Differential effects of psychotropic drugs on feeding in rats: is histamine blockade involved?

A case of insulinoma misidentified as schizophrenia due to its manifestation in neuropsychiatric symptoms

Insulinomas can present with neuroglycopenic symptoms suggesting neuropsychiatric disorders, delaying diagnosis and treatment. We recently treated a 65-year-old woman with insulinoma who was misdiagnosed at her nearby psychiatric clinic as having schizophrenia because of personality changes and memory impairment; she was treated with brexpiprazole, which was discontinued due to persistence of the symptoms. Despite her relatively low casual plasma glucose (70 mg/dL), the physician at the psychiatric clinic did not investigate the possibility of hypoglycemia, partly because her HbA1c level (5.2%) was within normal range. After skipping lunch one day, she was found by her family to be unable to communicate properly. She was transported to the emergency room of our hospital, where intermittently scanning continuous glucose monitoring (isCGM) use permitted detection of the hypoglycemia and led to a diagnosis of insulinoma and successful resection. A 72-h fasting test established hyperinsulinemic hypoglycemia. Contrast-enhanced computed-tomography and endoscopic ultrasonography together with selective arterial calcium stimulation test revealed an insulin-secreting tumor in the tail of the pancreas. Surgical resection of the tumor corrected her glucose and insulin levels as well as eliminated the insulinoma neuropsychiatric symptoms. Pathological examination showed that the tumor was positive for chromogranin A, synaptophysin and insulin. It is, therefore, important for physicians to be aware that insulinomas can manifest as neuroglycopenic symptoms and to consider the possibility of hypoglycemia by careful medical interview and isCGM, especially when patients suspected of psychiatric disorders do not show the expected response to antipsychotic drugs.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13340-024-00722-9.

The Diverse Network of Brain Histamine in Feeding: Dissect its Functions in a Circuit-Specific Way

Feeding is an intrinsic and important behavior regulated by complex molecular, cellular and circuit-level mechanisms, one of which is the brain histaminergic network. In the past decades, many studies have provided a foundation of knowledge about the relationship between feeding and histamine receptors, which are deemed to have therapeutic potential but are not successful in treating feeding- related diseases. Indeed, the histaminergic circuits underlying feeding are poorly understood and characterized. This review describes current knowledge of histamine in feeding at the receptor level. Further, we provide insight into putative histamine-involved feeding circuits based on the classic feeding circuits. Understanding the histaminergic network in a circuit-specific way may be therapeutically relevant for increasing the drug specificity and precise treatment in feeding-related diseases.

Small-intestinal necrosis due to non-occlusive mesenteric ischemia with diabetic ketoacidosis after quetiapine treatment

We report a 66-year-old male who developed diabetic ketoacidosis (DKA) and necrosis of the small intestine due to non-occlusive mesenteric ischemia (NOMI), 3 months after starting quetiapine treatment. He was transferred to our hospital and diagnosed as diabetic for the first time, associated with DKA. Despite improvement in DKA, abdominal pain worsened gradually 10 h after hospitalization. Computed tomography (CT) revealed bowel emphysema, and gas out of the gut wall, in the mesenteric veins and the intrahepatic portal vein, suggesting intestinal necrosis. He survived because of resection of necrotic small-intestinal tissue and he finally required no diabetes treatment. Mesenteric arteries were patent with good palpitation without occlusion or thrombosis, and pathological findings showed ischemic enteritis, which is consistent with NOMI. DKA is a rare but serious side effect of second-generation antipsychotic medications (SGAMs) such as quetiapine, which can result in NOMI: a life-threatening complication. We must keep in mind that the plasma glucose concentration may increase in patients taking SGAMs, or that NOMI may occur concurrently if DKA develops.

Perspectives on reasons for non-adherence to medication in persons with schizophrenia in Ethiopia: a qualitative study of patients, caregivers and health workers

BACKGROUND

Levels of non-adherence to antipsychotic medication in persons with schizophrenia in rural African settings have been shown to be comparable to those found in high-income countries. Improved understanding of the underlying reasons will help to inform intervention strategies relevant to the context.

METHODS

A qualitative study was conducted among persons with schizophrenia (n = 24), their caregivers (n = 19), research field workers (n = 7) and health workers (n = 1) involved in the ongoing population-based cohort study, 'The Butajira Study on Course and Outcome of Schizophrenia and Bipolar Disorder', based in rural Ethiopia. Six focus group discussions and 9 in-depth interviews were conducted to elicit perspectives on non-adherence to antipsychotic medication. Thematic analysis was used to identify prominent perspectives.

