TRH and TRH-Like Peptide Levels Co-Vary with Reproductive and Metabolic Rhythms

Photoperiod-synchronized rhythms in non-CSN tissues persist in total darkness. Clock genes involved in maintaining regular biorhythms within the suprachiasmatic nucleus (SCN) of the hypothalamus are expressed in extra-CNS tissues and continue periodic expression in vitro. Understanding the details of how the SCN clock is coupled with peripheral clocks is only incompletely understood and may involve a multiplicity of feedback systems. The present study is an extension of our previous work showing that brain levels of TRH (pGlu-His-Pro-NH₂) and TRH-like peptides (X-TRH: pGlu-X-Pro-NH₂, where "X" can be any amino acid residue) fluctuate throughout the day-night cycle. Male rats were maintained in a stable environment, lights on 6-18 h. TRH and TRH-like peptides in liver, pancreas, testis, prostate, epididymis, and heart were measured at 3, 10, 16, and 22 h. The greatest change in peptide level was a 12-fold increase for TRH in prostate at 16 h relative to the corresponding value at 3 h. The TRH, Tyr-TRH and Phe-TRH levels in liver declined steadily to about 40% of the 3-h values by 22 h. Changes, in the order of decreasing number of significant increases (↑) and/or decreases (↓), were: testis (5↑, 1↓), liver (3↓), epididymis (2↑), prostate (1↑, 1↓) and heart (1↑). Peptide levels in liver and testis correlated with serum leptin and serum corticosterone, respectively, which are potent releasers of these peptides. Testosterone and glucose were also highly correlated. These tripeptides may participate in the regulation of metabolic and reproductive functions, which change during the day-night cycle.

Autochthonous Hookworm-Related Cutaneous Larva Migrans Disease in Northeastern Italy: A Case Report

Here we report the case of a 42-yr-old patient who presented himself to us with a serpiginous erythematous lesion from the wrist of the right forearm up the arm to the right shoulder A similar lesion of a smaller size was also present in the left forearm. On the basis of clinical manifestations and progression of the lesion, combined with previous treatments and different diagnostic investigations, hookworm-related cutaneous larva migrans (HrCLM) disease was hypothesized. Albendazole was employed as treatment and the resolution of the symptoms confirmed the diagnosis. The relevance of the reported case relies on 3 main aspects: the acquisition of the disease in Italy, the initial treatment with topical corticosteroids that sped up the progression of the cutaneous trail, and the uncommon location of the lesions. Furthermore, the anamnestic data and the laboratory/clinical investigations strongly suggested an occupational exposure to the etiological agent. As illustrated here, HrCLM might represent a challenge for Western physicians in terms of diagnosis, treatment, and ways of acquisition. Describing the clinical presentation and the treatment of cases of cutaneous larva migrans might contribute to early and correct diagnosis, to an increase of our knowledge on this disease, and to an update on its epidemiology.

Valproate and copper accelerate TRH-like peptide synthesis in male rat pancreas and reproductive tissues

Treatment with valproate (Valp) facilitates the synthesis of TRH-like peptides (pGlu-X-Pro-NH(2)) in rat brain where "X" can be any amino acid residue. Because high levels of TRH-like peptides occur in the pancreas and pGlu-Glu-Pro-NH(2) (Glu-TRH) has been shown to be a fertilization promoting peptide, we hypothesized that these peptides mediate some of the metabolic and reproductive side effects of Valp. Male WKY rats were treated with Valp acutely (AC), chronically (CHR) or chronically followed by a 2 day withdrawal (WD). AC, CHR and WD treatments significantly altered TRH and/or TRH-like peptide levels in pancreas and reproductive tissues. Glu-TRH was the predominant TRH-like peptide in epididymis, consistent with its fertilization promoting activity. Glu-TRH levels in the epididymis increased 3-fold with AC Valp. Phe-TRH, the most abundant TRH-like peptide in the pancreas, increased 4-fold with AC Valp. Phe-TRH inhibits both basal and TRH-stimulated insulin release. Large dense core vesicles (LDCV's) contain a copper-dependent enzyme responsible for the post-translational processing of precursors of TRH and TRH-like peptides. Copper (500 microM) increased the in vitro C-terminal amidation of TRH-like peptides by 8- and 4-fold during 24 degrees C incubation of homogenates of pancreas and testis, respectively. Valp (7 microM) accelerated 3-fold the processing of TRH and TRH-like peptide precursors in pancreatic LDCV's incubated at 24 degrees C. We conclude that copper, an essential cofactor for TRH and TRH-like peptide biosynthesis that is chelated by Valp, mediates some of the metabolic and reproductive effects of Valp treatment via acceleration of intravesicular synthesis and altered release of these peptides.

