-independent model of experimental hypertension. 2. Sprague-Dawley rats were subjected to uninephrectomy and given either tap water or saline [1% (w/v) NaCl] to drink plus weekly injections of either saline or DOCA (25 mg/kg, subcutaneously). After 32 days, the rats were decapitated and 18 different brain nuclei were removed by a micropunch technique. 3. The systolic blood pressure of the DOCA-salt rats was significantly higher than that of control rats [154 +/- 3 mmHg vs 104 +/- 2 mmHg (20.53 +/- 0.40 kPa vs 13.86 +/- 0.27 kPa), P less than 0.001]. 4. Plasma ANF levels were significantly (P less than 0.01) higher in DOCA-salt hypertensive rats compared with control rats. 5. In DOCA-salt hypertensive rats, the ANF content was increased in the organum vasculosum of the lamina terminalis (31.4 +/- 2.1 vs 22.1 +/- 2.5 pg/mg of protein, P less than 0.05), the subfornical organ (32.5 +/- 5.0 vs 24.2 +/- 2.4 pg/mg of protein, P less than 0.05), the medial amygdaloid nucleus (49.0 +/- 6.4 vs 34.0 +/- 2.0 pg/mg of protein, P less than 0.05) and the locus coeruleus (86.9 +/- 4.1 vs 64.4 +/- 4.2 pg/mg of protein, P less than 0.01) compared with control rats. The ANF content of 14 other brain areas investigated did not alter after treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Amygdala↗
PubMed1989

Median eminence dopamine and serotonin neuronal activity. Temporal relationship to preovulatory prolactin and luteinizing hormone surges.

Using a high-performance liquid chromatography (HPLC) system coupled with an electrochemical detector, the concentrations of dopamine (DA) and 5-hydroxytryptamine (5-HT) and their major specific metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and 5-hydroxyindole-3-acetic acid (5-HIAA), respectively, were measured in the median eminence (ME) throughout the rat estrous cycle. The ME DA content remained fairly constant throughout the estrous cycle except on estrus when 17.00 h values were significantly lower than 10.00 h values (40% decrease, p less than 0.05). The ME 5-HT content determined at 10.00 h was higher on proestrus than on any other day of the cycle. The ME DOPAC concentrations did not differ between 10.00 and 17.00 h on diestrus I, diestrus II or estrus. On the contrary, there was an almost linear decline between 10.00 and 17.00 h on proestrus (36% decrease, p less than 0.05). The ME 5-HIAA content did not differ between 10.00 and 17.00 h on any day of the estrous cycle. Significant changes were recorded for the DOPAC/DA and 5-HIAA/5-HT ratio in the ME on proestrus. There was a progressive decrease, starting from 10.00 h in the DOPAC/DA ratio with minimal values (42% decrease, p less than 0.05) at 16.00 h followed by an increase from 16.00 to 19.00 h. On the other hand, the 5-HIAA/5-HT ratio increased between 10.00 and 17.00 h (97% increase, p less than 0.05) and subsequently declined until 19.00 h (67% decrease vs. 17.00 h, p less than 0.05).2+hese data show that a concomitant

3,4-Dihydroxyphenylacetic Acid↗
PubMed1989

Atrial natriuretic peptide in brain preoptic areas: implications for fluid and salt homeostasis.

The influence of adrenalectomy and mineralocorticoid and glucocorticoid treatment on atrial natriuretic peptide (ANP) concentration of 18 microdissected rat brain nuclei was investigated. Adrenalectomy increased ANP levels highly in those brain areas that control water intake (the subfornical organ and supraoptic nucleus) and in the drinking center (the perifornical nucleus and the lateral hypothalamus). In all of these brain regions, aldosterone elevated ANP levels in intact animals. Adrenalectomy decreased ANP levels markedly in the OVLT and preoptic periventricular nucleus, which constitute the so-called AV3V region. The ANP level of these two brain areas was nearly restored to baseline levels both after administration of sodium chloride and after replacement of aldosterone, whereas dexamethasone treatment failed to have any effect.

