Quantitative subregional distribution of serotonin1A receptors and serotonin transporters in the human dorsal raphe.

Subregional distributions of serotonin1A receptors and serotonin transporters within the human dorsal raphe nucleus (DR) were determined by quantitative autoradiographic analyses of radioligand binding in tissue sections. [3H]8-Hydroxy-2-(di-n-propyl)aminotetralin (8-OH-DPAT) and [3H]paroxetine were used to label, respectively, serotonin1A receptors and serotonin transporters in the subnuclei of the DR, which were delineated on the basis of tryptophan hydroxylase (TrpOH) immunoreactivity. [3H]8-OH-DPAT binding was coextensive with the TrpOH-immunoreactive cell bodies and fibers but was distributed unevenly among the subnuclei. In contrast, [3H]paroxetine binding was present throughout the central gray matter, with relatively homogeneous labeling across the subnuclei of the DR. In rostral sections, [3H]8-OH-DPAT binding (fmol/mg protein) in the dorsal subnucleus was lower than that in the ventral or the interfascicular subnucleus. Within the interfascicular subnucleus, [3H]8-OH-DPAT binding decreased progressively in a rostral-to-caudal fashion. The highest levels of [3H]8-OH-DPAT binding were found in the ventrolateral subnucleus at the level of the caudal extent of the trochlear nucleus. The influence of age and postmortem interval on radioligand binding was also examined. These data in the human DR indicate that serotonin1A receptors are differentially distributed among the subnuclei and along the rostro-caudal axis of the midbrain raphe, and serotonin transporters appear to be relatively evenly distributed throughout the DR. Subregional analyses of such serotonergic markers may prove useful in evaluating the role that serotonin may play in depression, schizophrenia, and suicide.

Effect of acute stress on hippocampal glutamate levels and spectrin proteolysis in young and aged rats.

Aging in rats is associated with a loss of hippocampal neurons, which may contribute to age-related cognitive deficits. Several lines of evidence suggest that stress and glucocorticoids may contribute to age-related declines in hippocampal neuronal number. Excitatory amino acids (EAAs) have been implicated in the glucocorticoid endangerment and stress-induced morphological changes of hippocampal neurons of young rats. Previously, we have reported that acute immobilization stress can increase extracellular concentrations of the endogenous excitatory amino acid, glutamate, in the hippocampus. The present study examined the effect of an acute bout of immobilization stress on glutamate levels in the hippocampus and medial prefrontal cortex of young (3-4-month) and aged (22-24-month) Fischer 344 rats. In addition, the effect of stress on spectrin proteolysis in these two brain regions was also examined. Spectrin is a cytoskeleton protein that contributes to neuronal integrity and proteolysis of this protein has been proposed as an important component of EAA-induced neuronal death. There was no difference in basal glutamate levels between young and old rats in the hippocampus or medial prefrontal cortex. During the period of restraint stress a modest increase in glutamate levels in the hippocampus of young and aged rats was observed. After the termination of the stress procedure, hippocampal glutamate concentrations continued to rise in the aged rats, reaching a level approximately five times higher than the young rats, and remained elevated for at least 2 h after termination of the stress. A similar pattern was also observed in the medial prefrontal cortex with an augmented post-stress-induced glutamate response observed in the aged rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Dose-response changes in plasma cortisol and lymphocyte glucocorticoid receptors following dexamethasone administration in combat veterans with and without posttraumatic stress disorder.

BACKGROUND: Our previous studies have suggested that combat veterans with posttraumatic stress disorder (PTSD) have alterations in hypothalamic-pituitary-adrenal axis functioning that are different from the well-documented biological changes observed in major depressive disorder and following exposure to stress. METHODS: In the present study, we examined cortisol and lymphocyte glucocorticoid receptor number before and after the administration of 0.50 and 0.25 mg of dexamethasone in 14 combat veterans with PTSD, 12 combat veterans without PTSD, and 14 nonpsychiatric healthy men. All subjects were medication free at the time of testing and none met diagnostic criteria for major depression or substance dependence. RESULTS: Combat veterans with PTSD suppressed cortisol to a greater extent than did combat veterans without PTSD and normal controls in response to both doses of dexamethasone. Differences in cortisol suppression could not be attributed to substance dependence history or differences in dexamethasone bioavailability. Combat veterans with PTSD showed a larger number of baseline glucocorticoid receptors compared with normal men. Combat veterans without PTSD also had a larger number of baseline glucocorticoid receptors compared with normal men and in fact were comparable to combat veterans with PTSD on this measure. However, only veterans with PTSD showed a decrease in lymphocyte glucocorticoid receptor number following dexamethasone administration. CONCLUSION: The data support the hypothesis of an enhanced negative feedback sensitivity of the hypothalamic-pituitary-adrenal axis in PTSD.