Rapid modulation of TRH and TRH-like peptide levels in rat brain and peripheral tissues by corticosterone

Disturbance of glucocorticoid signaling has been implicated in several neuropsychiatric disorders including unipolar and bipolar depression and anxiety induced by maternal deprivation. Antidepressants have been shown to be neuroprotective and able to reverse damage to glia and neurons. Thyrotropin-releasing hormone (TRH) is an endogenous antidepressant that reduces the expression of glycogen synthase kinase-3beta (GSK-3beta), an enzyme that hyperphosphorylates tau and is implicated in bipolar depression, diabetes and Alzheimer's disease. In order to understand the potential role of TRH and TRH-like peptides both as mediators of the depressogenic effects of glucocorticoids and as potential therapeutics for neuropsychiatric disease, 300 g male Sprague-Dawley rats were injected i.p. with 4 mg corticosterone/0.5 ml 50% DMSO+50% ethanol and sacrificed 0, 2, 4 and 8h later. Levels of TRH and TRH-like peptides were measured in various brain regions involved in mood regulation and pancreas and reproductive tissues that mediate the metabolic and reproductive impairments associated with high glucocorticoid levels. Significant increases, ranging from 2- to 12-fold, in TRH or TRH-like peptide levels were observed in almost all brain regions studied at 4h after corticosterone injection. In cerebellum, TRH and TRH-like peptides increased 4-14-fold by 8h. TRH-like peptide levels fell 86-98% at 4h after treatment in testis. TRH, derived only from Leydig cells, was not affected. TRH and TRH-like peptides increased 2-4-fold at 8h in pancreas. TRH and TRH-like peptide concentrations in prostate were not affected by corticosterone up to 8h after injection. The 4h needed to detect a highly significant change in the TRH and TRH-like peptide levels in brain and peripheral tissues is consistent with the mediation of most corticosterone-effects via alterations in gene transcription.

Open, Randomized, Multicentre Italian Trial on Peg-Ifn plus Ribavirin versus Peg-Ifn Monotherapy for Chronic Hepatitis C in HIV-Coinfected Patients on Haart

Background

Chronic hepatitis C is common and aggressive in HIV-positive patients, so the development of a well-tolerated HCV therapy is a priority. We evaluated the efficacy and safety of pegylated interferon α2b (PEG-IFN) plus ribavirin (RBV) versus PEG-IFN monotherapy in HIV/HCV-coinfected patients undergoing highly active antiretroviral therapy (HAART), and analysed the predictive factors of response.

Methods

An Italian, multicentre, open-label trial including 135 coinfected patients, randomized to PEG-IFN 1.5 μg/kg/week plus RBV 400 mg twice daily ( n=69, arm A) or PEG-IFN 1.5 μg/kg/week ( n=66, arm B) for 48 weeks. We assessed the predictive values of early virological response (EVR) at week 8 (HCV-RNA drop >2 log10 compared with baseline or undetectable levels) on sustained virological response (SVR).

Results

Fifty-five patients (28 from arm A and 27 from arm B) completed 48 weeks of therapy. At the end of treatment, 20/28 patients in arm A and 11/27 in arm B had HCV-RNA <50 IU/ml. In a per-protocol analysis, SVR was reached by 54% of patients in arm A (genotype 2–3, 11/16; genotype 1–4, 4/12) and 22% in arm B (genotype 2–3, 3/15; genotype 1–4, 3/12). In an intention-to-treat analysis, the SVR was 22% in arm A (genotype 2–3, 11/32; genotype 1–4, 4/37) versus 9% in arm B (genotype 2–3, 3/32; genotype 1–4, 3/34). The best predictors of SVR were the use of combination therapy, infection with HCV genotype 3 versus genotype 1, and EVR at week 8. Thirty patients (15 from arm A and 15 from arm B) dropped out of the trial prematurely due to side effects. The positive predictive value of EVR at week 8 was 65%, the negative predictive value was 86%.

Conclusions

PEG-IFN plus RBV can be considered a solid option for the treatment of HIV/HCV-coinfected patients. The key to successfully improving efficacy is strong compliance through strict overall patient monitoring, in order to best manage drug toxicity. EVR assessment at week 8 may become a useful stategy in the management of therapy.

