Nicotinic acid attenuates amyloid ß1-42-induced mitochondrial dysfunction and inhibits the mitochondrial pathway of apoptosis in differentiated SH-SY5Y cells.

Alzheimer's disease (AD) is a chronic neurodegenerative disease characterized by progressive memory loss and behavioral disorders. The excessive accumulation of amyloid ß (Aß) and the formation of neurofibrillary tangles (NFTs) damage synaptic connections and the death of neurons. However, the underlying mechanisms of pathogenesis of AD remain unclear. Growing evidence indicates that impaired mitochondrial function may play a crucial role in the development of AD. In the current study, we investigated whether nicotinic acid (NA) could protect against amyloid ß1-42-induced cytotoxicity in differentiated SH-SY5Y cells. Our results revealed the neuroprotective effects of NA on the differentiated SH-SY5Y cells treated with Aß1-42. In detail, the 1-h pre-incubation with NA increased cell viability and lowered LDH levels. NA pre-incubation abolished Aß1-42 treatment-associated alterations of mRNA levels of synaptic genes and enhanced the relative ß3 Tubulin fluorescence intensity. NA eliminated the Aß1-42-induced mitochondrial dysfunction by increasing the potential of mitochondrial membranes and maintaining a balance between the fusion and fission of mitochondria. Moreover, Aß1-42 decreased mRNA levels of anti-apoptotic bcl2 and increased mRNA levels of pro-apoptotic: bim, bak, cytochrome c, and caspase 9. At the same time, the NA pre-treatment reduced Aß1-42-dependent apoptotic death of differentiated SH-SY5Y cells. The above data suggest that NA presents a protective activity against Aß1-42-induced cytotoxicity in differentiated SH-SY5Y cells by inhibiting the mitochondrial pathway of apoptosis and restoring the proper function of mitochondria.

The effect of valproate (VPA) treatment on inositol phosphates (IPs) accumulation in non-stimulated and GnRH-treated female rat anterior pituitary cells in vitro.

OBJECTIVE: Mechanism(s) responsible for VPA-induced effects on reproductive axis activity are not fully recognized. Previously we reported that VPA suppressed only GnRH-stimulated but not the basal LH release from rat anterior pituitary (AP) cells in vitro. Since the inhibitory effect of VPA was exerted only in GnRH-activated cells, potential VPA impact on GnRH-R-coupled IP3/PKC signaling could not be excluded. In this study the effect of VPA on IPs synthesis in non-stimulated and GnRH-treated rat AP cells was examined. MATERIAL AND METHODS: In the first experiment 5 × 105 cells/ml were incubated for 3h with VPA (10 nM-10 µM), PMA (100 nM), GnRH (100 nM), PMA (100 nM) + VPA (10 nM-10 µM), GnRH (100 nM) + VPA (10 nM-10 µM). In the second experiment cells were preincubated for 24h with 1µCi myo-[23 H]-inositol, then for 30 min with 10 mM LiCl and finally for 3hr with GnRH (100 nM) VPA (1 µM, 10 µM), GnRH (100 nM) + VPA (1 µM, 10 µM). LH concentration was measured by RIA and intracellular IPs accumulation by ion-exchange chromatography analysis. RESULTS: VPA diminished GnRH-stimulated LH release without affecting PMA-induced LH release at any dose tested. Moreover, VPA-induced increase of IPs accumulation occurred in both non-stimulated and GnRH-treated cells and intensity of cellular response was similar in both groups. CONCLUSION: VPA affects IP3/PKC pathway activity through its up-regulatory effect on IPs synthesis in AP cells. VPA-induced inhibition of GnRH-stimulated LH release from gonadotrope cells appears to be the result of still unrecognized cellular mechanism.

The evaluation of estradiol and leptin action on the activity of the somatotropic and gonadotropic axes in peripubertal female rats.

