CRF-like Immunoreactivity Research Articles

The presence of corticotropin-releasing factor-like immunoreactive synaptic vesicles in axon terminals with nicotinic acetylcholine receptor-like immunoreactivity in the median eminence of the rat

Whether or not corticotropin-releasing factor (CRF) containing synaptic vesicles are located in axon terminals with nicotinic acetylcholine receptor (nAChR) in the median eminence (ME) of the rat was examined by electron microscopic double-labeling immunocytochemistry combining the pre-embedding avidin-biotin-peroxidase complex (ABC) method for nAChR with the post-embedding immunogold staining method for CRF. nAChR-like immunoreactivity (nAChR-LI) was found in the cell membranes of the axon terminals in the ME. CRF-like immunoreactivity (CRF-LI) was found in dense granular vesicles (about 100 nm in diameter) in the axon terminals. Double-labeling method revealed that some of nAChR-LI axon terminals were found to contain CRF-LI dense granular vesicles. The results indicate that nicotine may act on nAChR in axon terminals to release CRF.

Ultrastructural localization and afferent sources of corticotropin-releasing factor in the rat rostral ventrolateral medulla: implications for central cardiovascular regulation.

We investigated the ultrastructural localization, afferent sources, and arterial pressure effects of corticotropin-releasing factor (CRF) in the nucleus reticularis rostroventrolateralis (RVL), a region of the ventrolateral medulla containing C1 adrenergic neurons and sympatho-excitatory reticulospinal afferents to sympathetic preganglionic neurons. A polyclonal antibody to CRF was localized in acrolein-fixed sections through the rat RVL by the peroxidase-antiperoxidase (PAP) method. Light microscopy showed that 1-7 perikarya/30 micron section and numerous varicose processes contained CRF-like immunoreactivity (CRF-LI). By electron microscopy, CRF-LI was most intensely localized to large (80-100 nm) dense-core vesicles within numerous terminals and a few perikarya and large dendrites. Approximately half of the terminals containing CRF-LI were in direct contact with unlabeled perikarya or dendrites; the remainder were in apposition to either unlabeled terminals or astrocytes. Most synaptic specializations were asymmetric synapses on small, unlabeled dendrites. To examine potential extrinsic sources of CRF-containing terminals in the C1 area of the RVL, PAP immunocytochemical localization of CRF was combined with retrograde transport of wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP). In all cases examined, a number of dually labeled neurons were found in the paraventricular nucleus (PVN) of the hypothalamus and a few dually labeled neurons were observed in the nuclei of the solitary tract; these labeled neurons were ipsilateral to the unilateral injection of WGA-HRP into the C1 area. Fewer dually labeled perikarya were detected in the lateral hypothalamic area and the lateral parabrachial nuclei, ipsilateral to the WGA-HRP injection. Additional physiological studies showed that bilateral microinjections of CRF into the C1 area of the RVL of urethane-anesthetized rats elicited a dose-related increase in arterial pressure. The results suggest that within the C1 area of the RVL, CRF released from terminals, arising predominantly from the PVN of the hypothalamus and probably from local neurons as well, may excite sympathoexcitatory reticulospinal neurons.

Alterations of corticotropin-releasing factor-like immunoreactivity in different brain regions after acute cocaine administration in rats

Corticotropin-releasing factor (CRF) may mediate some of the neuroendocrine and behavioral responses to cocaine. In this study, the distribution of CRF-like immunoreactivity (CRF-LI) was determined in the hypothalamus and in several extrahypothalamic brain regions after acute cocaine administration in handled rats. CRF-LI decreased dose-dependently with cocaine administration in the hypothalamus and in the basal-forebrain structures. A small dose of cocaine (7.5 mg/kg) decreased CRF-LI in the hippocampus and in the frontal cortex. A significant, selective, dose-dependent increase in CRF-LI was found in the amygdala after cocaine injection. None of the investigated doses of cocaine altered CRF-LI in the striatum. These results suggest that acute cocaine administration alters brain CRF systems to contribute behavioral and neuroendocrine responses to cocaine.

Colocalization of corticotropin-releasing factor and vasopressin in the paraventricular nucleus of the human hypothalamus.

