Changes in body temperature after administration of amino acids, peptides, dopamine, neuroleptics and related agents

The open field assay is influenced by room temperature and by drugs that affect core body temperature

Background

The open field assay is used to study anxiety-related traits and anxiolytic drugs in rodents. This assay entails measuring locomotor activity and time spent in the center of a chamber that is maintained at ambient room temperature. However, the ambient temperature in most laboratories varies daily and seasonally and can differ between buildings. We sought to evaluate how varying ambient temperature and core body temperature (CBT) affected open field locomotor activity and center time of male wild-type (WT, C57BL/6) and Transient Receptor Potential Subfamily M Member 8 ( Trpm8) knock-out ( Trpm8 -/- ) mice. TRPM8 is an ion channel that detects cool temperatures and is activated by icilin.

Methods

Mice were placed in the open field at 4°C and 23°C for 1 hour. Distance traveled and time spent in the center were measured. Mice were injected with icilin, M8-B, diazepam, or saline, and changes in activity level were recorded.

Results

The cooling agent icilin increased CBT and profoundly reduced distance traveled and center time of WT mice relative to controls. Likewise, cooling the ambient temperature to 4°C reduced distance traveled and center time of WT mice relative to Trpm8 -/- mice. Conversely, the TRPM8 antagonist (M8-B) reduced CBT and increased distance traveled and center time of WT mice when tested at 4°C. The TRPM8 antagonist (M8-B) had no effect on CBT or open field behavior of Trpm8 -/- mice. The anxiolytic diazepam reduced CBT in WT and Trpm8 -/- mice. When tested at 4°C, diazepam increased distance traveled and center time in WT mice but did not alter open field behavior of Trpm8 -/- mice.

Conclusions

Environmental temperature and drugs that affect CBT can influence locomotor behavior and center time in the open field assay, highlighting temperature (ambient and core) as sources of environmental and physiologic variability in this commonly used behavioral assay.

Short-term effects of temperature-related indices on emergency ambulance dispatches due to mental and behavioral disorders in Shenzhen, China

Introduction

The precise associations between temperature-related indices and mental and behavioral disorders (MBDs) have yet to be fully elucidated. Our study aims to ascertain the most effective temperature-related index and assess its immediate impact on emergency ambulance dispatches (EADs) due to MBDs in Shenzhen, China.

Methods

EADs data and meteorological data from January 1, 2013, to December 31, 2020, in Shenzhen were collected. Distributed lag non-linear models (DLNMs) were utilized to examine the non-linear and lagged effects of temperature-related indices on EADs due to MBDs. The Quasi Akaike Information criterion (QAIC) was used to determine the optimal index after standardizing temperature-related indices. After adjusting for confounding factors in the model, we estimated the immediate and cumulative effects of temperature on EADs due to MBDs.

Results

The analysis of short-term temperature effects on EADs due to MBDs revealed Humidex as the most suitable index. Referring to the optimal Humidex (3.2th percentile, 12.00°C), we observed a significant effect of Humidex over the threshold (34.6th percentile, 26.80°C) on EADs due to MBDs at lag 0-5. The cumulative relative risks for high temperature (90th percentile, 41.90°C) and extreme high temperature (99th percentile, 44.20°C) at lag 0-5 were 1.318 (95% CI: 1.159-1.499) and 1.338 (95% CI: 1.153-1.553), respectively. No significant cold effect was observed on EADs due to MBDs.

Conclusion

High Humidex was associated with more EADs due to MBDs in subtropical regions. Health authorities should implement effective measures to raise public awareness of risks related to high temperature and protect vulnerable populations.

Behavioral and Pharmacokinetics Studies of N-Methyl-2-Aminoindane (NM2AI) in Mice: An Aminoindane Briefly Used in the Illicit Drug Market

Drug forums are considered as the main platform sources that have contributed to the increase in NPS popularity, especially for those not yet known to law enforcement and therefore not yet illegal. An example is the new synthetic stimulant NM2AI, which has a very short history of human use and abuse. Little is known regarding this compound, but some information from internet forums and the scientific literature indicates NM2AI as a structural derivate of MDAI, which is known for its entactogenic activity. Indeed, the purpose of this study is to evaluate, for the first time, the in vivo acute effect induced by the intraperitoneal injection of NM2AI (1-10-30-100 mg/kg) in mice. We demonstrate the sensory (by visual placing and object tests) and physiological (core temperature measurement) function variations, nociceptor (by tail pinch test) and strength (grip test) alterations, and sensorimotor (time on rod and mobility) decrease. Moreover, we verify the mild hallucinogenic effect of NM2AI (by startle/prepulse inhibition test). Lastly, we perform a pharmacokinetic study on mice blood samples, highlighting that the main active metabolite of NM2AI is 2-aminoindane (2AI). Taken together, our data confirm the suspected entactogenic activity of NM2AI; however, these in vivo effects appear atypical and less intense with respect to those induced by the classic stimulants, in surprising analogy with what is reported by networked users.

Schizophrenia and Infections: The Eyes Have It

The visual tract is prominently involved in schizophrenia, as evidenced by perceptual distortions and a type of nystagmus found in many individuals affected. Genetic explanations for these abnormalities have been suggested. This study proposes an alternate explanation based on infection. Several infectious agents thought to be associated with some cases of schizophrenia are known to cause both infection of the fetus and abnormalities of the eye. Toxoplasma gondii is examined in detail, and rubella, cytomegalovirus, varicella-zoster virus, and herpes simplex virus more briefly. Careful ophthalmic assessments, including funduscopy and direct examination of tissues for infectious agents, will clarify the role of such agents in ocular aspects of schizophrenia.

Heat stroke during long-term clozapine treatment: should we be concerned about hot weather?

OBJECTIVE

To describe the case of a patient with schizophrenia on clozapine treatment who had an episode of heat stroke.

CASE DESCRIPTION

During a heat wave in January and February 2014, a patient with schizophrenia who was on treatment with clozapine was initially referred for differential diagnose between systemic infection and neuroleptic malignant syndrome, but was finally diagnosed with heat stroke and treated with control of body temperature and hydration.