Lithium modulates expression of TRH receptors and TRH-related peptides in rat brain

Lithium is an established mood stabilizer and neuroprotective agent frequently used in the treatment of bipolar disorder and as an adjuvant in drug-resistant unipolar depression. The mechanisms underlying both the therapeutic efficacy of lithium and the exacerbation of symptoms following rapid withdrawal are not understood. From previous studies showing antidepressant and neuroprotective activities of thyrotropin releasing hormone (TRH) and TRH-related neuropeptides we hypothesized that lithium may have substantial effects on the expression and secretion of these peptides and/or their receptors in various rat brain regions involved in the regulation of mood. Chronic lithium effect on TRH receptor binding studies: The effect of 1 and 2 weeks of dietary lithium on [(3)H]3-Me-His-TRH binding to plasma membranes of nucleus accumbens, amygdala and pituitary of young adult male Wistar and the endogenously 'depressed' Wistar Kyoto (WKY) rats was measured by the method of Burt and Taylor [Burt, D.R., Taylor, R.L., Endocrinology 106 (1980) 1416-1423]. Acute, chronic and withdrawal effect of lithium on TRH and TRH-like peptide levels in young, adult male Sprague-Dawley rats: Rats were divided into four lithium treatment groups. Control animals received a standard laboratory rodent chow. The acute group received a single i.p. injection of 1.5 milli-equivalents of LiCl 2 h prior to killing. The chronic and withdrawal groups received standard rodent chow containing 1.7 g/kg LiCl for 2 weeks. Withdrawal rats were returned to standard chow 48 h prior to killing while the chronic animals continued on the LiCl diet. TRH, TRH-Gly (pGlu-His-Pro-Gly, a TRH precursor), EEP (pGlu-Glu-Pro-NH(2), a TRH-like peptide with antidepressant activity) and Ps4 (a prepro-TRH-derived TRH-enhancing decapeptide) immunoreactivity (IR) were measured in 13 brain regions. The remaining samples were pooled and fractionated by high-pressure liquid chromatography followed by EEP radioimmunoassay. Chronic lithium treatment increased [(3)H]3Me-TRH binding in the nucleus accumbens and amygdala about two-fold in both Wistar and WKY rats but no change was observed in pituitary binding. The most widespread changes in TRH and TRH-related peptide levels were observed in the withdrawal group compared to the controls. The direction of change for the total IR was consistent for all TRH-IR and TRH-related peptide-IR within a given tissue. For example, withdrawal increased all peptide levels in the pyriform cortex and striatum but decreased these levels in the anterior cingulate and lateral cerebellum. Both acute injection and chronic treatment with LiCl decreased TRH and TRH-related peptide levels in the entorhinal cortex. Acute injection and withdrawal both increased EEP-IR in striatum by more than two-fold. The acute effects are most likely due to changes in the release of these peptides since 2 h is not sufficient time for alterations in peptide biosynthesis. Chronic treatment increased levels of pGlu-Phe-Pro-NH(2) levels in hippocampus, pGlu-Leu-Pro-NH(2), and peak '2' in septum by more than four-fold. The present results are consistent with a component role for TRH and related peptides in the mood-altering effects of lithium administration and withdrawal frequently observed during treatment for depression and bipolar disorder.

Splenic infarct during infectious mononucleosis

We present a case of splenic infarct during infectious mononucleosis in a 17-y-old boy. The patient's condition improved without the need for surgery.

Antidepressant effects of thyrotropin-releasing hormone analogues using a rodent model of depression

The antidepressant potential of two naturally occurring analogues of thyrotropin-releasing hormone (TRH), pGLU-GLU-PRO-NH2 (EEP) and pGLU-PHE-PRO-NH2 (EFP), were examined using a rodent model of antidepressant efficacy. The Porsolt Swim Test was used to assay the antidepressant properties of these two peptides. Both analogues of TRH produced significant antidepressant effects, with EEP producing the stronger response. No effect of EEP upon triiodothyronine (T3) was observed at the dosage used. EFP, which has previously been demonstrated to crossreact with the TRH receptor, significantly increased serum T3. Since an effect upon T3 was only observed in the weaker of the two compounds, these data suggest that the behavioral effect of EEP was not secondary to stimulation of thyroid hormone. Additionally, the differential behavioral response to the two compounds suggests a degree of sequence specificity in the ability of TRH-like tripeptides to produce an antidepressant effect.

Regulation of TRH and TRH-related peptides in rat brain by thyroid and steroid hormones

To investigate the possibility that TRH (pGlu-His-Pro-NH(2)) and EEP (pGlu-Glu-Pro-NH(2)) contribute to the behavioral and mood changes attending hypothyroidism, hyperthyroidism and hypogonadism, we have treated young, adult, male Sprague-Dawley rats (5/group, 250 g bw at time of sacrifice) for one week with either daily ip injections of saline, 5 microg T(4), 3 mg PTU or castration. Immunoreactivity for TRH (TRH-IR), TRH-Gly (pGlu-His-Pro-Gly, a TRH precursor), EEP and Ps4 (prepro-TRH-derived TRH-enhancing peptide) was measured in 8 brain regions by RIA. Castration reduced the Ps4-IR levels in hippocampus by 80%. High pressure liquid chromatography revealed that in many brain regions EEP-IR and TRH-IR consisted of a mixture of TRH and other TRH-like peptides including EEP, Val(2)-TRH, Tyr(2)-TRH, Leu(2)-TRH and Phe(2)-TRH. Transition from the hyperthyroid to the hypothyroid state increased the Val(2)-TRH and Tyr(2)-TRH levels in the accumbens by 10-fold and 15-fold, respectively, and the corresponding ratios for the pyriform cortex increased 9-fold and 12-fold, respectively. Hypothyroidism and castration reduced the levels of TRH and the majority of other TRH-like peptides in the entorhinal cortex. This is the first report that thyroid and steroid hormones alter the levels of TRH, prepro-TRH-derived peptides, and a newly discovered array of TRH-like neuropeptides in limbic brain regions.