RESULTS

Predominant reasons for non-adherence specific to a low-income country setting included inadequate availability of food to counter appetite stimulation and the perceived strength of antipsychotic medications. The vital role of the family or other social support in the absence of a statutory social safety net was emphasised. Expectations of cure, rather than need for continuing care, were reported to contribute to non-adherence in the longer-term. Many of the factors associated with non-adherence in high-income countries were also considered important in Ethiopia, including lack of insight, failure to improve with treatment, medication side effects, substance abuse, stigma and dissatisfaction with the attitude of the care provider.

CONCLUSION

This study identifies additional barriers to medication adherence faced by persons with schizophrenia in Ethiopia compared to those in high-income countries. In this era of scaling up of mental health care, greater attention to provision of social and financial assistance will potentially improve adherence and thereby enable patients to benefit more fully from medication.

Shape-based reprofiling of FDA-approved drugs for the H₁ histamine receptor

Reprofiling of existing drugs to treat conditions not originally targeted is an attractive means of addressing the problem of a decreasing stream of approved drugs. To determine if 3D shape similarity can be used to rationalize an otherwise serendipitous process, we employed 3D shape-based virtual screening to reprofile existing FDA-approved drugs. The study was conducted in two phases. First, multiple histamine H(1) receptor antagonists were identified to be used as query molecules, and these were compared to a database of approved drugs. Second, the hits were ranked according to 3D similarity and the top drugs evaluated in a cell-based assay. The virtual screening methodology proved highly successful, as 13 of 23 top drugs tested selectively inhibited histamine-induced calcium release with the best being chlorprothixene (IC(50) 1 nM). Finally, we confirmed that the drugs identified using the cell-based assay were all acting at the receptor level by conducting a radioligand-binding assay using rat membrane.

Integrative role of the histaminergic system in feeding and taste perception

Feeding behavior is regulated by a complex interplay of many endogenous substances, such as peptides and neurotransmitters in the central nervous system. Histamine is a neurotransmitter which expresses an anorectic effect on food intake via histamine H(1) receptors. The histaminergic system exists downstream of leptin, a satiety factor secreted from white adipose tissue. Because direct stimulation of the histaminergic system by histamine H(3)-inverse agonists or antagonists can normalize the obese phenotype in which animal models with exogenous leptin resistance, which resembles human obesity, the potential roles of histamine H(3) receptors as a therapeutic target now draw attention. Histaminergic activity is enhanced during feeding, and an oral somatic sensation is thought to affect histaminergic activity while blood glucose levels do not. In addition, gustatory information can modulate histaminergic activity by two mechanisms: by physiological excitation of the chorda tympani nerve, one of the taste nerves and by emotions elicited by taste perception, i.e., taste palatability. Particularly, aversive and hazardous taste stimuli tonically facilitate histaminergic activity, suggesting that the histaminergic system is involved in the response to harmful stimuli. Together with recent findings, it is postulated that the histaminergic system responds to both mechanical and chemical sensory input from the oral cavity during feeding and is exerted as a part of the danger response system.

Serotonergic and histaminergic mechanisms involved in intralipid drinking?

Some newer antipsychotic agents are associated with weight gain in humans and a hyperphagic response to intralipid solutions in rodents. To examine the possible contribution of serotonin (5-HT) and histamine (H) receptor blockade in antipsychotic-associated hyperphagia, rats were trained to drink a palatable, high-calorie fat emulsion (10% intralipid) during 30-min sessions and were tested following pretreatment with mepyramine (H1 receptor antagonist), metergoline (5-HT(1/2) receptor antagonist), cyproheptadine (H1 and 5-HT(2A/2B/2C) and muscarinic receptor antagonist), SB 242084 (5-HT2C receptor antagonist) and an SB 242084-mepyramine combination. Total intake and ingestive behaviour microstructure were measured. Mepyramine (10 mg/kg) reduced intake, as did metergoline (3.0 mg/kg). Cyproheptadine (0.1-1.0 mg/kg) increased intake and microstructural analysis suggests that this was due to increased numbers of clusters of licking. SB 242084 (3 mg/kg) reduced intake, either when administered alone, or in combination with mepyramine (1 mg/kg). In conclusion, simple antagonism of either H1 (mepyramine) or 5-HT(1/2) receptors (metergoline) alone was not sufficient to increase intake. Furthermore, combined blockade of H1 and 5-HT2C receptors (SB 242084 and mepyramine) was also insufficient to produce hyperphagia. Conversely, simultaneous blockade of H1, 5-HT(2A/2C) and muscarinic receptors (cyproheptadine) led to a substantial hyperphagia and pattern of ingestive behaviour that was similar to that previously observed with some newer antipsychotic agents.