COMMENTS

This report aims to alert clinicians take this condition into consideration among other differential diagnoses, especially nowadays with the rise in global temperatures, and to highlight the need for accurate diagnosis of clinical events during pharmacological intervention, in order to improve treatment decisions and outcomes.

Using thermographic cameras to investigate eye temperature and clinical severity in depression

Previous studies suggest that altered corneal temperature may be a feature of schizophrenia, but the association between major depressive disorder (MDD) and corneal temperature has yet to be assessed. The aim of this study is to investigate whether eye temperature is different among MDD patients than among healthy individuals. We used a thermographic camera to measure and compare the temperature profile across the corneas of 16 patients with MDD and 16 age- and sex-matched healthy subjects. We found that the average corneal temperature between the two groups did not differ statistically, although clinical severity correlated positively with right corneal temperature. Corneal temperature may be an indicator of clinical severity in psychiatric disorders, including depression.

What about temperature? Haloperidol-induced hypotermia

The use of treatment with antipsychotic drugs highlights the difficulty of finding the right balance between the benefit on psychotic symptoms and the risk of the occurrence of adverse reactions. There is a strong genetic and pharmacological evidence supporting the hypothesis that activation of D2 receptors could lead to hypothermia and that the treatment haloperidol is capable of inducing hypothermia apomorfino similarily in laboratory animals. It also seems that, haloperidol is not the only antipsychotic able to determine this type of reaction, as some evidence suggests that other drugs such as reserpine, chlorpromazine would be capable of inducing hypothermia. Finally, while some studies suggest the possible occurrence of haloperidol-induced hypothermia only in laboratory animals, other authors argue that this same reaction can occur in humans as well. In this report, we describe the cases, rarely witnessed in the literature, of three patients in whom the administration of haloperidol caused hypothermia.

Altered thermoregulation in ambulatory schizophrenia patients: a naturalistic study

BACKGROUND

Schizophrenia patients may exhibit alterations in core/body temperature. Hence, we intended to examine the potential existence of thermoregulatory abnormalities in ambulatory schizophrenia patients.

METHODS

Anonymous electronic patient record data of the Leumit Health Fund (Israel) were screened for all schizophrenia patients who have no other apparent chronic co-morbidity (mental or non-mental) and had their oral temperature assessed during routine follow-ups (Schiz-rFUs) or for various transitory infectious/inflammatory processes (Schiz-Infect) during the years 1999-2005 (n = 535). The comparison group consisted of a comparable sample (n = 560) of healthy subjects (Control-rFUs and Control-Infect).

RESULTS

The sub-group of Schiz-rFUs (n = 216) exhibited significantly lower mean oral temperature compared to the matched group of Control-rFUs (n = 140) (36.72 +/- 0.54 vs. 36.94 +/- 0.64C, respectively; P<0.05). There was no significant difference in mean oral temperatures between the Schiz-Infect (n = 319) and the Control-Infect (n = 420) (37.32 +/- 0.92 vs. 37.28 +/- 0.98C, respectively; NS).

CONCLUSIONS

Ambulatory schizophrenia patients without a concomitant infectious/inflammatory process exhibit altered thermoregulation manifested by a substantial (about 0.2 C) and significantly lower oral temperature compared to healthy comparison subjects as well as a potential exaggerated increase in oral temperature during transitory infectious/inflammatory processes. The relevance of these phenomena to the pathophysiology of schizophrenia as well as the potential immune-mediated pathologies in schizophrenia merit further investigation.

The effect of changes in core body temperature on the QT interval in beagle dogs: a previously ignored phenomenon, with a method for correction

Background and purpose:

Body core temperature (Tc) changes affect the QT interval, but correction for this has not been systematically investigated. It may be important to correct QT intervals for drug-induced changes in Tc.

Experimental approach:

Anaesthetized beagle dogs were artificially cooled (34.2 °C) or warmed (42.1 °C). The relationship between corrected QT intervals (QTcV; QT interval corrected according to the Van de Water formula) and Tc was analysed. This relationship was also examined in conscious dogs where Tc was increased by exercise.

Key results:

When QTcV intervals were plotted against changes in Tc, linear correlations were observed in all individual dogs. The slopes did not significantly differ between cooling (−14.85±2.08) or heating (−13.12±3.46) protocols. We propose a correction formula to compensate for the influence of Tc changes and standardize the QTcV duration to 37.5 °C: QTcVcT (QTcV corrected for changes in core temperature)=QTcV–14 (37.5 – Tc). Furthermore, cooled dogs were re-warmed (from 34.2 to 40.0 °C) and marked QTcV shortening (−29%) was induced. After Tc correction, using the above formula, this decrease was abolished. In these re-warmed dogs, we observed significant increases in T-wave amplitude and in serum [K⁺] levels. No arrhythmias or increase in pro-arrhythmic biomarkers were observed. In exercising dogs, the above formula completely compensated QTcV for the temperature increase.

Conclusions and implications:

This study shows the importance of correcting QTcV intervals for changes in Tc, to avoid misleading interpretations of apparent QTcV interval changes. We recommend that all ICH S7A, conscious animal safety studies should routinely measure core body temperature and correct QTcV appropriately, if body temperature and heart rate changes are observed.

Baseline temperature in an animal model of schizophrenia: long-term effects of perinatal phencyclidine administration

Phencyclidine (PCP), a dissociative anaesthetic, acts as a noncompetitive N-methyl-d-aspartate (NMDA) receptor antagonist. PCP is a psychostimulant capable of producing both positive and negative symptoms of schizophrenia, including cognitive dysfunction in normal humans. Perinatal phencyclidine administration to rats has been widely accepted as an animal model of schizophrenia. It has been known for a long time that schizophrenia patients may develop various thermoregulatory disturbances. The aim of this study was to assess the acute effects of phencyclidine administration on the temperature of newborn rats, the long-term effects on the baseline temperature of perinatal phencyclidine administration and the effects of a PCP challenge on the temperature of adult perinatally treated rats. The animals were treated on the 2nd, 6th, 9th and 12th postnatal (PN) days with either phencyclidine (10 mg/kg) or saline. The interscapular skin temperature was measured during the first 40 postnatal days and subsequently the colonic temperature until PN day 62. The immediate effect of phencyclidine administration to pups was a significant decrease of the body temperature, while the application of PCP to adult rats perinatally treated with either saline or PCP caused a significant increase of the baseline temperature. Perinatal phencyclidine administration to rat pups produced a long lasting effect on the baseline temperature. It can be concluded that the nature of the response to acute phencyclidine administration differs between newborn and adult rats. Further experiments are necessary in order to clarify the role of specific neurotransmitter systems in the changes of temperature regulation provoked by phencyclidine administration.

