title: A functional study of the development of the cardiac sympathetic neuroeffector junction in the SHR.
abstract: We studied the function of the cardiac sympathetic nerve varicosity in isolated right atrial preparations of spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats at 4, 9, 14, 20 and 50 weeks of age. Cumulative concentration-atrial period response (C-R) curves to isoprenaline showed similar maximum response and sensitivity (EC50) at all ages but there was an age-related fall in resting atrial rate. Similar results were found for methoxamine (alpha 1-adrenoceptor agonist) although the maximum response was significantly less than for isoprenaline. The time-dependent recovery (T 1/2) of the fall in atrial period in response to sympathetic nerve stimulation from electrical field pulses (1-32 at 1 Hz) was enhanced by neuronal uptake inhibition by desipramine (0.1-1 mumol/l), to a similar degree at all ages. Pre-junctional alpha 2-adrenoceptor stimulation by clonidine caused progressively more inhibition of the number of field pulses-fall in period relationship with age. SHR atria were similar to WKY rat atria at all ages except for a further impairment of the development of pre-junctional alpha 2-adrenoceptors. These studies indicate that the function of the cardiac sympathetic varicosity matures early (by 4 weeks) and overall there is very little impairment in SHR versus WKY rat atria.
authors.affiliation: Baker Medical Research Institute, Prahran, Melbourne, Victoria, Australia.
authors.forename: A C
authors.initials: AC
authors.lastname: Dyke
authors.forename: J A
authors.initials: JA
authors.lastname: Angus
authors.forename: P I
authors.initials: PI
authors.lastname: Korner
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D001794:Blood Pressure; D003000:Clonidine / Q000494:pharmacology; D003891:Desipramine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D006321:Heart / Q000294:innervation*; D006339:Heart Rate / Q000187:drug effects*; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D008729:Methoxamine / Q000494:pharmacology; D009451:Neuroeffector Junction / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000502:physiology; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000502:physiology*
chemical_list: D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D008729:Methoxamine; D007545:Isoproterenol; D003000:Clonidine; D003891:Desipramine