OBJECTIVE: Available data suggest that estrogens and leptin play a role in the control of the pubertal process. In humans and some mammal species the increase of the activity of gonadotropic axis accompanies the decrease in the rate of growth at puberty. The effect of 17ß-estradiol and/or leptin administration on the somatotropic and gonadotropic axes was studied using prepubertal female rats as an animal model. MATERIAL AND METHODS: Prepubertal female rats received estradiol/saline, estradiol/leptin, oil/leptin or oil/saline (vehicles) respectively. The changes of growth rate, and serum 17ß-estradiol, leptin, GH, IGF-I and gonadotropins levels as well as LHRH and estrogen receptor (ER) concentrations in the medial basal hypothalamus (MBH) and the pituitary were determined. All hormones concentrations were measured by radioimmunoassay and ER by radioligand methods . RESULTS: In estradiol and/or leptin treated animals noticeable reduction of rate of growth was found. The decrease of growth in response to estradiol treatment accompanied the increase GH level and the decrease of IGF-I concentration in the circulation. Both hormones operating together activated reproductive axis, what was manifested by a significant increase of LHRH abundant in the hypothalamus as well as elevated LH and FSH levels in the circulation. In these rats a significant decrease of the estrogen receptor concentrations in the pituitary was observed. CONCLUSION: The role of estradiol and leptin in the control of growth and reproduction seems to overlap only partially. Estradiol plays a significant role in the activation of the reproductive axis, and leptin takes part as a permissive factor in pubertal process.

Evaluation of orexin A activity on LH and FSH release from primary culture pituitary cells in immature and mature female rats.

OBJECTIVES: Orexin A (OxA) is a regulatory neuropeptide which is involved in the control of various autonomic and neuroendocrine functions. It regulates sleep-wake cycle, food intake and modulates the hypothalamic and pituitary hormones secretion. Orexin A acts through two types of receptors, which proved to exist in the pituitary. This may indicate the possibility of direct action of OxA on the adenohypophysis level. The aim of this study was to evaluate the direct effect of orexin A on gonadotropin (LH and FSH) release from cultured pituitary cells of immature female rats as well as mature female rats (ovariectomized and ovariectomized and estradiol treated rats). MATERIAL AND METHODS: The effect of 0.1 nM and 100 nM orexin A on LH and FSH release from anterior pituitary cells after 1 h of incubation was examined in immature female rats (IM) as well as mature female (ovariectomized - M/OVX; and ovariectomized and estradiol treated - M/OVX+E2) rats. The concentration of LH and FSH in medium was determined by RIA method. RESULTS: Orexin A at a dose of 0.1 nM and 100 nM significantly stimulated LH secretion in IM group. In M/OVX group release of LH was inhibited by OxA only in higher dose (100 nM). No effect of orexin A on FSH secretion was found. CONCLUSIONS: OxA may directly modulate LH secretion from cultured pituitary cells and it has the contradictory effect on LH release in immature and ovariectomized mature female rats.

The influence of cocaine-amphetamine regulated transcript (CART) on pituitary hormones, corticosterone and leptin levels in starved rats.

OBJECTIVE: CART is involved in the control of food intake and hormonal secretion. We aimed to evaluate the effects of CART on hormonal profile in starved rats. METHODS: Study group included 100 male rats. Under conditions of food limitation CART (55-102) was given centrally (icv) or peripherally (iv). Non-starved animals underwent identical procedure. Vehicle (aCSF or saline)-injected rats served and as a controls. 60 minutes after CART or vehicle administration blood was collected to assess pituitary hormones (LH, FSH, PRL, GH, ACTH, TSH), corticosterone and leptin concentrations. RESULTS: Itracerebroventricular CART injection resulted in a significant increase in PRL, GH and corticosterone concentrations in non-starved rats compared with vehicle injected animals. However, in a group of starved animals only leptin levels were decreased in comparison with fasted controls. Peripheral CART administration caused a significant increase in PRL, GH and TSH levels in non-starved rats but no changes in investigated hormone levels were observed in starved animals when compared to saline injected controls. CONCLUSIONS: Our results indicate that CART is able to modulate hormonal profile in a non-starved rats. However, the modulatory effect depends on the CART administration method. Interestingly, CART administration, both icv and iv, does not have an impact on pituitary hormones and corticosterone levels in a course of food limitation.

Valproate inhibits GnRH-induced gonadotropin release from anterior pituitary cells of male rat in vitro.