Adrenalectomy↗
PubMed1988

Localization of corticotropin-releasing factor, somatostatin, and vasoactive intestinal polypeptide in the parabrachial nuclei of the human brain.

The immunocytochemical localizations of corticotropin-releasing factor (CRF), somatostatin (SRIF), and vasoactive intestinal polypeptide (VIP) were studied in the human parabrachial nuclei (PBN) using the avidin-biotin complex (ABC) technique. The brains were obtained from seven adult male human subjects of 38-74 years. In three cases, the brains were fixed within 2 hr, in four cases within 5 hr, postmortem. All of these peptides were detected in fibers through the orocaudal extent of the lateral PBN, whereas the medial nucleus contained only CRF immunoreactive fibers. Immunoreactive fibers were distributed unevenly within the lateral nucleus with the highest density in the dorsal and much fewer in the ventral part of the lateral subdivision. The highest to lowest density of immunostained processes were detected using CRF, SRIF, and VIP antisera, respectively. Since NPB is known as an important relay nucleus for the central autonomic pathway, the presence of the above noted neuropeptides in nerve fibers in this area may suggest a neurotransmitter or neuromodulatory role of CRF, somatostatin, and VIP in certain autonomic nervous mechanism of the human brain.

Adult↗
PubMed1988

Ontogenetic development of septal nuclei in the rat.

Prenatal development of septal cell groups was studied in the rat on samples taken daily from the 14th day of gestation until birth. Coronal serial sections of brains were prepared in which the topography coordinates of septal nuclei were determined, their section profiles measured and their volumes calculated. The rat septum begins to develop on embryonic days 14-15. First the individual neurons start to differentiate, then cell groups characteristic for the adult are formed between days 14 and 17, which is followed by the delineation of nuclei. The only exception is the anterior subdivision of the lateral septal nucleus where the formation of the nucleus precedes the differentiation of its constituent cells. The individual nuclei start to develop at different times defined by a medio-lateral gradient of cell migration. By embryonic day 20 the formation of the nuclei can be considered as complete: all septal nuclei and their subdivisions are to be recognized and distinguished from each other.

Animals↗
PubMed1988

Light microscopic triple-colored immunohistochemical staining on the same vibratome section using the avidin-biotin-peroxidase complex technique.

The sequential application of the avidin-biotin-peroxidase complex technique was used to localize multiple tissue antigens on a single free floating section of rat brain. Sequential visualization of individual antigens was achieved by the silver-gold-intensified diaminobenzidine (DAB) in the first step, nickel-intensified DAB in the second step, and the DAB alone in the third step of the immunostain procedure. For the demonstration of this method, tyrosine hydroxylase (TH), corticotropin-releasing factor (CRF), and vasopressin (VAS) antisera were used. Sections from the hypothalamic paraventricular nucleus (PVN) of rats pretreated with colchicine were stained. Black TH containing cell bodies were clearly distinguished from blue stained CRF cells and from yellow stained VAS-containing cell bodies in the PVN on the 25-30 micron thick vibratome sections. The sequential immunostaining procedure presented here results in superior staining of multiple antigens as compared to that achieved by the sequential application of the peroxidase-antiperoxidase (PAP) technique.

3,3'-Diaminobenzidine↗
PubMed1988

Interactions between 17 beta-estradiol and the hypothalamo-pituitary beta-endorphin system in the regulation of the cyclic LH secretion.