Thyronamines inhibit plasma membrane and vesicular monoamine transport

Thyroid hormone has long been known to have important transcriptional regulatory activities. Recently, however, the presence of endogenous derivatives of thyroid hormone, thyronamines, has been reported in various mammalian tissues. These derivatives have potent in vitro activity with a class of orphan G-protein-coupled receptors, the trace amine-associated receptors, and profound in vivo effects when administered to mice. We report here a novel neuromodulatory role for thyronamines. In synaptosomal preparations and heterologous expression systems, thyronamines act as specific dopamine and norepinephrine reuptake inhibitors. Thyronamines also inhibit the transport of monoamines into synaptic vesicles. These observations expand the nontranscriptional role of thyroid hormone derivatives and may help to explain the pharmacological effects of thyronamines in vivo.

Differential sensitivity to neurotensin-induced hypothermia, but not analgesia, in Fischer and Lewis rats

Neurotensin (NT) produces behavioral and physiological effects, including analgesia and hypotheria, when administered into the CNS. Fischer and Lewis rats exhibit differential behavioral responses to central NT receptor activation. To further characterize these differences, we assessed central NT-induced analgesia and hypothermia in independent groups of rats from each strain. Fischer and Lewis rats showed a similar dose-orderly analgesic response in a hot-plate test. Such an isosensitivity was not observed for NT-induced hypothermia. Although NT produced a dose-orderly decrease in mean rectal temperature in both strains, the magnitude of the hypothermic response was significantly smaller in Fischer than in Lewis rats. These findings provide further evidence of genetic differences in central neurotensinergeric neurotransmission in these two strains.

Influence of the hypothalamus on the midbrain tonic inhibitory mechanism on metabolic heat production in rats

Influence of the hypothalamus on increased body temperature was examined in male rats. Body temperature was increased by removing the midbrain tonic inhibitory mechanism (TIM) on heat production from brown adipose tissue (BAT) by microinjections of a local anesthetic, procaine, into the midbrain. Procaine microinjections in unanesthetized rats increased rectal temperature that was followed by a strong tail skin temperature rise. Procaine microinjections in unanesthetized and decerebrated rats also increased rectal temperature but without skin temperature rise. These decerebrated animals fatally developed hyperthermia. In anesthetized rats, procaine microinjections increased temperature of the interscapular BAT (IBAT) higher with shorter onset for temperature rise than rectal temperature. Increased IBAT temperature by procaine microinjections in anesthetized rats was attenuated during hypothalamic warming, and enhanced during hypothalamic cooling when compared with that observed during thermoneutral hypothalamic temperature. These results suggest that the midbrain TIM is able to function in unanesthetized conscious rats, and that the integrity of the midbrain mechanism to tonically inhibit metabolic heat production does not require the presence of intact hypothalamus. These results also suggest that the hypothalamus modulates directly or indirectly IBAT heat production that was induced by removal of the midbrain TIM.

CYP2D6 HhaI genotype and the neuroleptic malignant syndrome

To investigate the relationship between CYP2D6 genotypes (reported to be associated with the susceptibilities to Parkinson's disease and multisystem atrophy) and the possible susceptibility to neuroleptic malignant syndrome (NMS) and subacute myelo-optico-neuropathy (SMON), we analyzed the CYP2D6 gene by polymerase chain reaction and restriction fragment length polymorphism in Japanese schizophrenia patients with a history of NMS. There was no significant difference in the frequency of the poor metabolizer genotype of CYP2D6 between the cases with a history of NMS and controls (p > 0.05). The frequency of the mutation located at the HhaI site in exon 6 of CYP2D6 in the cases was higher, but not significantly (p > 0.05; the mutated allele frequency was 0.25), than that in the controls, schizophrenia patients without NMS (0.11) and healthy controls (0.09). The frequency (0.10) of the HhaI mutation type in patients with a diagnosis of SMON was also not significantly higher than in healthy controls. These results suggest that the poor metabolizer and HhaI polymorphism of CYP2D6 may not be a useful molecular marker for predicting the onset of NMS and SMON.

Disruption of temporo-entorhinal connections abolishes recognition memory-enhancing effect of angiotensins in rats

In our laboratory, the positive influence of angiotensin II and its 3-7 fragment on learning and memory processes was found to be mediated by excitatory amino acids, because it was abolished by N-methyl-D-aspartate (NMDA) receptor antagonists. The purpose of the present study was to investigate whether bilateral disruption of glutamatergic temporo-entorhinal connections may have an influence on the facilitatory effect of both angiotensin peptides on recognition memory. The bilateral transections of temporo-entorhinal connections were made in 32 male rats 10 days before testing the effect of intracerebroventricular AII or AII(3-7) injection on the recognition of objects evaluated in an object-recognition test. Thirty additional rats served as sham-operated controls. The final analysis was based on 29 lesioned and 26 sham-operated animals. AII and its 3-7 fragment significantly improved object recognition in the sham-operated groups of rats. Bilateral disruption of temporo-entorhinal connections totally abolished the facilitatory effect of both angiotensins on object recognition. Moreover, bilateral disruption of temporo-entorhinal connections significantly attenuated crossings of squares and rearings, without affecting bar approaches and defecation evaluated in an open-field test. These results may suggest that the facilitatory recognition memory effect of AII and AII(3-7) requires a reciprocal glutamatergic connection between the lateral entorhinal cortex and the temporal cortex.

