Depletion of striatal somatostatin by local cysteamine injection

Local injection of cysteamine into rat striatum resulted in a dose-dependent reduction in somatostatin-like immunoreactivity (SLI). The effect was seen at 1 h, and persisted for up to 72 h, but was reversible at 1 week. The maximal depletion of SLI was approximately 50%. Histologic damage was largely confined to the needle tract. Of interest was a depletion of SLI in the contralateral striatum beginning at 3 h and maximal at 72 h. Cysteamine induced depletion of striatal SLI was not accompanied by alterations in dopamine or serotonin metabolism. Cysteamine is a useful pharmacologic tool for local somatostatin depletion.     

Influence of cysteamine and cysteine on open-field behaviour,and on brain concentrations of catecholamines,somatostatin, neuropeptide Y,and corticotropin releasing hormone in the rat

Summary Cysteamine (1.95 or 3.90 mM/kg) administered subcutaneously (sc) markedly decreased the open-field activity of the rats, while the structurally related amino acid cysteine had only minor influence. Cysteamine (1.95 or 3.90 mM/kg) reduced the noradrenaline and increased the dopamine and dihydroxyphenyl acetic acid (DOPAC) levels in the hypothalamus. In striatum the drug decreased both the noradrenaline (1.95 or 3.90 mM/kg) and dopamine (3.90 mM/kg) levels without influencing the DOPAC content. Neither the hypothalamic nor the striatal catecholamines are influenced by administration of equimolar doses of cysteine.Cysteamine (1.95 or 3.90 mM/kg) decreased the somatostatin levels both in the hypothalamus and in the striatum without influencing neuropeptide Y (NPY) and corticotropin releasing hormone (CRH) concentrations. Cysteine administered in equimolar doses did not influence the peptide levels in these brain structures.These data suggest that the cysteamine-induced behavioural changes are related to the decrease of brain noradrenaline and somatostatin concentrations. The structurally related amino acid cystein does not influence the behaviour or the central monoaminergic and peptidergic concentrations in the hypothalamus and striatum of rats.     

A comparison of regional somatostatin and neuropeptide Y distribution in rat striatum and brain

Somatostatin-like immunoreactivity (SLI) and neuropeptide Y-like immunoreactivity (NPYLI) were detected using specific radioimmunoassays in extracts from rat brain. Since we have previously found a topographic distribution of SLI in rat striatum the distribution of NPYLI was examined in the same regions. NPYLI showed an identical distribution to SLI in rat striatum and levels were significantly correlated (r = 0.93, P less than 0.01). Concentrations of both neuropeptides were consistently highest in ventromedial striatum and nucleus accumbens while they were lowest in dorsolateral striatum. These findings provide further evidence of neurochemical heterogeneity in the striatum. Concentrations of NPYLI and SLI were also significantly correlated in cerebral cortex (r = 0.99, P less than 0.01). Concentrations of NPYLI were generally higher than SLI and showed a similar predilection for limbic system nuclei. The present findings support the concept that somatostatin and neuropeptide Y may be co-localized in both striatal and cortical neurons.     

Release of somatostatin from extra-hypothalamic rat brain slices: inhibition by dopamine and morphine

Calcium-dependent potassium-evoked release of somatostatin-like immuno-reactivity (SSLI) and preloaded [3H]noradrenaline ([3H]NA) could be demonstrated simultaneously from slices of rat cerebral cortex, globus pallidus and trigeminal nucleus. The release of [3H]NA from cortical slices differed from that of somatostatin (SS) in its K+-dependency, with the release of SS having a higher threshold. Both morphine (10 microM) and dopamine (50 microM) significantly inhibited the potassium-evoked release of SS from the cerebral cortex, without affecting its basal release. The effect of morphine was naloxone reversible.     

Behavioral changes following central injection of cysteamine in rats

When tested 3 days following 4 daily intracerebroventricular injections of 250 μg cysteamine, which depletes somatostatin, rats demonstrated a significant increase in locomotor activity that was not observed in animals treated similarly with 350 μg cysteamine. A significant deficit in passive avoidance was observed in animals treated with the 350-μg dose, but not in animals treated with 250 μg cysteamine. These data suggest that altered activity of the somatostatinergic system disrupts specific processes underlying neural integration of complex behaviors.     

Intracerebroventricular infusion of somatostatin selectively increases paradoxical sleep in rats

Chronic intracerebroventricular (i.c.v.) infusion of somatostatin (SRIF) elicited a specific increase of the daily duration of paradoxical sleep (PS) in rats. I.c.v. administration of cysteamine, a selective SRIF depletor, brought about a dose-dependent reduction of PS. Slow wave sleep (SWS) remained unaffected in both cases. These results suggest that SRIF may be involved in the regulation of PS.     

