RESUMEN
In order to help to organize the understanding of the bewildering complexities of the innervation of the mammalian heart by the vagus nerve and to clear up of confusions as regards the vagus cardiac branches, we scrutinized these branches in the adult house shrew, Suncus murinus, under a stereomicroscope. A number of branches were given off from the vagus nerve not only to the heart, but also to the adjoining great vessels, both outflowing and inflowing. When compared from the developmental viewpoint, the basic conformations of these branches on two sides were found not to differ from each other, but rather presented a symmetrical configuration, the feature which has been ascertained also in mammalian embryos. Relying on developmental criteria, we classified them into the arterial porta-related and the venous porta-related groups, formulating a new terminology by naming them on the basis of their destination. This version of terminology allowed us to define the vagus cardiac branches of the house shrew more accurately than the current terminology (e.g., Nomina Anatomica), and seems to provide us a clue for clearing up confusions concerning the terminology of the vagus cardiac branches in mammals.
Asunto(s)
Corazón/inervación , Terminología como Asunto , Nervio Vago/anatomía & histología , Animales , Aorta Torácica/inervación , Tronco Braquiocefálico/inervación , Arteria Carótida Común/inervación , Femenino , Masculino , Arteria Pulmonar/inervación , MusarañasRESUMEN
The characteristics of brachiocephalic and carotid sinus baroreceptors with non-medullated afferents have been studied in rabbits. The conduction velocities of 18 non-medullated fibers arising from the brachiocephalic baroreceptors were 0.4-0.8 m/s (0.59 +/- 0.03 m/s, mean +/- SE) and their thresholds were 74-104 mmHg (84 +/- 2 mmHg). 29 non-medullated carotid sinus baroreceptor afferents had thresholds ranging from 60 to 125 mmHg (92 +/- 3 mmHg). Their conduction velocities were 0.5-1.1 m/s (0.65 +/- 0.05 m/s). Blood pressure-baroreceptor response curves of both the brachiocephalic and the carotid sinus baroreceptors were constructed. As the aortic arch non-medullated baroreceptor afferents, the brachiocephalic and the carotid sinus baroreceptors with non-medullated afferents exhibited thresholds about 30 mmHg higher than the medullated ones, considerably lower firing rates, comparatively rapid adaptation and remarkable irregular discharge pattern. It is suggested that the non-medullated baroreceptor afferents are of little importance for the cardiovascular regulation under normal conditions but are likely to play an important role during a sudden rise in arterial pressure.