6-OHDA lesions to the central amygdala abolish angiotensins facilitation of object recognition in rats

1. We have previously reported that the dopaminergic projection from A10 ventral tegmental neurons and A9 neurons of substantia nigra to the central amygdala (CA) is, in part, responsible for the facilitatory effect of angiotensin II (AII) and its 3-7 fragment [AII(3-7)] on the retrieval of information in memory that is motivated affectively. 2. In this study, the influence of both angiotensins, given intracerebroventricularly at the dose of 1 nmol each in rats lesioned with 6-OHDA to CA, on recognition memory, was tested. 3. AII and its 3-7 fragment significantly improved object recognition in sham-operated groups of rats. Bilateral 6-OHDA lesions to CA totally abolished the facilitatory effect of both angiotensins on object recognition. As insignificant increase of spontaneous locomotor activity in rats lesioned to CA did not interfere with the cognitive effect of AII and AII(3-7). 4. These results suggest that the dopaminergic projection at the CA takes part in the facilitatory effect of angiotensins on recognition memory.

Postischemic hypothermia. A critical appraisal with implications for clinical treatment

The use of hypothermia to mitigate cerebral ischemic injury is not new. From early studies, it has been clear that cooling is remarkably neuroprotective when applied during global or focal ischemia. In contrast, the value of postischemic cooling is typically viewed with skepticism because of early clinical difficulties and conflicting animal data. However, more recent rodent experiments have shown that a protracted reduction in temperature of only a few degrees Celsius can provide sustained behavioral and histological neuroprotection. Conversely, brief or very mild hypothermia may only delay neuronal damage. Accordingly, protracted hypothermia of 32-34 degrees C may be beneficial following acute clinical stroke. A thorough mechanistic understanding of postischemic hypothermia would lead to a more selective and effective therapy. Unfortunately, few studies have investigated the mechanisms by which postischemic cooling conveys its beneficial effect. The purpose of this article is to evaluate critically the effects of postischemic temperature changes with a comparison to some current drug therapies. This article will stimulate new research into the mechanisms of lengthy postischemic hypothermia and its potential as a therapy for stroke patients.

Protective efficacy of a hypothermic pharmacological agent in gerbil forebrain ischemia

BACKGROUND AND PURPOSE

The novel muscarinic cholinergic partial agonist U-80816E was tested in the gerbil brief bilateral carotid occlusion ischemia model based on the rationale that the compound's hypothermic properties might afford effective protection of the selectively vulnerable hippocampal CA1 region.

METHODS

Male gerbils were subjected to either 10 or 15 minutes of bilateral carotid occlusion, followed by histopathological assessment of the CA1 neuronal survival 7 days later.

RESULTS

In saline-treated animals, 10 minutes of bilateral carotid occlusion resulted in a 30.5% loss of CA1 neurons, whereas a 15-minute insult resulted in a 49.6% loss. Administration of U-80816E (6 mg/kg i.p. 30 minutes before bilateral carotid occlusion and again 2 hours after reperfusion) resulted in a significant protective effect of the CA1 neuronal population with either duration of ischemia; neuronal loss was reduced to 12.6% in the milder model (p < 0.05 versus saline-treated) and 24.9% in the more severe model (p < 0.04 versus saline). However, the 6 mg/kg i.p. dose of U-80816E was found to produce a 1.0 degree C decrease in brain temperature (measured with a tympanic temperature probe) at 10 minutes of ischemia compared with that of saline-treated gerbils. At 10 minutes of reperfusion, after the 10-minute episode of ischemia, the brain temperature of the U-80816E-treated gerbils was 2.2 degrees C lower than that of saline-treated animals. When the U-80816E-treated gerbils were subjected to either 10 or 15 minutes of ischemia but placed in a heated chamber that prevented the hypothermic effects, no cerebroprotection was observed.

CONCLUSIONS

These results show that the anti-ischemic efficacy of U-80816E is mediated through its hypothermic properties, thus suggesting the feasibility of pharmacologically induced hypothermia as a cerebroprotective approach.

Thermal biology of the laboratory rat

The purpose of this paper is to thoroughly review the literature and present a data base of the basic thermoregulatory parameters of the laboratory rat. This review surveys the pertinent papers dealing with various aspects of the thermal biology of the laboratory rat, including: metabolism, thermoneutrality, core and brain temperature, thermal tolerance, thermal conductance and insulation, thermoregulatory effectors (i.e., thermogenesis, peripheral vasomotor tone, evaporation, and behavior), thermal acclimation, growth and reproduction, ontogeny, aging, motor activity and exercise, circadian rhythm and sleep, gender differences, and other parameters. It is shown that many facets of the thermoregulatory system of the laboratory rat are typical to that of most homeothermic species. However, is several instances the rat exhibits unique thermoregulatory responses which are not comparable to other species.

Influence of two beta-adrenoceptor antagonists, propranolol and pindolol, on cold adaptation in the rat

1. Adult male rats were treated with propranolol (2.0 mg kg-1 day-1 i.p.), pindolol (0.2 mg kg-1 day-1 i.p.) or 0.9% NaCl day-1 i.p. and exposed to +4 degrees C for 42 days, or treated with 0.9% NaCl day-1 i.p. and kept at +23 degrees C for 42 days. They were weighed once a week, when a 24 h urine sample was also collected and colon temperature measured. 2. Urinary noradrenaline (NA), adrenaline (Ad) and dopamine were analysed by high-performance liquid chromatography with an electrochemical detector. After the acclimatization period the interscapular brown adipose tissue was excised and weighed and the activity of the oxidative enzymes succinate dehydrogenase and cytochrome oxidase measured. 3. The pindolol-treated and propranolol-treated rats gained weight during the cold-acclimatization period. The amount of interscapular brown adipose tissue increased in the cold, but the increase was lowest in the pindolol-treated group. No changes were seen in the other brown adipose tissue parameters in cold-exposed animals. The excretion of catecholamines followed the same pattern in all three cold-exposed groups, with an initial rise in noradrenaline and adrenaline excretion and a slight rise in dopamine excretion. 4. The results suggest possible connections between beta-adrenoceptor antagonists, weight gain and cold acclimatization. Pindolol had a slight inhibitory effect on cold-induced brown adipose tissue hypertrophy in rats.

