Endocrinology, Vol 131, 1547-1555, Copyright © 1992 by Endocrine Society

ARTICLES

Beta-endorphin innervation of dopamine neurons in the rat hypothalamus: a light and electron microscopic double immunostaining study

TL Horvath, F Naftolin and C Leranth
Department of Obstetrics and Gynecology, University School of Medicine, New Haven, Connecticut 06510.

Pharmacological data suggest that opiates, acting indirectly via the catecholaminergic system, are involved in the inhibition of LH release and the stimulation of PRL secretion. The aim of this study was to demonstrate on the ultrastructural level whether beta-endorphin- immunoreactive fibers form synaptic contacts with hypothalamic dopaminergic neurons. Light and electron microscopic double immunostaining experiments were performed on vibratome sections prepared from the hypothalamus of acrolein-fixed female rat brains. Immunoreactivity for beta-endorphin was visualized by a dark blue to black nickel ammonium sulfate-intensified diaminobenzidine reaction, and in a consecutive immunostaining procedure, the tyrosine hydroxylase- immunoreactive dopamine cells were labeled with the brown diaminobenzidine reaction product. Under the light microscope, beta- endorphin axon terminals were found to contact dopamine cell bodies and dendrites throughout the hypothalamus. The majority of opiate target dopamine neurons were found in the periventricular area, retrochiasmatic area, and lateral part of the zona incerta. A much smaller number was observed in the dorsomedial hypothalamic nucleus and the anterior hypothalamus, and only a very few dopamine cells could be detected in contact with beta-endorphin axons in the arcuate nucleus (particularly in the posterior part where the beta-endorphin cells are located) and the medial part of the zona incerta. After light microscopic examination and color photography, the double immunostained sections were embedded for correlated electron microscopy to verify and characterize the putative synaptic connections. Electron microscopy revealed symmetric synaptic connections between beta-endorphin- immunoreactive boutons and tyrosine hydroxylase-immunopositive cell bodies and dendrites. These results together with the observation of dopamine innervation of LHRH-producing neurons and progesterone receptor-containing cells indicate that neurons of the hypothalamic dopaminergic system probably mediate opiate effects on hypophyseal hormone secretion.

This article has been cited by other articles:

				R. L. Goodman, L. M. Coolen, G. M. Anderson, S. L. Hardy, M. Valent, J. M. Connors, M. E. Fitzgerald, and M. N. Lehman Evidence That Dynorphin Plays a Major Role in Mediating Progesterone Negative Feedback on Gonadotropin-Releasing Hormone Neurons in Sheep Endocrinology, June 1, 2004; 145(6): 2959 - 2967. [Abstract] [Full Text] [PDF]

				N. Ibrahim, M. A. Bosch, J. L. Smart, J. Qiu, M. Rubinstein, O. K. Ronnekleiv, M. J. Low, and M. J. Kelly Hypothalamic Proopiomelanocortin Neurons Are Glucose Responsive and Express KATP Channels Endocrinology, April 1, 2003; 144(4): 1331 - 1340. [Abstract] [Full Text] [PDF]

				N. Ben-Jonathan and R. Hnasko Dopamine as a Prolactin (PRL) Inhibitor Endocr. Rev., December 1, 2001; 22(6): 724 - 763. [Abstract] [Full Text] [PDF]

				T. L. Horvath, S. Diano, and A. N. van den Pol Synaptic Interaction between Hypocretin (Orexin) and Neuropeptide Y Cells in the Rodent and Primate Hypothalamus: A Novel Circuit Implicated in Metabolic and Endocrine Regulations J. Neurosci., February 1, 1999; 19(3): 1072 - 1087. [Abstract] [Full Text] [PDF]

				L. A. Arbogast and J. L. Voogt Endogenous Opioid Peptides Contribute to Suckling-Induced Prolactin Release by Suppressing Tyrosine Hydroxylase Activity and Messenger Ribonucleic Acid Levels in Tuberoinfundibular Dopaminergic Neurons Endocrinology, June 1, 1998; 139(6): 2857 - 2862. [Abstract] [Full Text] [PDF]

				T. L. Horvath An Alternate Pathway for Visual Signal Integration into the Hypothalamo-Pituitary Axis: Retinorecipient Intergeniculate Neurons Project to Various Regions of the Hypothalamus and Innervate Neuroendocrine Cells Including Those Producing Dopamine J. Neurosci., February 15, 1998; 18(4): 1546 - 1558. [Abstract] [Full Text] [PDF]

				J. A. Maurer and S. Wray Luteinizing Hormone-Releasing Hormone (LHRH) Neurons Maintained in Hypothalamic Slice Explant Cultures Exhibit a Rapid LHRH mRNA Turnover Rate J. Neurosci., December 15, 1997; 17(24): 9481 - 9491. [Abstract] [Full Text] [PDF]

				T. L. Horvath Suprachiasmatic Efferents Avoid Phenestrated Capillaries but Innervate Neuroendocrine Cells, Including Those Producing Dopamine Endocrinology, March 1, 1997; 138(3): 1312 - 1320. [Abstract] [Full Text] [PDF]