Clozapine-induced weight gain predicts improvement in psychopathology

BACKGROUND

Some, but not all, previous studies have indicated that weight gain is associated with greater improvement in psychopathology during clozapine treatment. Possible reasons for the inconsistent results include failure to adjust for initial body weight and level of psychopathology, differences in trial duration, outcome measures, reliability of assessment, concomitant medications and clozapine dosage. The purpose of this study was to test the hypothesis that clozapine-induced weight gain is related to antipsychotic efficacy at 6 weeks and 6 months after adjusting for initial body weight and severity of illness.

METHODS

Weight and psychopathology were determined in 74 patients with schizophrenia or schizoaffective disorder at baseline and after 6 weeks and 6 months of open treatment with clozapine monotherapy. The primary measures of psychopathology were the Brief Psychiatric Rating Scale (BPRS) Total and Positive symptoms subscales, Schedule for Assessment of Negative Symptoms (SANS), Schedule for Assessment of Positive Symptoms (SAPS) and Global Assessment of Function Scale (GAFS).

RESULTS

Significant improvement in the key measures of psychopathology was noted at 6 weeks and 6 months. Mean weight gains at 6 weeks and 6 months were 3.7+/-5.7 S.D. and 7.3+/-7.9 S.D. kg, respectively, with the increase between 6 weeks and 6 months being significant. Age, but not gender, initial body weight, clozapine dosage or plasma levels predicted weight gain at both time points. At 6 weeks and 6 months, after adjustment for age, initial weight and level of psychopathology, the percentage change in weight significantly predicted the improvement in the BPRS Total and Positive symptoms subscale, the SANS Global score, as well as other measures of psychopathology.

CONCLUSIONS

Increase in weight with clozapine predicted improvement in psychopathology. This suggests that effects of clozapine on neurotransmitters which influence weight gain, e.g. 5-HT(2C) and 5-HT(1a) antagonism, in association with individual variations in these receptors and others molecules, e.g. peptides and transporters, due to polymorphisms or post-translational editing of mRNAs, may also contribute to the improvement in psychopathology.

Optimization of a mathematical topological pattern for the prediction of antihistaminic activity

Molecular topology was used to develop a mathematical model capable of classifying compounds according to antihistaminic activity. The equations used for this purpose were derived using multilinear regression and linear discriminant analysis. The topological pattern of activity obtained allows the reliable prediction of antihistaminic activity in drugs frequently used for other therapeutic purposes. Based on the results, the proposed pattern is seemingly only valid for drugs that interact with histamine through competitive inhibition with H1 receptors.

An analysis of parotid salivary gland function with desipramine and age in female NIA Fischer 344 rats

Cyclic antidepressants are still a dominating group of psychotherapeutic drugs used in the treatment of depression. Dry mouth is one of their major side effects. In this study we analyzed the effects of the long-term administration of the tricyclic antidepressant desipramine and the reversibility of this treatment following a 15-day washout period on different parameters in parotid gland function in aging rats. We hypothesized that glandular function would be decreased, and recovery delayed with age. Drug treatment affected body weight, glandular weight, DNA synthesis, and the concentration of soluble and structural membrane proteins. Surprisingly, parotid flow rate was increased with desipramine in all ages. While the concentration of secreted proteins was generally decreased with treatment, total proteins secreted were quite stable. SDS/PAGE analysis revealed prominent changes with desipramine. Amylase activity was depressed with treatment, but only low residual cellular enzyme activity was detected in the glandular supernatant. Therefore, a secretory impairment with desipramine was excluded. The content of the antimicrobial proteins peroxidase and lysozyme was increased with desipramine in all age groups. Most parameters measured revealed delayed recovery with age. These data indicate that the tricyclic antidepressant desipramine has profound effects on parotid gland function, accented with age.

An analysis of submandibular salivary gland function with desipramine and age in female NIA Fischer 344 rats

Dry mouth is one of the major side effects of cyclic antidepressants, which are still a dominating group of psychotherapeutic drugs used in the treatment of depression. In this study we analyzed the effects of 28 day tricyclic antidepressant administration and the reversibility of this treatment following a 15 day washout period on different parameters in submandibular gland function in aging rats. We postulated that desipramine would decrease gland function, accented with age, and delay recovery in senescent animals. In contrast to body weight, desipramine had no effect on glandular wet weight. While glandular DNA synthesis was changed with age and treatment, the concentration of total membrane and soluble proteins was not affected. Flow rate was significantly changed with age, but desipramine increased salivary flow in the youngest animals only. Neither age nor treatment influenced salivary protein concentrations, but the total amount of proteins secreted, revealed perturbation with age. SDS- polyacrylamide gel analysis revealed changes in protein expression with treatment and age. Desipramine decreased epidermal growth factor (EGF) levels in all age groups, but increased the secretion of peroxidase and lysozyme. Analysis of total RNA showed a pronounced decrease with age. These data indicate that desipramine has profound effects on submandibular salivary gland function.