Reduction in opioid and non-opioid forms of swim analgesia by 5-HT2 receptor antagonists

Acute exposure to continuous (CCWS) or intermittent (ICWS) cold-water swims elicits non-opioid and opioid forms of analgesia respectively. Intrathecal administration of methysergide blocks ICWS, but not CCWS analgesia. The present study evaluated the role of serotonin (5-HT) receptor subtypes in the mediation of CCWS and ICWS analgesia on the tail-flick and jump tests following administration of methysergide, a non-specific 5-HT antagonist and pirenpirone and ketanserin, two 5-HT2 receptor subtype antagonists. Systemic methysergide was more effective in reducing CCWS analgesia (50-58%, 0.1-1.0 mg/kg) than ICWS analgesia (21%, 5 mg/kg) on both pain tests. Systemic pirenpirone (0.04-0.2 mg/kg) and ketanserin (1-5 mg/kg) were also more effective in reducing CCWS analgesia (43-57%) on both tests than ICWS analgesia (pirenpirone: 0.4 mg/kg, 34%; ketanserin: 5 mg/kg, 21%) on the tail-flick test. Indeed, both 5-HT2 receptor antagonists potentiated ICWS analgesia on the jump test. While serotonin antagonist effects upon hypothermia could not account for CCWS analgesia effects, similar potentiations in ICWS analgesia and hypothermia were observed following pirenpirone and ketanserin. Finally, both 5-HT2 receptor antagonists differentially reduced CCWS hypothermia and potentiated ICWS hypothermia. These data suggest differential serotonergic modulation of the two forms of swim analgesia with opioid-mediated ICWS analgesia acting through spinal 5-HT1 receptors and non-opioid-mediated CCWS analgesia acting through supraspinal 5-HT2 receptors.

Comparison of the effects of the acute administration of dexoxadrol, levoxadrol, MK-801 and phencyclidine on body temperature in the rat

Some of the dioxolanes produce pharmacological effects that have much in common with phencyclidine and phencyclidine-like drugs. Dioxadrol can be resolved into two enantiomers, dexoxadrol and levoxadrol. Dexoxadrol has an affinity for phencyclidine receptors that is much greater than that of levoxadrol, but dexoxadrol and levoxadrol have nearly equal affinities for sigma receptors. The systematic analysis of the relative potencies of dexoxadrol and levoxadrol can be used as an approach to define effects mediated by phencyclidine vs sigma receptors. Compounds that act on phencyclidine receptors, as well as affecting behavior, alter body temperature in the rat. The purpose of the present study was to compare and contrast the effects of the acute administration of dexoxadrol, levoxadrol, MK-801 and phencyclidine on body temperature in the rat. Dexoxadrol and levoxadrol (5.0, 10.0, 20.0 or 40.0 mg/kg), MK-801 (0.12, 0.6 or 1.2 mg/kg) or phencyclidine (5.0, 10.0 or 20.0 mg/kg) were administered subcutaneously and body temperature was measured. Both dexoxadrol and MK-801 produced hyperthermia but levoxadrol did not affect body temperature. In contrast to the hyperthermic effects of dexoxadrol and MK-801, phencyclidine produced hypothermia. These findings indicate that hypothermia induced by phencyclidine is not due to interactions with phencyclidine receptors and, while dexoxadrol, MK-801 and phencyclidine may share some similar receptor binding and behavioral characteristics, they can be differentiated on the basis of their effects on body temperature.

Metaphit antagonizes phencyclidine-induced hypothermia in the rat

The acute administration of phencyclidine (PCP) causes hypothermia in the rat. Metaphit (1-[1-(3-isothiocyanatophenyl)cyclohexyl]-piperidine) is a derivative of PCP that has been shown to irreversibly acylate PCP receptors in vitro and in vivo and can antagonize the behavioral and electrophysiological effects of PCP in the rat. The purpose of the present study was to determine whether pretreatment with metaphit can block the hypothermic effects of PCP in the rat. Metaphit or PCP (1.0 mumol/rat) were injected into the lateral ventricles of rats, and 24 hr later the subjects were challenged with PCP (20.0 mg/kg s.c.). Pretreatment with metaphit blocked PCP-induced hypothermia; however, pretreatment with PCP did not affect the subsequent hypothermic response to PCP. These results indicate that the antagonism of PCP-induced hypothermia by metaphit was a specific effect and not due to PCP receptor desensitization.

Effects of D1 and D2 antagonists on basal and apomorphine decreased body temperature in mice and rats

In these experiments representative selective antagonists at D1 (SCH 23390) and D2 (haloperidol) receptors were studied for their effects on basal and apomorphine decreased body temperature in mice and rats. In mice, SCH 23390 (up to 3 mg/kg SC) neither affected basal body temperature nor blocked apomorphine-induced hypothermia (AIH). On the other hand, haloperidol alone was hypothermic and paradoxically also blocked AIH in mice. In rats, SCH 23390 alone produced hyperthermia; the mechanism by which this occurred is not known. SCH 23390 also blocked AIH in rats. However, the inhibition of AIH only occurred at doses of SCH 23390 that were themselves hyperthermic. Haloperidol did not alter basal body temperature but did block AIH in rats. These data suggest that apomorphine-induced body temperature changes are D2 mediated.

