Expression of nerve growth factor, brain-derived neurotrophic factor, and neurotrophin-3 in the somatosensory cortex of the mature rat: coexpression with high-affinity neurotrophin receptors

Neurotrophins, including nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3), are critical for the maintenance and plasticity of central nervous system (CNS) neurons. We tested the hypothesis that cortical neurons participate in redundant autocrine/paracrine systems. Three sets of studies determined the distribution of NGF-, BDNF-, and NT-3-expressing neurons, the frequency of neurons coexpressing NGF and BDNF, and the frequency of neurons expressing a neurotrophin and its associated high-affinity receptor. The distribution of NGF-, BDNF, and NT-3-immunoreactive neurons was identical. Neurotrophin-positive cells were parceled throughout the cortex, although the labeling frequency was not the same in all layers. More than 30% of the neurons in layers II/III, V, and VI were labeled, whereas only 5-10% of the neurons in layer IV was immunopositive for a neurotrophin. Some glia were also neurotrophin positive, particularly BDNF-positive glia. About 70% of the neurons in layers II/III and V coexpressed NGF and BDNF or coexpressed NGF and NT-3. Ligand-receptor colabeling was also common among cortical neurons. For example, nearly 70% of the NGF-, BDNF-, and NT-3-positive neurons in layer V colabeled with their respective high-affinity receptors, i.e., trkA, trkB, and trkC, respectively. Thus, (a) neurons express multiple neurotrophins and (b) cortical neurons (e.g., layer V neurons) contain the components required for autocrine/paracrine and/or anterograde communication (e.g., neurons in layer II/III support layer V neurons). These systems mean that the cortex is capable of regulating itself autonomously.

CRH challenge test in anxious depression

Recently, renewed interest has developed in the concept of anxious depression. Using an operational definition of "anxious depression" based on the SADS interview, 25 patients with major depressive disorder were separated into anxious (n = 14) and nonanxious (n = 11) subtypes. These two patient groups and normal control subjects received an intravenous corticotropin-releasing hormone challenge test. Adrenocorticotropic hormone (ACTH) and cortisol responses were compared among the three groups. Patients with anxious depression had significant attenuation of ACTH response when compared to nonanxious patients and normal control subjects.

Expression of nerve growth factor, p75, and trk in the somatosensory and motor cortices of mature rats: evidence for local trophic support circuits

Neurotrophins such as nerve growth factor (NGF) are critical for the maintenance of CNS neurons. We determined the expression of NGF and the neurotrophin receptors p75 and trk in the somatosensory and motor cortices of mature rats with immunohistochemical techniques. Sections of mature rat cortex were processed immunohistochemically with primary antibodies directed against NGF, p75, or trk. The distribution of immunoreactive elements was examined, and stereological techniques were used to determine the density and size of immunoreactive cell bodies. Some sections processed for trk immunoreactivity were examined with an electron microscope. From the size and morphology of the labeled cells, it appeared that only neurons in the gray matter were NGF-positive. NGF was detected in one-third of the neurons in layers II-III, V, and VI of both somatosensory cortex and motor cortex; however, fewer than 1 in 12 of the layer IV neurons was NGF-positive. With the notable exception of layer V, few cell bodies (2-10% of the total population) were p75- or trk-immunoreactive. Layer Vb was replete with receptor-positive cell bodies; more than one-third of the layer Vb neurons were p75- or trk-positive. All labeled cells appeared to be pyramidal neurons. The distribution of p75 labeling with the two anti-p75 antibodies was indistinguishable. In addition, the neuropil in the supragranular laminae was p75- or trk-positive. Electron microscopy showed that trk immunoreactivity was also expressed by dendrites. Only rarely were immunoreactive axons detected. In summary, NGF is expressed by cortical neurons throughout cortex, and neurotrophin receptors are widely produced by postsynaptic targets. Thus, NGF appears to participate in an intracortical autoregulatory system. The strong expression of neurotrophin receptors by pyramidal neurons in layer Vb (the origin of brainstem and spinal cord projections) suggests that the neurotrophins are especially critical for the regulation of corticofugal projection systems.

