Distribution of dopamine-containing neurons and fibres in the feline medulla oblongata: a comparative study using catecholamine-synthesizing enzyme and dopamine immunohistochemistry.
The distribution of dopamine-immunoreactive neurons and fibres in the feline medulla oblongata was examined by immunocytochemistry with antisera to the catecholamine-synthesizing enzymes tyrosine hydroxylase, dopamine-beta-hydroxylase and phenylethanolamine-N-methyltransferase, and with antisera to the catecholamines dopamine and L-dihydroxyphenylalanine. Neurons immunoreactive for the catecholamine-synthesizing enzymes were found in two regions of the medulla, the ventrolateral A1 region and the dorsomedial A2 region. Double-staining studies with antisera to the enzymes indicated that a population of neurons within both regions were immunoreactive for tyrosine hydroxylase but not dopamine-beta-hydroxylase or phenylethanolamine-N-methyltransferase, implying that they synthesize dopamine. Studies using the dopamine antisera demonstrated the presence of dopamine-immunoreactive neurons in both the ventrolateral and dorsomedial regions of the medulla; in the dorsomedial region, they were found in the area postrema, nucleus tractus solitarius and dorsal motor vagal nucleus, mainly at levels caudal to the obex. Dopamine-immunoreactive fibres were found in several areas of the medulla including the nucleus tractus solitarius, inferior olive, dorsal motor vagal, spinal trigeminal, hypoglossal, cuneate, gracile, and raphe nuclei. Double-staining studies with antisera to dopamine and dopamine-beta-hydroxylase revealed a population of cells immunoreactive for dopamine alone. The presence of some double-stained neurons, however, implies some cross-reactivity of the dopamine antiserum with noradrenaline or adrenaline and/or recognition of dopamine present as a metabolic intermediary in some noradrenergic neurons. No L-dihydroxyphenylalanine-immunoreactive neurons were found in the medulla, although fibres were seen. These data provide evidence for the existence of catecholamine neurons which utilize dopamine as a final synthetic product within the medulla oblongata.
Maqbool
A
A
University of Leeds, U.K.
Batten
T F
TF
Berry
P A
PA
McWilliam
P N
PN
D000818:Animals; D002395:Catecholamines / Q000096:biosynthesis*; D002415:Cats; D003429:Cross Reactions; D004298:Dopamine / Q000378:metabolism / Q000502:physiology*; D004299:Dopamine beta-Hydroxylase / Q000276:immunology / Q000378:metabolism; D007150:Immunohistochemistry; D007980:Levodopa / Q000494:pharmacology; D008526:Medulla Oblongata / Q000166:cytology / Q000201:enzymology / Q000502:physiology*; D009412:Nerve Fibers / Q000201:enzymology / Q000502:physiology*; D009474:Neurons / Q000201:enzymology / Q000502:physiology*; D010625:Phenylethanolamine N-Methyltransferase / Q000276:immunology / Q000378:metabolism; D014446:Tyrosine 3-Monooxygenase / Q000276:immunology / Q000378:metabolism
D002395:Catecholamines; D007980:Levodopa; D014446:Tyrosine 3-Monooxygenase; D004299:Dopamine beta-Hydroxylase; D010625:Phenylethanolamine N-Methyltransferase; D004298:Dopamine