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Localization of tyrosine hydroxylase in neuronal targets and efferents of the area postrema in the nucleus tractus solitarii of the rat.
J Comp Neurol. 1993 Mar 15; 329(3):337-53.JC

Abstract

Catecholamines in the nucleus tractus solitarii (NTS) have been implicated in autonomic responses to circulating hormones that act on neurons in the area postrema, the most caudal circumventricular organ in brain. We combined immunoperoxidase labeling of the anterograde tracer, Phaseolus vulgaris leucoagglutinin (PHAL) with immunogold-silver labeling of tyrosine hydroxylase to determine whether this enzymatic marker for catecholamines was present in efferents from the area postrema or their targets in the rat NTS. At survival periods of 10-12 days after PHAL injections into the area postrema, light microscopy revealed numerous varicose processes containing peroxidase reaction product for PHAL in the dorsomedial, medial, and commissural NTS. Some of these labeled processes were located near neuronal perikarya and processes containing immunogold-silver intensified reaction product for tyrosine hydroxylase. Electron microscopy of the commissural and dorsomedial NTS established that the majority of the labeling for PHAL was in axon terminals, whereas immunogold labeling for tyrosine hydroxylase was mainly in soma and dendrites. Only 3 out of 579 PHAL-labeled terminals also contained detectable tyrosine hydroxylase immunoreactivity. Fifty-eight percent (335/579) of the PHAL-labeled terminals formed synapses with recognized symmetric junctions, whereas the remainder lacked synaptic specializations within the examined series of serial sections. Of those PHAL terminals forming recognized symmetric junctions, 22% were on tyrosine hydroxylase-immunoreactive dendrites, 74% on unlabeled dendrites and 4% on unlabeled axon terminals. From a total of 1,250 observed contacts on tyrosine hydroxylase labeled dendrites, 88 (7%) contained PHAL, 9 (< 1%) contained TH, and 1,180 (93%) lacked detectable immunoreactivity and formed primarily symmetric synapses. We conclude that a few catecholamine, but mainly noncatecholamine efferents from the area postrema provide a monosynaptic, and most likely inhibitory input to target neurons both with and without tyrosine hydroxylase immunoreactivity in the dorsomedial and commissural NTS. Synapses between the efferent terminals from the area postrema and tyrosine hydroxylase labeled and unlabeled dendrites as well as unlabeled axons in these specific subnuclei of the NTS suggest multiple sites for modulation of gastric and cardiovascular reflexes in response to circulating peptides.

Authors+Show Affiliations

Department of Neurology and Neuroscience, Cornell University Medical College, New York, New York 10021.No affiliation info available

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

8096227

Citation

Kachidian, P, and V M. Pickel. "Localization of Tyrosine Hydroxylase in Neuronal Targets and Efferents of the Area Postrema in the Nucleus Tractus Solitarii of the Rat." The Journal of Comparative Neurology, vol. 329, no. 3, 1993, pp. 337-53.
Kachidian P, Pickel VM. Localization of tyrosine hydroxylase in neuronal targets and efferents of the area postrema in the nucleus tractus solitarii of the rat. J Comp Neurol. 1993;329(3):337-53.
Kachidian, P., & Pickel, V. M. (1993). Localization of tyrosine hydroxylase in neuronal targets and efferents of the area postrema in the nucleus tractus solitarii of the rat. The Journal of Comparative Neurology, 329(3), 337-53.
Kachidian P, Pickel VM. Localization of Tyrosine Hydroxylase in Neuronal Targets and Efferents of the Area Postrema in the Nucleus Tractus Solitarii of the Rat. J Comp Neurol. 1993 Mar 15;329(3):337-53. PubMed PMID: 8096227.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Localization of tyrosine hydroxylase in neuronal targets and efferents of the area postrema in the nucleus tractus solitarii of the rat. AU - Kachidian,P, AU - Pickel,V M, PY - 1993/3/15/pubmed PY - 1993/3/15/medline PY - 1993/3/15/entrez SP - 337 EP - 53 JF - The Journal of comparative neurology JO - J. Comp. Neurol. VL - 329 IS - 3 N2 - Catecholamines in the nucleus tractus solitarii (NTS) have been implicated in autonomic responses to circulating hormones that act on neurons in the area postrema, the most caudal circumventricular organ in brain. We combined immunoperoxidase labeling of the anterograde tracer, Phaseolus vulgaris leucoagglutinin (PHAL) with immunogold-silver labeling of tyrosine hydroxylase to determine whether this enzymatic marker for catecholamines was present in efferents from the area postrema or their targets in the rat NTS. At survival periods of 10-12 days after PHAL injections into the area postrema, light microscopy revealed numerous varicose processes containing peroxidase reaction product for PHAL in the dorsomedial, medial, and commissural NTS. Some of these labeled processes were located near neuronal perikarya and processes containing immunogold-silver intensified reaction product for tyrosine hydroxylase. Electron microscopy of the commissural and dorsomedial NTS established that the majority of the labeling for PHAL was in axon terminals, whereas immunogold labeling for tyrosine hydroxylase was mainly in soma and dendrites. Only 3 out of 579 PHAL-labeled terminals also contained detectable tyrosine hydroxylase immunoreactivity. Fifty-eight percent (335/579) of the PHAL-labeled terminals formed synapses with recognized symmetric junctions, whereas the remainder lacked synaptic specializations within the examined series of serial sections. Of those PHAL terminals forming recognized symmetric junctions, 22% were on tyrosine hydroxylase-immunoreactive dendrites, 74% on unlabeled dendrites and 4% on unlabeled axon terminals. From a total of 1,250 observed contacts on tyrosine hydroxylase labeled dendrites, 88 (7%) contained PHAL, 9 (< 1%) contained TH, and 1,180 (93%) lacked detectable immunoreactivity and formed primarily symmetric synapses. We conclude that a few catecholamine, but mainly noncatecholamine efferents from the area postrema provide a monosynaptic, and most likely inhibitory input to target neurons both with and without tyrosine hydroxylase immunoreactivity in the dorsomedial and commissural NTS. Synapses between the efferent terminals from the area postrema and tyrosine hydroxylase labeled and unlabeled dendrites as well as unlabeled axons in these specific subnuclei of the NTS suggest multiple sites for modulation of gastric and cardiovascular reflexes in response to circulating peptides. SN - 0021-9967 UR - https://www.unboundmedicine.com/medline/citation/8096227/Localization_of_tyrosine_hydroxylase_in_neuronal_targets_and_efferents_of_the_area_postrema_in_the_nucleus_tractus_solitarii_of_the_rat_ L2 - https://onlinelibrary.wiley.com/resolve/openurl?genre=article&amp;sid=nlm:pubmed&amp;issn=0021-9967&amp;date=1993&amp;volume=329&amp;issue=3&amp;spage=337 DB - PRIME DP - Unbound Medicine ER -