Cells of origin of sympathetic pre‐ and postganglionic cardioacceleratory fibers in the pigeon

Abstract

The pre-and postganglionic cardioacceleratory innervation is described in the pigeon. The peripheral coursc of the postganglionic cardiac nerves has been determined using microdissection and electrical stimulation. Using these techniques and retrograde degeneration methods, the distribution within the sympathetic ganglia of the cells of origin of these fibers has been localized to the three right caudal cervical ganglia (12, 13 and 14). It has also been shown o n the basis of electrical stimulation combined with selective ablation of the right sympathetic chain that cardioaccelerator preganglionic fibers probably arise from the most caudal cervical segment of the spinal cord (14), always arise from the upper two thoracic segments (15 and 1 6 ) , and occasionally arise from a mid-thoracic segment (17). The left sympathetic chain was shown to have an inconsistent influence o n heart rate. On the basis of retrograde degeneration, the cells of origin of sympathetic preganglionic fibers have been localized to a welldefined cell column dorsal to the central canal (column of Terni).This paper is the third in a series of studies designed to describe the cells of origin of vagal and sympathetic fibers controlling heart rate in the pigeon. While the preceding two papers have dealt with the dorsal motor nucleus and peripheral vagus nerve (Cohen, Schnall, Macdonald and Pitts, '70; Cohen and Schnall, ' 7 0 ) , the present report is concerned with the sympathetic innervation of the heart. Specifically, this study was directed toward describing ( a ) the peripheral course of the postganglionic cardioaccelerator nerves; ( b ) the distribution within the sympathetic ganglia of the cells of origin of these fibers; ( c ) the spinal segments contributing cardioacceleratory preganglionic fibers; and ( d ) the localization within the spinal cord of the cells of origin of sympathetic preganglionic fibers. MATERIALS A N D METHODS Dissection of sympathetic nerves and the paravertebral chainDissections were performed on 25 White Carneaux pigeons using a Zeiss Operation Microscope (1OX-16X). All birds were sacrificed by intraperitoneal administration J. COMP. NEUR, 140; 343-358.of an overdose of sodium pentobarbital. In five cases dissection was undertaken immediately upon sacrifice. However, the remaining 20 cases were perfused through the left ventricle with avian saline (0.75%) followed by 10% formalin, and dissections were performed after one to seven days of refrigeration.The surgical approach to the paravertebra1 chain and peripheral sympathetic nerves was as follows. A dorsal midline incision was made from segments 10-19 ' (middle cervical to lower thoracic) and the skin reflected laterally. All muscles inserting on the vertebral column were severed at the midline to allow the muscles and scapula to be reflected laterally and held in position with a retractor, This procedure exposed the intercostal muscles of segments 15-18 and the brachial plexus of

Localization of Sympathetic, Parasympathetic and Sensory Neurons Innervating the Heart of the Beijing Duck by Means of the Retrograde Transport of Horseradish Peroxidase.

“…This may be related to functional differences between the right and left sympathetic cardiac nerves. In the pigeon, electrical stimulation of the right cardiac nerve consistently increases heart rate, whereas this is not true for the left [20]. In parasympathetic and sensory innervation to the heart of the duck, we could not detect obvious laterality.…”

“…In the present study, however, sympathetic postganglionic neurons innervating the heart were observed in the paravertebral ganglia C15 to T3, especially in the ganglion T1. After transection of the sympathetic cardiac nerve in the pigeon, chromatolytic neurons were observed in the paravertebral ganglia C12 to C14 and the proportion of such cells was highest in the ganglion C14, intermediate in the ganglion C13 and lowest in the ganglion C12 [20]. Moreover, HRP-labeled neurons were found in the paravertebral ganglion C14 following application of HRP to the sympathetic cardiac nerve of the pigeon [3].…”

“…This generalization appears to be true at least for the duck and chicken, since bilateral vagotomy of the duck increases heart rate by 65-200%, whereas the same procedure in the chicken increases heart rate by only 20-36% [17]. These species differences are related to the activity pattern of the birds in normal life.The distribution of sympathetic, parasympathetic and sensory neurons innervating the avian heart was only studied in the pigeon using retrograde axonal transport of horseradish peroxidase (HRP) [3], electrical stimulation [7,25] and retrograde degeneration [8,20]. These studies demonstrated that sympathetic postganglionic neurons were located mainly in the paravertebral ganglion C14 (the last cervical segment in the pigeon), parasympathetic preganglionic neurons were observed in the dorsal motor nucleus of the vagus nerve and sensory neurons were found in the dorsal root ganglia C13 and C14.…”

Distribution of choline acetyltransferase and NADPH diaphorase in the spinal cord of the pigeon

“…The last cervical segment, all thoracic segments, and the first two lumbar segments contain preganglionic neurons of the sympathetic nervous system. Caudal to the lumbosacral enlargement there are preganglionic neurons of the parasympathetic system (Terni 1923;Huber 1936;MacDonald and Cohen 1970;Ohmori et al 1984;Hosoya et al 1992). All studies in avian species agree that preganglionic autonomic neurons are localized in a welldefined intermediomedial cell column dorsal to the central canal, the column of Terni (CT).…”

Identification and connections of inspiratory premotor neurons in songbirds and budgerigar

“…The medial ones, which also receive projections as a result of the same medullary injection, and therefore possibly from the same neurons, extend into the column of Terni. Since preganglionic neurons for the heart are located in the column of Terni at upper thoracic levels (Macdonald and Cohen, 1970;Cohen, 1977a, 1977b), it is possible that the descending axons mediate influences upon both the cardiac and respiratory systems, an arrangement possibly conducive to cardio-respiratory integration. The column of Terni is also known to receive projections from the raphe nucleus (Cabot et al, 1979), which probably accounts for the presence of retrogradely labeled cells in the raphe following spinal injections in the present study.…”