This paper further substantiates the physiological role of beta-endorphin (beta-END) in the control of the cyclic LH secretion and provides new data on the interactions between 17 beta-estradiol (17 beta-E2) and beta-END at both the hypothalamic and pituitary levels. At the hypothalamic level, during the estrous cycle in rats, beta-END concentrations were highest on diestrus I in the arcuate nucleus, median preoptic area and median eminence and lowest at the time of the preovulatory 17 beta-E2 surge on proestrus, before the subsequent preovulatory hypothalamic GnRH and plasma LH surges. Data obtained in ovariectomized 17 beta-E2-treated ewes support the direct involvement of 17 beta-E2 in changes in beta-END and GnRH concentrations in these hypothalamic areas. At the anterior pituitary level, in vitro results obtained using anterior pituitaries from the proestrus morning cycling female rat have shown that 17 beta-E2 strongly suppresses beta-END secretion and that GnRH stimulates the release of beta-END. Furthermore, marked fluctuations were observed for plasma beta-END throughout the menstrual cycle in the woman. Low beta-END concentrations were observed in the period preceding the LH preovulatory surge. Taken together, these results show that: (1) decreases in hypothalamic beta-END concentrations, which are controlled at least by circulating levels of 17 beta-E2, modulate GnRH synthesis and/or release and contribute to the mechanisms which initiate the LH surge; (2) anterior pituitary beta-END might be involved in the mechanisms which terminate the LH surge.

Animals↗
PubMed1988

Synaptic interconnections among growth hormone-releasing hormone (GHRH)-containing neurons in the arcuate nucleus of the rat hypothalamus.

The existence of a growth hormone-releasing hormone (GHRH)-containing local neuronal network in the arcuate nucleus of the rat has been established on the basis of light and electron microscopic immunohistochemistry. GHRH-immunostained nerve terminals were demonstrated in synaptic contact with GHRH-immunoreactive dendrites and perikarya. These neuronal circuits may allow arcuate GHRH neurons to operate synchronously, or may provide morphological evidence for the existence of a neuronal ultrashort feedback mechanism for regulating GHRH release in the hypothalamo-hypophyseal system.

Animals↗
PubMed1988

Atrial natriuretic factor in specific brain areas of spontaneously hypertensive rats.

Atrial natriuretic peptides (atrial natriuretic factor, ANF) are present in a great number of brain areas inside and outside of the blood-brain barrier. The pattern of distribution implies the involvement of ANF in different physiological functions, such as blood pressure regulation, electrolyte and fluid homeostasis, and modulation of the neuroendocrine system. To further investigate a possible involvement of central ANF in spontaneous hypertension, we measured levels of ANF in 18 selected, microdissected brain areas of prehypertensive (4-week-old) and hypertensive (12-week-old) spontaneously hypertensive rats (SHR) and their normotensive control, Wistar-Kyoto rats (WKY), by radio-immunoassay. ANF was significantly decreased in seven brain areas in SHR at both ages investigated; the most pronounced decreases were found in the subfornical organ, in the perifornical and periventricular hypothalamic nuclei, and in the medial preoptic nucleus. In addition, in young SHR ANF was significantly decreased in the organum vasculosum laminae terminalis and increased in the median eminence. After the development of hypertension, a significant decrease of ANF could be detected in four more brain areas (bed nucleus of the stria terminalis, paraventricular and arcuate nuclei, dorsal raphe nucleus) of SHR, as compared with normotensive controls, and the increase in the median eminence was no longer detectable. These results suggest a role for ANF in genetic hypertension and the specific importance of certain brain regions.

Animals↗
PubMed1987

Pro-opiomelanocortin-derived peptides (ACTH/beta-endorphin/alpha-MSH) in brainstem baroreceptor areas of the rat.

Relatively high concentrations of adrenocorticotropic hormone (ACTH), beta-endorphin and alpha-melanocyte-stimulating hormone (alpha-MSH) were determined by radioimmunoassay in the nucleus of the solitary tract (NTS) of rats. Dense networks of immunoreactive fibers for these peptides were most prominent in the commissural part of the nucleus, where immunostained perikarya (8-15 per section) were also seen in colchicine-treated rats. Moderate peptide levels and moderately dense immunoreactive networks of these peptides were found in the lateral reticular nucleus (including the A1 and A5-C1 catecholaminergic cell groups) and the nucleus ambiguus. Ten different types of surgical lesions or transections were performed in the hypothalamus and the lower brainstem to determine the origin of ACTH, beta-endorphin and alpha-MSH in the brainstem baroreceptor centers. Except the commissural part of the NTS, the baroreceptor areas receive ACTH, beta-endorphin and alpha-MSH innervations from both the hypothalamic arcuate cells and local neurons in the NTS. Fibers in the commissural part of the NTS seem to be of local origin. Hypothalamic fibers to the rostral part of the NTS and the vasomotor A5-C1 cell groups descend in both a medial (through the periaqueductal central gray) and a lateral (ventrolateral tegmental fibers) pathway, whereas fibers to the caudal lateral reticular nucleus (A1 cell group) and the nucleus ambiguus may run only in the lateral pathway. The descending fibers may decussate somewhere in the caudal hypothalamus-rostral midbrain, but caudal to that level they run and terminate ipsilaterally. Fibers from the ACTH-, beta-endorphin- and alpha-MSH-containing cells in the NTS form a bundle arching between the NTS and the ventrolateral medulla and partially (40-55%) innervate the vasomotor and the vasodepressor areas, as well as the nucleus ambiguus.