OBJECTIVE: Valproate (VPA) a potent antiepileptic drug has been claimed to induce reproductive disturbances in men. Long-term VPA treatment can affect sperm morphology and induce testicular atrophy in non-epileptic rats. It has been reported that VPA reduced testosterone secretion stimulated by hCG in isolated rat Leydig cells. These results suggest direct effect of VPA on testes in rats. However centrally mediated effects at hypothalamo-pituitary level can therefore not be excluded. This study focused on the dose and time-dependent effects of VPA on basal and GnRH-induced LH and FSH release from the primary anterior pituitary cells culture of male rats. MATERIAL AND METHODS: The dose-dependent effect of 10 nM-100 mM of VPA on basal LH release from anterior pituitary cells after 3h of incubation was examined. To determine the time-dependent effects on LH, FSH, TSH and PRL release short (3 h) and long-term (24 h) incubations in the presence of 10 nM, 100 nM and 1 µM of VPA were maintained.To assess whether VPA can affect GnRH-induced LH and FSH release, cells were incubated for 3 h with 10 nM, 100 nM and 1 µM of VPA in the presence of GnRH. The concentration of rLH, rFSH, rPRL and rTSH in incubation medium was determined by RIA method. RESULTS: VPA did not affect the basal LH, FSH, PRL and TSH release from the primary anterior pituitary cells culture of male rats. VPA in concentration 1µM significantly suppressed GnRH-induced LH secretion. However VPA at all tested doses diminished GnRH-induced FSH release. CONCLUSIONS: VPA may diminish gonadotropin release in vitro but this effect can only be achieved after GnRH-dependent specific receptor activation. Both gonadotropins differ in their pattern of response for increasing doses of VPA.

Exogenous orexin-A downregulates luteinizing hormone secretory activity in prepubertal female rats.

INTRODUCTION: Orexin-A is a neuropeptide synthesized in the lateral hypothalamus. Orexin-A immunoreactive fibres overlap distribution with GnRH neurons. In adult rats, orexin A is known to affect LH secretion via GnRH release modulation. Because data concerning the impact of orexin-A on the hypothalamo-pituitary axis activity are limited, we focused on the involvement of orexin-A and receptors of NPY in the modulation of LH release and LH subunit b (Lhb) mRNA expression in prepubertal female rats. MATERIAL AND METHODS: Forty immature female Wistar rats were divided into 4 groups and received 2 intracerebroventricular (icv) microinjections of: 1 - artificial cerebrospinal fluid (CSF) (controls); 2 - CSF followed by orexin A; 3 - selective NPY receptor antagonist (BIBP) followed by CSF; 4 - BIBP followed by orexin A. One hour after the last microinjection, all rats were decapitated. Trunk blood was collected, and serum was stored at -20°C for the LH RIA examination. The adenohypophysis was immediately excised, flash-frozen, and kept at -80°C for RNA extraction. Real-time PCR amplification was carried out, and relative Lhb gene expression was calculated. RESULTS: In comparison to the CSF-treated controls with a mean LH serum concentration of 0.40 ± 0.02 ng/mL, the mean LH serum level was diminished both after orexin-A (0.27 ± 0.01 ng/mL) and after BIBP (0.30 ± 0.02 ng/mL) icv microinjections. In the presence of BIBP, orexin-A more effectively inhibited LH release (0.20 ± 0.01 ng/mL) when compared to the BIBP-treated group. Orexin-A and BIBP exerted a consistent inhibitory effect on Lhb mRNA expression levels in the anterior pituitary gland. In comparison to the CSF-treated controls, orexin-A, and BIBP-treated females responded with, respectively, 35% and 40% reduction of Lhb mRNA expression. Orexin-A and BIBP co-administration evoked a further reduction of Lhb gene transcriptional activity. CONCLUSIONS: Orexin-A exerts a down-regulatory effect on LH synthesis and release in immature female rats. Considering that Y1R-oriented down-regulation of endogenous NPY activity did not reverse the suppressive effect of exogenous orexin-A, it might be suggested that NPY and orexin A systems can operate independently to affect gonadotropin activity in the anterior pituitary of the immature female rats.

All-trans-retinoic acid ameliorates atherosclerosis, promotes perivascular adipose tissue browning, and increases adiponectin production in Apo-E mice.

