Increased alpha 2-adrenoceptor density in the frontal cortex of depressed suicide victims

The density of brain alpha 2-adrenoceptors, quantitated by means of the binding of the agonist [3H]clonidine, was studied in post-mortem cortical membranes of matched control subjects and depressed suicide victims. In the depressed suicide group, the specific high affinity binding of [3H]clonidine was found to be significantly increased (Bmax, 72% greater; p less than 0.01) without significant changes in the KD value for the radioligand. These preliminary results indicate that alpha 2-adrenoceptor density in the high affinity state (alpha 2H) is increased in the brain of depressed patients and add strong support to the hypothesis that endogenous depression is related to supersensitive alpha 2-adrenoceptors.

An increase in glial fibrillary acidic protein follows brain hyperthermia in rats

Previously, we have demonstrated that an increase in the astrocyte-associated protein, glial fibrillary acidic protein (GFAP), accompanies brain injury induced by a variety of chemical insults. In the present study we examined the effects of microwave-induced hyperthermia of the CNS on the concentration of GFAP in several brain regions of the Long-Evans rat. Irradiation resulted in a time-related increase in GFAP in olfactory bulbs and cortex, areas of maximum heating. The increase in GFAP following a brain temperature increase suggests that heating of brain tissue may be sufficient to provoke an injury response comparable to that induced by chemical and physical insult.

Effects of injury on the indoleamines in cerebral cortex

It was shown previously that focal cortical freezing lesions in rats cause widespread depression of local cerebral glucose utilization (LCGU) in cortical areas of the lesioned hemisphere. This was interpreted as reflecting functional depression. The underlying mechanisms were postulated to involve alterations of biogenic amine systems. Accordingly, levels of serotonin (5-HT), its metabolite 5-hydroxyindoleacetic acid (5-HIAA), and its precursor tryptophan were determined by an HPLC method with electrochemical detection in frontoparietal cortical areas of both hemispheres at 4 h and 1, 3, 6, 8, and 10 days after a unilateral cortical freezing lesion. The 5-HT content was significantly lower than normal in the lesioned hemisphere only at 24 h, whereas the 5-HIAA level peaked at 24 h but was significantly elevated above normal values between 4 h and 6 days after lesioning. No changes were noted in 5-HT and 5-HIAA contents in the hemisphere contralateral to the lesion. These results indicate that cortical 5-HT metabolism is increased throughout the lesioned hemisphere of a focally injured brain. The increase in tryptophan content of the lesioned brain appeared to have a time course more closely related to previously demonstrated changes in cortical LCGU than to the increase in 5-HIAA content.

Monoaminergic fibers form conventional synapses in the cerebral cortex

The morphological characteristics of the monoaminergic axon-terminals in the mammalian cerebral cortex have been the subject of controversy in recent years. Systematic analysis of serial ultrathin sections, immunocytochemically stained with antibodies against noradrenaline and serotonin, has shown that nearly all stained terminals form synapses characterized by specialized junctional appositions. These results suggest that, contrary to the widely held view, monoamines in the cortex are released at specialized junctions.

Histaminergic neuromodulation of the release of vasopressin

In an attempt to clarify the nature of histaminergic neuromodulation of the vasopressinergic system, several studies under different experimental paradigms were carried out. L-Histidine loads (8 mmol/kg, i.p.) induced a marked increase in histamine (HA) in the anterior (AHR) and posterior (PHR) hypothalamic regions, the median eminence (ME) and adenohypophysis (Ah) with no apparent effect on the concentration of HA in the neurohypophysis (Nh), as measured by high-performance liquid chromatography. These findings correlated with decreases in vasopressin (VP) levels in the AHR and ME, accompanied by increases of the neuropeptide in the PHR and Ah. Intraperitoneal injections of HA (6 mumol/kg), resulted in a significant (p less than 0.005) rise in VP levels in the PHR, ME and Ah. HA induced an elevation of VP in the prefrontal cortex (PFC) from 6.23 +/- 2.02 to 43 +/- 4.05 microU/mg, as well as a 60% reduction in neurohypophyseal VP. These HA-induced VP responses were abolished by both mepyramine (3 mumol/kg) and famotidine (4 mumol/kg) in the PHR and PFC. Mepyramine suppressed the HA-induced VP response in the Ah and enhanced it in the Nh, while famotidine did the opposite. When alpha-fluoromethylhistidine (FMH), an irreversible inhibitor of histidine decarboxylase, was administered at doses of 100 mg/kg/day (i.p.), hypothalamic HA levels fell by 40-45% after 1 h, by 50% after 3 h, and by 65-80% after 24 h in adrenalectomized rats. In the same conditions, but after a week of treatment with FMH, the VP response to adrenalectomy was clearly impaired.(ABSTRACT TRUNCATED AT 250 WORDS)