The anatomical relationship between corticotropin-releasing factor (CRF)-containing cells and arginine vasopressin (AVP)-containing cells in the human hypothalamus was investigated by immunocytochemistry. In the paraventricular nucleus of the hypothalamus (PVH), CRF-like immunoreactivity (CRF-LI) was present exclusively in parvocellular cells, while AVP-like immunoreactivity (AVP-LI) was present in both parvocellular and magnocellular cells. No CRF-immunoreactive neurons were observed in the supraoptic nucleus. All CRF-immunoreactive parvocellular cells in the PVH were also AVP immunoreactive. We confirmed the presence of AVP in the CRF-immunoreactive cells by using two kinds of anti-AVP antisera, one of which recognized the side chain of AVP while the other recognized the ring structure of AVP. Colocalization of CRF-LI and AVP-LI was observed not only in the same perikarya but also in the same nerve fibers of parvocellular cells. The present results raise the possibility that AVP and CRF may be secreted together into the human portal circulation.

Colocalization of enkephalin-, glucagon-, and corticotropin-releasing factor-like immunoreactivity in GABAergic amacrine cells in turtle retina

The large number of amacrine cells which contain γ-aminobutyric acid (GABA) in the turtle retina makes it difficult to examine specific GABAergic cell types. In order to seletively label subpopulations of GABAergic neurons, we have used fluorescent double-labeling immunocytochemical techniques to examine the localization of GABA-like immunoreactivity (LI) in amacrine cells which contain antigens resembling the neuropeptides glucagon (GLUC), corticotropin-releasing factor (CRF) or enkephalin (ENK). GABA-LI was found in 41% of the cells with GLUC-, 100% of the cells with CRF-, and 69% of the cells with ENK-LI. There were regional differences in the presence of GABA-LI in amacrine cell populations with ENK-LI. GABA-LI was present in about 80% of the cells with ENK-LI outside of the visual streak, while only 37% of the cells within the streak had GABA-LI. Based on the distinct morphologies and regional distributions of these peptidergic amacrine cells, we conclude that they represent different subpopulations of GABAergic amacrine cells in the turtle retina. Future studies can now utilize existing information regarding the synaptic connectivity of these peptidergic amacrine cells to help delineate the functions of GABAergic amacrine cells in the turtle retina.

The 5-hydroxytryptamine agonist fenfluramine increases fos-like immunoreactivity in the brain

This study was designed to assess the effects of the 5-hydroxytryptamine (5-HT) indirect agonist fenfluramine on the brain distribution of Fos- and corticotropin-releasing factor-like immunoreactivity (F-LI and CRF-LI). A single intraperitoneal injection of either dl-fenfluramine (25 mg/kg) or saline was given to resting Sprague-Dawley rats housed on a 12-12 h light-dark cycle and fed libitum. Sixty min following injections, rats were killed and brains removed and sliced (40 μm thick) in a coronal plane from the anterior olfactory bulb to the brainstem. Brain slices were then stored at −40°C pending the tissue localization of F-LI and CRF-LI were determined by means of a double immunostaining procedure using the peroxidase-avidin: biotin complex (ABC) method. Fenfluramine injection led to a marked increase in F-LI in the caudate-putamen (CPu), the parvocellular division of the hypothalamic paraventricular nucleus (PVN), and the central amygdaloid nucleus (CeA). In the PVN, most of the F-LI was co-localized with CRF-LI. There was no attempt to identify which types of neurons displayed F-LI in CPu and CeA. While F-LI was readily observable in all rats treated with fentluramine, it was not discernible in the control animals. This study provides evidence for an involvement of the immediate-early genes c- fos in the central action of fenfluramine.

Distribution of corticotropin-releasing factor-like immunoreactivity in squirrel monkey (Saimiri sciureus) amygdala.