In vivo receptor binding, neurochemical and functional studies with the dopamine D-1 receptor antagonist SCH23390

A series of in vivo experiments were undertaken, relating functional (motor activity, body temperature), dopamine (DA) receptor binding and neurochemical (catecholamine synthesis and utilization, DA release) aspects of the pharmacology of SCH23390 in the rat. The compound inhibited the locomotor hyperactivity, but not the hypothermia, induced by the potent DA stimulant DP-5,6-ADTN. Interstingly, SCH23390 simultaneously failed to displace DP-5,6-ADTN from its binding sites in the rat striatum--used as a direct in vivo biochemical index of DA (D-2) receptor interaction. The spontaneous locomotion in non-pretreated rats was likewise inhibited by SCH23390. The locomotor-suppressive action, but not the DP-5,6-ADTN-displacing capacity of the D-2 blocker haloperidol was significantly enhanced by SCH23390, suggesting that motility can be suppressed by either enhanced D-1 or D-2 (postsynaptic) receptor blockade, but also that the D-1 and D-2 sites involved may be physically distinct. SCH23390 only slightly altered in vivo neurochemical of DA synthesis, release and nerve-impulse flow, indicating that, while similar in suppressing dopaminergic behaviour, the D-1 antagonist is less effective than traditional neuroleptics as an activator of DA neuronal feedback mechanisms. The weak increases of DA synthesis and release nonetheless obtained were equal in magnitude (30-40%) in the limbic vs. striatal brain areas; also in this respect, SCH23390 thus differs from classical neuroleptics, which generally display more marked effects in the striatum than in limbic tissue. No major changes in the in vivo indices of NA synthesis and utilization (or in 5-HT synthesis) were found after SCH23390 administration, by and large supporting the DA receptor specificity of the compound. In summary, the studies demonstrated that SCH23390 can offset and accentuate, respectively, behavioural consequences of D-2 receptor stimulation and blockade. Importantly, at the same time no direct interaction at the level of D-2 DA receptor sites in the striatum was detected. Only slight, D-2 antagonist-like, changes in neurochemical indices of dopaminergic activity were observed after D-1 receptor blockade by means of SCH23390. With regard to DA agonist hypothermia, SCH23390 was without effect per se, but (at a high dose) attenuated the action of the D-2 antagonist haloperidol. The observations may indicate that the complex interactions between central D-1 and D-2 receptor-controlled mechanisms that influence behaviour, neurochemistry, and possibly autonomic nervous expression, are not identical.

Apomorphine-induced hypothermia increases during ethanol withdrawal

Changes in several measures of dopamine function have been observed following acute or chronic ethanol exposure. The present study examined the effects of chronic ethanol exposure on the hypothermia following acute administration of the dopamine agonist apomorphine. Animals withdrawn from chronic ethanol exposure showed a significantly greater decrease in body temperature following apomorphine than did ethanol-naive controls, suggesting an increase in sensitivity to dopaminergic stimulation during ethanol withdrawal.

Interaction between clozapine and a lipophilic alpha 1-adrenergic agonist

Acute intraperitoneal injection of clozapine produced marked hypothermia and ataxia in Swiss-Webster mice. These two effects were almost completely blocked by the lipophilic alpha 1-adrenergic agonist, St 587, but not by the peripherally-acting alpha 1 agonist methoxamine. It was inferred that these effects of clozapine are central in origin and probably resulted from alpha 1 adrenergic blockade. However, since prazosin, a selective alpha 1-adrenergic antagonist did not elicit either hypothermia or ataxia in mice it became clear that the alpha 1 adrenergic blocking effect of clozapine is not entirely responsible for these effects, but has a major contributory role in their production. Both clozapine and prazosin inhibited the d-amphetamine-induced locomotor stimulation in mice. St 587 did not significantly reduce this amphetamine-blocking effect of clozapine. It was inferred that this response to d-amphetamine involving the release of mesolimbic dopamine is distinct from the other two St 587-sensitive responses. The hypothermic and ataxic effects of clozapine developed complete tolerance after just four days of treatment, but ten days of such treatment was required for the development of tolerance to the amphetamine-blocking effect of clozapine. The possible relationships between St 587-sensitive and insensitive effects of clozapine and its antipsychotic property are discussed.

Chlordecone-induced effects on thermoregulatory processes in the rat

To investigate the mechanism(s) involved in chlordecone (CLD)-induced hypothermia, we examined colonic (Tcol) and tail skin (Tsk) temperatures, preferred ambient temperature (Ta), evaporative water loss, and metabolic rate following CLD exposure in the rat. Single ip dosages (0, 50, and 75 mg/kg) in corn oil were administered to Fischer-344 rats. At a Ta of 22.5 degrees C, Tcol was reduced by 50 and 75 mg/kg as early as 0.5 hr, and this effect persisted for 4 hr after dosing. Tcol was increased 24 hr after both CLD dosages. Tsk was elevated 2, 3, 4, and 6 hr after 75 mg/kg and 2 hr after 50 mg/kg. At Ta of 30.5 degrees C, Tcol was decreased at early exposure times after both dosages and was increased 3, 4, and 6 hr after 75 mg/kg. At 10.0 degrees C, an enhanced hypothermia was observed 1-6 hr following 50 and 75 mg/kg CLD. The preferred Ta was significantly decreased by approximately equal to 2.8 degrees C following CLD exposure while activity within the temperature gradient was unchanged. At 25.0 degrees C, evaporative water loss was decreased while metabolic rate was not affected by CLD administration. To study the enhanced hypothermia at 10.0 degrees C, metabolic rate was measured continuously for 2 hr following 75 mg/kg CLD and found to be significantly different from controls. The intensified hypothermia in the cold may be due to the inability of the CLD-treated rat to stimulate metabolic thermogenesis in response to cold in addition to the loss of body heat following cutaneous vasodilation. These data suggest that CLD-induced hypothermia at a neutral Ta is associated with cutaneous vasodilation and not with a decreased metabolic rate or increased evaporative water loss.

Behavioural and electrocortical changes induced by muscimol in rats withdrawn from chronic treatment with diazepam

In rats withdrawn from a chronic treatment with diazepam, the effects of muscimol, given into the III cerebral ventricle, on behaviour and spectrum power of activity in the electrocorticogram (ECoG) were studied. In comparison to control rats which received only muscimol, in rats pretreated with diazepam (1 mg/kg/day for 30 consecutive days) the behavioural and ECoG effects of muscimol were significantly reduced or abolished. In fact, in rats pretreated with diazepam a small dose (50 ng) of muscimol did not affect behaviour or ECoG activity, in contrast to control animals in which the same dose produced, after a period of locomotor stimulation and ECoG desynchronization, typical and long-lasting behavioural sedation or sleep accompanied by a significant increase in total voltage power and in the lower frequency bands in the ECoG. In addition, larger doses (100 and 200 ng) of muscimol, which in control rats produced a typical biphasic pattern of ECoG and behavioural changes, i.e. an initial period of ECoG desynchronization and behavioural stimulation, followed by a second period of behavioural and ECoG sleep, in animals pretreated with diazepam, produced only an increase in total voltage power and in the lower frequency bands in the ECoG resembling the effects of the smaller (50 ng) dose. The present experiments suggest that, after chronic stimulation of benzodiazepine receptors a decrease in sensitivity of receptors for gamma-aminobutyric acid (GABA) occurs, since the effects of muscimol on behaviour and spectrum power were significantly reduced or abolished.

