The nucleus tractus solitarii of the cat: A comparison of Golgi impregnated neurons with methionine‐enkephalin‐ and substance P‐immunoreactive neurons

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Abstract
Golgi-impregnated and methionine-enkephalin (ME)- and substance P (SP)-immunoreactive neurons were studied throughout the feline nucleus tractus solitarii. The majority of Golgi-impregnated neurons in the NTS range in size from 5 to 18 μm. A noticeable exception is the large (15–30 μm) neurons of the ventrolateral subdivision. The Golgi-impregnated neurons possess dendritic trees which remain within the nucleus and even at times within the particular subdivisions. Golgi-impregnated neurons had a variety of spine forms: pedunculated, sessile, filiform, and complex. A number of neurons exhibited axons originating from the cell and they could be followed for distances up to 100 μm. ME- and SP-immunoreactive neurons were found in commissural, medial, lateral, and parvocellular subdivisions while ME-immunoreactive neurons were situated additionally in the intermediate and ventrolateral subdivisions. Both types of immunostained neurons were similar in size (6–20 μm) and shape of dendritic arbor. One population of ME-immunoreactive neurons resembled the large ventrolateral neurons of the Golgi impregnations. Neither type of immunostained neuron possessed the extensive dendritic arbor, numbers of spines, or axons of the Golgi–impregnated neurons. The presence of ME- and SP-immunoreactive neurons in regions which are associated with autonornic regulation suggests that these two peptides are involved in this process.