title: Electrical properties of purinergic transmission in smooth muscle of the guinea-pig prostate.
abstract: Prostatic smooth muscle develops spontaneous myogenic tone which is modulated by autonomic neuromuscular transmission. This study aimed to investigate the role of purinergic transmission in regulating electrical activity of prostate smooth muscle and whether its contribution may be altered with age. Intracellular recordings were simultaneously made with isometric tension recordings in smooth muscle preparations of the guinea-pig prostate. Immunostaining for P2X1 receptors on whole mount preparations was also performed. In prostate preparations which generated spontaneous slow waves, electrical field stimulation (EFS)-evoked excitatory junction potentials (EJPs) which were abolished by guanethidine (10 μM), α-β-methylene ATP (10 μM) or pyridoxal phosphate-6-azophenyl-2,4-disulfonic acid (PPADS, 10 μM) but not phentolamine (1 μM). Consistently, immunostaining revealed the expression of P2X1 receptors on prostatic smooth muscle. EJPs themselves did not cause contractions, but EJPs could sum to trigger a slow wave and associated contraction. Yohimbine (1 μM) and 3,7-dimethyl-1-propargylxanthine (DMPX, 10 μM) but not propranolol (1 μM) potentiated EJPs. Although properties of EJPs were not different between young and aging guinea-pig prostates, ectoATPase inhibitor ARL 67156 (100 μM) augmented EJP amplitudes by 64.2 ± 29.6% in aging animals, compared to 22.1 ± 19.9% in young animals. These results suggest that ATP released from sympathetic nerves acts on P2X1 purinoceptors located on prostate smooth muscle to evoke EJPs, while pre-junctional α2-adrenergic and adenosine A2 receptors may play a role in preventing excessive transmitter release. Age-related up-regulation of enzymatic ATP breakdown may be a compensatory mechanism for the enhanced purinergic transmission which would cause hypercontractility arising from increased ATP release in older animals.
authors.affiliation: Department of Cell Physiology, Nagoya City University Graduate School of Medical Sciences, Kawasumi-1, Mizuho-ku, Nagoya 467-8601, Japan. Electronic address: mishella86@gmail.com.
authors.forename: Michelle
authors.initials: M
authors.lastname: Lam
authors.affiliation: Department of Cell Physiology, Nagoya City University Graduate School of Medical Sciences, Kawasumi-1, Mizuho-ku, Nagoya 467-8601, Japan.
authors.forename: Retsu
authors.initials: R
authors.lastname: Mitsui
authors.affiliation: Department of Cell Physiology, Nagoya City University Graduate School of Medical Sciences, Kawasumi-1, Mizuho-ku, Nagoya 467-8601, Japan.
authors.forename: Hikaru
authors.initials: H
authors.lastname: Hashitani
mesh_terms: D018663:Adrenergic Agents / Q000494:pharmacology; D058669:Adrenergic alpha-2 Receptor Antagonists / Q000494:pharmacology; D000367:Age Factors; D000779:Anesthetics, Local / Q000494:pharmacology; D000818:Animals; D004558:Electric Stimulation; D006145:Guanethidine / Q000494:pharmacology; D006168:Guinea Pigs; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D011467:Prostate; D058905:Purinergic Agents / Q000494:pharmacology; D058474:Receptors, Purinergic P2X1 / Q000378:metabolism*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology; D015016:Yohimbine / Q000494:pharmacology
chemical_list: D018663:Adrenergic Agents; D058669:Adrenergic alpha-2 Receptor Antagonists; D000779:Anesthetics, Local; D058905:Purinergic Agents; D058474:Receptors, Purinergic P2X1; D015016:Yohimbine; D013779:Tetrodotoxin; D006145:Guanethidine
keywords: ATP; Excitatory junction potentials; Guinea-pig; Prostate; Purinergic innervation