Depletion of cardiac vagal motoneurons in the diabetic rat: a wheat germ agglutinin-horseradish peroxidase neurohistomchemical study

The projections of vagal neurons to the heart were studied in streptozotocin-induced diabetic Sprague-Dawley rats using the Wheat germ Agglutinin-Horseradish peroxidase (WGA-HRP) neural tracing technique. Experimental rats were rendered diabetic by intraperitoneal injection of streptozotocin (STZ) in 0.5 M citrate buffer at pH 4.5 in a dosage of 60mg/kg body weight. The rats became diabetic within 24 hours of treatment with streptozotocin. The diabetic rats were maintained in a stable diabetic state by daily injections of insulin for 16 weeks. Age-matched control rats were injected intraperitoneally with the same volume of citrate buffer not containing STZ. The blood glucose level of control rats was confirmed to be within normal range prior to and 24 hours after injection. with citrate buffer. Control rats were also kept alive for 24 hours after citrate buffer injection. At the end of 24 hours the treated and control groups were injected with WGA-HRP, and sacrificed 48-72 hours after tracer injection. Transverse serial sections of frozen brainstem were prepared, processed for WGA-HRP neurohistochemistry, and examined under light and dark field microscopy. The analyses of the sections taken from the chronic diabetic rats revealed further WGA-HRP neurons in the nucleus ambiguous (nA) than sections taken from the control normoglycaemic rats. There was also sporadic labelling of the dorsal motor nucleus of the vagus nerve (DMNV) in the control rat but none at all in the diabetic rats. The depletion of labelled neurons in the diabetic rats compared with the normoglycaemic rats is indicative of impairment of retrograde neuronal transport of WGA-HRP in chronic diabetic state.

The localization of cardiac vagal motoneurons in the medula of the ferret (Mustela Putorius Furo)

Using the Horseradish peroxidase (HRP) retrograde axonal transport labelling technique, the central origins of cardiac vagal preganglionic neurons were investigated in the ferret. The atrial and ventricular walls of the heart were injected with HRP following exposure of the heart through a left thoracotomy. A set of control ferrets was injected in the same manner as the experimental rat with normal saline, while another set was injected with HRP after bilateral cervical vagotomy. The last set of control ferrets received HRP injections into the lest ventricular cavity. After 48-72 hours of survival period, serial transverse frozen sections of the brainstem and upper spinal cord were taken and processed for HRP neurohistochemistry using the tetramethylbenzidine method as earlier described by Mesulam (1,2.). Examinations of the sections under bright and dark-field illumination revealed the presence of HRP labeled neurons bilaterally in the nucleus ambiguus (nA). Few labeled neurons were also seen in the dorsal motor nucleus of the vagus nerve (DMX). HRP labeled neurons were not seen in any of the control sets. It is concluded that the heart in the ferret receives its' vagal preganglionic innervation principally from the nA and partly from the DMX (AU)

Preganglionic parasympathetic vagal innervation of the pylorus: a HRP study in the ferret (Mustela Putorius Furo)

The brainstem origins of vagal preganglionic parasympathetic neurons innervating the pylorus was studied in the ferret using the Horseradish peroxidase (HRP) neurohistochemical technique. A total of 12 adult male and female ferrets (8 experimental and 4 controls) were used for the study (AU)