Short-term and long-term effects of p-chloroamphetamine on hippocampal serotonin and corticosteroid receptor levels.

Hippocampal corticosteroid receptors are regulated by corticosterone as well as by neurotransmitters, such as serotonin (5-HT). Studies have demonstrated that long-term changes in 5-HT levels are associated with alterations in hippocampal glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) number. However, the effect of short-term manipulations of 5-HT levels on hippocampal corticosteroid receptor levels has not been thoroughly investigated. The present set of studies examined the effect of para-chloroamphetamine (PCA) administration on both short-term and long-term regulation of hippocampal 5-HT and corticosteroid receptor levels. PCA is a selective serotonergic neurotoxin which initially releases 5-HT to cause a short-term depletion of 5-HT stores, followed by a long-term decrease in 5-HT levels which presumably reflects the destruction of 5-HT nerve terminals. In the initial study rats were adrenalectomized and 24 h later injected with PCA (20 mg/kg) and sacrificed 3 h later. PCA produced a large decrease in hippocampal 5-HT (-79%) and 5-hydroxyindoleacetic acid (5-HIAA) (-40%) concentrations. In addition, PCA significantly decreased both hippocampal GR (-28%) and MR (-35%) levels. Pretreatment with fluoxetine (20 mg/kg), which presumably blocks the uptake of PCA into 5-HT nerve terminals, completely blocked the PCA-induced decreases in both 5-HT and corticosteroid receptor concentrations. In a final experiment, the long-term (7 days) effect of PCA administration on hippocampal 5-HT and corticosteroid receptor levels was examined. PCA (10 mg/kg given on 2 consecutive days) was administered to adrenal-intact rats which were adrenalectomized 6 days later and subsequently sacrificed following a 24 h interval. PCA produced an 87% decrease in hippocampal 5-HT and 5-HIAA levels, but did not alter hippocampal GR or MR levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenalectomy attenuates kainic acid-induced spectrin proteolysis and heat shock protein 70 induction in hippocampus and cortex.

Glucocorticoids have been shown to exacerbate the damaging effects of a variety of neurotoxic insults in the hippocampus and other brain areas. Evidence suggests that the endangering effects of glucocorticoids may be due to augmenting the cascade of events, such as elevations in intracellular calcium levels, because of excitatory amino acid (EAA) receptor stimulation. A potential mechanism responsible for EAA-induced neuronal damage is activation of calcium-sensitive proteases, such as calpain, which then proteolytically degrade cytoskeleton structural proteins, such as spectrin. The present study was designed to determine if glucocorticoids can regulate the spectrin proteolysis produced by the EAA agonist, kainic acid. Rats were adrenalectomized (ADX) or sham operated and 7 days later injected with kainic acid (10 mg/kg). Twenty-four hours later rats were killed and tissues obtained for western blot analyses of the intact spectrin molecule and the proteolytically derived breakdown products. Kainic acid produced an approximate sevenfold increase in the 145-155-kDa spectrin breakdown products in the hippocampus relative to ADX or sham rats injected with vehicle. ADX attenuated the kainic acid-induced increase in breakdown products by 43%. In a similar way, kainic acid produced a large 10-fold increase in spectrin breakdown products in the frontal cortex, which was also significantly attenuated (-80%) by ADX. Induction of heat shock protein 70 (hsp70) by neurotoxic insults has been suggested to be a sensitive indicator of cellular stress in neurons. Kainic acid induced large amounts of hsp70 in both hippocampus and frontal cortex of sham-operated rats that was markedly attenuated (85-95%) by ADX.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal size is increased in multiple sclerosis.

