Immunohistochemical demonstration of regionally selective projections from locus coeruleus to the vestibular nuclei in rats

This study describes a regionally selective projection of tyrosine hydroxylase and dopamine beta-hydroxylase-immunoreactive fibers from locus coeruleus (LC) and the A4 region of nucleus subcoeruleus to the vestibular nuclear complex in Long-Evans and Sprague-Dawley rats. These fibers travel in two distinct pathways. A lateral descending noradrenergic bundle provides input from LC to the superior vestibular nucleus (SVN), the cochlear nuclei, and the cerebellar cortex. A medial descending noradrenergic bundle provides input to the lateral vestibular nucleus (LVN), medial vestibular nucleus (MVN), and the inferior vestibular nucleus (IVN) before continuing on to the cochlear and cerebellar nuclei. The terminal plexus of these fibers varies markedly across these vestibular nuclear regions. Immunoreactive axons form a dense plexus around somata and proximal dendrites of Deiters' neurons in dorsal LVN. The axon plexus is less dense in SVN and ventral LVN, and relatively sparse in MVN and IVN. This regional selectivity of noradrenergic innervation suggests that central adrenergic systems may selectively modulate vestibulospinal reflexes at the level of the vestibular nuclear complex.

Resistance of hippocampal CA-1 noradrenergic fibers to five minutes of transient cerebral ischemia in the gerbil

We examined changes in the tyrosine hydroxylase (TH)-immunoreactive fibers following 5 min of cerebral ischemia in gerbils using an immunohistochemical method 1, 3 and 30 days after ischemia. Almost all CA-1 pyramidal neurons were lost 3 days after ischemia, whereas noradrenergic fibers were maintained 30 days after ischemia. The present study demonstrated that TH-immunoreactive fibers and cells were resistant to transient ischemia, and that there was no sprouting or hyperactivity in noradrenergic systems after ischemia.

Spinal projections of the locus coeruleus and the nucleus subcoeruleus in the Harlan and the Sasco Sprague-Dawley rat

The descending projections of the locus coeruleus (LC) and the nucleus subcoeruleus (SC) to the lumbar spinal cord were examined in rats from two vendors using retrograde transport of fluorescent latex beads. There was a vendor difference observed which agrees with previous findings. The differential dorsal horn and ventral horn projections of the Harlan and the Sasco Sprague-Dawley rats, reported by Fritschy and Grzanna, and Clark and Proudfit were confirmed. In the Harlan rat more cells were labeled in the LC following injections in the dorsal horn. In contrast, in the Sasco rat, more cells were labeled in the LC from injections in the ventral horn. Although, in all studies, the LC in rats from these vendors projected to some extent to both the dorsal and the ventral horn. A difference in labeling was noted also for the depth of placement of the tracer in the dorsal horn. When the site of injection was in the nucleus proprius, a predominantly contralateral projection of the LC was noted. In contrast, when horseradish peroxidase (HRP) gel implants were placed to include the superficial laminae, the cells in the LC were labeled predominantly ipsilaterally. The SC has a major projection to the dorsal horn in the Harlan rats while cells in the SC were predominantly labeled following ventral horn injection in the Sasco rats. These cells send mostly ipsilateral projections to the dorsal and ventral horn of the spinal cord. Double labeled studies confirmed that 91% of LC and 86% of SC neurons projecting to the spinal cord were noradrenergic.(ABSTRACT TRUNCATED AT 250 WORDS)

Ultrastructural analysis of noradrenergic nerve terminals in the cat lumbosacral spinal dorsal horn: a dopamine-beta-hydroxylase immunocytochemical study

Noradrenaline-containing nerve terminals within the cat spinal dorsal horn were studied by immunocytochemical localization of dopamine-beta-hydroxylase. Immunoreactive terminals formed symmetrical (Gray type II) synaptic specializations with dendrites and somata throughout laminae I-IV, but no junctions were formed with other axons. These findings suggest that noradrenaline regulates sensory transmission through the dorsal horn via a postsynaptic action.

