Sympathetic neurotransmission in isolated rat atria after sensory-motor denervation by neonatal treatment with capsaicin.
Long-term interactions between sympathetic and sensory-motor nerves have been shown in several tissues. Previous investigations in this laboratory have demonstrated an increase in cardiac sensory-motor innervation after neonatal sympathectomy by guanethidine and an increase of perivascular sympathetic neurotransmission after neonatal treatment by capsaicin. The present study evaluated the effects of sensory-motor denervation on sympathetic neurotransmission in the heart. Newborn rats were injected with capsaicin or its vehicle (Tween 80). Sympathetic neurotransmission was studied in isolated atria driven at a constant rate (4 Hz) by measuring cardiac responses to electrical field stimulation, in the presence of atropine 1 microM. Inotropism of tyramine, norepinephrine and calcitonin gene-related peptide was also tested. Neonatal capsaicin treatment did not affect cardiac responses to trains of an increasing number (2-32) of field pulses. Moreover, inotropic responses to tyramine did not differ between control, capsaicin- and Tween 80-treated preparations. Neither maximal effect nor pD2 values were significantly different between the groups. Similarly, the inotropism of calcitonin gene-related peptide was comparable in all groups of atrial preparations. In marked contrast to earlier papers on blood vessels, this study shows a lack of effect of sensory-motor denervation by neonatal capsaicin treatment on cardiac sympathetic neurotransmission. The different neuronal plasticity of vascular and cardiac sensory innervation will be discussed. The present results also indicate that capsaicin-induced sensory-motor denervation is not associated with changes in cardiac responsiveness to calcitonin gene-related peptide.
Rubino
A
A
Department of Anatomy and Developmental Biology, University College London, England.
Ralevic
V
V
Burnstock
G
G
D000818:Animals; D000831:Animals, Newborn; D015740:Calcitonin Gene-Related Peptide / Q000494:pharmacology; D002211:Capsaicin / Q000494:pharmacology*; D003714:Denervation; D004558:Electric Stimulation; D006325:Heart Atria / Q000187:drug effects* / Q000294:innervation; D066298:In Vitro Techniques; D009638:Norepinephrine / Q000494:pharmacology; D014677:Pharmaceutical Vehicles; D051381:Rats; D017207:Rats, Sprague-Dawley; D013564:Sympathetic Nervous System / Q000187:drug effects* / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects*; D014439:Tyramine / Q000494:pharmacology
D014677:Pharmaceutical Vehicles; D015740:Calcitonin Gene-Related Peptide; D002211:Capsaicin; D009638:Norepinephrine; D014439:Tyramine