Psychological and thyroid-stimulating hormone changes after thyrotropin-releasing hormone in normal women: antagonism by pretreatment with thyroid hormones

TRH-like antidepressant peptide, pyroglutamyltyroslyprolineamide, occurs in rat brain

We have previously reported the occurrence of pGlu-Glu-Pro-NH(2)(Glu-TRH, EEP), Val-TRH, Tyr-TRH, Leu-TRH, Phe-TRH, and Trp-TRH in rat brain using a combination of HPLC and radioimmunoassays with antibodies that cross-react with the general structure pGlu-X-Pro-NH(2) where 'X' maybe any amino acid residue (Peptides 2004; 25 : 647). This new family of TRH-like peptides, along with TRH (pGlu-His-Pro-NH(2)), has neuroprotective, anticonvulsant, antidepressant, euphoric, anti-amnesic, and analeptic effects. We now report that a combination of affinity chromatography using a rabbit antibody specific for Tyr-TRH and Phe-TRH, along with HPLC and tandem mass spectrometry operating in the multiple reaction monitoring (MRM) mode, provide conclusive evidence for the presence of Tyr-TRH in rat brain. Furthermore, synthetic Tyr-TRH is active in the Porsolt Swim Test suggesting that it is a fourth member of this family of in vivo neuroregulatory agents that have psychopharmacotherapeutic properties.

Rapid antidepressant response after nocturnal TRH administration in patients with bipolar type I and bipolar type II major depression

BACKGROUND

Thyrotropin-releasing hormone (TRH) is a tripeptide that produces endocrine and behavioral effects in animals and humans. Some studies have shown transient antidepressant activity after morning administration of TRH. We hypothesized that nocturnal administration of TRH, when the circadian sensitivity of the TRH receptor is at its peak, may result in a more robust antidepressant effect.

METHODS

Twenty patients with bipolar (BP) type I or BP type II major depressive episode (MDE) were given nocturnal intravenous TRH 500 microg (n = 10) or saline (n = 10) at midnight in a randomized, double-blind fashion. Antidepressant activity was assessed using the Hamilton Depression Rating (HAM-D), Young Mania Rating (YMR), and Profile of Mood (POMS) scales over a 48-hour period. Thyrotropin (TSH), total T4, and free T3 concentrations were measured before and after TRH administration. Data were analyzed using chi test, Fisher exact test, and repeated-measures ANOVA.

RESULTS

Sixty percent of the TRH group and 10% of the saline group showed a > or =50% reduction in baseline total HAM-D score within 24 hours (P = 0.03). HAM-D ratings fell by an average of 52% after TRH administration versus 12% after saline administration (P = 0.038). There was a modest increase in YMR scores after TRH compared with saline (P < 0.032). No manic or hypomanic episodes were observed. Antidepressant effects of TRH lasted up to 48 hours. There was no correlation between DeltaTSH, DeltaT4, or DeltaT3 measures after TRH (or saline) administration and the change in HAM-D scores.

CONCLUSIONS

Nocturnal TRH administration may produce a rapid antidepressant effect in some patients with BP I and BP II MDE.

Cocaine regulates TRH-related peptides in rat brain

Cocaine administration has previously been reported to alter the levels of prepro-TRH mRNA and TRH (pGlu-His-Pro-NH(2)) in the limbic system of rats (J. Neurochem. 60 (1993) 1151). We have now demonstrated that a previously unrecognized family of TRH-like peptides is involved in the actions of cocaine. We treated young adult male Sprague-Dawley rats (five per group, 250g body weight at sacrifice) for 2 weeks with either twice daily injections of saline (control group), twice daily injections of 15mg/kg cocaine until sacrifice (chronic group), single injection of 15mg/kg cocaine 2h prior to sacrifice (acute group) or chronic cocaine injections replaced by saline injections 72h prior to sacrifice (withdrawal group (WD)). Twelve different brain regions were dissected and immunoreactivity for TRH (TRH-IR), EEP (pGlu-Glu-Pro-NH(2); EEP-IR) and related peptides were measured by radioimmunoassay (RIA). High pressure liquid chromatography (HPLC) revealed that in many brain regions EEP-IR and TRH-IR consisted of a mixture of TRH, and other TRH-like peptides including EEP, pGlu-Val-Pro-NH(2) (Val(2)-TRH), pGlu-Tyr-Pro-NH(2) (Tyr(2)-TRH), pGlu-Leu-Pro-NH(2) (Leu(2)-TRH), and pGlu-Phe-Pro-NH(2) (Phe(2)-TRH). Following i.p. injection, these TRH-like peptides readily crossed the blood-brain barrier but cleared very slowly from brain tissues. Acute cocaine produced a 4.1-fold increase in Val(2)-TRH level in medulla while Val(2)-TRH and Tyr(2)-TRH, increased 6.2- and 2.9-fold, respectively in pyriform cortex PYR. TRH and Leu(2)-TRH, decreased 47 and 93%, respectively in the nucleus accumbens (AM) while other EEP-IR peaks decreased 50-100% consistent with the significant decrease in total EEP-IR in the AMs following acute cocaine treatment. Because 2h is too short a time to alter levels of neuropeptides via changes in the rate of biosynthesis, the acute cocaine-induced elevation or reduction in TRH and related peptides is most likely due to suppression or stimulation, respectively, of the corresponding peptide secretion rate. Because TRH and TRH-like peptides have antidepressant, analeptic and euphorigenic properties, we conclude that these endogenous substances are potential mediators of both the cocaine "high" and withdrawal symptoms.

