Biomedical subjects
Publications and source records attributed to W C DeGroat.
Horseradish peroxidase (HRP) was applied to the cornea in cats using a variety of methods. Small numbers of labeled neurons were observed in the superior cervical ganglion (SCG), the majority were located in the rostral half. This confirms previous histofluorescence data which indicated the SCG was the likely source of adrenergic fibers to the cornea.
Retrograde and transganglionic transport of horseradish peroxidase (HRP) was used to trace afferent and efferent pathways in the left inferior cardiac nerve of the cat. Cardiac efferent and afferent neurons were located, respectively, in the stellate ganglion (average cell count per experiment:2679) and in the ipsilateral dorsal root ganglia (DRG) from C8 to T9 (average cell count per experiment:213). Labeled cardiac afferent projections to the spinal cord were most dense in segments T2-T6 where they were located in Lissauer's tract and in lamina 1 on the lateral border of the dorsal horn. Labeled afferent axons extended ventrally through lamina 1 into lamina 5 and the dorsolateral region of lamina 7 in proximity to the intermediolateral nucleus. A weak projection was noted on the medial side of the dorsal horn. These sites of termination are similar to projections by other sympathetic afferent pathways (i.e. renal, hypogastric and splanchnic nerves) to the lower thoracic and lumbar spinal cord, indicating that visceral afferents may have a uniform pattern of termination at various segmental levels. This pattern of termination in regions of the gray matter containing spinothalamic tract neurons and neurons involved in autonomic mechanisms is consistent with the known functions of sympathetic afferent pathways in nociception and in the initiation of autonomic reflexes.
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1. Electrophysiological techniques were used to study the sacral para-sympathetic input to pelvic ganglia located on the surface of the urinary bladder of the cat. 2. Synaptic transmission in pelvic ganglia was mediated primarily via nicotinic receptors although muscarinic excitatory receptors were present. 3. The most prominent characteristic of transmission in pelvic ganglia was the marked recruitment elicited by increasing frequencies of preganglionic nerve stimulation. Post-ganglionic action potentials were of low amplitude at low frequencies of stimulation (0-1-0-5c/s), but commonly increased to five to twenty times control amplitudes during continuous stimulation at frequencies between 5 and 10c/s. Thus, it is proposed that vesical ganglia may act as "filters" in the micturition pathway; blocking the excitatory input to the bladder when intravesical pressure and parasympathetic firing is low and facilitating the neural input to the bladder during micturition when preganglionic activity is high. 4. Information was also obtained about the characteristics of the parasympathetic post-ganglionic neurones innervating the bladder. Stimulation of the preganglionic fibres in the pelvic nerve elicited a bimodal contraction consisting of an initial phasic response, which was atropine-resistant and a tonic response which was blocked by atropine. This suggests that two types of neurones, cholinergic and non-cholinergic, may mediate the sacral input to the vesical smooth muscle.
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