Previous anatomical studies of corticotropin-releasing factor (CRF)-like immunoreactivity in rat brain have reported prominent clustering of neuronal elements containing this peptide within the amygdala. The highest concentrations of both CRF-positive cells and fibers were evident in the central nucleus, an observation consistent with the putative role of this peptide in autonomic and endocrine regulation. In addition, lower densities of CRF-positive somata and processes have been noted in other amygdaloid nuclei. However, the distribution of CRF-like immunoreactivity in the amygdala has not been described for any primate species. Such a description would be of interest since substantial differences in the distribution of CRF in rodent and primate have been reported for other brain regions. The present study uses immunohistochemical methods, with a polyclonal antiserum directed against the human form of CRF, to determine the distribution of this peptide in non-colchicine-treated monkeys (Saimiri sciureus). Within the amygdaloid complex, the most numerous and concentrated collections of CRF-positive neurons were seen in the basal and lateral nuclei. The highest densities of CRF-positive fibers and terminals were seen in the lateral and central amygdaloid nuclei. Moderately dense plexuses of CRF-positive fibers also were seen in layer Ia of the periamygdaloid cortex, nucleus of the lateral olfactory tract, anterior and posterior cortical nuclei, and the medial nucleus. Thus, the distribution of CRF-like immunoreactivity differs substantially in monkey and rat amygdala. Since CRF-positive perikarya in monkey are most prominent in nuclei with pronounced interconnections with neocortex, these differences may be an integral component of the increased cortical development that characterizes the primate brain.

Corticotropin-releasing factor innervation of the locus coeruleus region: Distribution of fibers and sources of input

Electrophysiologic studies support the hypothesis that corticotropin-releasing factor, the neurohormone that initiates adrenocorticotropin release during stress, also serves as a neurotransmitter in the pontine noradrenergic nucleus, the locus coeruleus. To elucidate the circuitry underlying proposed corticotropin-releasing factor neurotransmission in the locus coeruleus, the present study utilized immunohistochemical techniques to characterize corticotropin-releasing factor innervation of rat locus coeruleus and pericoerulear regions. Corticotropin-releasing factor-like immunoreactive fibers were identified in the locus coeruleus of colchicine- and non-colchicine-treated rats. However, corticotropin-releasing factor innervation of pericoerulear regions rostral and lateral to the locus coeruleus was more dense than that of the locus coeruleus proper. Double-labeling studies utilizing antisera directed against corticotropin-releasing factor and tyrosine hydroxylase indicated that corticotropin-releasing factor-like immunoreactive fibers overlap with tyrosine hydroxylase-like immunoreactive processes of locus coeruleus neurons, particularly in rostral medial and lateral regions. A group of corticotropin-releasing factor-like immunoreactive neurons was localized just lateral to the locus coeruleus and numerous corticotropin-releasing factor-like immunoreactive neurons were visualized just ventral to the rostral pole of the locus coeruleus in a region corresponding to Barrington's nucleus. None of these corticotropin-releasing factor-like immunoreactive neurons were tyrosine hydroxylase-positive. To determine the source of corticotropin-releasing factor-like immunoreactive fibers in the locus coeruleus, injections of the retrograde tracer [wheat germ agglutinin conjugated to inactivated (apo) horseradish peroxidase coupled to gold particles] were made into the locus coeruleus and sections were processed for corticotropin-releasing factor-like immunoreactivity. Locus coeruleus injections of the retrograde tracer labeled numerous neurons in the medullary nuclei, prepositus hypoglossi and paragigantocellularis, consistent with previous results. In prepositus hypoglossi, retrogradely labeled neurons were a distinct population from a prominent group of more laterally situated corticotropin-releasing factor-like immunoreactive neurons. In contrast to prepositus hypoglossi, approx. 8% of retrogradely labeled neurons in the paragigantocellularis were corticotropin-releasing factor-like immunoreactive, implicating the paragigantocellularis as a source of corticotropin-releasing factor-like immunoreactive fibers in locus coeruleus. In addition, occasional corticotropin-releasing factor-like immunoreactive neurons were visualized in the area of the dorsal cap of the paraventricular nucleus of the hypothalamus that were retrogradely labeled. The present study confirms findings of others describing corticotropin-releasing factor-like immunoreactive cells and fibers in brainstem and extends previous findings by demonstrating an overlap of corticotropin-releasing factor-like immunoreactive fibers with tyrosine hydroxylase-like immunoreactive processes in pericoerulear regions. Additionally, these findings implicate the paragigantocellularis as a potential source of corticotropin-releasing factor-like immunoreactivity in the locus coeruleus. The present study also provides anatomic support for electrophysiologic evidence of a neurotransmitter role for corticotropin-releasing factor in the rat locus coeruleus.

