The possible role of histamine receptors in the hippocampal formation on the exploratory motivation and emotionality of the rat was studied. An elevated asymmetric plus-maze composed of 4 different arms (no walls, single high wall, high and low walls and two high walls) arranged at 90 degrees angles was used. The exploration score, considered to be an index of exploratory motivation, and the pe...

The histaminergic system influences various activities of the central nervous system, including cardiovascular regulation. Histamine administered intracerebroventricularly (i.c.v.) in anesthetized rats produces the increase in mean arterial pressure (MAP) and heart rate (HR), however, in contrast to normotensive animals, histamine-induced rises in MAP and HR in critically hypotensive animals ar...

The recently identified histamine H4 receptor has revealed a potential new complexity for the role of histamine in the immune system. To begin to understand the role of this receptor in humans, one must first determine whether homologs exist and can be studied in lower species. To address this, we cloned the rat, mouse, and guinea pig cDNAs corresponding to the recently identified human histami...

BACKGROUND Histamine drives pruritus in allergic skin diseases which clinically constitutes a most disruptive symptom. Skin pathology in allergic skin diseases is crucially influenced by different T-helper subsets. However, the contribution of different histamine-receptors to T-helper cell dependent skin pathology has not been definitively answered. Models which can specifically address the fun...

Histamine elevates the intracellular cyclic AMP levels in cultured embryonic chick retinal pigment epithelium. The half-maximal activity is 6 X 10(-6) M. The effect of histamine is mediated by H2 receptors, i.e., inhibited by the H2 antagonist cimetidine and not affected by the H1 antagonists diphenhydramine and pyrilamine. The inhibition constant (KI) of cimetidine is 1.3 X 10(-8) M. Thus, the...

Sunburn, wound repair, and chronic renal failure with hemodialysis are usually accompanied by both pigmentation and itching. Proopiomelanocortin-derived α-melanocyte-stimulating hormone (α-MSH) is produced in response to external stimuli, such as UV irradiation, and is involved in cutaneous pigmentation. However, it is unclear whether α-MSH is also involved in the itching. We therefore investig...

Few drugs have so rapidly gained an established place in modern medicine as the histamine H, receptor antagonists. As a result of the inventiveness of James Black and his colleagues, the theoretical concept of a second class of histamine receptors became a therapeutic reality. The failure of classic antihistamine drugs (more appropriately H1 receptor antagonists) to block the actions of histami...

Histamine caused a fall in blood pressure in anesthetized dogs and cats which was only partially attenuated by mepyramine (pyrilamine), a histamine type H1-receptor antagonist. Further treatment with burimide or metiamide, type H2-receptor antagonists, caused nearly complete attenuation of the response to histamine. Burimamide alone had no effect on vasodilatation produced by histamine in the d...

We examined the effects of histamine and its agonists on the expression of the c-fos and c-myc proto-oncogenes at the transcriptional and translational levels in the human promonocytic U937 cell line. Histamine transiently increased cAMP and c-fos expression through H2 receptors. Dibutyryl cAMP also increased c-fos mRNA and protein, and levels remained elevated even after 12 hr of treatment. Do...

The determinants for recognition at H3 histamine receptors are considered. Findings based on quantum-chemical calculations suggest that H3 histamine receptor is less hydrophilic than the H2. The form most likely to be recognized by the H3 receptor is an intramolecularly hydrogen-bonded form of alpha-methylhistamine. Receptor environment and hydration effects of active form of histamine analogs ...