Evidence for a cardiovascular role of central galanin neurons: focus on interactions with alpha 2-adrenergic and neuropeptide Y mechanisms.
By means of immunocytochemical analysis using the indirect immunofluorescence method, and by means of receptor autoradiography using 125I-galanin as a radioligand, further evidence has been obtained for the existence of pre- and postsynaptic features of galanin neurons in the nucleus tractus solitarius (nTS) and the dorsal motor nucleus of the vagus (dmnX) of the male rat. Thus, a high density of galanin immunoreactive nerve terminals was found within the medial subnucleus of the nTS, in the periventricular region and within the medial part of the dmnX. High densities of 125I-galanin binding sites were found in the entire medial and lateral part of the nTS and in the dmnX as evaluated at a level approximately 1-2 mm rostral to obex. The physiological studies were performed in alpha-chloralose anesthetized male rats by injecting galanin in the nmolar range i.c. and measuring mean arterial blood pressure and heart rate (HR). The results showed a weak hypotensive action of galanin (3 nmol) and a clearcut tachycardic action (10 nmol). When administered simultaneously with clonidine no additive effects were observed on mean arterial blood pressure but the bradycardic action of clonidine was blocked and the tachycardiac action of galanin prevailed. Similar results were obtained when galanin was injected simultaneously with NPY. These results indicate a cardiovascular role of galanin, and the morphological evidence favors the view that the galaninergic mechanism involved is located within the dorsal cardiovascular center of the medulla oblongata.(ABSTRACT TRUNCATED AT 250 WORDS)
Härfstrand
A
A
Department of Histology, Karolinska Institutet, Stockholm, Sweden.
Fuxe
K
K
Melander
T
T
Hökfelt
T
T
Agnati
L F
LF
D000818:Animals; D001345:Autoradiography; D001794:Blood Pressure; D002320:Cardiovascular Physiological Phenomena; D002319:Cardiovascular System / Q000187:drug effects; D019004:Galanin; D007150:Immunohistochemistry; D007278:Injections, Spinal; D008297:Male; D008526:Medulla Oblongata / Q000033:anatomy & histology / Q000276:immunology / Q000378:metabolism*; D009478:Neuropeptide Y / Q000378:metabolism; D009479:Neuropeptides / Q000493:pharmacokinetics / Q000494:pharmacology*; D010455:Peptides / Q000493:pharmacokinetics / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism; D044088:Receptors, Galanin; D011964:Receptors, Gastrointestinal Hormone / Q000276:immunology / Q000378:metabolism; D012119:Respiration
D009478:Neuropeptide Y; D009479:Neuropeptides; D010455:Peptides; D011942:Receptors, Adrenergic, alpha; D044088:Receptors, Galanin; D011964:Receptors, Gastrointestinal Hormone; D019004:Galanin