All-trans-retinoic acid (atRA), an active metabolite of vitamin A, exerts a potential role in the prevention of cardiovascular diseases. It has been shown that atRA ameliorates atherosclerosis while the exact mechanism underlying this protection remains unknown. This study investigated the influence of atRA on insulin resistance (IR), atherosclerosis, and the process of perivascular adipose tissue (PVAT) browning. Moreover, syntheses of adiponectin, adipokine with anti-atherogenic effects, and tumor necrosis factor-alpha (TNF-α), a pro-inflammatory cytokine, were determined in PVAT. Apolipoprotein E-deficient mice (Apo-E) and control C57BL/6J wild-type mice were treated with atRA (5 mg/kg/day) or vehicle (corn oil) by plastic feeding tubes for 8 weeks. Long-term atRA treatment in Apo-E mice did not affect insulin resistance. AtRa administration ameliorated atherosclerosis, induced PVAT browning, and increased adiponectin production in PVAT in Apo-E mice. Furthermore, atRA increased nitric oxide (NO) level but did not affect adiponectin concentration in the aorta of Apo-E mice. These results indicate that atRA ameliorates atherosclerosis in Apo-E mice. We also observed the browning of PVAT. Besides, atRA increased the synthesis of adiponectin in PVAT and augmented NO level in the aorta in ApoE mice.

The Effects of Alpha-Linolenic Acid on the Secretory Activity of Astrocytes and ß Amyloid-Associated Neurodegeneration in Differentiated SH-SY5Y Cells: Alpha-Linolenic Acid Protects the SH-SY5Y cells against ß Amyloid Toxicity.

Alzheimer's disease (AD) is the most common neurodegenerative disorder. Amyloid ß- (Aß-) induced mitochondrial dysfunction may be a primary process triggering all the cascades of events that lead to AD. Therefore, identification of natural factors and endogenous mechanisms that protect neurons against Aß toxicity is needed. In the current study, we investigated whether alpha-linolenic acid (ALA), as a natural product, would increase insulin and IGF-I (insulin-like growth factor I) release from astrocytes. Moreover, we explored the protective effect of astrocytes-derived insulin/IGF-I on Aß-induced neurotoxicity, with special attention paid to their impact on mitochondrial function of differentiated SH-SY5Y cells. The results showed that ALA induced insulin and IGF-I secretion from astrocytes. Our findings demonstrated that astrocyte-derived insulin/insulin-like growth factor I protects differentiated SH-SY5Y cells against Aß 1-42-induced cell death. Moreover, pretreatment with conditioned medium (CM) and ALA-preactivated CM (ALA-CM) protected the SH-SY5Y cells against Aß 1-42-induced mitochondrial dysfunction by reducing the depolarization of the mitochondrial membrane, increasing mitochondrial biogenesis, restoring the balance between fusion and fission processes, and regulation of mitophagy and autophagy processes. Our study suggested that astrocyte-derived insulin/insulin-like growth factor I suppresses Aß 1-42-induced cytotoxicity in the SH-SY5Y cells by protecting against mitochondrial dysfunction. Moreover, the neuroprotective effects of CM were intensified by preactivation with ALA.

Involvement of the cocaine-amphetamine regulated transcript peptide (CART 55-102) in the modulation of rat immune cell activity.

OBJECTIVE: Cocaine-amphetamine regulated transcript peptides (CART) belong to a neuropeptide family expressed in the central nervous system, especially in the hypothalamus, and also in peripheral tissues. The physiological functions of CART include modulation of pituitary hormone release, regulation of body weight, and the control of feeding behavior and metabolic activity. The reciprocal relationships between CART and immune system function have to be established. Therefore, in the present study we aimed to investigate the influence of CART, administered intracerebroventricularly (icv), on selected immune parameters and pituitary-adrenal axis hormone secretion in the rat. RESEARCH METHODS: In rats submitted to icv infusion of CART or artificial cerebrospinal fluid (aCSF, control) selected immune parameters: splenocyte proliferation (spontaneous and mitogen-stimulated) and peritoneal leukocyte (PTL) activity (spontaneous and phorbol myristate acetate (PMA)-stimulated) were examined 60 and 120 min after treatment. The direct effect of CART on splenocytes in culture in vitro was also examined. Concentration of adrenocorticotrophic hormone (ACTH) and corticosterone was also measured in serum of control and CART infused rats. RESULTS: Splenocytes isolated 60 min after CART infusion exhibited a decreased, albeit non-significant, ability to proliferate spontaneously and were unable to answering to the mitogenic stimulation. This effect was not seen 120 min after CART treatment, which restored splenocyte proliferation decreased by aCSF infusion. CART addition in vitro did not influence proliferation of splenocytes from control rats. Spontaneous activity of peritoneal leukocytes was not modified by CART infusion. PMA-stimulated PTL activity was significantly decreased in aCSF-infused rats 120 min after treatment and CART infusion antagonized this effect. Non-significant increase in serum cortisol after 60 min followed by a significant decrease after 120 min with no change in ACTH concentration was found. CONCLUSION: The immunomodulatory activity of icv-infused CART appears to consist in the creation of a short-lasting immunosuppressive internal milieu, followed by the immunostimulatory one. This first effect was most probably due to the activation of the HPA axis and/or other immunosuppressive peptides, but not through the direct action of CART on immune cells. Thus, CART appears to be short-lasting and indirect modulator of immunity.