Fine structure and possible origins of nerve fibers with corticotropin-releasing factor-like immunoreactivity in the rat central amygdaloid nucleus

The fine structure of nerve fibers with corticotropin-releasing factor (CRF)-like immunoreactivity in the central amygdaloid nucleus and CRF-containing afferents to the nucleus were investigated by pre-embedding immunoelectron microscopy and by the combination of fluoro-gold tracing and the indirect immunofluorescence method. Significant numbers of CRF nerve endings and dendrites formed synapses with non-immunoreactive dendrites and axon terminals, respectively. Axon terminals devoid of CRF frequently made synapses with the soma of immunoreactive and non-immunoreactive neurons; CRF nerve endings in contact with the soma were fewer in number. Occasionally, CRF was localized to both pre- and postsynaptic structures in the central amygdaloid nucleus. After flouro-gold injection into the central amygdaloid nucleus and adjacent areas, double-labeled cells with the tracer and CRF were observed mainly in the lateral hypothalamic area and occasionally in the dorsal raphe nucleus, and they were less numerous than single-labeled cells. These findings suggest that part of the CRF axon terminals identified in the electron micrographs arises from neurons in the lateral hypothalamic area and the dorsal raphe nucleus and the others from intra-amygdaloid CRF neurons. The immunoreactive dendrites are likely to derive from neurons in the central amygdaloid nucleus, which are shown to send axons to the lower brainstem. Thus, this study demonstrates that CRF structures constitute a more complex neuronal network in the central amygdaloid nucleus than previously considered.

Localization of corticotropin-releasing factor-like immunoreactivity in monkey olfactory bulb and secondary olfactory areas.

Electrophysiological and anatomical observations suggest that terminals of olfactory bulb mitral cells ending in rat primary olfactory cortex exert certain postsynaptic effects via an excitatory amino acid neurotransmitter. Recent anatomical studies have shown that several peptides, most notably corticotropin-releasing factor (CRF) (Imaki et al., '89) Brain Res., 496: 35-44), are also localized within rat olfactory bulb projection neurons, thus raising the possibility that there is a peptide cotransmitter in this system. In contrast to the availability of data for rodents, very little is known about the distribution of peptides and other putative transmitters in the olfactory systems of primate species. In the present study, sections through the olfactory bulb and its target areas were obtained from two monkey species (Saimiri sciureus and Macaca fascicularis) and processed for immunohistochemistry with a well-characterized polyclonal antiserum directed against the human form of CRF. Virtually identical results were obtained in the two species. Within the olfactory bulb, nearly all mitral and many tufted cells contained CRF-like immunoreactivity. CRF-positive fibers were seen within the olfactory tract and olfactory stria, which contain the axons of mitral and tufted cells. Within the anterior olfactory nucleus and layer Ia of the olfactory tubercle and piriform cortex, immunoreactivity was seen within fine processes, as well as in coarse, varicose fibers and isolated puncta. CRF-positive cells were seen within layer III of the olfactory tubercle and piriform cortex. Immunoreactive fibers and varicosities were also seen within olfactory-recipient regions of the amygdala and entorhinal cortex. These observations suggest that CRF may act as a transmitter and/or neuromodulator in primate olfactory system.

Activation of corticotropin-releasing factor-containing neurons in the paraventricular nucleus of the hypothalamus by interleukin-1 in the rat

Interleukin-1 (IL-1) alpha was injected into the lateral ventricle of the rat. An antiserum against Fos oncoprotein was used to detect the activated neurons immunohistochemically. A large number of neurons in the parvocellular paraventricular nucleus of the hypothalamus, in an area corresponding to the location of the corticotropin-releasing factor (CRF)-containing neurons, were strongly Fos-like immunoreactive (LI). Double immunostaining for Fos and CRF revealed that many of the Fos-LI cells were CRF-LI. Furthermore, the CRF-like immunoreactivity was greatly enhanced in the rats injected with IL-1 alpha, indicating an increase in CRF synthesis.