Electroconvulsive seizures modulate levels of thyrotropin releasing hormone and related peptides in rat hypothalamus, cingulate and lateral cerebellum

We have studied the neuroanatomic extent of electroconvulsive (ECS)-responsive prepro-TRH and TRH-related gene expression and its possible interaction with forced swimming. Young adult male Wistar rats were treated in a 2x2 Latin square protocol of swimming, no swimming, three daily ECS or sham ECS. Sixteen different brain regions were dissected and immunoreactivity measured for TRH (pGlu-His-Pro-NH(2)); TRH-Gly, a TRH precursor; Ps4, a prepro-TRH-derived TRH-enhancing decapeptide, and EEP (pGlu-Glu-Pro-NH(2)). ECS, in addition to elevating TRH-immunoreactivity (TRH-IR), TRH-Gly-IR, Ps4-IR and EEP-IR levels in the limbic regions, as we have previously reported, also significantly increased Ps4-IR levels in hypothalamus, posterior cingulate and lateral cerebellum, and increased TRH-Gly-IR levels in hypothalamus. Interestingly, the combination of ECS and swimming significantly reduced the levels of TRH-Gly-IR in the anterior cingulate compared to the sham ECS-no swim group. The combined use of high-pressure liquid chromatography and the EEP radioimmunoassay (RIA) revealed that pGlu-Tyr-Pro-NH(2) and/or pGlu-Phe-Pro-NH(2) occur in amygdala, anterior cingulate, frontal cortex, entorhinal cortex, lateral cerebellum and striatum and make a substantial contribution to the EEP-IR and TRH-IR. We conclude that ECS can alter the expression and secretion of TRH-related peptides in the hypothalamus, cingulate and lateral cerebellum. Such effects have not previously been reported in these limbic and extra-limbic regions which are increasingly implicated in the autonomic, behavioral and volitional changes which accompany severe depression and its treatment.

The role of TRH and related peptides in the mechanism of action of ECT

Thyrotropin-releasing hormone (TRH) has been known anecdotally to produce antidepressant (AD) effects since the 1970s. Recent clinical reports have shown that intrathecal administration of TRH can more reliably induce remissions of major depression that last for 2-3 days. Although clinically impractical, it is important to note that these remissions are rapid within hours, and they survive at least 1 night's sleep. This review summarizes and integrates clinical and preclinical research on TRH and related peptides, which have regulatory effects in the limbic forebrain. Electroconvulsive shock (ECS) in rats induces synthesis of TRH in multiple subcortical limbic and frontal cortical regions, which are known, in humans, to be involved in both depression and in sleep. The increases in TRH and related peptides are regionally specific. The quantitative TRH increases in individual limbic regions have been correlated with the amount of forced swimming done by the individual animal after ECS (forced-swim test of AD effects). Intraperitoneal TRH also gives a positive response in this test, as do all effective AD medications. By considering neurobiological phenomena in depression and sleep, it is possible to outline a role for TRH and related peptides that may assist in the understanding both of depression and of the depressogenic effect of sleep in depressively vulnerable people. It is concluded that TRH and related peptides are likely to play a significant role in the inhibition of glutamatergic subcortical limbic neurons, which may be hyperactive in depression. Electroconvulsive therapy is believed to act, in part, by augmenting this inhibition. AD medications are believed to act indirectly, by activation of a subset of GABAergic interneurons, which then inhibit the pathologically hyperactive glutamatergic limbic neurons. Continued exploration of TRH and related peptides will be essential for further progress toward the control of these debilitating and often lethal diseases.