Acute effects of high-dose thyrotropin releasing hormone infusions in Alzheimer's disease

Thyrotropin releasing hormone (TRH) was administered intravenously to ten patients with Alzheimer's Disease (AD) in a high-dose paradigm, thought to maximize central nervous system effects and potentially produce facilitation of cholinergic function, a known property of the neuropeptide. Acute effects of TRH on behavioral, cognitive and physiologic measures were assessed after patients received 0.1 mg/kg TRH, 0.3 mg/kg TRH and placebo, the higher TRH dose and placebo being given in a randomized, double-blind fashion. Patients showed statistically significant increases in arousal and improvement in affect, as well as a modest improvement in semantic memory, all after receiving the higher TRH dose. Both TRH doses produced transient rises in systolic blood pressure, with no effect on diastolic blood pressure, heart rate or temperature. This study suggests that high-dose TRH can be safely administered to AD patients and is neurobehaviorally active; further studies are needed to determine the extent and mechanism of the cognitive and psychobiological properties of this peptide in AD and other neuropsychiatric disorders.

TRH: behavioral and endocrine effects in man

1. The tripeptide TRH exerts a spectrum of biological activities in both animals and man. Some of these activities have been extensively studied, particularly in psychiatric patients. 2. Behaviorally, TRH appears to increase the sense of well-being, motivation, relaxation, and coping capacity in both normal subjects and patients with psychiatric and neurologic disease. These effects are not disease-specific; attempts to use TRH as a treatment tool have thus been disappointing. 3. Endocrinologically, administration of TRH stimulates the response of TSH; this response has been reported to be blunted in approximately 30% of patients with major depression. However, TSH blunting is not specific for depression, it has also been observed in a variety of other psychiatric conditions. 4. The relevance of these effects for psychiatry in general, and for psychoneuroendocrinology especially, is discussed in this review.

Improvement in ratings of tension after TRH administration in healthy women

Administration of thyrotropin releasing hormone (TRH), 400 micrograms i.v., to healthy premenopausal women resulted in improvement in ratings of tension on the 100 mm line test. The max. mean improvement in tension ratings was significantly greater after TRH than after saline (t = 2.27, df = 9, p less than 0.05); after TRH administration, eight of 10 subjects showed greater than 30% improvement in tension ratings, while only three of 10 subjects receiving saline reported a comparable degree of improvement. No significant improvement in ratings of mood state were noted after administration of either TRH or saline. These findings extend previous reports of behavioral effects of TRH in normal subjects. The possibility that the behavioral effects of TRH may be influenced by the state of activity of the CNS is discussed.

Endocrine and behavioral changes in depression after thyrotropin-releasing hormone (TRH). Alteration by pretreatment with thyroid hormones

The effects of pretreatment with a single dose of thyroid hormones (TH) on the subsequent endocrine and behavioral response to TRH was evaluated in unipolar depressed women. TH pretreatment altered neither serum levels of thyroid hormones nor the TRH-induced TSH response. It antagonized, however, the behavioral response to TRH. This was apparent in 2 self-assessment scales but not in an objective rating scale. Taken together the data suggest that (a) there is an impaired pituitary response to TH feedback in depressed patients; (b) TH pretreatment may affect self-assessment of behavioral effects of TRH in depression.