BACKGROUND AND PURPOSE Tryptophan hydroxylase activity was assayed in cell-free extracts of rat brain base arteries as marker of a serotonergic innervation. METHODS Estimation of the enzymatic activity was made in untreated male Sprague-Dawley rats (n = 53) and in those who underwent destruction of the dorsal and median raphe nuclei (n = 10). RESULTS Tryptophan hydroxylase activity was meas...

Adrenal adenosine 3',5'-cyclic monophosphate (cAMP) and corticosterone responses to exogenous ACTH were found to be about 2.5 times greater in the evening (at lights off) than in the morning (at lights on) in rats. The rhythm in adrenal responsiveness to ACTH was found to persist in rats treated with dexamethasone 15 and 3 h before exogenous ACTH (in the presumed absence of a rhythm in endogeno...

A study was made of the interrelationship of serotonin, cAMP, and calcium ions in the regulation of regeneration of cilia by Tetrahymena pyriformis. All these compounds stimulated the regeneration, whereas a blocker of serotonin synthesis, p-chlorophenylalanine, and a calcium chelator, EGTA, inhibited the process. This inhibition could be overcome by the addition of any of the stimulatory compo...

To investigate the role of serotonin (5-HT), an important neurotransmitter and hormone/paracrine agent in the small intestine, in the transport activity of P-glycoprotein (P-gp), the intestinal transport of quinidine, a P-gp substrate, was examined in 5-HT-depleted rats prepared by intraperitoneal administration of p-chlorophenylalanine, a specific inhibitor of tryptophan hydroxylase in 5-HT bi...

The memory effects of agonists and antagonists of some serotonin (5-HT) receptor subtypes were examined in experiments on rats using an active avoidance method (shuttle-box). The 5-HT receptor antagonists NAN 190 (1 mg/kg i.p.) and pindolol (6 mg/kg i.p.) improved some indices for memory; the 5-HT2 and 5-HT3 receptor antagonists ritanserin (1 mg/kg i.p.) and ondansetron (0.1 mg/kg i.p.) exerted...

In both experimental groups an intraperitoneal injection of a single dose of 450 mg/kg p-Chlorophenylalanine (p-CPA) containing 1.0% arabic gum and 450 mg/kg p-CPA containing 0.1% Tween 80 resulted in a similar drop of the serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) level in the anterior (HA) and posterior (HP) hypothalamus, midbrain (GC) and amygdala (AM). Despite the fact that ju...

Serotonin (5-HT) levels in the hemolymph of crustaceans has been implied to alter aggressiveness which influences social interactions. The activation of IP3 as a second messenger cascade within crayfish motor neurons in response to application of 5-HT, suggests that the 5-HT receptor subtypes on the motor neurons are analogous to the vertebrate 5-HT2A receptors. Based on evidence in other syste...

Abstract Epimerization can change the catechin content and composition of samples during extraction analytical analyses. To control effect epimerization, we developed a novel stable isotope dilution liquid chromatography-mass spectrometry (LC–MS) method using catechin-2,3,4- 13 C 3 epicatechin-2,3,4- as stable-isotope-labeled internal standards (SIL-ISs). When SIL-ISs were used, epicatechin con...