TRH in therapeutic vs. nontherapeutic seizures: affective and motor functions

We have modeled some aspects of electroconvulsive therapy (ECT) in rats. In addition to sham-treated controls, one group received two electroconvulsive (ECS) current-doses at grand mal seizure threshold. Two more groups received three additional ECSs at two higher current-doses. Only the two suprathreshold groups showed significant antidepressant (AD) effects in the forced-swim test, but all three seizure groups showed significant increases in TRH and related peptides in anterior cortex (AC), pyriform cortex (PYR), amygdala/entorhinal cortex (AY), and hippocampus (HC). In motor cortex (MC), TRH appeared to be increased only in the lower dose suprathreshold ECS condition. No condition increased TRH in striatum (STR). These results fell short of directly implicating limbic TRH in AD effects, but in HC, MC, and STR, correlations of peptide levels with individual swim scores raise the possibility that this peptidergic system might be involved in motor as well as affective functions. Other peptides related to TRH might also be implicated in affective regulation and antidepressant effects.

Electroconvulsive seizures increase levels of pGlu-Glu-Pro-NH2 (EEP) in rat brain

We have previously reported that electroconvulsive seizures (ECS) increases the level of prepro-TRH-derived peptides in hippocampus, amygdala and pyriform cortex but not the striatum of male rats and that this increase is significantly correlated with reduced immobility (increased swimming) in the Porsolt forced swim test. An abstract by Mabrouk and Bennett published in 1993 described increased locomotor activity in rats following IP injection of TRH (pGlu-His-Pro-NH2) and EEP (pGlu-Glu-Pro-NH2). We have examined the effect of three daily transcorneal ECS on the levels of EEP in various brain regions and their correlation with results from the Porsolt forced swim test. The EEP level (ng/g wet weight) was measured by RIA in 6 brain regions: amygdala (AY), hippocampus (HC), pyriform cortex (PYR), anterior cortex (AC), striatum (STR) and motor cortex (MC). ECS significantly increased EEP levels in AY, HC and PYR. The increased swim behavior following ECS, as measured in the Porsolt test, correlated significantly with the EEP levels in HC and MC within individual subjects. Intraperitoneal (IP) injection of EEP (1.0 mg/kg) resulted in a rapid and sustained rise in EEP levels throughout the brain and a clearance half-time from blood of 2.0 h. Intracardiac injection of 0.5 mg EEP resulted in a peak EEP level in CSF at 2 h followed by a t1/2 of 0.35 h. A 3 compartment model for EEP transport from blood into CSF and then brain was developed. This model revealed a 1.75 h delay in the transit time of EEP from blood to CSF followed by rapid clearance from the CSF but long retention time within various brain tissues. We conclude that (1) ECS significantly increases EEP levels in limbic regions, but not in striatum, of the rat brain, (2) EEP, like TRH, is a potential mediator of the antidepressant effect of ECS and (3) EEP, after IP or IV administration, is readily taken up by, and has a long residence time in, brain tissue.

A heuristic model of mental depression derived from basic and applied research on thyrotropin-releasing hormone

Recent clinical reports have shown that intrathecal administration of thyrotropin-releasing hormone (TRH) can induce 2 to 3 day remissions of major depression more reliably than i.v. administration. Although clinically impractical, these remissions are rapid, occur within hours, and they survive at least one night's sleep. TRH and related peptides have regulatory effects in the limbic forebrain. Electroconvulsive shock (ECS) in rats induces synthesis of TRH in multiple subcortical limbic and frontal cortical regions, which are known in humans to be involved in both depression and in sleep. The increases in TRH and related peptides are regionally specific. The quantitative TRH increases in individual limbic regions have been correlated with the amount of forced-swimming done by the individual animal after ECS. Intraperitoneal TRH also gives a positive response in this test, as do all effective antidepressants. This article provides a heuristic framework for interdisciplinary neuroscientific study of the interrelated fields of depression and sleep, with a focus on TRH. Preclinical data suggest that glutamatergic, subcortical limbic circuits contain TRH and related peptides as inhibitory cotransmitters that may normally restrain glutamatergic hyperactivity. It is suggested that, in depression, pathologically overdriven glutamatergic circuits escape inhibitory regulation by TRH. This escape is especially pronounced during rapid eye movement (REM) sleep, and these phenomena may explain the prolonged latency of antidepressant treatment.

Electroconvulsive seizures increase levels of PS4, the TRH-enhancing peptide [prepro-TRH(160-169)], in rat brain

