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Pflügers Archiv

, Volume 430, Issue 6, pp 901–908 | Cite as

Enhanced excitatory junction potentials in mesenteric arteries from spontaneously hypertensive rats

  • J. A. Brock
  • D. F. Van Helden
Original Article Neurophysiology, Muscle and Sensory Organs

Abstract

Excitatory junction potentials (EJPs) were examined using intracellular recording techniques in mesenteric arteries isolated from 12- to 15-week-old spontaneously hypertensive (SHR), Wistar Kyoto (WKY) and Sprague Dawley (SD) rats. The amplitudes of EJPs evoked by single supramaximal stimuli were larger in arteries from SHRs (12.9±0.7 mV,n=16) than in arteries from either WKYs (5.2±0.5 mV,n=24) or SDs (8.6±0.8 mV,n=15). The time constant of decay of EJPs did not differ significantly, suggesting that the passive electrical properties of the vascular smooth muscle are similar in the three rat strains. Spontaneous EJPs recorded in tissues from SHRs and WKYs had similar amplitude frequency distributions, suggesting that the quantal size is also similar between strains. In some arteries from SHRs, EJPs evoked by single stimuli triggered muscle action potentials (MAPs). Visible constriction only occurred following a MAP. In tissues from all three strains, summation of EJPs triggered MAPs. As EJPs are generated by the sympathetic co-transmitter adenosine 5′-triphosphate (ATP), the findings of the present study indicate that purinergic transmission is enhanced in mesenteric arteries from SHRs, probably as a result of an increase in quantal release. A consequence is that when nerves are activated SHR arteries more readily undergo constriction that is dependent on voltage-activated Ca2+ influx.

Key words

Sympathetic nerve Artery Neurovascular transmission Co-transmission ATP Spontaneously hypertensive rat 