Adrenocorticotropic Hormone↗
PubMed1987

Prostacyclin (PGI2) induces rapid depletion of cyclic AMP levels in brain nuclei of rats.

Intravenous injection of prostacyclin (100 micrograms/kg) in rats resulted in a decrease of systolic blood pressure within 2 minutes. Concentrations of cAMP in 15 brain regions and nuclei were determined by radioimmunoassay. In lower brain stem nuclei, such as the nucleus of the solitary tract and the lateral reticular nucleus (A1 and C1 catecholaminergic cell groups) cAMP levels were depleted significantly, while in others, including the locus coeruleus and the periaqueductal central gray, cAMP levels did not show any alterations. Levels of cAMP were also depleted in some of the hypothalamic nuclei (periventricular, anterior hypothalamic, ventromedial), and in cerebral cortical areas. Lowered cAMP levels in brain areas might indicate lower cellular activity in cells participating in baroreceptor control mechanisms.

Animals↗
PubMed1987

Neurotensin in the rat median eminence: the possible sources of neurotensin-like fibers and varicosities in the external layer.

The possible sources of neurotensin-like immunoreactive axons in the median eminence were studied after several experimental surgical approaches including unilateral lateral retrochiasmatic area transection, midsagittal knife cut through the median eminence, complete surgical isolation of the medial basal hypothalamus and bilateral paraventricular nucleus lesions. Both immunohistochemical and radioimmunoassay data demonstrate that neurotensin-containing neuronal somata located in the hypothalamic arcuate nuclei represent the main source of neurotensin occurring in the external zone of the median eminence of the rat: neither the complete isolation of the medial basal hypothalamus nor the transection of the major neuronal input channel to the median eminence in the lateral retrochiasmatic area altered neurotensin-like immunoreactivity in the median eminence; bilateral lesioning of the paraventricular nucleus resulted in insignificant changes of neurotensin level in the median eminence; and two days after lesioning the median eminence an increased amount of retrogradely accumulated neurotensin-like immunoreactivity was found in several perikarya of the arcuate nuclei due to the blockage of axonal transport in the transected fibers. Retrograde accumulation of neurotensin-like material in other cells scattered in the anterior hypothalamus (in the paraventricular, periventricular and anterior hypothalamic nuclei) indicates that in addition to the arcuate neurons these neurons may also participate in the neurotensin innervation of the median eminence.

Animals↗
PubMed1987

Alterations in the adenylate cyclase-cAMP-phosphodiesterase system in the locus coeruleus during the development of spontaneous hypertension of the rat.

The quantitatively most important noradrenergic cell group of the brain is the locus coeruleus. Significantly increased cAMP concentration could be measured in spontaneously hypertensive rats in comparison to normotensive Wistar-Kyoto control rats at every stage investigated. Furthermore, both the basal activity and maximal stimulation of Ca++- and GTP-dependent adenylate cyclase as well as phosphodiesterase activity were significantly decreased in the spontaneously hypertensive rats at 14 weeks of age. The possible role of the locus coeruleus in spontaneous hypertension is presumed in counterregulatory mechanisms against rising blood pressure.

3',5'-Cyclic-AMP Phosphodiesterases↗