Cholinergic link in the histamine-mediated increase in homovanillic acid in the rat striatum

From past to future: 50 years of pharmacological interventions to treat narcolepsy

The history of narcolepsy research began with the pioneering work of Jean-Baptiste-Édouard Gélineau in the late 19th century. In the 1880s, Gélineau introduced the term "narcolepsy" to describe a condition characterized by sudden and uncontrollable episodes of sleep. His clinical descriptions laid the foundation for our understanding of this complex disorder. Over the last half-century, the pharmacological landscape for narcolepsy treatment has evolved remarkably, shifting from merely managing symptoms to increasingly targeting its underlying pathophysiology. By the 1930s, treatments such as ephedrine and amphetamine were introduced to alleviate excessive daytime sleepiness, marking significant advancements in narcolepsy management. These stimulants provided temporary relief, helping patients maintain wakefulness during the day. As research progressed, the focus shifted towards understanding the disorder's underlying mechanisms. The discovery of orexin (also known as hypocretin) in the late 1990s revolutionized the field. This breakthrough underscored the importance of orexin in regulating sleep-wake cycles and provided new targets for pharmacological intervention. Looking ahead, the future of narcolepsy pharmacotherapy is poised for further innovation. The ongoing exploration of orexin receptor agonists and the potential development of neuroprotective therapeutic targets underscore a promising horizon. Emerging research into the genetic and immunological underpinnings of narcolepsy opens new avenues for personalized medicine approaches and the identification of biomarkers for more precise treatment strategies. Additionally, the refinement of existing treatments through improved delivery systems and the investigation of combination therapies offer opportunities for enhanced efficacy and improved quality of life for patients with narcolepsy.

Effects of prenatal diphenhydramine exposure on dopaminergic function in adult rats

Female pregnant rats were treated with 20.0 mg/kg diphenhydramine (DPH) or the same volume of saline solution (NaCl 0.9%), SC, daily during pregnancy. As adults, male pups were tested for stereotyped behavior in response to apomorphine (1 mg/kg, SC) administration. No differences between DPH-exposed and control rats were evident. In another group of rats, dopamine (DA) and homovanillic acid (HVA) levels were quantified in striatal samples. DA levels were equivalent, but increased levels of HVA were observed. Based upon these data we suggest that prenatal exposure to DPH, a histamine (H1) receptor antagonist, reduces presynaptic dopaminergic mechanisms without altering postsynaptic dopaminergic function in adulthood.

Decrease in blood histamine in drug-treated parkinsonian patients

Blood histamine and serum histaminase activity were determined in a group of patients with Parkinson disease (PD) and in a group of healthy controls. Untreated PD patients present significantly higher blood histamine than normal controls. Therapy with L-dopa + cardidopa results in a significant decrease in blood histamine. This decrease becomes more accentuated when anticholinergics are added to this therapy. No significant changes were detected in plasma histaminase. The authors suggest, as a hypothesis, that the CNS contributes to blood histamine concentration and that its rise is the result of increased neuronal destruction.

The effects of intracerebroventricular administration of compound 48/80 on behaviour and regional brain amine concentrations in the rat

The intracerebroventricular injection of the mast cell degranulator, compound 48/80 (C48/80, 10 micrograms/kg), produced a marked behavioural syndrome in rats which included head and body shakes, paw tremor, excessive grooming, unusual posture and gait, mild diarrhoea, piloerection, extreme agitation and irritability to touch, sedation and catatonia. Fifteen minutes after C48/80, the histamine concentrations were decreased significantly in all brain regions examined, i.e. the cortex, cerebellum, midbrain, medulla oblongata-pons (MO-P) and hypothalamus. The noradrenaline (NA) concentrations were decreased in the cerebellum, hypothalamus and MO-P, whereas the dopamine (DA) content was decreased in the MO-P only. The concentrations of serotonin were not affected. As such, the behaviours following the acute degranulation of brain mast cells by C48/80 may result predominantly from the release of histamine and possibly NA and DA.

Direct or indirect action of histamine on dopamine metabolism in the rat striatum?

Intraventricular administration of 500 microgram of 2-pyridylethylamine, an agonist of the histamine (Hi) H1-receptor, produced a 20% increase of striatal HVA in the rat while the Hi H2-receptor agonist 4-methylhistamine had no influence on HVA and DOPAC levels. L-Histidine (1.5 g/kg) or amodiaquine (60 mg/kg) given i.p. increased HVA and DOPAC levels to the same extent as did pyridylethylamine. Histidine combined with tremorine had an additive effect with respect to the increase of DA acidic metabolites while mepyramine slightly attenuated the tremorine-induced rise of HVA.