Biochemical mapping of somatostatinergic systems in rat brain: Effects of periventricular hypothalamic and medial basal amygdaloid lesions on somatostatin-like immunoreactivity in discrete brain nuclei

Immunohistochemical studies have demonstrated the presence of somatostatin (growth hormone release-inhibiting factor)-positive cell bodies in the periventricular nucleus of the hypothalamus and in the medial-basal amygdala. In order to map biochemically the projections of these cell groups, electrolytic lesions were made in these structures and somatostatin was measured by radioimmunoassay in microdissected brain nuclei. Bilateral destruction of the periventricular nucleus significantly decreased somatostatin-like immunoreactivity (SLI) in the median eminence, and in the rostral periventricular, medial preoptic and arcuate nuclei. Bilateral lesions placed in the medial-basal amygdala significantly decreased SLI in the median eminence and suprachiasmatic nucleus. Similar depletions were observed following lesions of the stria terminalis. These results suggest that both the periventricular and amygdaloid somatostatin systems may participate in the regulation of growth hormone secretion via their projections to the median eminence and other hypothalamic nuclei.     

Distribution of somatostatin in the rat brain: Telencephalon and diencephalon

The distribution of somatostatin (SRIF) was examined using the unlabeled antibody enzyme method of immunocytochemistry on thick 30-50 microns Vibratome sections. The greatest population of SRIF-neurons was observed along the ventricular wall in the preoptic area and anterior hypothalamus. Dense accumulations of fibers were observed in the suprachiasmatic, ventromedial and arcuate nuclei, the internal and external zone of the median eminence, the organum vasculosum of the lamina terminalis and the subfornical organ. Extrahypothalamic sites of SRIF-containing neurons and fibers were also observed throughout the telencephalon. The widespread distribution of SRIF is consistent with radioimmunoassay data and suggests a diverse physiological role for somatostatin.     

大鼠脊髓背角浅层神经元中神经肽Y Y1受体与生长抑素共存

用间接免疫荧光双标记方法,研究大鼠脊髓Ⅱ层神经元中神经肽Ｙ Ｙ１受体与生长抑素共存关系。结果显示在Ⅱ层深部许多神经元含Ｙ１受体－免疫反应性物质,只观察到少量的生长抑素免疫反应阳性神经元胞体,其中个别Ｙ１受体阳性神经元也含生长抑素免疫反应性物质;在局部使用秋水仙素后,大多数Ｙ１受体免疫反应阳性神经元含有生长抑素免疫反应性物质。推论脊髓背角Ⅱ层神经元中的Ｙ１受体可能与生长抑素在脊髓水平的功能有关。     

The regional distribution of somatostatin, substance P and neurotensin in human brain

The regional distribution of somatostatin-, substance P- and neurotensin-like immunoreactivity was determined in 41 areas of 10 human brains. Each peptide is distributed widely in the human central nervous system and for each the pattern of distribution is unique. No significant relationship was found between peptide levels and patient age, interval between death and autopsy, and tissue storage time prior to assay. The regional distribution of these peptides is similar to that seen in several animal species and the pattern of this distribution is consistent with the idea that peptides function as neurotransmitters within the central nervous system.The problems of using human post-mortem material for peptide assay are discussed.     

Lack of effect of chronic carbamazepine on brain somatostatin in the rat

Summary We investigated the effects of chronic carbamazepine treatment in rats on brain somatostatin. Following 12 days of carbamazepine treatment, no changes in somatostatin levels were found in any of the brain areas examined which included: amygdala, hippocampus, caudate-putamen, median eminence, arcuate nucleus, nucleus accumbens, nucleus interstitialis of the stria terminalis, nucleus periventricularis, parietal cortex, and occipital cortex. Thus, carbamazepine in low doses does not affect basal levels of brain somatostatin in the rat, in contrast to the previous reports of decreased somatostatin in the cerebrospinal fluid of affectively ill patients.     

Localization and characterization of brain somatostatin receptors as studied with somatostatin-14 and somatostatin-28 receptor radioautography

The localization and characterization of receptors for somatostatin-14 (S-14) and somatostatin-28 (S-28) were studied in the rat brain using the iodinated agonists [Tyr0,D-Trp8]S-14 and [Leu8,D-Trp22,Tyr25]S-28 as tracers. Slide-mounted frozen sections were used for the radioautographic localization and biochemical characterization of somatostatin receptors. In the latter case counting was performed on scraped off serial sections from rostral regions of the brain. Specificity studies demonstrated that either tracer could be displaced with S-28, S-14 or their agonists. The N-terminus fragment (1-12) of S-28 as well as a number of unrelated peptides were unable to compete with either tracer, indicating that the binding capacity for ligand-receptor recognition is located in the C-terminal portion of S-28. Scatchard analysis of saturation curves gave a one-site interaction with Kd values of 0.42 +/- 0.09 nM and 0.32 +/- 0.04 nM for the S-14 and S-28 iodinated agonists, respectively. By radioautography, the distribution of receptors for both S-14 and S-28 appeared very similar with high levels of binding in the deep layers of the cortex, the cingulate cortex, the claustrum, the locus coeruleus and most structures of the limbic system. Treatment with cysteamine, which caused a somatostatin depletion in the brain, was required to observe labeling in the hypothalamus. In some caudal areas of the brain, especially in the cerebellar nuclei, the solitary tract nucleus and the nucleus of the vagus nerve, only labeling with the S-28 agonist could be detected. This S-28 binding could be displaced by native S-14 (10(-6) M). Generally, there was a correlation between the localization of somatostatin receptors and that of immunoreactive somatostatin, as evaluated by immunocytochemistry. However, in some areas, an inverse correlation between receptor and peptide concentrations was observed. These results are in agreement with previous data suggesting that somatostatin could act as a neurotransmitter or neuromodulator in several brain areas.     

