Effects of volume loading on paraventriculo-spinal neurones in the rat.
Experiments were carried out to investigate the effects of volume loading on the activity of antidromically identified paraventriculo-spinal neurones in rats anaesthetised with urethane. Intravenous infusion of isotonic saline (1.5-4.2 ml) inhibited amino acid induced activity in 12/20 cells. Of the remainder, 4 cells were excited and 4 were unaffected by volume loading. In 4/4 neurones inhibited by volume expansion, subsequent activation of vagal afferent nerve endings by i.v. bolus injection of 5-hydroxytryptamine (25-100 micrograms) also inhibited cell firing. The onset (0.5-7 min) and duration (5-29 min) of the inhibition evoked by volume loading showed considerable variation in different animals. The inhibitory effects of volume loading were absent in bilaterally vagotomised rats (n = 4). In these preparations the activity of paraventriculo-spinal neurones was facilitated by volume loading. It is suggested that during volume loading inhibitory vagally mediated inputs and excitatory non-vagal influences converge on paraventriculo-spinal neurones.
Lovick
T A
TA
Department of Physiology, Medical School, Birmingham, U.K.
Coote
J H
JH
D000344:Afferent Pathways / Q000502:physiology*; D000818:Animals; D001794:Blood Pressure; D004558:Electric Stimulation; D006339:Heart Rate; D007552:Isotonic Solutions; D008297:Male; D009474:Neurons / Q000502:physiology*; D010286:Paraventricular Hypothalamic Nucleus / Q000166:cytology / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D012965:Sodium Chloride / Q000494:pharmacology*; D013116:Spinal Cord / Q000502:physiology*; D014628:Vagotomy; D014630:Vagus Nerve / Q000502:physiology*
D007552:Isotonic Solutions; D012965:Sodium Chloride