Elevated cerebrospinal fluid protein in men with unipolar or bipolar depression

We studied a large sample of rigorously diagnosed, generally unmedicated patients with major depressive disorder (n = 179), bipolar affective disorder (n = 102), or schizophrenia (n = 125) to determine if increased cerebrospinal fluid (CSF) protein is associated with a particular diagnosis or gender. Men had a higher mean CSF protein level than women across all diagnoses (p < 0.001). There were no differences across diagnosis among the female patients. Men with unipolar depression had a higher mean CSF protein content than other male patients (n = 0.029), but depressed bipolar males had an equivalently elevated mean level. Considered apart from unipolar or bipolar diagnosis, the depressive syndrome was strongly associated with increased CSF protein in men (p = 0.004); again, there was no difference across type of illness (depression versus mania) among women. Elevated CSF protein content seems to be associated with illness syndrome rather than diagnosis, and may represent an important finding among men with depression.

Pituitary-adrenal axis response to arginine vasopressin in patients with major depression

Arginine vasopressin (AVP) was administered to 21 patients with major depression and 20 normal control subjects. Thirty-two subjects also underwent an overnight dexamethasone suppression test. The patient group did not differ significantly from the control group in adrenocorticotropic hormone (ACTH) or cortisol response. Dexamethasone suppression status did not affect ACTH or cortisol response. This study supports the hypothesis that unlike the response to corticotropin releasing hormone, the ACTH response to AVP is not attenuated in depression.

Blunted ACTH response to hypoglycemic stress in depressed patients but not in patients with schizophrenia

In this study, 7 hospitalized patients with major depression (MD), 5 hospitalized patients with schizophrenia (S), and 13 control subjects (C) were administered 0.15 units/kg of regular insulin at 1600 h by intravenous bolus infusion. ACTH, cortisol, and glucose levels were measured intermittently for 2h following infusion. Baseline ACTH, cortisol and glucose levels were similar in Cs, MDs, and Ss. The mean glucose nadir was equivalent for Cs, patients with MD, and patients with S. Patients with MD had a blunted ACTH response (F = 3.28; df = 12,126; p = .0004) and cortisol response (F = 4.20; df = 12,132; p = .0001) to hypoglycemia when compared to Cs and patients with S. Carroll Depression Rating Scale scores in patients with S (23 +/- 10) were similar to patients with MD (30 +/- 8) and significantly higher than in controls (1 +/- 2) (F = 55.2; df = 2.22; p = .0001). These findings suggest that patients with MD show different ACTH and cortisol responses to hypoglycemic stress which are not explained by negative feedback of baseline ACTH or cortisol, glucose nadir, or the number of depressive symptoms per se.

ras isoprenylation is required for ras-induced but not for NGF-induced neuronal differentiation of PC12 cells

We have used compactin, an inhibitor of mevalonate biosynthesis, to block p21ras posttranslational modification and membrane association in PC12 cells. Previous studies have demonstrated a requirement for isoprenylation for mitogenic effects of activated p21ras in mammalian cells and for function of RAS gene products in yeast. Immunoprecipitation of [35S]methionine-labeled p21ras from PC12 cell homogenates confirmed that the processed p21ras species is missing from compactin-treated PC12 cells. Immunoprecipitation from particulate and cytosolic fractions of PC12 cells confirmed that compactin blocks p21ras membrane association: p21ras is confined to the cytosol fraction. Induction of neuronal differentiation and ornithine decarboxylase (ODCase) transcription by oncogenic p21N-ras does not occur in compactin-treated cells indicating that activity of oncogenic p21N-ras expressed in PC12 cells is abolished by compactin treatment. Thus, p21ras isoprenylation or association with the membrane appears to be required for early responses and neuronal differentiation attributable to p21ras activation. In contrast, blockade of p21ras isoprenylation and membrane association by compactin treatment did not significantly reduce PC12 cell responses to NGF. Responses examined included rapid phosphorylation of tyrosine hydroxylase, rapid induction of ODCase expression, survival in serum-free medium and neuronal differentiation. Compactin blocked growth factor-induced rapid changes in cell surface morphology but did so whether this response was induced by NGF or by EGF. These results indicate that functional p21ras is not necessary for responses to NGF which in turn implies that if a ras-dependent NGF signal transduction pathway exists, as has been previously suggested, at least one additional ras-independent pathway must also be present.