Comparative distribution of bombesin/GRP- and substance-P-like immunoreactivities in rat hypothalamus

Immunohistochemical localization of bombesin/gastrin-releasing peptide ( GRP )-like immunoreactivity (BN/ GRP -LI) and substance P-like immunoreactivity (SP-LI) in consecutive sections of rat hypothalamus was studied. Bombesin/ GRP -like immunoreactivity in the hypothalamus was partially characterized by gel filtration chromatography followed by radioimmunoassay. In the hypothalamus, SP-LI was more widely distributed than BN/ GRP -LI. Only the anterior and medial parvocellular parts of the nucleus paraventricularis and the nucleus suprachiasmaticus contained numerous cell bodies which exhibited BN/ GRP -LI. Neurons in these areas did not exhibit SP-LI. In contrast, cell bodies exhibiting SP-LI were numerous in the nucleus preopticus medialis and lateralis, nucleus anterior, nucleus ventromedialis and dorsomedialis, nucleus lateralis, nucleus arcuatus, and nucleus premamillaris ventralis and dorsalis. Only occasional cell bodies in these areas exhibited BN/ GRP -LI. It is concluded that the neuronal systems in the hypothalamus containing BN/ GRP -LI and SP-LI are separate, though the terminal fields in many areas overlap. Two peaks of BN/ GRP -LI were detected after gel filtration chromatography from extracts of the rat nucleus paraventricularis. The high molecular weight form coeluted with synthetic GRP (1-27), and the small molecular weight form eluted after synthetic bombesin. Thus, the endogenous BN/ GRP -LI is probably not authentic bombesin.     

Regional somatostatin distribution in the rat striatum

Somatostatin-like immunoreactivity (SLI) was detected by a specific radioimmunoassay in extracts from rat striatum. There was a topographic distribution of somatostatin with the highest levels in the nucleus accumbens and ventromedial striatum and the lowest levels in the dorsolateral striatum. This suggests that somatostatin-containing afferents to the striatum may originate from limbic system nuclei which project in a similar distribution. Gel permeation chromatography showed 5 distinct peaks of immunoreactive somatostatin. The two largest peaks coeluted with somatostatin 14 (SS-14) and somatostatin 28 (SS-28) and accounted for 72 and 12% of the total immunoreactivity, respectively. Reversed phase high pressure liquid chromatography confirmed that the majority of immunoreactive material co-chromatographs with SS-14; a smaller amount co-chromatographed with SS-28.     

Distribution of cholecystokinin (CCK) in the rat lower brain stem nuclei

The cholecystokinin (CCK) concentration in individual brain stem nuclei of rat was determined using the Palkovits punch method¹⁹ and the CCK RIA³. CCK has a unique distribution in the brain stem, unlike other neuropeptides and biogenic amines^8,19. In general, the CCK levels in the brain stem are 5–20% of rat cerebral cortex. The colliculi, midbrain central gray, nucleus of the solitary tract, and the interpeduncular nucleus had the highest CCK content (2.7-1 ng CCK mg protein).     

Androgen receptors in the perinatal rat brain

Androgen receptors were identified and characterized in the cytosol and nuclear fractions of the perinatal female rat brain. Cytosol receptors have sedimentation coefficients in the range of 8 to 10S and bind to DNA cellulose columns. These receptors are detected in low concentrations in hypothalamus-preoptic area-amygdala-septum (HPAS) during the last few days of fetal life, less than 1/10th of levels found in adult HPAS. They undergo the most dramatic increase in concentration between postnatal days 7 and 15. Their appearance thus coincides temporally with the appearance of estrogen and progestin receptors, but the time course of their development is delayed, by comparison. Cell nuclear androgen receptors were also identified by gel exclusion chromatography and protamine sulfate precipitation after salt extraction of neonatal brain cell nuclei following in vivo labeling with both a synthetic and a natural androgen. Two well-known anti-andorgens, cyproterone acetate and flutamide, are shown to inhibit the in vivo androgen binding to these cell nuclear receptors. The results are discussed in relation to androgen action in the perinatal rat brain, and the information currently available suggests that androgens influence both gonadotropin secretion and aspects of brain sexual differentiation.     

Nuclear, nucleolar repair, or turnover of DNA in adult rat brain

Labeled thymidine administered to adult rats is incorporated at a low level into brain DNA as shown by biochemical and autoradiographic methods. This incorporation takes place in part into neuronal nuclei and nucleoli and also into glial nuclei. While incorporation into glial nuclei is interpreted to represent known glial cell proliferation, incorporation into neuronal nucleoli may be related to nucleolar DNA synthesis, which in turn is responsible for the regulation of nucleolar RNA synthesis. It could also be due to DNA repair synthesis. Assuming this latter phenomenon, our results suggest that nucleolar DNA is more sensitive than chromosomal DNA to ionizing radiations and other factors.