Corticotropin releasing factor-like immunoreactivity (CRF-LI) in horizontal cells of the developing rat retina

This study describes a phenomenon of transient expression of corticotropin releasing factor-like immunoreactivity (CRF-LI) in immature horizontal cells of the developing rat retina. These cells could be distinguished from those destined to become CRF-LI amacrine cells in the adult by their location within the outer portion of the neuroblastic layer (NBL) and by their ontogenetic pattern. Upon initial detection on postnatal day 3 (PD-3), faint CRF-LI cellular profiles were found in the outer portion of the NBL, limited to the central region of the retina. Subsequently, on PD-5, these profiles began to appear in the periphery, forming a single horizontal row along the outermost aspect of the developing inner nuclear layer (INL), concomitant with the establishment of the outer plexiform layer (OPL). The results of our birth-dating study combining immunohistochemistry and [3H]-thymidine autoradiography indicated that these cells were generated between embryonic day 14 and 18. These findings are consistent with them being horizontal cells. Between PD-7 and PD-9, CRF-LI in horizontal cells began to diminish progressively following a center-to-periphery gradient such that only sporadic, faintly immunoreactive patches of cells could be seen by the time of eye opening (PD-15). Around PD-19, it declined to levels below immunohistochemical detection. However, when rats were reared in complete darkness beginning at birth until PD-21, the period of CRF-LI expression in horizontal cells was prolonged and persisted throughout the first three postnatal weeks of development.

Synaptic organization of two types of amacrine cells with CRF-like immunoreactivity in the turtle retina

The ultrastructural features and synaptic contacts of two amacrine cell types with corticotropin-releasing factor-like immunoreactivity in the turtle retina were examined using electron immunocytochemistry. Type A cells were found only in the visual streak and had elongated dendritic arborizations that ran parallel to the visual streak. These cells arborized primarily in stratum 1 and near the border of strata 2 and 3 of the inner plexiform layer, with some processes extending into stratum 5. Type B cells were found only ventral to the visual streak and arborized primarily in a wide band in strata 4 and 5, with sparse dendritic arborizations in stratum 1. There was a diffuse cytoplasmic reaction product within each cell type; however, large labeled vesicles were rarely observed. Type A amacrine cells received many conventional synaptic contacts from amacrine cells in stratum 1 and at the border of strata 2 and 3, but only a small number of contacts in stratum 5. Bipolar synaptic contacts onto type A amacrine cells were observed in strata 1 and at the border of strata 2 and 3. The only positively identified synaptic outputs of type A cells were conventional synapses onto amacrine cells in strata 1 and at the border of 2 and 3. Type B amacrine cells received synaptic contacts from amacrine cells in strata 1 and 5, and bipolar cell synaptic input in stratum 5. They made conventional synapses onto amacrine cells in strata 1 and 5, and onto bipolar cells in stratum 5. We also found conventional synaptic contacts between unlabeled amacrine cells and type B amacrine cells outside of the primary layers of stratification. In addition, there were specialized junctions observed between type A cell profiles in stratum 1 and between type B cell profiles in stratum 5. The unique regional distributions of the type A and B cells, as well as their differences in synaptic connectivity, suggested that these amacrine cells play distinct physiological roles although they contain the same neuropeptide.

Subcellular Distribution of Corticotropin-Releasing-Factor-Like Immunoreactivity in Rat Central Nervous System

Corticotropin-releasing-factor-like immunoreactivity (CRF-LI) was measured in a number of subcellular fractions from rat brain using a highly sensitive and specific radioimmunoassay. CRF-LI was highly enriched in the crude synaptosomal/mitochondrial fraction (P2) relative to the homogenate, P1, S1, and S2 fractions. Separation of the P2 fraction into synaptosomal, myelin, and mitochondria-enriched subfractions on a rapid one-step sucrose gradient revealed that CRF-LI was present at higher concentration in the synaptosomal fraction than in the mitochondrial and myelin fractions. The distribution of CRF-LI paralleled that of synapsin, a synaptic vesicle marker phosphoprotein, but not that of pyruvate dehydrogenase, a mitochondrial phosphoprotein. These results are consistent with a nerve terminal localization of CRF and a potential role for this peptide as a central nervous system neurotransmitter.