OBJECTIVE: To determine if adrenal glands are enlarged in multiple sclerosis (MS). Patients with MS and major depression are insensitive to glucocorticoid feedback regulation. Depressed patients have excessively high glucocorticoid levels and enlarged adrenal glands. To our knowledge, this is the first study of adrenal size in MS. Chronic high levels of adrenal glucocorticoid in MS may downregulate responses to exogenous or endogenous steroids. DESIGN: Retrospective postmortem analysis compared adrenal size in MS with that in other neurologic and non-neurologic diseases. SETTING: Autopsy cases were obtained from the records of a tertiary care hospital. PATIENTS: Ten patients had definite MS; 13, amyotrophic lateral sclerosis; and 14, acute myocardial infarction. MAIN OUTCOME MEASURES: Adrenal and body weight at autopsy. RESULTS: At postmortem examination, the adrenal glands of patients with MS were enlarged in comparison with the adrenal glands of patients who died of acute myocardial infarction or amyotrophic lateral sclerosis. The adrenal glands of the patients with MS were 36% larger than those of the patients with amyotrophic lateral sclerosis who had comparable body weights. The adrenal-body weight ratio was 40% greater in patients with MS than in patients who died of acute myocardial infarction. CONCLUSIONS: The increased adrenal size in patients with MS may allow excessive glucocorticoid secretion in response to stress and affect immune regulation.

Methamphetamine-induced decrease in neural glucocorticoid receptors: relationship to monoamine levels.

Methamphetamine (MA) is a potent psychostimulant drug which is neurotoxic to dopamine (DA) and serotonin (5-HT) neurons. It has been previously reported that acute MA administration to adrenalectomized rats produced large dose-related decreases in hippocampal and striatal glucocorticoid receptors (GR). The present study was designed to determine if MA could decrease neural and peripheral GR when administered to adrenal-intact rats using a neurotoxic dosing regimen which produces depletions of brain DA and 5-HT levels. MA (0, 6.25, 12.5 and 25 mg/kg) was administered to adrenal-intact rats every 2 h for a total of 4 doses. Rats were adrenalectomized (ADX) 6 days later and subsequently sacrificed 24 h later. GR and mineralocorticoid receptors (MR) were measured using radioligand binding assays. Tissue levels of 5-HT and DA were measured in order to confirm the neurotoxic effects of MA and also to relate corticosteroid receptor levels to monoamine concentrations. MA produced dose-related decreases in GR levels in the hippocampus, striatum, frontal cortex and hypothalamus. Hippocampal MR were not affected by MA. 5-HT was also decreased in all of these same 4 brain regions, whereas DA was significantly decreased only in the striatum. MA did not decrease GR in cerebellum and similarly had no effect on DA and 5-HT in this region. MA also did not decrease GR or 5-HT levels in the spleen. These results demonstrate that MA produces a decrease in GR in a variety of brain areas, which is related primarily to 5-HT depletions.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenalectomy attenuates stress-induced elevations in extracellular glutamate concentrations in the hippocampus.

Glucocorticoids and stress have deleterious effects on hippocampal cell morphology and survival. It has been hypothesized that these effects are mediated via an excitatory amino acid mechanism. The present study was designed to evaluate the effects of acute stress on the extracellular levels of glutamate in the hippocampus and to determine if adrenalectomy modifies this response. Rats were adrenalectomized or sham-adrenalectomized and implanted with microdialysis probes in the CA3 region of the hippocampus. Three days later rats were subjected to an acute 1-h period of immobilization stress. Stress significantly increased extracellular glutamate levels in the sham-operated rats, which peaked at 20 min following the initiation of stress. Extracellular glutamate levels also increased immediately following the termination of stress. In the adrenalectomized rats there was a 30% decrease in basal extracellular concentrations of glutamate and a marked attenuation (-70%) of the stress-induced increase in extracellular glutamate levels. Extracellular concentrations of taurine were not modified by adrenalectomy and did not change in response to stress. These results suggest that glucocorticoid-induced elevations in extracellular glutamate concentrations may contribute to the deleterious effects of stress on hippocampal neurons.