Dietary induced anorexia: a review of involvement of the histaminergic system

This review examines possible relationships between anorexia, dietary intake and central nervous system histaminergic activity. The hypothesis being reviewed is that one component of normal or pathophysiological neuroregulation of food intake involves histaminergic activity in the central nervous system, as influenced by concentrations and bioperiodicities of histamine and/or histamine receptors. Changes in concentrations of receptors are gender specific. Low protein quality or quantity diets elevate both central histamine and histamine receptors (H1) in rats while significantly decreasing their food intake. When injected with histaminergic antagonists, rats fed low protein diets increase food intake and have improved efficiency of weight gain. This review supports a dual hypotheses: central histaminergic activity is involved in the regulation of food intake, but food intake patterns (including dietary composition or energy content) can modify central histaminergic activity. This review also suggests that modified histamine and/or H1 receptor concentrations are potential mechanisms for elevated central histaminergic activity in food intake-related pathophysiological states. Thus, dietary interventions (clinically- or self-imposed) which modify food intake or diet composition have the potential of affecting the histaminergic system. Also, drugs with antihistaminergic properties have the potential of affecting food intake/weight gain patterns by interfering with normal neurochemical signals.

The effect of metoprine on glucoprivic feeding induced by 2-deoxy-D-glucose

Metoprine is a histamine N-methyltransferase inhibitor that elevates endogenous histamine (HA) levels. Because the histaminergic mechanism may be involved in the regulation of feeding behavior as well as in body glucose homeostasis, the effect of metoprine on glucoprivic feeding was studied in Wistar rats. Although metoprine treatment (10 and 20 mg/kg, IP) decreased feeding, the rats still responded to the administration of 400 mg/kg of 2-deoxy-D-glucose (2-DG) by increasing their feed intake. No difference was seen in the 6-h cumulative feed intake after administration of 2-DG between the metoprine- and solvent-treated rats. However, the response was delayed, and with 20 mg/kg metoprine the feed intake was significantly reduced during 2 h after 2-DG application. Both 2-DG and metoprine elevated plasma glucose concentration despite their opposite effects on feeding. Hypothalamic HA or its metabolite levels were not affected by 2-DG. The results suggest that the effects of metoprine and 2-DG are largely independent of each other, and that the feeding modulating function of HA is on such a level that it does not prevent the glucoprivic emergency response.

FMH-induced decrease in central histamine levels produces increased feeding and body weight in rats

The present study tested the long-term effects of the histamine (H) synthesis inhibitor alpha-fluoromethylhistidine (FMH) on feeding and body weight in rats. FMH (administered via 2-week osmotic minipumps) increased feeding significantly throughout the test period. Body weights were also significantly increased toward the end of the test period. Hypothalamic H assays, performed at the end of the study, confirmed that FMH-treated rats had significantly lower H levels than controls. In general, the results suggest that H activity and feeding are inversely related.

Cyproheptadine prevents the initial occurrence of successive negative contrast

Rats shifted from 32% to 4% sucrose make fewer licks for 4% sucrose than rats having only experienced the lower reward. In Experiment 1, the occurrence of this contrast effect was prevented by the administration of the nonspecific serotonin antagonist cyproheptadine (3.0 or 6.0 mg/kg). These results of Experiments 2 and 3 demonstrated that the contrast-reducing action of cyproheptadine was not mediated by the antiserotonergic properties of the drug since systemic administration of the serotonin synthesis inhibitor, PCPA (150 or 300 mg/kg), failed to influence either the occurrence of contrast or the attenuation of contrast by cyproheptadine. The results of Experiment 4 indicated that the contrast-reducing action of cyproheptadine was not mediated by the antihistaminergic properties of the drug since the antihistamine, pyrilamine (6 or 12 mg/kg), also failed to prevent the occurrence of contrast. Finally, the contrast-reducing action of cyproheptadine was not due to rate-dependent and/or appetite stimulating effects since cyproheptadine did not serve to increase lick frequency in rate-dependent controls.