title: 5-HT7 receptors and tryptophan hydroxylase in lymphocytes of rats: mitogen activation, physical restraint or treatment with reserpine.
abstract: OBJECTIVE
  Serotonin (5-HT)7 receptors in lymphocytes play a relevant role as modulators of T cell functions and might be modified by stress protocols. The aims of this work were to evaluate: (i) the presence of 5-HT7 receptors in specific lymphocyte populations, (ii) the probable modifications of them by inflammatory stress with mitogen and (iii) the effects of physical and pharmacological stress.
  
  
  METHODS
  Blood lymphocytes were isolated by density gradients and differential adhesion to plastic. Concanavalin A (Con A) was systemically administered (500 μg/kg) or added to lymphocyte cultures (2.5 μg/ml, final volume 200 μl). Physical restraint was performed in Plexiglass boxes for 5 h per day for 5 days. Reserpine administration was 2.5 mg/kg for 3 days. Immunocytochemical labeling of CD4+, CD8+ and 5-HT7 receptors, and also tryptophan hydroxylase cells was performed. mRNA of 5-HT7 receptors was evaluated by RT-PCR. Controls were included for each protocol.
  
  
  RESULTS
  Con A treatment or culture exposure increased the number of lymphocytes expressing 5-HT7 receptors or tryptophan hydroxylase, as compared to absence of the mitogen. Receptors were present in 12-16% of total rat lymphocytes, in ∼10% of CD4+ and in ∼5% of CD8+ cells from control rats. CD4+ decreased, and CD8+ and 5-HT7 cells increased after physical restraint. Reserpine treatment elevated CD8+ and 5-HT7 cells. Con A and physical restraint, but not reserpine treatment, significantly augmented 5-HT7 receptor mRNA in lymphocytes.
  
  
  CONCLUSIONS
  Rat lymphocytes, expressing tryptophan hydroxylase, could synthesize 5-HT, functioning as a direct autocrine modulator. The modifications of CD4+, CD8+ and 5-HT7 receptors in lymphocytes by three stress protocols could have an impact on immune responses. In addition, the differential distribution of 5-HT7 receptors indicates potential specific physiopathological roles.
authors.affiliation: Laboratorio de Neuroquímica, Centro de Biofísica y Bioquímica, Instituto Venezolano de Investigaciones Científicas (IVIC), Caracas, Venezuela.
authors.forename: Mary
authors.initials: M
authors.lastname: Urbina
authors.forename: Rubén
authors.initials: R
authors.lastname: Arroyo
authors.forename: Lucimey
authors.initials: L
authors.lastname: Lima
mesh_terms: D000818:Animals; D014150:Antipsychotic Agents / Q000494:pharmacology; D008214:Lymphocytes / Q000276:immunology* / Q000378:metabolism*; D008297:Male; D008934:Mitogens / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011985:Receptors, Serotonin / Q000096:biosynthesis*; D012110:Reserpine / Q000494:pharmacology; D012149:Restraint, Physical / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013315:Stress, Psychological / Q000276:immunology / Q000378:metabolism; D014365:Tryptophan Hydroxylase / Q000096:biosynthesis*
chemical_list: D014150:Antipsychotic Agents; D008934:Mitogens; D011985:Receptors, Serotonin; C104425:serotonin 7 receptor; D012110:Reserpine; D014365:Tryptophan Hydroxylase