Serum prolactin levels in active multiple sclerosis and during cyclosporin treatment.

Prolactin is essential for immune function. Excess prolactin augments some immune reactions, whereas low serum levels of prolactin inhibit immune function and prevent experimental allergic encephalomyelitis, an animal model of multiple sclerosis (MS). Activated lymphocytes, characteristics of MS, release prolactin. In this study, serum prolactin levels were normal in 35 patients with chronic progressive MS and 19 patients with acute exacerbations. These results suggest it is unlikely that prolactin contributes to the enhanced immune reactivity characteristic of MS. Acute cyclosporin A (CsA) administration increases circulating prolactin levels in animals and might paradoxically augment some immune reactions. We find that chronic CsA therapy for MS does not cause elevations in serum prolactin and should not reverse any therapeutic effect of CsA. Disturbances of prolactin regulation are not characteristic of MS.

Interferon-beta treatment does not elevate cortisol in multiple sclerosis.

Interferons (IFN) are used to treat cancer and multiple sclerosis (MS). High doses of IFN elevate serum cortisol, which may indirectly affect the course of either of these diseases. IFN-induced elevation of serum cortisol could speed recovery from exacerbations of MS. We find that IFN-beta at 9 or 45 MU every other day does not elevate serum or urine cortisol in MS. Clinical effects of IFN-beta in MS are likely to be direct, and not mediated indirectly through alteration of serum cortisol levels.

Effects of intravenous and oral dexamethasone on selected lymphocyte subpopulations in normal subjects.

Our studies describe the effects of 1 mg oral (PO) and intravenous (IV) administration of dexamethasone (DEX) on certain subpopulations of circulating lymphocytes in normal subjects. We compared the outcomes of PO and IV DEX administration because of individual differences in gastro-intestinal absorption of DEX and the issue of noncompliance in patients undergoing the dexamethasone suppression test (DST). Both routes of DEX administration were equally effective in suppressing plasma cortisol levels below 5 micrograms/dl, the customary criterion level. Both routes of DEX administration also significantly decreased the percent and absolute number of CD4+ cells, the CD4+/CD8+ ratio, and the percent and absolute number of virgin, but not of memory, CD4+ cells.

Kainic acid-induced decrease in hippocampal corticosteroid receptors.

The potential role of excitatory amino acids in the regulation of brain corticosteroid receptors was examined using systemic administration of kainic acid. Administration of kainic acid (5, 10, and 15 mg/kg) to 24-h adrenalectomized rats that were killed 3 h later produced large, dose-related decreases in glucocorticoid receptors (GR) in hippocampus (23-63%), frontal cortex (22-76%), and striatum (41-49%). Kainic acid did not decrease hypothalamic GR. Hippocampal mineralocorticoid receptors (MR) were also markedly decreased (50-71%) by kainic acid. Significant decreases in corticosteroid receptors could be detected as soon as 1 h after kainic acid (10 mg/kg) administration. Decreases in hippocampal, cortical, and hypothalamic GR as well as hippocampal MR were observed 24 h after administration of kainic acid (10 mg/kg) to adrenalectomized rats. Kainic acid (10 mg/kg) also significantly decreased hippocampal GR and MR as well as GR in the other three brain regions when administered to adrenal-intact rats that were subsequently adrenalectomized and killed 48 h after drug administration. The kainic acid-induced decreases in hippocampal GR and MR binding were due to decreases in the maximum number of binding sites (Bmax) with no change in the apparent affinity (KD). Kainic acid when added in vitro did not displace the GR and MR radioligands from their respective receptors. These studies demonstrate that excitatory amino acids play a prominent role in the regulation of hippocampal corticosteroid receptors. In addition, the data indicate that noncorticosterone factors are involved in corticosteroid receptor plasticity.

Hypothalamic-pituitary-adrenal dysfunction in posttraumatic stress disorder.