Tail-pinch stress increases extracellular DOPAC levels (as measured by in vivo voltammetry) in the rat nucleus accumbens but not frontal cortex: antagonism by diazepam and zolpidem

The effect of a tail-pinch stress on dopamine metabolism in the nucleus accumbens and frontal cortex was investigated in the awake unrestrained rat by measuring extracellular 3,4-dihydroxyphenylacetic acid (DOPAC) levels through the use of in vivo differential pulse voltammetry. Mild tail pressure for 8 min caused a large (maximal effect + 70%) and sustained (more than 2 h) increase in the amplitude of the DOPAC oxidation peak in the nucleus accumbens but not in the prefrontal cortex. A similar increase in DOPAC levels was observed in the nucleus accumbens postmortem 1 h after tail-pinch stress. The tail-pinch induced increase in extracellular DOPAC levels in the nucleus accumbens was antagonized by pretreatment with diazepam (5 mg/kg i.p.) or zolpidem (5 mg/kg i.p.), a novel non-benzodiazepine hypnotic possessing anxiolytic properties. These results suggest that in contrast to other stressors, tail-pinch selectively activates dopaminergic systems projecting to the nucleus accumbens.

Multiple mode of binding of phencyclidines: high affinity association between phencyclidine receptors in rat brain and a monovalent ion-sensitive polypeptide

Two populations of phencyclidine (PCP) binding sites are shown to exist in the rat brain: a high-affinity monovalent ion-sensitive site (Kd of 10-14 nM for [3H]TCP, [3H]N-[1-(2-thienyl)cyclohexyl]piperidine), which exists in both the frontal cortex and the hippocampus, and a lower affinity site (Kd of 80-130 nM for [3H]TCP) which is found in the hippocampus but not in the frontal cortex. The nature of the interactions between the ion-binding sites and the high affinity PCP receptors depend on both ligand structure (PCP or TCP) and the ion involved (K' or Na'). The high-affinity sites are associated with an Mr 90,000 polypeptide whose labeling by [3H]azido phencyclidine is selectively inhibited by monovalent ions.

Monoaminergic innervation of the frontal and temporal lobes in Alzheimer's disease

Seven markers of ascending (corticopetal) dopaminergic, noradrenergic and serotonergic neurones and choline acetyltransferase activity have been studied postmortem in frontal and temporal cortex from subjects with Alzheimer's disease and compared with a matched group of controls. Dopaminergic neurones (concentrations of dopamine, dihydroxyphenylacetic acid and homovanillic acid) were not deficient but some markers of the other neurones were affected. Noradrenaline and serotonin concentrations were reduced whereas the concentrations of their metabolites were either unaltered (5-hydroxyindoleacetic acid) or increased (3-methoxy-4-hydroxyphenylglycol). All deficits were most pronounced in the temporal cortex. Severely demented subjects had evidence of generalized neuronal loss, whereas those with moderate dementia showed significant loss of only choline acetyltransferase activity. In Alzheimer subjects, a significant relationship (inverse) was found between 5-hydroxyindoleacetic acid concentration and the number of neurofibrillary tangles.