Plasma beta amyloid and cytokine profile in women with Alzheimer's disease.

Alzheimer's disease (AD) belongs to a group of neurodegenerative disorders. It is characterized by irreversible and progressive memory loss accompanied with decline in other cognitive functions. At a microscopic level, the typical neuropathologic features, senile plaques and neurofibrillary lesions are found. The pathological processes lead to neuronal loss, synaptic dysfunction and inappropriate activity of neurotransmitters. The major constituent of senile plaques is abnormally aggregated beta amyloid protein. Beta amyloid (Abeta) is a short (40-42 amino acid) product of proteolysis of the transmembrane amyloid precursor protein (APP). Extracellular depositions of Abeta 1-42 may initiate a wide range of pathological processes including glia activation, neuroinflammation and neuronal apoptosis. There is convincing evidence that inflammatory response to accumulation of beta amyloid plays a pivotal role in the progression of neuropathological changes found in AD. Current research was directed at assessing beta amyloid, cytokines (IL-6, IL-10 and TNF alpha) plasma levels in women with AD. Hundred and twenty four women, aged between 59 to 86 years, were enrolled in the study. Amongst them 57 were diagnosed with AD (29 subjects in early stage and 28 subjects with moderate to severe stadium of disease) and 67 women without dementia were investigated as a control group. The lowest values of Abeta 1-42 were found in AD subjects in moderate to severe stage of disease as compared with the early stage of AD (p< 0.05) and the control group (p<0.01). Change in IL-6 values was significantly different between groups with the lowest values found in women without dementia. Both subset of AD patients demonstrated statistically enhanced IL-6 levels when compared with the control group (p<0.001, p<0.01 respectively for early and moderate/severe stage of AD). Moreover, our study revealed a trend to increase in TNF alfa and IL-10 values in AD. However, those differences were not statistically significant. In addition, we did not detect any correlations between plasma beta amyloid and investigated cytokines.

A method for evaluation of activity of growth hormone-releasing hormone analogues.

OBJECTIVE: It has been found that hGH-RH analogues with increased resistance to enzymatic degradation have a much higher potency than the native hGH-RH (1-29)-NH2 and have an ability to partially reverse growth hormone deficiencies. THE AIM: The aim of these studies was to elaborate a method which can be used for preliminary evaluation of new GH-RH analogues both from the point of view of their potency to release GH and enzymatic stability. METHOD: Two highly active GH-RH analogues with increased resistance to trypsin-like enzymes, and hGH-RH(1-29)-NH2 used as a standard, in doses 1 nM, 10 nM, and 100 nM were added to pituitary rat cell culture, and medium was collected after 30, 60, 120 and 240 min. GH concentration was measured by RIA kit. RESULTS: It was observed that the potency of these two GH-RH analogues was several times higher than that of native compound. Moreover, the stimulation was much longer. This suggests that high activity of these analogues in vivo could be the result of increased enzymatic stability. CONCLUSION: This method can be used for selecting more potent and more stable releasing peptides before in vivo evaluation.

PACAP 38 inhibits adiponectin release.