Neuroendocrine studies examining the hypothalamic-pituitary-adrenal (HPA) axis under baseline conditions and in response to neuroendocrine challenges have supported the hypothesis of altered HPA functioning in posttraumatic stress disorder (PTSD). However, to date, there is much debate concerning the nature of HPA changes in PTSD. Furthermore, in studies showing parallel findings in PTSD and major depressive disorder there is controversy regarding whether the HPA alterations suggest a specific pathophysiology of PTSD, or, rather, reflect comorbid major depressive disorder. This review summarizes findings of HPA axis dysfunction in both PTSD and major depressive disorder, and shows distinct patterns of HPA changes, which are probably due to different mechanisms of action for cortisol and its regulatory factors.

Corticosterone regulation of brain and lymphoid corticosteroid receptors.

Circulating lymphocytes are often used as a model for brain corticosteroid receptor regulation in clinical disease states, although it is not known if lymphoid receptors are regulated in a similar manner as brain receptors. In the present study the regulation of brain (hippocampus, frontal cortex, hypothalamus and striatum), lymphoid (circulating lymphocytes, spleen and thymus) and pituitary glucocorticoid receptors in response to alterations in circulating corticosterone levels was examined. Seven days following adrenalectomy, type II corticosteroid receptors (i.e. glucocorticoid receptors) were significantly increased in the hippocampus, frontal cortex and hypothalamus, but not in any other tissues. Administration of corticosterone (10 mg/kg) for 7 days significantly decreased type II as well as type I (i.e. mineralocorticoid receptors) receptors in the hippocampus. Type II receptors in the frontal cortex, circulating lymphocytes and spleen were also significantly decreased by chronic corticosterone treatment. Immobilization stress (2 h a day for 5 days) failed to alter receptor density in any of the tissues. These results demonstrate that homologous regulation of corticosteroid receptors by corticosterone does not invariably occur in all tissues and emphasize the complex degree of regulation of these receptors. However, the simultaneous downregulation of both hippocampal and lymphocyte glucocorticoid receptors by corticosterone provides support for the hypothesis that circulating lymphocytes do reflect some aspects of brain glucocorticoid receptor regulation.

Lymphocyte glucocorticoid receptor number in posttraumatic stress disorder.

OBJECTIVE: The authors' objective was to investigate the possibility that glucocorticoid receptor changes may be involved in the dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis in posttraumatic stress disorder (PTSD). METHOD: They measured the number of lymphocyte cytosolic glucocorticoid receptors and plasma cortisol concentrations in 15 consecutively admitted male combat Vietnam veterans with PTSD and in a normal comparison group of 11 subjects. RESULTS: Both the patients and the normal comparison subjects showed a morning-to-afternoon decline in glucocorticoid receptor concentrations, paralleling the normal diurnal decline in cortisol levels. The number of glucocorticoid receptors was 63% greater in the morning and 26% greater in the afternoon in the patients with PTSD than in the normal subjects. No group differences in cortisol levels were observed, nor were glucocorticoid receptor number and cortisol levels correlated. The number of morning glucocorticoid receptors was positively correlated with symptoms of PTSD and anxiety. CONCLUSIONS: These results provide further evidence for a dysregulation of the HPA axis in PTSD. The finding that patients with PTSD had a substantially greater number of lymphocyte glucocorticoid receptors than normal comparison subjects is consistent with the authors' previous observations of low 24-hour urinary cortisol excretion in subjects with PTSD. Furthermore, the receptor changes observed are opposite of those reported in major depressive disorder. The present data, along with other findings of HPA abnormalities in PTSD, support the possibility of a greater negative feedback sensitivity at one or more levels of the HPA axis.

MK-801 antagonizes methamphetamine-induced decreases in hippocampal and striatal corticosteroid receptors.

Administration of methamphetamine (15 mg/kg) to adrenalectomized rats significantly decreased hippocampal type I and II corticosteroid receptors as well as type II receptors in the striatum. Type II receptors in the frontal cortex and hypothalamus were unaffected by methamphetamine administration. Pretreatment with MK-801, a non-competitive antagonist of N-methyl-D-aspartate receptors, antagonized the methamphetamine-induced decrease in hippocampal and striatal corticosteroid receptors. These results are in agreement with previous studies demonstrating that some of the neurobiological effects of methamphetamine may be mediated via a mechanism involving excitatory amino acids.