Histogenesis of corticotropin releasing factor-like immunoreactive amacrine cells in the rat retina

The histogenesis of amacrine cells expressing corticotropin releasing factor-like immunoreactivity (CRF-LI) was examined in the rat retina by incorporating [ 3H]thymidine autoradiography and immunohistochemistry. Our results indicate that, during the period of amacrine cell generation, the population of CRF-LI amacrine cells are generated within a window of time from gestational days (ED)-16 to -20; the majority of them are produced by ED-18. No CRF-LI cells have been found to be ‘born’ postnatally. The histogenetic pattern of these cells follows a center-to-periphery gradient. Furthermore, CRF-LI cells in both the inner nuclear layer and the ganglion cell layer are generated in the same histogenetic wave and follow an identical temporo-spatial pattern. These results are consistent with and extend our previous findings of a differential change in CRF-LI cell density and total cell number during postnatal development.

Differential alpha-1 and alpha-2 adrenergic effects on hypothalamic corticotropin-releasing factor and plasma adrenocorticotropin

There is presently no consensus as to the nature of the catecholaminergic influence on the regulation of corticotropin-releasing factor. The potential role that the alpha-adrenergic system plays was investigated by measuring hypothalamic corticotropin-releasing factor-like immunoreactivity and plasma adrenocorticotropin, following manipulation of alpha-1 and alpha-2 adrenergic receptor activation. Administration of the alpha-1 agonist methoxamine did not significantly alter either plasma adrenocorticotropin or hypothalamic corticotropin-releasing factor. Administration of the alpha-2 agonist clonidine resulted in a 24-fold increase in plasma adrenocorticotropin and a significant decrease in median eminence corticotropin-releasing factor, consistent with its release. Corticotropin-releasing factor in the remainder of the hypothalamus was not altered. Concurrent administration of clonidine with the selective alpha-2 antagonist yohimbine prevented the clonidine-induced changes in plasma adrenocorticotropin and hypothalamic corticotropin-releasing factor, consistent with the clonidine effect being mediated through alpha-2 receptors. Concurrent administration of clonidine with methoxamine did not prevent these effects, suggesting that the effect of clonidine was not mediated through presynaptic inhibition of noradrenergic-adrenergic neurotransmission. Inhibition of protein synthesis by anisomycin induced changes in corticotropin-releasing factor and adrenocorticotropin which were not altered by combined treatment with methoxamine or clonidine. These data suggest differential roles for alpha-1 and alpha-2 systems in the regulation of corticotropinreleasing factor. Results from alpha-2 adrenergic activation were consistent with stimulation of corticotropin-releasing factor release, an effect mediated by a postsynaptic alpha-2 mechanism. These data also suggest a near-maximal alpha-1 adrenergic effect exists physiologically which topically maintains corticotropin-releasing factor concentrations in hypothalamus by either stimulation of synthesis or inhibition of release.

Localization of corticotropin-releasing hormone (CRF)-like immunoreactivity in the central nervous system of the elasmobranch fish, Scyliorhinus canicula

The occurrence and localization of immunoreactive corticotropin-releasing factor (CRF) in the brain and pituitary of the elasmobranch fish Scyliorhinus canicula, were studied by means of specific radioimmunoassay and immunohistochemistry using the indirect immunofluorescence method. Brain and pituitary extracts showed a good cross-reactivity with the ovine CRF antiserum, but serial dilutions of tissue samples did not completely parallel the standard curve. Relatively high concentrations of CRF-like material were found within the pituitary, diencephalon, and telencephalon. CRF-like immunoreactive perikarya were observed in the preoptic nucleus and in the nucleus lateralis tuberis. Numerous immunoreactive cells appeared to be of the CSF-contacting type. CRF-like immunopositive fibers were seen to run through the hypothalamus within the ventro-medial floor of the infundibular region. A dense plexus of immunoreactive nerve endings terminated in the median eminence and the neurointermediate lobe of the pituitary. These results indicate that a neurosecretory system containing CRF-like immunoreactivity exists in the brain of elasmobranchs, a group of vertebrates which has diverged early from the evolutionary line leading to mammals. In addition, our data support the notion that a CRF-like molecule is involved in the regulation of corticotropic and melanotropic cell activity in this primitive species of fish.

