Modulation by adrenergic transmitters of the efferent function of capsaicin-sensitive nerves in cardiac tissue.
In atrial preparations obtained from reserpine-pre-treated guinea-pigs, incubated in the presence of 1 microM atropine plus 1 microM CGP 20712A (a beta 1 blocking drug), a positive inotropic effect due to CGRP release from capsaicin-sensitive sensory neurons was induced by electrical field stimulation (EFS). This response was concentration-dependently reduced by noradrenaline (0.01-3 microM), neuropeptide Y (NPY, 3-300 nM) and adenosine triphosphate (ATP, 1-30 microM). On the other hand, the overflow of [3H]-noradrenaline from sympathetic nerve terminals induced by EFS in isolated atria obtained from normal untreated animals was not modified in 10 nM calcitonin gene-related peptide (CGRP). Substance P (SP) and neurokinin A (NKA), at concentrations ranging from 0.01 to 1 microM did not affect the cardiac response to field stimulation of adrenergic terminals of atrial tissue. These findings demonstrate that all the co-transmitters stored in adrenergic nerve terminals have a modulatory role on the efferent function of cardiac capsaicin-sensitive sensory neurons, while cardiac adrenergic neurotransmission is not influenced by the peptidergic transmitters released from sensory neurons.
Amerini
S
S
Department of Pharmacology, University of Florence, Italy.
Rubino
A
A
Filippi
S
S
Ledda
F
F
Mantelli
L
L
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000818:Animals; D001285:Atropine / Q000494:pharmacology*; D015740:Calcitonin Gene-Related Peptide / Q000494:pharmacology; D002211:Capsaicin / Q000494:pharmacology*; D004558:Electric Stimulation; D006168:Guinea Pigs; D006325:Heart Atria; D006329:Heart Conduction System / Q000187:drug effects*; D007093:Imidazoles / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D015288:Neurokinin A / Q000494:pharmacology; D009475:Neurons, Afferent / Q000187:drug effects / Q000502:physiology*; D009478:Neuropeptide Y / Q000494:pharmacology; D009638:Norepinephrine / Q000378:metabolism / Q000494:pharmacology*; D010643:Phenoxybenzamine / Q000494:pharmacology; D013373:Substance P / Q000494:pharmacology
D000319:Adrenergic beta-Antagonists; D007093:Imidazoles; D009478:Neuropeptide Y; D010643:Phenoxybenzamine; D013373:Substance P; D001285:Atropine; D015288:Neurokinin A; D000255:Adenosine Triphosphate; C049763:CGP 20712A; D015740:Calcitonin Gene-Related Peptide; D002211:Capsaicin; D009638:Norepinephrine