title: Electrophysiological effects of tachykinin agonists on sympathetic ganglia of spontaneously hypertensive rats.
abstract: This study investigated the cellular basis for the enhanced ganglionic responsiveness to NK1 agonists in the spontaneously hypertensive rat (SHR) in comparison to their normotensive counterpart, the Wistar-Kyoto (WKY) rat. Rats for in vivo studies were anesthetized with pentobarbital and treated with chlorisondamine (10.5 micromol/kg). Extracellular recordings from the external carotid nerve showed a greater responsiveness of decentralized SHR superior cervical ganglia (SCG) to intravenous injection of SP (32 nmol/kg). Blood pressure and heart rate were increased in SHRs, whereas WKY rats responded with a decrease in blood pressure and only slight tachycardia. Membrane properties of SCG neurons, as shown by intracellular microelectrode recordings, were similar between strains. Picospritzer application of the NK1 agonist GR-73632 (100 microM, 1 s) evoked slow depolarization and increased neuron excitability. Spontaneous firing was evoked only in some neurons. Depolarization amplitudes were similar between strains; however, the NK1 agonist depolarized a greater number of neurons in hypertensive rats. In conclusion, SHRs are more responsive to ganglion stimulation by NK1 agonists due to a greater number of responsive cells within the SCG rather than an enhanced responsiveness of individual neurons.
authors.affiliation: Department of Pharmacology, James H. Quillen College of Medicine, East Tennessee State University, Johnson City 37614-1708, USA.
authors.forename: John D
authors.initials: JD
authors.lastname: Tompkins
authors.forename: John C
authors.initials: JC
authors.lastname: Hancock
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D004246:Dimethylphenylpiperazinium Iodide / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005728:Ganglia, Sympathetic / Q000187:drug effects* / Q000503:physiopathology; D006339:Heart Rate / Q000187:drug effects; D006973:Hypertension / Q000503:physiopathology*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D010446:Peptide Fragments / Q000494:pharmacology; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D018040:Receptors, Neurokinin-1 / Q000187:drug effects / Q000502:physiology; D018039:Receptors, Tachykinin / Q000819:agonists*; D013373:Substance P / Q000031:analogs & derivatives* / Q000494:pharmacology; D015320:Tachykinins / Q000494:pharmacology
chemical_list: D010446:Peptide Fragments; D018040:Receptors, Neurokinin-1; D018039:Receptors, Tachykinin; D015320:Tachykinins; C068032:GR 73632; D013373:Substance P; D004246:Dimethylphenylpiperazinium Iodide