Opposite regulation of serotonin-S2 and dopamine-D2 receptors in rat brain following chronic receptor blockade

Rats were chronically treated with setoperone, a mixed serotonin and dopamine antagonist. Alterations in serotonin-S2 and dopamine-D2 receptors in the brain and changes in behavioural responses to tryptamine and apomorphine were studied along with duration of treatment and drug withdrawal. As with neuroleptics, behavioural supersensitivity to apomorphine and increase in the number of striatal dopamine-D2 receptor sites were apparent after 2 days setoperone treatment, both effects were maximal with 14 days treatment and were maintained over more than 20 days drug withdrawal. In contrast to the changes in the dopaminergic system, the rats showed a decreased response to tryptamine and serotonin-S2 receptor sites in the frontal cortex were significantly reduced in numbers. Both effects developed in parallel over 14 days treatment and extinguished over 10 days drug withdrawal. KD-values of radioligand binding to dopamine-D2 and serotonin-S2 receptor sites were unchanged by the setoperone treatment. The concomitant development and extinction of the in vivo and in vitro effects suggests a causal relationship between them. Chronic treatment with a selective histamine-H1 antagonist (levocabastine) or the tranquilizer diazepam did not affect dopamine-D2 or serotonin-S2 receptor sites. These observations demonstrate that in contrast to the receptor regulation theory, serotonin-S2 receptors are down regulated following persistent receptor blockade. Implications for the clinical use of serotonin antagonists and possible molecular mechanisms involved in the receptor regulation have been discussed.

Reduced number of [3H]nicotine and [3H]acetylcholine binding sites in the frontal cortex of Alzheimer brains

Nicotinic cholinergic receptors were measured in human frontal cortex using [3H]nicotine and [3H]acetylcholine (in the presence of atropine) as receptor ligands. A parallel marked reduction in number of [3H]nicotine (52%; P less than 0.01) and [3H]acetylcholine (-55%; P less than 0.05) binding was found in the frontal cortex of Alzheimer brains (AD/SDAT) when compared to age-matched control brains. As a comparison the number of muscarinic receptors was quantified using [3H]quinuclidinyl benzilate and found to be significantly increased (+23%; less than 0.01) in AD/SDAT compared to controls.

Decreased serotonin S2 and increased dopamine D2 receptors in chronic schizophrenics

Serotonin S2 and dopamine D2 receptors in the prefrontal cortex and caudate nucleus of postmortem brains of chronic schizophrenics were studied using 3H-ketanserin and 3H-spiperone, respectively. In the prefrontal cortex of schizophrenics, we found a significant decrease in the maximum number of 3H-ketanserin binding sites (Bmax), with no change in the dissociation constant (Kd). Conversely, both Bmax and Kd of 3H-spiperone binding to the caudate nucleus were significantly increased in the schizophrenic patients. There were no differences in receptor indices between patients who were taking neuroleptics until their death and those who had taken none for 2 months or more prior to death. These findings suggest that alterations in S2 receptors in the prefrontal cortex may reflect the disease process, per se, and that the increase in the number of D2 receptors in the caudate nucleus of schizophrenics is not due solely to neuroleptic medication.

Age-related changes in neurotensin content and receptors in various rat brain areas

Neurotensin immunoreactivity (NT-IR) is significantly reduced in striatum, nucleus accumbens and hippocampus but not in frontal cortex, hypothalamus and septum of 24-month-old male Sprague Dawley rats. Neurotensin binding in cortex, striatum, hypothalamus and hippocampus shows a rather uniform decline with age. The changes in NT-IR content in striatum and nucleus accumbens are of particular interest in view of the existence of a functional relationship between dopamine and neurotensin.

Increased serotonin2 and beta-adrenergic receptor binding in the frontal cortices of suicide victims

A statistically significant 28% increase in the mean (+/- SD) number of serotonin2 receptors (127.8 +/- 13.4 vs 99.6 +/- 11.1 fmol/mg of protein) and a 73% increase in beta-adrenergic receptor binding (14.5 +/- 1.5 vs 8.4 +/- 1.5 fmol/mg) was found in the frontal cortices of violent suicide victims compared with matched controls. No significant differences were found in the number of serotonin1 binding sites (109.5 +/- 13.4 vs 99.9 +/- 8.8 fmol/mg). We have previously reported a reduced density of presynaptic tritiated imipramine binding sites on serotonergic nerve terminals in the frontal cortices of suicide victims. These data support the hypothesis that suicide completed by violent methods is associated with reduced presynaptic serotonergic activity that has generated compensatory upregulation of the postsynaptic serotonin2 receptor sites. The increase observed in beta-adrenergic binding suggests that there may also be a concomitant reduction in presynaptic noradrenergic activity associated with suicide. If antidepressant pharmacotherapies specifically downregulate cortical beta-adrenergic and/or serotonin2 receptors in depressed subjects, as has been demonstrated in animal studies, and since these effects would be in the opposite direction of the receptor changes found in suicide victims, they may account for the therapeutic action of antidepressants on suicidal behavior and depressive disorders.