Neuroleptic-induced hypothermia in mice: lack of evidence for a central mechanism

The present study investigated the ability of neuroleptic drugs to induce hypothermia in mice when they were administered intraperitoneally (i.p.) or intracerebroventricularly (i.c.v.). Twelve neuroleptics belonging to five chemical classes including phenothiazines, butyrophenones, benzamides, thioxanthenes and diphenylbutylpiperidines were injected i.p. All of them, except benzamides, induced a dose-dependent decrease in rectal temperature. Neuroleptics were administered i.c.v. via cannulae previously implanted in mice to determine whether this response might have a central origin. None of the drugs tested induced hypothermia at doses which did not produce toxic effects. These negative results suggest that neuroleptics act to elicit hypothermia via a peripheral, rather than a central mechanism. Since some neuroleptics possess alpha-adrenolytic properties which could induce hypothermia by promoting vasodilatation, we attempted to antagonize the hypothermia produced by peripheral administration of two neuroleptics with phenylephrine, an alpha-adrenoceptor agonist that does not cross the blood-brain barrier. The hypothermia induced by both chlorpromazine and haloperidol was attenuated by phenylephrine, supporting the view that peripheral alpha-adrenoceptors may mediate neuroleptic-induced hypothermia.

Changes in body temperature after administration of antipyretics, LSD, delta 9-THC and related agents: II

Antipyretics, in particular acetaminophen, aspirin and ibuprofen, constitute the single most important class of drugs used therapeutically for an effect on body temperature. Hallucinogens exert prominent actions on the central nervous system, and it is not surprising that, like so many other centrally-acting agents, they too often affect temperature. This compilation primarily covers the considerable amount of data published from 1981 through 1985 on the interactions of these drugs and thermoregulation, but data from many earlier papers not included in a previous compilation are also tabulated. The effects of agents not classically considered as antipyretics on temperatures of febrile subjects are also covered. The information listed includes the species used, the route of administration and dose of drug, the environmental temperature at which experiments were performed, the number of tests, the direction and magnitude of change in body temperature and remarks on special conditions, such as age or brain lesions. Also indicated is the influence of other drugs, such as antagonists, on the response to the primary agent.

Sodium selenite-induced hypothermia in mice: indirect evidence for a neural effect

The effect of sodium selenite (SS) on the body temperature of adult male ICR mice was examined. SS (10-60 mumol/kg) administered subcutaneously resulted in a transient and dose-dependent hypothermia at ambient temperatures (Ta) of 20 and 30 degrees C. Reduced oxygen consumption accompanied the changes in body temperature. In addition, SS-treated mice exhibited transient cold-seeking behavior in the thermogradient. This SS-induced hypothermia was very similar to those induced by ethanol, tetrahydrocannabinol, triethyltin, sulfolane, and chlordimeform in that these all were transient, dependent on Ta, and not counteracted by behavioral thermoregulation. From these results, involvement of neural afferent or integral pathways is suggested. Further, acute mortality of SS-injected mice was enhanced with the elevation of Ta, as in the case of the chemicals mentioned above. Considering the diverse chemical and pharmacological properties of these chemicals, these results may suggest a possible interrelation between the hypothermic response and the modification of toxicity.

Different roles of intrahypothalamic and nigrostriatal dopaminergic systems in thermoregulatory responses of the rat

Classically, two neurotransmitters in the brain have been implicated in thermoregulation: 5-hydroxytryptamine and norepinephrine. A dopamine action is less well-known and usually has been studied by means of pharmacological rather than physiological procedures. In the present work using a physiological approach to the problem, the role of different central dopaminergic systems in the thermoregulatory response of rats exposed to cold (4 degrees C) or warm (45 degrees C) environments has been studied. Rostral incertohypothalamic neurons in the medial preoptic area synthesized and released more dopamine in response to a warm but not to a cold environment. On the other hand DA and DOPAC levels in nigrostriatal systems were decreased by cold but not warm environments. The dopaminergic neurons projecting to nucleus accumbens or hypothalamus do not appear to be related to the thermoregulatory response in the rat.

Differential effects of amphetamine and related compounds on locomotor activity and metabolic rate in mice

Locomotor activity was measured by photobeam interruptions, and metabolic rate by the production of CO2 (as minute volume expired CO2, or VECO2) in mice. d-Amphetamine (0.3 to 10 mg/kg IP) increased locomotor activity in a dose-dependent manner while suppressing VECO2 over the same 72-min test period, compared to saline-injected controls. This phenomenon of divergent effects on locomotor activity and metabolic rate required central stimulation, as neither ammonium sulfate nor p-hydroxyamphetamine suppressed VECO2. Oxygen consumption was also suppressed by d-amphetamine, indicating that the suppression of VECO2 involved more than a change in respiratory quotient. When baseline activity rates were increased with running wheels, VECO2 and activity were both suppressed by d-amphetamine; VECO2 was suppressed by d-amphetamine more in exercising mice than in sedentary mice. Anorexigenic agents phenmetrazine, aminoxaphen, and fenfluramine, when administered in doses equimolar to maximally effective doses of d-amphetamine, did not consistently affect activity or VECO2. Evidence for mediation of the VECO2 response by corticosterone and endogenous opioid peptides was negative. Further work, with other mediators of the stress response, or with more complete dose-effect studies with anorexigenic compounds, may be necessary to explicate the mechanism of this counter-intuitive divergence of two measures of activity in mice.