BACKGROUND: Pituitary adenylate cyclase activating peptide (PACAP 38) is a neuropeptide with anti-inflammatory activity. Vasoactive intestinal peptide (VIP)/PACAP receptors are found in immune cells, endocrine glands and also in adipose tissue. Adiponectin is an adipocyte-derived protein hormone which possesses anti-inflammatory, antidiabetic and antiatherogenic properties. The aim of this study was to examine the influence of PACAP 38 on adiponectin release in basal conditions and during lipopolysaccharide (LPS)-induced acute inflammation. METHODS: Male Wistar-Kyoto rats were divided into four groups which received intraperitoneal injections of 0.9% NaCl, LPS, PACAP 38 or LPS+PACAP 38, respectively. Serum adiponectin concentrations were measured using an ELISA test. RESULTS: LPS administration did not change adiponectin concentration; however, PACAP 38 administered alone decreased serum adiponectin concentration after 2 h (p<0.05) and 4 h (p<0.01). In the group that received LPS+PACAP38, compared with LPS alone, no difference in adiponectin concentration was observed. CONCLUSIONS: We conclude that PACAP 38 may directly modulate adiponectin secretion by adipocytes in basal conditions.

Controversial opinions on the role of cocaine and amphetamine-regulated transcript (CART) in prolactin release.

Cocaine and amphetamine regulated transcript (CART) is widely expressed in the central nervous system and in several endocrine organs. The physiological role of this peptide includes modulation of appetite control, energy expenditure, thermoregulation and hormone secretion. It has been suggested that CART influences prolactin (PRL) secretion both directly and indirectly. However, the mechanism underlying the regulation of PRL release by CART remains unclear.

PACAP 38 as a modulator of immune and endocrine responses during LPS-induced acute inflammation in rats.

The effect of PACAP 38 administration on neuroendocrine and immune parameters was examined in rats with LPS-induced peritonitis. Treatment with PACAP 38 alone did not influence the serum level of the cytokines and hormones examined, but significantly decreased immune cell activity. When administered together with LPS, PACAP 38 reversed its effect on immune and humoral parameters, causing a decrease in the serum concentrations of TNFalpha and corticosterone, and an increase in T4 and GH. The majority of PACAP 38 effects disappeared earlier than those previously observed for VIP. PACAP 38 appears to represent a short-lasting modulator of immune and endocrine responses during acute inflammation.

Can PACAP-38 modulate immune and endocrine responses during lipopolysaccharide (LPS)-induced acute inflammation?

Pituitary adenylate cyclase-activating polypeptide (PACAP) shows a potential anti-inflammatory activity and interacts with the endocrine system. The aim of the present article was to evaluate the effects of PACAP38 on the endocrine and immune systems during acute inflammation. Rats used in the experiments, divided into four groups, were given intraperitoneal injection of, respectively 0.9% NaCl, LPS, PACAP38, and LPS+PACAP38. Hormone (pituitary, adrenal, and thyroid) and cytokine (TNF-alpha, IL-6, IL10) concentrations were measured 2 and 4 h after the injection. Treatment with LPS + PACAP, as compared to LPS, caused TNF-alpha and corticosterone to decrease and T4 to increase after 2 h. These data suggest that PACAP modulates both the endocrine and immune responses in this model of septic shock.

Orexin A and its role in the regulation of the hypothalamo-pituitary axes in the rat.

Orexin A (OxA), a recently discovered neuropeptide, is synthesized mainly by neurons located in the posterolateral hypothalamus and is a 33 amino acid peptide with N-terminal pyroglutamyl residue and two inter-chain disulfide bonds. It is a potent agonist for both the orexin-1 (OxR1) and orexin-2 (OxR2) receptors. Orexin A and its receptors are widely distributed in the central nervous system (CNS) and peripheral organs suggesting the pleiotropic functions of this peptide. Orexin A is involved in food intake and energy expenditure in many species, but also plays an important role in the regulation of the hypothalamo-pituitary axes. The role of orexin A in the regulation of the hypothalamo-pituitary-adrenal, -thyroid, -somatotropic, and -gonadal axes has been inadequately investigated. Orexinergic fibres project to the septal-preoptic and arcuate nucleus-median eminence regions--two areas of the brain directly involved in the synthesis and release of gonadotropin-releasing hormone (GnRH). Contentious opinions concerning the influence of orexin A over the hypothalamo-gonadotropic axis have been reported in both in vivo and in vitro studies. Further studies are necessary to clarify relationships between orexin A and the hypothalamo-pituitary hormones involved in reproduction.