Decreased somatostatin immunoreactivity but not neuropeptide Y immunoreactivity in cerebral cortex in senile dementia of Alzheimer type

The content of two neuropeptides, somatostatin (SRIF) and neuropeptide Y (NPY) has been determined in two cerebral cortical areas of Alzheimer's disease brain and in age-matched control brains. The content of SRIF-like immunoreactivity (SRIF-LI) was found to be decreased in Alzheimer temporal cortex (Brodmann area 21) compared to control temporal cortex. The decreased content of SRIF was significantly correlated with the observed number of neuritic plaques and neurofibrillary tangles. No difference was observed in NPY-LI between Alzheimer cerebral cortex and control cortex. Furthermore, no correlations were observed between NPY content and plaque count, neurofibrillary tangle estimate or SRIF content despite widespread reports of NPY/SRIF coexistence.

Mild footshock stress dissociates substance P from substance K and dynorphin from Met- and Leu-enkephalin

Mild footshock stress selectively activates ventral tegmental area dopamine neurons innervating the prefrontal cortex. The same stressor rapidly dissociates ventral tegmental substance P from its preprotachykinin-derived co-transmitter substance K, and preproenkephalin B-derived dynorphin B from preproenkephalin A-derived Met-enkephalin-Arg-Gly-Leu and Leu-enkephalin. Mild footshock stress may provide a paradigm for studying both peptidergic modulation of brain dopaminergic neurons and the dynamic regulation of tachykinin and opioid peptide transcription, processing and utilization.

Brain gangliosides in the presenile dementia of Pick

Histochemical analysis of frontal and temporal lobes from four patients with Pick presenile dementia indicated intracellular and extracellular deposits of gangliosides. Thin layer chromatography of gangliosides disclosed the presence of an unknown ganglioside, a decrease of N-acetylgalactosamine-GDla and an increase of GTla and/or GD2 in white matter of Pick brain. Chromatography of gray matter and quantitation of the sialic acid content yielded results similar to controls. It is suggested that degradation and removal of gangliosides is incomplete in Pick disease.

In vivo voltammetric measurement of extracellular DOPAC levels in the anteromedial prefrontal cortex of the rat

Differential pulse voltammetric recordings with carbon fiber electrodes performed in vivo in the anteromedial prefrontal cortex of the rat yielded 3 oxidation peaks at -100, +100 and +300 mV, respectively. Pharmacological manipulations revealed that 3,4-dihydroxyphenylacetic acid (DOPAC) is the main contributor to the oxidation current recorded at +100 mV (peak 2). Thus, systemic administration of FLA 63 did not alter whereas pargyline caused a disappearance of cortical peak 2. Moreover, haloperidol and sulpiride increased peak 2 amplitude both in normal and in N-(2-chloroethyl)N-ethyl-2-bromobenzylamine (DSP4)-lesioned rats. Peak 2 was detected only in those prefrontal cortex regions known to receive a dopamine input. It is concluded that in vivo voltammetry with carbon fiber electrodes is a useful means of monitoring dopaminergic activity in the prefrontal cortex of the rat.

[CRF-like immunoreactivities in mammalian brains examined with a radioimmunoassay for CRF]

A sensitive and useful radioimmunoassay for CRF was established using synthetic ovine CRF. CRF-like immunoreactivities of hypothalami in the bovine, human, rat, guinea pig, and mouse could be detected with this radioimmunoassay. A variety of CRF-like immunoreactivities of hypothalami in the mammalian brains led us to discuss a putative species difference of amino-acid structure in CRF. In the bovine, CRF-like immunoreactivities of the frontal cortex, caudate nucleus, putamen, and hippocampus could be detected in addition to CRF-like immunoreactivity of hypothalamus. These observations suggested a wide distribution of CRF in the central nervous system, and gave room for discussion about a physiological role of extrahypothalamic CRF. Gel chromatographic studies revealed a high-molecular-weight form of CRF-like immunoreactivity in the bovine frontal cortical profile that was not found in the hypothalamic profile. The results show a multiplicity of CRF-like immunoreactivity in the bovine brain.