Changes in body temperature after administration of adrenergic and serotonergic agents and related drugs including antidepressants: II

This survey continues a second series of compilations of data regarding changes in body temperature induced by drugs and related agents. The information listed includes the species used, the route of administration and dose of drug, the environmental temperature at which experiments were performed, the number of tests, the direction and magnitude of change in body temperature and remarks on the presence of special conditions, such as age or brain lesions. Also indicated is the influence of other drugs, such as antagonists, on the response to the primary agent. Most of the papers were published from 1980 to 1984 but data from many earlier papers are also tabulated.

Hyperthermic effect of neurotensin in the rabbit

Neurotensin injected into the anterior hypothalamus of the rabbit induces a consistent upward shift of the threshold core temperatures for inducing cold thermogenesis, peripheral vasomotor tone and respiratory evaporative heat loss, while leaving the efficiency and the intensity of these thermoregulatory outputs unchanged. Neurotensin injections into the PH are without effect on body temperature control. The effect of neurotensin is interpreted as a selective inhibition of activity of warm sensors in the anterior hypothalamus. The possible mediating role of dopaminergic pathways in the neurotensin action is discussed.

Dopamine and thermoregulation: an evaluation with special reference to dopaminergic pathways

The complex role of dopamine (DA) in the diencephalic mechanisms involved in the control of body temperature is reviewed and evaluated. In the context of the monoamine theory of thermoregulation, catecholaminergic synapses in the anterior hypothalamic pre-optic area, are proposed mediate the pathways in the brain-stem which subserve heat dissipation. Within this theoretical framework, hypothalamic DA is considered to underlie a portion of the functional component of the heat loss system. This deduction is based on pharmacological studies in which both the catecholamine and receptor antagonists have been infused directly into the hypothalamus. In view of the action of DA applied to the substantia nigra and other subcortical structures, the unique anatomical circuitry of the central dopaminergic projections has also been analyzed in terms of specific connections within critical morphological regions related to thermal functions. In particular, the nigro-striatal pathway could be involved in the mediation of one or more of the different aspects of the thermoregulatory system integrating both autonomic and behavioral responses. Finally, an anatomical schema which portrays the suggested mechanisms of DA activity is presented.

Interleukin 1 reduces opioid binding in guinea pig brain

Interleukin 1 (IL1) is a macrophage-derived polypeptide which signals neurons in the preoptic-anterior hypothalamus to initiate fever and the acute-phase glycoprotein response. Recently, increases in cerebrospinal fluid and hypothalamic levels of beta-endorphin have been reported during endotoxin (LPS)- and IL1-induced fevers, suggesting that this opioid may participate in the modulation of IL1 effects in the CNS. In this study, we investigated whether purified (human) IL1 influences the specific binding of three prototypic opioid agonists (2-D-alanine-5-L-methionineamide, DAME; (-)-ethylketocyclazocine, EKC; dihydromorphine, DHM) and one antagonist (naloxone) to opioid receptor-enriched membrane preparations in cerebral cortex, hypothalamus, midbrain, pons, medulla, and cerebellum of guinea pig brain. IL1 reduced the binding of these ligands to their receptors during a 30-min incubation. The extent of IL1 inhibition of a given ligand for its binding sites varied according to the brain region; within some regions, the extent of this inhibition also varied with the four ligands tested. But in cortex the effect of IL1 on the specific binding of DHM is dose-dependent. Similar results were obtained with crude homologous IL1. S. enteritidis endotoxin, suspended in pyrogen-free saline at concentrations from 4 to 36 micrograms/ml, did not inhibit the binding of these opioid ligands to their receptors in any brain region. These results indicate that IL1 interacts with the opiate receptors in guinea pig brain. This interaction, moreover, is not limited to the hypothalamus alone, the primary site of the pyrogenic action of IL1, but also occurs in other brain regions.

Comparison of the action of prostaglandin with endotoxin on thermoregulatory response thresholds

Prostaglandin E2 (PGE2) and lipopolysaccharide (LPS) derived from E. coli were injected into the lateral cerebral ventricle of rabbits at 30 degrees C ambient temperature. The threshold core temperatures for ear cutaneous vasoconstriction (Thv) and shivering (Thsh) were determined by whole-body cooling with an intestinal thermode. Each threshold, as determined at the plateau phase of LPS fever and PGE2 hyperthermia respectively, were compared with the control values before LPS and PGE2 injection. Thsh was not changed by the injection of LPS, while Thv was increased. After PGE2 injection both Thsh and Thv were increased in comparison to their control levels. These changes paralleled the elevation of core temperature. The present study does not exclude prostaglandins as humoral mediators involved in some of the central processes generating fever, but suggest at the same time that there are additional properties of LPS fever for which prostaglandins do not account.

Changes in body temperature after administration of acetylcholine, histamine, morphine, prostaglandins and related agents: II

This survey continues a second series of compilations of data regarding changes in body temperature induced by drugs and related agents. The information listed includes the species used, the route of administration and dose of drug, the environmental temperature at which experiments were performed, the number of tests, the direction and magnitude of change in body temperature and remarks on the presence of special conditions, such as age or brain lesions. Also indicated is the influence of other drugs, such as antagonists, on the response to the primary agent. Most of the papers were published since 1979, but data from many earlier papers are also tabulated.

Neurotransmitter effects on body temperature are modified with increasing age

This study reports effects on body temperature, in two different age groups of Sprague Dawley rats, of intracerebroventricular (ICV) administration of prostaglandin E2, noradrenaline, serotonin, dopamine, and carbachol. Young animals (3-5 months) developed fevers in response to administration of prostaglandin E2 (+ 1.02 +/- 0.26 degrees C), while no significant changes in colonic temperature were observed in the older (15-18 months) group of rats. Noradrenaline (10.0 micrograms), caused a decrease in colonic temperature in the younger group of animals (-2.02 +/- 0.70 degrees C), but had no significant effects on the body temperature of the older group. Similarly, differences between the temperature responses of the young as compared with the older group of animals were observed following ICV administration of carbachol, dopamine and serotonin. These data suggest that the roles of these substances in the hypothalamic control of body temperature may be modified with increasing age.