Electrophysiological properties of paraventriculo-spinal neurones in the rat.
In rats anaesthetized with urethane, electrical stimulation of the thoracic cord at T9-10 evoked antidromic response in neurones in the parvocellular portion of the ipsilateral paraventricular nucleus. Estimated conduction velocities in the spinally-projecting axons ranged from 0.6-5.9 m/sec. The majority (97%) of spinally projecting neurones were quiescent. Increases or decreases in the level of baroreceptor stimulation produced by intravenous injection of phenylephrine (1-5 micrograms) or sodium nitroprusside (10-15 micrograms) inhibited and excited amino acid-induced activity in 5/8 and 4/11 neurones respectively. Stimulation of vagal afferent endings by rapid bolus injection of 5-HT, to evoke the Bezold-Jarisch reflex. inhibited amino acid-induced activity in 15/18 cells. Activation of gastric vagal afferents by distension of the stomach had no effect on paraventriculo-spinal cells. It is suggested that at rest the excitability of paraventriculo-spinal neurones is depressed by a tonic inhibitory input which arises from vagal afferent fibres in the heart.
D000200:Action Potentials / Q000187:drug effects; D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D004558:Electric Stimulation; D005971:Glutamates / Q000494:pharmacology; D018698:Glutamic Acid; D006339:Heart Rate / Q000187:drug effects; D006710:Homocysteine / Q000031:analogs & derivatives / Q000494:pharmacology; D008297:Male; D009599:Nitroprusside / Q000494:pharmacology; D010286:Paraventricular Hypothalamic Nucleus / Q000187:drug effects / Q000502:physiology*; D010656:Phenylephrine / Q000494:pharmacology; D011311:Pressoreceptors / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D013116:Spinal Cord / Q000502:physiology*; D014628:Vagotomy
D005971:Glutamates; D006710:Homocysteine; C007956:homocysteic acid; D009599:Nitroprusside; D010656:Phenylephrine; D018698:Glutamic Acid