The changes of serotonin (5HT-1, 5HT-1A, 5HT-1B, 5HT-2) receptor densities in rat brain following chronic zotepine treatment

The changes of serotonin (5HT-1, 5HT-1A, 5HT-1B and 5HT-2) receptor densities following a chronic zotepine (ZTP) alone or combined lithium (Li)-ZTP treatment were investigated in several regions of the rat brain. As a result, the densities of the 5HT-2 receptors in the frontal cortex (FC) decreased remarkably and those of the 5HT-1 and 5HT-1A receptors in the striatum (ST) increased in the ZTP alone group and the combined Li-ZTP group compared with the saline group. None of the serotonin receptors changed in the hippocampus (HIP). Judging from these findings, we suppose that the decreases of the 5HT-2 receptors in FC may have been induced not only by the chronic antidepressant treatment, but also by the other chronic 5HT-2 antagonist (ZTP, chlorpromazine, etc.) treatment. In addition, the increases of the 5HT-1 and 5HT-1A receptors in ST may not have been associated with ZTP's clinically potent antimanic effect because of a lack of Li's enhancement in the changes of the 5HT-1 and 5HT-1A receptors in contrast to its clinical effect and a lack of the changes in the 5HT-1B receptors where ZTP may have acted potently in vitro.

Regional brain homovanillic acid following delta 9-tetrahydrocannabinol and cocaine

delta 9-Tetrahydrocannabinol (10 mg/kg) increased homovanillic acid in rat prefrontal cortex and olfactory tubercle. This dose did not affect homovanillic acid in the caudate. Higher doses increased homovanillic acid in all 3 regions. Cocaine (20, 30, or 50 mg/kg) did not affect homovanillic acid in any of these brain regions.

Activation of the locus coeruleus induced by selective stimulation of the ventral tegmental area

The effects of selective stimulation of perikarya, but not axons of passage, within the ventral tegmental area (VTA) on the locus coeruleus (LC) noradrenergic system were examined. Anterograde and combined retrograde-immunohistochemical studies indicated both dopaminergic and non-dopaminergic projections to the region of the LC originating from the VTA. Kainic acid (KA) stimulation of the VTA resulted in a dose-dependent increase in the levels of the dopamine metabolite dihydroxyphenylacetic acid (DOPAC) in the prefrontal cortex, and also elevated levels of the norepinephrine (NE) metabolite 3-methoxy-4-hydroxyphenolglycol (MHPG). Prefrontal cortical MHPG levels did not increase in response to vehicle injection or KA infusion into the hippocampus, nor did concentrations of this metabolite increase in the prefrontal cortex in response to intra-VTA KA in animals with neurotoxic lesions of the VTA. KA injection into the VTA resulted in increased MHPG levels in the hippocampus, but not the hypothalamus. Dorsal noradrenergic bundle knife cuts prevented the KA-elicited prefrontal cortical MHPG increase. These data suggest that stimulation of the mesocoeruleo dopaminergic projection arising from the VTA results in selective excitation of the LC-derived dorsal bundle noradrenergic system.

Reconstitution of solubilized serotonin-S2 receptors into phospholipid vesicles

Serotonin-S2 receptors from rat frontal cortex were solubilized using CHAPS/sodium chloride. Reconstitution of the solubilized receptors was achieved by dilution of the soluble preparation, followed by centrifugation to remove the detergent. The receptors were truly reconstituted as judged by sedimentation, increased thermostability and electron microscopy. The reconstituted preparation showed high-affinity binding of [3H]7-aminoketanserin. The binding characteristics resembled those obtained for membrane-bound receptors.

Somatostatin-like immunoreactivity and acetylcholinesterase activities in cerebrospinal fluid of patients with Alzheimer disease and senile dementia of the Alzheimer type

Somatostatin-like immunoreactivity (SLI) and acetylcholinesterase (AchE) activities were measured in the cerebrospinal fluid of 25 patients with senile dementia of the Alzheimer type (SDAT). Both SLI levels and AchE activities were reduced in the CSF of SDAT patients. The SLI levels and AchE activities were not correlated with the duration and the dementia score. However, in two patients the CSF SLI concentration was in agreement with the SLI levels in the frontal cortex obtained by biopsy. Our findings suggest that CSF SLI may be a good index of cortical SLI activities.