We report the development of a radioimmunoassay for prepro-TRH(160-169) (PS4), a thyrotropin-releasing hormone (TRH) enhancing peptide, and its use in characterizing the effect of electroconvulsive seizures on the levels of this peptide in various brain regions of male Wistar rats. We found that electroconvulsive seizures significantly elevated the PS4 levels in hippocampus, amygdala, pyriform (olfactory) cortex, and anterior cortex but not in striatum, motor cortex, locus ceruleus, or ventral lateral medulla. The levels of PS4 were highly correlated with the corresponding TRH (p-Glu-His-Pro-NH2) and TRH-Gly (p-Glu-His-Pro-Gly) levels in hippocampus, amygdala, and pyriform cortex, consistent with the prepro-TRH source of all of these peptides. The PS4 levels in hippocampus and amygdala were significantly correlated with the immobility time in the Porsolt forced swim test, an established animal model for antidepressant effects. The PS4 levels in peripheral blood, hypothalamus, anterior cortex, amygdala, and eyes increased severalfold at 20 min following intracisternal injection of 228 microg of this peptide, suggesting that it readily crosses the blood-brain barrier. The pituitary levels of PS4 and TRH-Gly, on the other hand, were decreased within 20 min by intracisternal PS4, suggesting PS4 stimulated the release of prepro-TRH peptides from the pituitary. Fresh rat and human serum rapidly degraded PS4, indicating that it may act primarily as a paracrine modulator of TRH effects in pituitary, brain, and reproductive system.

TRH gene products are implicated in the antidepressant mechanisms of seizures

1. After a series of electroconvulsive seizures, levels of TRH-Gly (the immediate precursor of TRH) in four limbic regions correlate significantly and highly with increased swimming in the forced-swim test model of antidepressant efficacy. Only in hippocampus did TRH itself correlate with swimming. 2. After ECS, limbic forebrain regions differ in the relationship of TRH to its precursor peptides. This probably results from differences in the coordination of induction of TRH-processing enzymes, as well as differences in the level of prepro-TRH following seizures. 3. Sprague-Dawley rats that are partially kindled with corneal stimulation swim less in the forced-swim test, opposite to the effect seen with antidepressant agents. 4. Pyriform cortex is unique among the four limbic regions examined in showing decreased amounts of the TRH precursor following swim/stress. 5. Combining ECS with the forced-swim test of antidepressant effects creates a useful model for studying the involvement of TRH and its precursor peptides in both the antidepressant and anticonvulsant effects of controlled therapeutic seizures in the treatment of major depressive disorders. Regional differences between the effects of pinnate and corneal ECS on peptides and behavior support the idea that corneal ECS is a better model than pinnate ECS for human bitemporal ECT. 6. Together with recent results in other laboratories, our results suggest that a series of generalized seizures results in prolonged and increased release and action of TRH in limbic forebrain.

Some regional anatomical relationships of TRH to 5-HT in rat limbic forebrain

It is now a recognized principle that various neuropeptides are neuronally co-localized with biogenic amine or aminoacid neurotransmitters. In the rat CNS it has previously been shown that TRH is co-localized with 5-HT (and also with substance P) in cell bodies of the posterior raphe that project to the spinal cord. Although TRH cell bodies are known to be widely distributed throughout the forebrain there is no other known co-localization with 5-HT. In this study we further specify the forebrain there is no other known co-localization with 5-HT. In this study we further specify the anatomical relationship of TRH with 5-HT by use of surgical and neurotoxic lesioning with reference to limbic forebrain regions wherein TRH is greatly increased following seizures. In groups of rats, the fimbria-fornix was lesioned alone, or combined with a lesion of the dorsal perforant path or the ventral perforant path. There was a sham lesioned control group. Additional groups were lesioned with 5,7 dihydroxytryptamine, 100 micrograms i.v.t., 45 min. after i.p. desipramine, 25 mg/kg. All rats were sacrificed three weeks after lesions. Indoleamines were determined by HPLC in left anterior cortex, left pyriform/olfactory cortex, left dorsal hippocampus and left ventral hippocampus. TRH was determined by specific RIA in the corresponding right brain regions. The modal n was 7 rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution of thyrotropin-releasing hormone (TRH) in the hippocampal formation as determined by radioimmunoassay

The distribution of thyrotropin-releasing hormone (TRH) in the hippocampal formation was determined using a radioimmunoassay (RIA) specific for TRH. RIA of hippocampal subregions revealed that the CA3 region of the hippocampal formation contained the highest amount of TRH, followed by intermediate levels in region CA1 and the dentate gyrus. The hilus and subiculum contained the lowest levels. The issue of whether hippocampal TRH is derived from extrinsic and/or intrinsic sources was evaluated by making lesions of the major subcortical afferent to the hippocampus, the fornix pathway. Analysis of the hippocampal formation by RIA revealed that the ventral hippocampus contains higher levels of TRH than the dorsal hippocampus (6.01 +/- 0.62 pg/mg tissue weight vs 1.11 +/- 0.19 pg/mg tissue weight). Lesions of the fornix produced significant decreases in ventral TRH to 52.9% of its control level and in dorsal TRH to 28.8% of its control level. The results from these studies suggest that (1) there is a differential distribution of TRH in the hippocampal formation, (2) the hippocampal formation might be composed of extrinsic and intrinsic sources of TRH, and (3) extrinsic sources of TRH might enter the hippocampus via the fornix pathway. In addition (4) the greater post-lesion decrement in ventral vs dorsal hippocampal TRH suggests that TRH fibers traversing the fornix innervate the ventral hippocampal formation in preference to its dorsal counterpart.