Elevated CSF protein in male patients with depression

Elevation of total protein is the most frequent pathologic finding in the cerebrospinal fluid (CSF) examination. It occurs in a variety of situations, such as inflammation or tumors of the central nervous system (CNS), degenerative disorders, and subarachnoid hemorrhage, or as a result of traumatic taps. It has also been reported, for unknown reasons, in patients with psychiatric disease. In a study of hormone changes in depression, 9 of 24 (38%) patients (13 male, 11 female) were found to have elevated CSF protein levels (greater than 45 mg/dl), whereas no elevations were found in healthy controls (8 male, 9 female). Eight of the patients with the elevated CSF protein levels were male (62%) and one was female (9%). Depressed patients had significantly higher CSF protein levels (44.7 +/- 18.0 mg/dl) than controls (31.5 +/- 6.0 mg/dl) (t = 3.32, df = 30.37, p = 0.002). No relationship was found between CSF protein levels and (1) the use of medication (tricyclic antidepressants, lithium carbonate, or monoamine oxidase inhibitors) or (2) post-dexamethasone suppression test cortisol levels. Female controls, however, tended to have lower protein levels than male controls, whereas female patients had significantly lower levels than male patients. Protein electrophoresis was performed on 21 of the 41 subjects (13 patients, 8 controls). Male patients had nonsignificantly higher absolute concentrations of CSF albumin and the globulin fractions when compared to male controls. These differences in CSF protein do not suggest monoclonal CSF protein production, nor are they the result of this elevated peripheral protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Simulated acute hemorrhage through lower body negative pressure as an activator of the hypothalamic-pituitary-adrenal axis

While insulin induced hypoglycemia is the principle method of producing hypothalamic-pituitary-adrenal stress response, the mechanism by which this occurs may be different from that produced by other stressors. In a pilot study, we explored ways to standardize lower body negative pressure (LBNP), as a simulator of hemorrhage, to determine its utility for future studies of hypothalamic-pituitary-adrenal (HPA) axis function. Reduced atmospheric pressure of -40 mmHg applied at the level of the iliac crests during LBNP rapidly lowers blood pressure in most subjects, simulating acute hemorrhage. In 6 normal subjects, ACTH and cortisol values were measured before, during and after the application LBNP at 0800, 1600 and 2300 hours in the baseline state and at 1600 hours on the day following 1 mg of dexamethasone. Peak ACTH values of 60-250 pg/ml occurred 2 to 10 minutes after the cessation of the stimulus in subjects experiencing presyncope or having a systolic or diastolic blood pressure decrease of greater than 20 mmHg with a rise in pulse of 30 beats per minute or more. There was no significant difference between ACTH responses at different times of day. Peak cortisol values of 25-30 micrograms/dl occurred 15-20 minutes after cessation of the stimulus. In all subjects, administration of dexamethasone greatly attenuated the ACTH response and decreased but did not ablate the cortisol response. In conclusion, these data indicate that LBNP may be used to simulate hemorrhage as a stimulus of the HPA axis. HPA axis changes occur only when physiologic evidence of hypovolemic stress is present. Dexamethasone may be used to modulate the response to this stress paradigm.

The urban epidemic of phencyclidine (PCP) use: clinical and laboratory evidence from a public psychiatric hospital emergency service

Routine blood samples of 145 consecutive patients seen in the Los Angeles County Psychiatric Hospital Emergency Room during a 48-hour weekday period in June 1979 were examined for phencyclidine (PCP) using a sensitive and specific gas capillary gas chromatographic nitrogen detector (GC2-N) method. Of these 145 samples 63 (43.4%) were positive and PCP levels ranged 0.34 to 142.9 nanograms/ml (mean 14.6 ng/ml +/- 3.4 S.E.M.). An analysis of the records of these 63 patients revealed a wide variety of psychotic clinical pictures resembling mania, depression or schizophrenia with relatively few of the supposedly characteristic manifestations of PCP intoxication. Each of the 63 patients had at least one manifestation of toxic psychosis and/or acute delirium, in addition to the florid symptoms characteristic of functional states. PCP measurement, pharmacokinetics and the possible relationships of this intoxication to the psychiatric manifestations are discussed.

Suicide among U.S. women physicians, 1967-1972

The authors examined AMA records of the deaths of 751 women physicians during 1967-1972. Forty-nine (6.56%) committed suicide. The suicide rate for women physicians (40.7 per 100,000 per year) was higher than for men physicians and about four times that for white American women of the same age. From the known morbid risk for suicide among women with primary affective disorder, the authors calculated that about 65% of American women physicians have primary affective disorder.