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References

  1. 1.
    Angus JA, Broughton A, Mulvany MJ (1988) Role of α-adrenoceptors in constrictor responses of rat, guinea-pig and rabbit small arteries to neural activation. J Physiol (Lond) 403:495–510Google Scholar
  2. 2.
    Åstrand P, Stjärne L (1989) ATP as a sympathetic co-transmitter in rat vasomotor nerves-further evidence that individual release sites respond to nerve stimuli by intermittent release of single quanta. Acta Physiol Scand 136:355–365PubMedGoogle Scholar
  3. 3.
    Brock JA (1994) Modulation of neurotransmitter release by autoreceptors. In: Powis DA, Bunn SJ (eds) Neurotransmitter release and its modulation. Cambridge University Press, Cambridge, (in press)Google Scholar
  4. 4.
    Brock JA, Cunnane TC (1992) Electrophysiology of neuro-effector transmission in smooth muscle. In: Burnstock G, Hoyle CHV (eds) Autonomic neuroeffector mechanisms. Harwood Academic, Chur, pp 121–213Google Scholar
  5. 5.
    Cassell JF, McLachlan E, Sittiracha T (1988) The effect of temperature on neuromuscular transmission in the main caudal artery of the rat. J Physiol (Lond) 397:31–49Google Scholar
  6. 6.
    Cheung DW, Fujioka M (1986) Inhibition of the junction potential in the guinea-pig saphenous artery by ANAPP3. Br J Pharmacol 89:3–5PubMedGoogle Scholar
  7. 7.
    Dempster JD (1993) Computer analysis of electrophysiological signals. Academic, LondonGoogle Scholar
  8. 8.
    Evans RJ, Cunnane TC (1992) Relative contributions of ATP and noradrenaline to the nerve evoked contractions of the rabbit jejunal artery: dependence on stimulation parameters. Naunyn Schmiedebergs Arch Pharmacol 345:424–430CrossRefPubMedGoogle Scholar
  9. 9.
    Furshpan EJ (1956) The effects of osmotic pressure changes on the spontaneous activity at motor nerve endings. J Physiol (Lond) 134:689–697Google Scholar
  10. 10.
    Games PA, Howell JF (1976) Pairwise multiple comparison procedures with unequal n's and/or variances: a Monte Carlo study. J Ed Stats 1:113–125Google Scholar
  11. 11.
    Head R (1989) Hypernoradrenergic innervation: its relationship to functional and hyperplastic changes in the vasculature of the spontaneously hypertensive rat. Blood Vessels 26:1–20PubMedGoogle Scholar
  12. 12.
    Head R, Cassis LA, Robinson RL, Westfall DP, Stitzel RE (1985) Altered catecholamine contents in vascular and non vascular tissues in genetically hypertensive rats. Blood Vessel 22: 196–204Google Scholar
  13. 13.
    Hirst GDS, Edwards FW (1989) Sympathetic neuro-effector transmission in arteries and arterioles. Physiol Rev 69:546–604PubMedGoogle Scholar
  14. 14.
    Jarrot B (1991) Changes in central catecholamine neurons in cardiovascular diseases. In: Ganguly PK (ed) Catecholamines and heart disease. CRC, Boca Raton, pp 177–200Google Scholar
  15. 15.
    Jobling P, McLachlan EM (1992) The effect of the purinoceptor antagonist suramin on neurotransmission in the main caudal artery of the rat. Proc Aust Physiol Pharmacol Soc 23:69PGoogle Scholar
  16. 16.
    Kazda S, Knorr A (1990) Calcium antagonists. In: Ganten D, Mulrow PJ (eds) Handbook of experimental pharmacology, vol 93. Pharmacology of antihypertensive therapuetics. Springer, Berlin Heidelberg New York, pp 301–375Google Scholar
  17. 17.
    Lee RMKW, Garfield RE, Forrest JB, Daniel EE (1983) Morphometeric study of structural changes in the mesenteric blood vessels of spontaneously hypertensive rats. Blood Vessels 20:57–71PubMedGoogle Scholar
  18. 18.
    Morris JL, Gibbins IL (1992) Co-transmission and neuromodulation. In: Burnstock G, Hoyle CHV (eds) Autonomic neuroeffector mechanisms. Harwood Academic, Chur, pp 33–119Google Scholar
  19. 19.
    Nilsson H, Folkow B (1982) Vasoconstrictor nerve influence on isolated mesenteric resistance vessels from normotensive and spontaneously hypertensive rats. Acta Physiol Scand 116: 205–208PubMedGoogle Scholar
  20. 20.
    Ohya Y, Abe I, Fujii K, Takata Y, Fujishima M (1993) Voltage-dependent Ca2+ channels in resistance arteries from spontaneously hypertensive rats. Circ Res 73:1090–1099PubMedGoogle Scholar
  21. 21.
    Rump LC, Wilde K, Schollmeyer P (1990) Prostaglandin E2 inhibits noradrenaline release and purinergic pressor responses to renal nerve stimulation at 1 Hz in isolated kidneys of young spontaneously hypertensive rats J Hypertens 8:897–908PubMedGoogle Scholar
  22. 22.
    Rush NJ, Hermsmeyer K (1988) Calcium currents are altered in the vascular muscle cell membrane of spontaneously hypertensive rats. Circ Res 63:997–1002PubMedGoogle Scholar
  23. 23.
    Scott TM, Pang SC (1983) The correlation between the development of sympathetic innervation and the development of medial hypertrophy in jejunal arteries in normotensive and spontaneously hypertensive rats. J Auton Nerv Syst 8:25–32PubMedGoogle Scholar
  24. 24.
    Sjöblom-Widfeldt N (1990) Neuro-muscular transmission in blood vessels: phasic and tonic components. Acta Physiol Scand Suppl p 587Google Scholar
  25. 25.
    Sjöblom-Widfeldt N, Nilsson H (1989) Sympathetic transmission in small mesenteric arteries from the rat: highly calcium-dependent at low stimulation rates. Acta Physiol Scand 135: 505–511PubMedGoogle Scholar
  26. 26.
    Sjöblom-Widfeldt N, Gustafsson H, Nilsson H (1990) Transmitter characteristics of small mesenteric arteries from the rat. Acta Physiol Scand 138:203–212PubMedGoogle Scholar
  27. 27.
    Sneddon P, Burnstock G (1984) ATP as a co-transmitter in rat tail artery. Eur J Pharmacol 106:149–152PubMedGoogle Scholar
  28. 28.
    Stekiel WJ, Contney SJ, Lombard JH (1986) Small vessel membrane potential, sympathetic input and electrogenic pump rate in SHR. Am J Physiol 250:C547-C556PubMedGoogle Scholar
  29. 29.
    Stephens N, Bund SJ, Jagger C, Heagerty AM (1991) Arterial neuroeffector responses in early and mature spontaneously hypertensive rats. Hypertension 18:674–682PubMedGoogle Scholar
  30. 30.
    Van Helden DF, Woolridge S (1990) Role of nerves in hypertension. Nature 348:118–119PubMedGoogle Scholar
  31. 31.
    Vidal M, Hicks PE, Langer SZ (1986) Differential effects ofα,β methylene ATP on responses to nerve stimulation in SHR and WKY tail arteries. Naunyn Schmiedebergs Arch Pharmacol 332:384–390PubMedGoogle Scholar
  32. 32.
    Westfall TC, Meldrum MJ, Carpentier S, Naes L, Zhang S-Q (1985) Alterations in the release of norepinephrine at the vascular neuroeffector junction in hypertension. Blood Vessels 24:94–99Google Scholar

Copyright information

© Springer-Verlag 1995

Authors and Affiliations

  • J. A. Brock
    • 1
  • D. F. Van Helden
    • 1
  1. 1.Neuroscience Group, Discipline of Human Physiology, Faculty of Medicine and Health SciencesThe University of NewcastleCallaghanAustralia

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