Tetrahydroaminoacridine (THA) as a pharmacological probe in Alzheimer's disease (AD) and other neurodegenerative disorders

Unlike other potent enhancers of cholinergic function in the central nervous system (CNS), THA appears to sustain improved function in many moderately impaired AD patients when the Summers procedure is followed. THA has a complex pharmacology. In addition to its enhancement of cholinergic transmission a hydroxylated metabolite might chelate aluminum (A1), thereby removing multiple toxicological constraints on CNS function. This mobilized THA metabolite-A1 complex might either be re-distributed to less sensitive sites or removed from the CNS across the blood-brain barrier (BBB). Since the known presence of A1 in AD brain is not necessarily causal, a positivistic approach to research and treatment with THA and its metabolites might serve to clarify this difficult and challenging problem.

Tetrahydroaminoacridine blocks potassium channels and inhibits sodium inactivation in Myxicola

In voltage-clamped Myxicola giant axons internally and externally applied tetrahydroaminoacridine (THA) blocked K+ channels with a dissociation constant of 100 microM and slowed their rate of activation. At a concentration of 10 microM, internal THA primarily slowed inactivation of conducting Na+ channels. At 100 microM the decline of the Na+ current during depolarizing pulses was biphasic, with an initial phase 2 to 3 times faster than in control axons. In the presence of THA there was a steady-state inward current accompanied by an increase in amplitude and time constant of Na+ tail currents, as if THA blocked Na+ channels by first entering them and then rendered THA-occluded channels resistant to fast inactivation. THA did not alter activation, prepulse-induced fast inactivation or slow inactivation. The effects of THA on voltage-dependent axonal ion channels might account for central nervous system hyperexcitability seen in some patients treated with THA. Because THA is a potent, centrally active anticholinesterase, even subtle ion channel-directed effects might contribute to its putative antidementia action in clinical states involving a central nervous system deficiency of acetylcholine by selective augmentation of acetylcholine release and/or negation of autoreceptor effects of endogeneous acetylcholine.

The prolonged increase in thyrotropin-releasing hormone in rat limbic forebrain regions following electroconvulsive shock

We have previously demonstrated substantial increases in thyrotropin-releasing hormone (TRH) in specific regions of rat forebrain two days after single or repeated alternate-day electroconvulsive shock (ECS). To determine longer term effects of ECS-induced seizures on forebrain TRH content, we extended the time of the post-ECS observations to 6 and 12 days following 1 (ECS x 1) or 3 (ECS x 3) alternate-day ECS. Previous observations at 2 days post-ECS were confirmed except that hippocampal content of TRH was higher after ECS x 1. In pyriform cortex TRH remained elevated for 6 days after ECS x 1 and 3, and for 12 days after ECS x 3. In hippocampus TRH was elevated for 6 days after ECS x 1 and tended to remain elevated beyond 2 days after ECS x 3. In anterior cortex the increase persisted 6 days after ECS x 1 and 12 days after ECS x 3. These data show that convulsive seizures can induce sustained elevations of TRH beyond 48 h. This finding may be especially important in pyriform cortex and hippocampus where TRH may function as an endogenous anti-epileptic. Our data are also consistent with a possible role for TRH in affective regulation in the hippocampus, amygdala, pyriform and other cortical regions. Moreover, the present results further advance the analogy of the time-course of the TRH changes in rat to the course of the antidepressant response to electroconvulsive treatment in humans.

Effects of ECT given two vs. three times weekly

The benefits and side effects of electroconvulsive therapy (ECT) given two vs. three times per week were examined in depressed inpatients. Twenty subjects were randomly assigned to one of two treatment conditions (unilateral ECT two or three times weekly). Examiners without knowledge of treatment condition rated depression and psychiatric status and administered tests of memory and visual-motor problem solving; subjects also provided self-ratings of depression. Measures were collected before treatment and 2 and 4 weeks after treatment began. Both schedules of treatment produced significant and equivalent improvements in psychiatric symptomatology, but visual memory impairment was significantly lower in the twice-weekly group.

