title: Effects of chronic l-DOPA administration on neurogenic and endothelium-dependent relaxation responses in rabbit corpus cavernosum.
abstract: BACKGROUND
  Dopamine is a crucial central neurotransmitter that plays a fundamental role in the autonomic and somatic components of penile reflexes in animals and humans. Similar to the erectile responses of dopamine, systemic administration of l-DOPA induces yawning and penile erection in some species. The possible effects of l-DOPA on nitric oxide (NO)-dependent and -independent non-adrenergic non-cholinergic (NANC) relaxation responses mediated by electrical field stimulation (EFS) and endothelium-dependent relaxation were investigated in this study.
  
  
  METHODS
  Thirty-two adult albino male rabbits, in two- and four-week-treatment groups, were divided into three subgroups: control group (saline-injected) (n=4), 3mg/kg/day (low dose) l-DOPA-injected groups (n=6) and 12mg/kg/day (high dose) l-DOPA-injected groups (n=6). After the intraperitoneal injection treatments, the corpus cavernosum tissues were placed in organ bath chambers. The EFS-mediated responses, and the concentration-response curve to carbachol, sodium nitroprusside (SNP), sildenafil were assessed.
  
  
  RESULTS
  The two-week treatment with high-dose l-DOPA decreased the NO-dependent NANC relaxation responses, while there was no change in the low-dose two- and four-week treatment groups. The NO-independent NANC relaxation responses in the two-week groups decreased, and the responses in the four-week groups were unchanged when compared to the controls. The relaxation responses to carbachol showed no differences among all groups except for the high-dose four-week l-DOPA group. The relaxation responses of SNP and sildenafil were increased in all of the treatment groups when compared to the controls.
  
  
  CONCLUSIONS
  The observed increases in SNP- and sildenafil-induced responses, along with the decreased EFS-mediated responses, suggest increased sensitivity in the NO-signalling pathway following l-DOPA administration.
authors.affiliation: Department of Medical Pharmacology, Kırıkkale University, Kırıkkale, Turkey. Electronic address: seniz.yy@gmail.com.
authors.forename: Şeniz
authors.initials: Ş
authors.lastname: Yıldırım
authors.affiliation: Department of Medical Pharmacology, Gazi University, Ankara, Turkey.
authors.forename: Gökçe Sevim
authors.initials: GS
authors.lastname: Öztürk Fincan
authors.affiliation: Department of Rational Drug Use and Supply Management, Turkish Medicines and Medical Devices Agency, Ministry of Health, Ankara, Turkey.
authors.forename: Fatma
authors.initials: F
authors.lastname: İşli
authors.affiliation: Member of Turkish Academy of Science, Turkey.
authors.forename: Sevim
authors.initials: S
authors.lastname: Ercan
authors.affiliation: Department of Medical Pharmacology, Gazi University, Ankara, Turkey.
authors.forename: Yusuf
authors.initials: Y
authors.lastname: Sarıoğlu
mesh_terms: D000818:Animals; D002217:Carbachol / Q000008:administration & dosage; D004558:Electric Stimulation / Q000379:methods; D004727:Endothelium / Q000187:drug effects*; D007980:Levodopa / Q000008:administration & dosage*; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism; D055495:Neurogenesis / Q000187:drug effects*; D018377:Neurotransmitter Agents / Q000008:administration & dosage; D009569:Nitric Oxide / Q000378:metabolism; D009599:Nitroprusside / Q000008:administration & dosage; D010410:Penile Erection / Q000187:drug effects*; D010413:Penis / Q000187:drug effects* / Q000378:metabolism; D011817:Rabbits; D000068677:Sildenafil Citrate / Q000008:administration & dosage
chemical_list: D018377:Neurotransmitter Agents; D009599:Nitroprusside; D009569:Nitric Oxide; D007980:Levodopa; D002217:Carbachol; D000068677:Sildenafil Citrate
keywords: Corpus cavernosum; Electrical field stimulation (EFS); Peripheral nervous system; Rabbit; l-DOPA