The effects of ageing on prejunctional 5-hydroxytryptamine receptors in the rat vas deferens.
The prejunctional inhibitory effects of a series of 5-HT1 receptor agonists were examined against the isometric contraction of epididymal portions of rat vas deferens evoked by single stimulus pulses in the presence of nifedipine (10 mumol/l). The 5-HT1A ligand flesinoxan produced inhibition of contractions which was not inhibited by cyanopindolol or yohimbine. However, the prejunctional inhibitory concentration response curve for the 5-HT1 agonist 5-carboxamidotryptamine (5-CT) was biphasic in tissues from 1.5 month old animals but monophasic in tissues from 24 months animals. Cyanopindolol (1 mumol/l) antagonised the inhibitory effects of 5-CT in tissues from 1.5 and 3 month animals but not in tissues from 8 or 24 months animals. Inhibitory actions of 5-CT were not prevented by pretreating animals with pertussis toxin (6 micrograms/kg i.v.), a dose which abolished the negative inotropic response to acetylcholine in rat left atria. It is concluded that the nerve terminals of vas deferens from 1.5 month old animals contain both 5-HT1B and other as yet unclassified 5-HT1 receptors, but that this 5-HT1B-mediated response is lost in maturation and ageing.
Borton
M
M
Department of Clinical Pharmacology, Royal College of Surgeons, Dublin, Ireland.
Docherty
J R
JR
D000375:Aging / Q000502:physiology*; D000818:Animals; D004558:Electric Stimulation; D066298:In Vitro Techniques; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects* / Q000502:physiology; D009200:Myocardial Contraction / Q000187:drug effects; D037342:Pertussis Toxin; D010869:Pindolol / Q000031:analogs & derivatives / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011985:Receptors, Serotonin / Q000187:drug effects*; D012701:Serotonin / Q000031:analogs & derivatives / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology; D014649:Vas Deferens / Q000187:drug effects / Q000502:physiology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology; D015016:Yohimbine / Q000494:pharmacology
D010879:Piperazines; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D010566:Virulence Factors, Bordetella; D015016:Yohimbine; D012701:Serotonin; C056895:flesinoxan; C047975:cyanopindolol; C047087:5-carboxamidotryptamine; D010869:Pindolol; D037342:Pertussis Toxin