Consciousness histamine

A series of novel l-substituted-4-phenyl-l,2,3-triazolo(4,3-a)quinazolin-5(4H)-ones 1 were synthesized by the cyclization of 2-hydrazino-3-phenyl-quinazolin-4(3H) 2 with various one carbon donors. The starting material 2-hydrazino-3-phenylquinazolin-4(3H)-one 2, was synthesized from aniline 7 by a novel innovative route. When tested for their in vivo Hi-antihistaminic activity on conscious guinea pigs all the test compounds protected the animals from histamine-induced bronchospasm significantly, whereas the compound l-methyl-4-phenyl-l,2,3-triazolo(4,3-a)quinazolin-5(4H)-one lb (percentage protection 70.7%) was found to be equipotent with the reference standard chlorpheniramine maleate (percentage protection 71%). These compounds show negligible sedation (5%) when compared to the reference standard (26%). Hence they could serve as prototype molecules for future development [1,4,5]. 

Kalivas, P. W. (1982). Histamine-induced arousal in the conscious and pentobarbital-pretreated rat. J. Pharmacol Exp. Then 222, 37-42. 

Prast, H., Died, H. Philippu, A. (1992). Pulsatile release of histamine in the hypothalamus of conscious rats. J. Auton. Nerv. Syst. 39, 105-10. 

The S-enantiomer of citalopram (escitalopram) is over 100 times more potent in inhibiting the reuptake of 5-HT into brain slices than the R-form and is devoid of any activity at the neurotransmitter of other receptor types (racemic citalopram has an affinity for histamine receptors and causes sedation). In in vivo studies, escitalopram is more potent than the R-form or the racemate in releasing 5-HT in the cortex of conscious rats it has been... 

Van Schaick EA, Jacobson KA, Kim HO, IJzerman AP, Danhof M (1996) Hemodynamic effects and histamine release elicited by the selective adenosine A3 receptor agonist 2-Q-IB-MECA in conscious rats. Eur J Pharmacol 308(3) 311—314 Varani K, Caramori G, Vincenzi F, Adcock I, Casolari P, Leung E, Maclennan S, Gessi S, Morello S, Barnes PJ, Ito K, Chung KF, Cavallesco G, Azzena G, Papi A, Borea PA (2006) Alteration of adenosine receptors in patients with chronic obstructive pulmonary disease. Am J Respir Crit Care Med 173(4) 398-406... 

Conscious cat Gastric fistula and Heidenhain pouch 1 (food and Pgas) 0 (basal and histamine) Bado et al., 1991... 

Conscious dog Gastric fistula 1 (2-DG, Pgas and BBS 0 (basal and histamine) Soldani et al., 1993 1994... 

Additionally, cardiac function can also be modulated by centrally-located H3-receptors. The intracerebroventricular administration of (R)a-methylhistamine in conscious animals is associated with a marked reduction of the heart rate, an effect which is antagonised by thioperamide (McLeod et al., 1991). The peripheral administration of ipratropium, a muscarinic antagonist which does not cross the blood-brain barrier, prevents such inhibition, demonstrating that the activation of centrally-located histamine H3-receptors leads to an increase in the vagal tone to the heart, rather than to a facilitatory effect on the sympathetic efferent fibers. 

Coruzzi, G., Bertaccini, G., Schwartz, J.C., 1991a. Evidence that histamine H3 receptors are involved in the control of gastric acid secretion in the conscious cat. Naunyn-Schmiedeberg s Arch. Pharmacol. 343, 225-227. 

McLeod, R.L., Gertner, S B., Hey, J.A., 1991. Modulation of cardiovascular function by central histamine H3 receptors in conscious guinea pigs. Eur. J Pharmacol. 206, 141-142. 

Histamine apparently acts primarily on the sympathetic nerves of the body, while curare acts primarily on the nerves connected with the voluntary muscles, paralyzing the victim without necessarily causing him to lose consciousness. From our point of view, it is immaterial for the moment whether curare and the quaternary organic nitrogen salts coagulate the proteins of the nerve or the proteins of a substance between the nerve and the muscle, as Bayliss4 suggests. 

Sharma, H. S., Nyherg, F, Cervos-Navarro, J., and Dey, P. K. (1992). Histamine modulates heat stress-induced changes in blood-brain barrier permeability, cerebral blood flow, brain oedema and serotonin levels An experimental study in conscious young rats. Neuroscience 50, 445-454. 

In order to prepare themselves for cross-circulation experiments in conscious dogs. Ivy and Lim first asked whether a cross-effect might be expected. They connected the central end of one carotid artery of an anesthetized dog to the peripheral end of the carotid artery of another anesthetized dog and arranged for return of blood by corresponding anastomosis of the external jugular veins. They found that when they injected a large dose of epinephrine or histamine into one dog, there was a cross-effect in the other dog 75 to 90% of the time. With moderate doses, the cross-effect occurred 25 to 40% of the time. 

Jacobson ED, Eisenberg MM, Swan KG. Gastric blood flow in conscious animals, abstracted. Clin Res 13 536, 1965. The abstract was submitted December 1965, giving the latest date for the development of the aminopyrine clearance method, idem. Effects of histamine on gastric blood flow in conscious dogs. Gastroenterology 51 466-472, 1966. 

Vasovagal reaction (bradycardia, pallor, and loss of consciousness) is related to pain rather than contrast medium. The lower limbs are elevated atropine is sometimes useful. Mild allergic accident (itching, urticaria) can be treated by corticoids and an anti-histaminic medication. 

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