Reserpine-induced decrease in type I and II corticosteroid receptors in neuronal and lymphoid tissues of adrenalectomized rats.

The effect of the biogenic amine depleting drug, reserpine, on the concentration of type II corticosteroid receptors (i.e., glucocorticoid receptors) in neuronal (hippocampus, frontal cortex, hypothalamus), lymphoid (circulating lymphocytes, spleen, thymus) and pituitary tissues as well as hippocampal type I (i.e., mineralocorticoid) receptors was examined in adrenal-intact and adrenalectomized (ADX) rats. Reserpine (2 mg/kg) or vehicle was administered to adrenal-intact rats for 2 consecutive days. Following the second injection rats were ADX and sacrificed 24 h later. Reserpine significantly decreased type I and II hippocampal receptors as well as type II receptors in frontal cortex, hypothalamus, lymphocytes and spleen. Since the reserpine-induced decreases in receptor content could be due to reserpine-induced elevations in circulating corticosterone levels, reserpine (2 mg/kg) or vehicle was administered to 1-day ADX rats which were then sacrificed 2 days later (i.e., 3 days post ADX). A 1-day ADX control group was also included. The 3-day ADX regimen produced significant or nearly significant increases in type II receptors in hippocampus, frontal cortex, hypothalamus, lymphocytes and spleen in vehicle-treated rats. Reserpine attenuated the ADX-induced upregulation of type II receptors in hippocampus, frontal cortex, lymphocytes and spleen, but had no effect on the ADX-induced upregulation of type II receptors in the hypothalamus. The ADX-induced increase in hippocampal type I receptors was not affected by reserpine treatment. In a final experiment, reserpine (2 mg/kg) or vehicle was administered immediately after ADX and rats were sacrificed 24 h later in order to assess the effect of reserpine on basal (i.e., nonupregulated) corticosteroid receptor levels in the absence of circulating corticosterone levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantification of type I and II adrenal steroid receptors in neuronal, lymphoid and pituitary tissues.

Circulating lymphocytes are frequently used to study glucocorticoid receptor (GR) regulation in various clinical disease states, such as depression. Since little is known about the relationship between lymphoid and neuronal GR, type II adrenal steroid receptors (i.e., GR) were quantitated in neuronal (hippocampus, frontal cortex, hypothalamus), lymphoid (circulating lymphocytes, spleen, thymus) as well as pituitary tissues of adrenal-intact and 1 day adrenalectomized (ADX) rats using the selective type II receptor ligand, [3H]RU 28362. Specific, high affinity (dissociation constant = 0.2-0.3 nM) type II receptors were present in all tissues examined with the density in 1 day ADX rats being thymus greater than frontal cortex = spleen greater than hippocampus = pituitary greater than hypothalamus greater than lymphocytes. Adrenal intact rats had fewer type II receptors in frontal cortex, hippocampus and spleen as compared to 1 day ADX rats. Dose-response competition studies using [3H]RU 28362 and various unlabelled steroids revealed a binding profile indicative of a type II receptor with the potency being RU 28362 greater than triamcinolone acetonide greater than dexamethasone = corticosterone much greater than aldosterone in both whole brain and spleen soluble fractions. In contrast to the high concentration of type II receptors in the various tissues, the density of type I (i.e., mineralocorticoid) receptors was very low or nondetectable in the same tissues of 1 day ADX rats with the notable exception of the hippocampus where there were approximately comparable levels of both receptors. These results document the widespread distribution of type II adrenal steroid receptors in neuronal and lymphoid tissues which are similar in affinity and steroid specificity.

Selective reduction of striatal type II glucocorticoid receptors in rats by 3,4-methylenedioxymethamphetamine (MDMA).

A single 20 mg/kg dose of 3,4-methylenedioxymethamphetamine (MDMA) administered to rats markedly decreased serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) levels in hippocampus, frontal cortex and striatum seven days following injection. MDMA also significantly decreased type II glucocorticoid receptor levels in the striatum, but not in hippocampus or frontal cortex. Since no difference in basal serum corticosterone levels was observed between the two groups, MDMA may decrease striatal type II glucocorticoid receptors via a corticosterone-independent mechanism.