The effect of cocaine-amphetamine regulated transcript (CART) on the activation of the pituitary-adrenal axis.

OBJECTIVE: It has been reported that the cocaine and amphetamine regulated transcript (CART) is widely expressed in the hypothalamic nuclei involved in the mechanism of hormonal secretion. RESEARCH METHODS: In order to evaluate the effect of CART on the activation of the pituitary-adrenal axis in the rat, CART (55-102) in a dose of 0.5 microg in 5 microl CSF was infused into the third ventricle (icv) with an automatic pump. At 10, 30, 60, 120 min after the infusion of CART or vehicle, the animals were decapitated and the trunk blood was collected. Serum ACTH and corticosterone concentrations were measured with RIA kits provided by Phoenix Pharmaceuticals and ICN Biomedicals USA, respectively. RESULTS: The stimulating effect of CART on ACTH concentration was observed only 30 min after icv injection. However, CART stimulated corticosterone release at 10, 30, 60 min after icv injection. CONCLUSIONS: CART (55-102) administered intracerebroventricularly (icv) stimulated ACTH and corticosterone release. The stimulating effect of CART on ACTH was short-lived.

Direct effect of cortistatin on GH release from cultured pituitary cells in the rat.

OBJECTIVE: Cortistatin (CST) is a 17-amino acid neuropeptide expressed mainly in the cortex and hippocampus. It is also found in the peripheral tissues such as the stomach, kidney, pancreas and the immune system. Two forms of cortistatin CST-17, CST-29 bind with high affinity all somatostatin (SS) receptor subtypes. It has been reported that a receptor called MrgX(2) is able to selectively bind both CST-17 and CST-14 rather than SS. In human tissues CST-17 and CST-29, rather than SS, also bind ghrelin receptor GHS-r1a. In in vivo experiments CST inhibited GH and insulin secretion. THE AIM: The aim of this study was to evaluate the effect of cortistatin on GH release in in vitro experiments. RESEARCH METHODS: CST-14 and SS-14 in doses of 1nMol, 10nMol, and 100nMol were added after 48 hrs of pituitary cell culture, and the medium was collected 30, 60, 120, 240 min thereafter. rGH was measured with RIA kits provided by Linco. RESULTS: CST-14 stimulated GH release from cultured pituitary cells in a dose dependent manner. The maximum effect of CST-14 was observed after 60 min of incubation. However, SS-14 in doses of 10 nMol and 100 nMol inhibited GH release. CONCLUSION: A direct stimulating effect of Cortistatin-14 on GH release from cultured pituitary cells was found.

Bombesin inhibits LH release in ovariectomized (OVX), estrogen primed rats.

OBJECTIVE: Bombesin, 14-amino acid peptide, discovered in the gastrointestinal tract, is widely distributed in the central nervous system (CNS). The specific receptors of bombesin in the pituitary have been characterized. Bombesin plays an important role in the gastric and pancreatic secretion, in the mechanism of food intake, thermoregulation and in pituitary hormone secretion. There are contentious opinions about the effect of bombesin on hormone secretion. THE AIM: The aim of this study was to evaluate the effect of estrogens in the modulation of bombesin action on LH release. RESEARCH METHODS: Female Wistar-Kyoto rats, two weeks after ovariectomy (OVX), were implanted with a cannula being located in the third cerebroventricle. Thereafter, the rats were primed with 17beta estradiol in a dose of 25microg/0.2ml s.c. for three consecutive days. On the day of the experiment, bombesin at a concentration of 0.5 microg in 5microl vehicle (artificial cerebrospinal fluid) or equal volume of the vehicle was infused into the third ventricle with an automatic pump. At 60 or 120 min after the infusion the animals were decapitated, and the trunk blood was collected. Rat serum LH was measured by RIA kit supplied by Dr A.F. Parlow from NIDDK Baltimore, MD. RESULTS: Bombesin inhibited LH release at 120 min and it did not change LH release at 60 min after icv administration. CONCLUSIONS: The response of LH release after central injection of bombesin is modified by estrogens.