Effects of subconvulsive and repeated electroconvulsive shock on thyrotropin-releasing hormone in rat brain

Male Sprague-Dawley rats were given a single electroconvulsive shock (ECS) on alternate days and sacrificed 48 hrs after 1, 3, or 5 seizures. The content of TRH in hippocampus, pyriform cortex and amygdala was increased 2.5-fold, 5.4-fold and 4.3-fold respectively, 48 hrs. after 3 alternate-day electroconvulsive shocks (ECS) and remained unchanged after 2 additional shocks. Pyriform cortex exhibited a significant intermediate increase (1.7-fold) after only 1 ECS. In a second study, rats were sacrificed 48 hrs after a series of 5 alternate-day ECS vs. subconvulsive shocks (SCS). SCS had no significant effect in these same regions, but was seen to alter TRH in striatum. These results provide an interesting parallel to several aspects of clinical electroconvulsive treatment (ECT) of depression. Together with other findings, these data suggest also, that endogenous TRH may play a role in the modulation of convulsive seizures.

Effect of electroconvulsive shock on the content of thyrotropin-releasing hormone in rat brain

Five grand-mal seizures were electrically induced in rats on alternate days. Forty-eight hours following the last seizure, TRH was quantitated in extracts of anterior cortex, hippocampus, striatum, thalamus plus midbrain, and hypothalamus. When compared to sham treated controls, TRH was found to be elevated 5-fold in the hippocampus and 2-fold in the striatum with no changes observed in the remaining regions. Since the time chosen for analysis excludes acute post-ictal effects, these results draw attention to a prolonged alteration of TRH levels in specific brain regions in an animal model of electroconvulsive treatment.

Comparison of MAO, D beta H, and COMT activities in chronic schizophrenics selected on the basis of nailfold capillary pattern

A group of 17 white male chronic schizophrenic subjects were divided on the basis of plexus visualization score (PVS). High and low PVS subjects were compared to each other and to low PVS controls on measures of platelet monamine oxidase (MAO), rbc catechol-o-methyl transferase (COMT), and plasma dopamine-beta-hydroxylase (D beta H). There were no differences between high and low PVS subjects on any biochemical variable. Schizophrenic subjects had lower platelet MAO activity than controls. Platelet MAO and rbc COMT were significantly correlated in schizophrenic subjects.

Regulation of cyclic adenosine 3',5'-monophosphate levels in guinea-pig cerebral cortex by interaction of alpha adrenergic and adenosine receptor activity

Direct assay of adenosine 3',5'-monophosphate (cyclic AMP) in guinea-pig cerebral cortex in vitro has shown that an alpha adrenergic receptor that was previously found to increase tissue content of cyclic AMP requires the co-presence of adenosine. This alpha adrenergic receptor complex was characterized with blocking agents and contrasted with other activities by examining the effect of other biogenic amines on cyclic AMP content in the presence of adenosine. Phentolamine (but not propranolol) reduced the potentiated response to norepinephrine (NE) (or epinephrine) plus adenosine to the level seen with adenosine alone. Theophylline, an adenosine antagonist, blocked the entire effect of NE plus adenosine. The failure of a high Mg++/Ca++ ratio to block the effect of NE plus adenosine argues against indirect mediation of the alpha receptor effect via the release of K+ or via an unknown neurohumoral agent. The complex variety of potentiative interactions between biogenic amines and adenosine is unique to brain. These interactions may be explained by the proposed existence of both independent and dependent receptors. The dependent receptors respond only to the co-presence of two or more neurohumoral agents. An alternative explanation would involve a compartmentally selective impairment of cyclic AMP degradation.

Separation of adenosine diphosphate--adenosine triphosphate-exchange activity from the cerebral microsomal sodium-plus-potassium ion-stimulated adenosine triphosphatase

1. A microsomal fraction from ox cerebral cortex catalysed [(14)C]ADP-ATP exchange at a speed similar to that at which it liberated P(i) from ATP in the presence of Na(+), K(+) and Mg(2+). 2. Repeated washing the fraction with MgATP solutions solubilized most of the exchange activity and left the adenosine triphosphatase insoluble and little changed in activity. The exchange activity was accompanied by negligible adenosine-triphosphatase activity and was enriched by precipitation at chosen pH and by DEAE-Sephadex. At no stage was its activity affected by Na(+), K(+) or ouabain. 3. The washed microsomal fraction was exposed to a variety of reagents; a sodium iodide-cysteine treatment increased both adenosine-triphosphatase and exchange activities, as also did a synthetic zeolite. Preparations were obtained with exchange activities less than 3% of their Na(+)-plus-K(+)-stimulated adenosine-triphosphatase activity. Some contribution to the residual exchange activity was made by an adenylate kinase. 4. Thus over 95% of the microsomal ADP-ATP-exchange activity does not take part in the Na(+)-plus-K(+)-stimulated adenosine-triphosphatase reaction. Participation of some of the residual 3% of the ADP-ATP-exchange activity has not been excluded, but there appears no firm evidence for its participation in the adenosine triphosphatase; the bearing of this conclusion on mechanisms proposed for the Na(+)-plus-K(+)-stimulated adenosine triphosphatase is indicated.