CNS alpha 1 receptor in tonic pain during estrous cycle in rats.

Estrogen and progesterone are known to affect nociception. The plasma concentrations of these hormones vary during estrous cycle in rodents. The aim of the present study was to investigate the effect of evidence of alpha1 receptor agonist and antagonist on tonic pain in all phases of estrous cycle in female rats. Phenylephrine (alpha1 agonist) and prazosin (alpha1 antagonist) were administered via intracerebroventicular (ICV) injection. Adult female rats weighting 200-220 g were maintained on 12 h light/dark cycle for 10-14 days prior to the experiment. Food and water were made available ad libitum. Formalin test was performed in all phases of estrous cycle. Results showed that phenylephrine caused significant (P<0.05) reduction in pain sensitivity. This reduction was more pronounced during proestrus phase. Prazosin significantly (P<0.05) increased pain sensitivity, particularly during metestrus phase. It is possible that fluctuation in pain sensitivity during estrous cycle is related to the level of sex hormones during estrous cycle.

Drug binding sites on chicken albumin: a comparison to human albumin.

Mammalian albumins have two main structurally selective ligand binding sites. Site I binds drugs such as azapropazone, phenylbutazone and warfarin; whereas benzodiazepines, some dansyl amino acids, such as dansylsarcosine, and short chain fatty acids like octanoic acid interact with site II. However, it is not known if non-mammalian albumins have similar binding loci. In this study, drug binding sites on chicken albumin were investigated using site selective fluorescent probes (warfarin and dansylsarcosine) and p-nitrophenyl acetate (NPA); the hydrolysis of which is selectively inhibited by site II ligands. Azapropazone and phenylbutazone decreased the binding of warfarin and dansylsarcosine to a similar extent. Diazepam and octanoic acid also inhibited binding of the two fluorescent probes in a non-selective manner. However, the fluorescence intensity of the warfarin-chicken albumin complex decreased when the pH was increased from 6.0-9.0; but by contrast, the fluorescence of bound dansylsarcosine remained unchanged. Furthermore, the hydrolysis of NPA was selectively inhibited by dansylsarcosine, diazepam and octanoic acid (ligands selective for site II on mammalian albumins), but not by site I selective ligands such as azapropazone and warfarin. Overall, the results suggest that chicken albumin, like mammalian albumins, has discrete binding sites for warfarin and dansylsarcosine.