Neuropeptide Y-induced effects on hypothalamic corticotropin-releasing factor content and release are dependent on noradrenergic/adrenergic neurotransmission

Neuropeptide Y (NPY) administration increases both hypothalamic corticotropin-releasing factor-like immunoreactivity (CRF-ir) and plasma adrenocorticotropin (ACTH). The dependence of these effects on noradrenaline and adrenaline was investigated by selectively depleting these neurotransmitters with 6-hydroxydopamine (6-OHDA) prior to administration of NPY. This combined treatment decreased hypothalamic CRF-ir ( P < 0.025), an effect isolated to the median eminence ( P < 0.025), whereas plasma ACTH increased greatly compared to 6-OHDA treatment alone ( P < 0.0005). In order to further investigate the potential mechanism of this NPY effect, theα 2-adrenergic agonist clonidine was administered to normal rats. This treatment increased plasma ACTH ( P < 0.005) and decreased hypothalamic CRF-ir ( P < 0.025), an effect localized to the median eminence ( P < 0.01). The results from both of these treatments are consistent with increased release of hypothalamic CRF. These data imply that the NPY-induced effects are dependent on normal noradrenergic/adrenergic neurotransmission. Depletion of these neurotransmitters allowed NPY to profoundly stimulate CRF release with no evidence for alteration in synthesis, a result common toα 2 stimulation.

Estradiol or ovariectomy decreases crf synthesis in hypothalamus

Gonadectomy and gonadectomy plus chronic estradiol administration decrease the content of hypothalamic corticotropin-releasing factor-like immunoreactivity (CRF-ir). This investigation was conducted to determine whether this was a result of chronic inhibition of CRF synthesis or stimulation of release. Administration of the protein synthesis inhibitor anisomycin one hour prior to sacrifice in otherwise untreated controls resulted in a 21% decrease in median eminence CRF-ir ( p < 0.01). Rats were ovariectomized and then administered either estradiol or vehicle daily for 3 weeks. Compared to vehicle-treated controls, estradiol treatment decreased CRF-ir in median eminence ( p < 0.01). In contrast to controls, administration of anisomycin to these ovariectomized rats did not significantly decrease median eminence CRF-ir in either the vehicle or estradiol-treated groups, implying that CRF synthesis was already depressed. Plasma adrenocorticotropin (ACTH) was increased by anisomycin treatment in all groups whether intact, ovariectomized or estradiol-treated ( p < 0.0005). Adrenal weights did not differ between these groups, or in comparison to sham-ovariectomized rats, indirectly implying lack of chronically elevated plasma ACTH. These data suggest that the mechanism for both the ovariectomy and chronic estradiol-induced decrease in CRF-ir content is an inhibition of CRF synthesis as opposed to a stimulation of CRF release.

CSF corticotropin-releasing factor (CRF) in Alzheimer's disease: Its relationship to severity of dementia and monoamine metabolites

The concentration of corticotropin-releasing factor-like immunoreactivity (CRF-LI) in the cerebrospinal fluid (CSF) of 15 probable Alzheimer's disease (AD) patients with mild to moderate dementia and 10 neurologically normal age-matched controls was examined. There were no significant alterations in the mean CSF CRF-LI concentration in AD compared to controls. However, in the AD group, CSF CRF-LI correlated significantly with the global neuropsychological impairment ratings, suggesting that greater cognitive impairment was associated with lower CSF CRF-LI concentrations. There was a significant reduction in the CSF concentration of homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) in the AD patients, and there was a positive correlation between the concentration of CRF-LI and 5-HIAA in CSF. This latter finding suggests that serotoninergic neuronal systems may interact with CRF-containing neurons.