Coincidence of "ladder-like patterns" in distributions of monoaminergic terminals and sympathetic preganglionic neurons in the rat spinal cord

A ladder-like pattern of distribution of sympathetic preganglionic neurons (SPNs) was compared with that of monoaminergic terminals in the upper thoracic spinal cord of the rat. SPNs were identified by a retrograde labeling with cholera toxin subunit B (CTb) injected into the superior cervical ganglia of both sides. Monoaminergic terminals were stained immunohistochemically by using antisera raised against 5-hydroxy-tryptamine (5-HT) or dopamine-beta-hydroxylase (DBH). SPNs showing full dendritic arbors were found in all of the sympathetic preganglionic nuclei. They formed a ladder in the horizontal plane. The nucleus intermediolateralis was connected with the central autonomic nucleus by many transverse dendritic bundles. Photomontages of serial sections of material stained alternatively with antisera against CTb and 5-HT or DBH clearly showed a close correlation between SPNs and monoaminergic terminals. There is no transverse dendritic bundle of SPNs without the accompaniment of monoaminergic terminals.

Production and immunocytochemical application of a highly sensitive and specific monoclonal antibody against rat dopamine-beta-hydroxylase

A highly sensitive and specific monoclonal antibody against the enzyme dopamine beta-hydroxylase (DBH) from rat was produced and coded DBH 41. The generated hybridoma secreted immunoglobulins of mouse IgG1 subtype, as determined by radial immunodiffusion. This antibody, characterized by immunoblotting against a crude rat DBH preparation, was found to specifically recognize two bands of molecular weight 70 and 75 kDa corresponding to the soluble and membrane bound forms of the enzyme, respectively. With regard to species specificity, the anti-DBH antibody recognizes only the rat DBH molecule as it exhibits no cross-reactivity with either mouse, human, rabbit, guinea pig, cat or bovine DBH. Comparative immunocytochemical localization of DBH and TOH immunoreactivity was performed in different brain regions and we found that the DBH 41 antibody specifically stained DBH-containing neurons and fibers in the rat central nervous system (CNS). The high sensitivity of the DBH 41 antibody permitted us to detect immunologically the presence of the enzyme even in areas where only scattered DBH-containing fibers were present.

Antibodies raised against different oligopeptide segments of human dopamine-beta-hydroxylase

We raised antibodies against 3 oligopeptide segments of human dopamine-beta-hydroxylase (hDBH) corresponding to the N-terminal (hDBH-N), the intermediate (hDBH-I), and the C-terminal (hDBH-C) amino acid sequences (residues 26-43, 452-468, and 582-598), respectively. We characterized the antibodies in terms of specificity by means of Western blotting and immunohistochemistry. Anti-hDBH-N antiserum recognized DBH in the brain (noradrenergic neurons in the pons and medulla oblongata) and adrenal medulla, not only of human but also of mouse, rat and house shrew. In contrast, anti-hDBH-C antiserum recognized only human DBH. These observations suggest that the antibody raised against the hDBH-C terminal peptide may specifically recognize only human DBH.

Noradrenergic innervation of human inferior olivary complex

Antisera to human dopamine beta-hydroxylase (DBH) was used to stain noradrenergic axons in the inferior olivary complex (IOC) of human controls. A modest plexus of thin, beaded, immunoreactive fibers was present in all subdivisions of the IOC, and many fibers coursed in the rostrocaudal axis. This noradrenergic plexus is similar to that of monkey, provides complementary evidence to reports of beta-adrenergic receptors in human IOC, and supports the concept of noradrenergic projections to IOC.

Noradrenergic innervation of the substantia innominata: a light and electron microscopic analysis of dopamine beta-hydroxylase immunoreactive elements in the rat

Noradrenergic input to the rat substantia innominata (SI) was analyzed in this study by immunocytochemical localization of dopamine beta-hydroxylase (DBH), the synthetic enzyme for noradrenaline. DBH immunoreactive (DBH+) axons ramified extensively within the SI and appeared to be contiguous with the DBH+ terminal fields within the bed nucleus of stria terminalis and the amygdaloid complex. DBH+ axons in the SI exhibited many large boutons en passant and boutons terminaux. These DBH+ boutons appeared much larger than those in the cerebral cortex, hippocampus, and thalamus. Electron microscopic analysis revealed that DBH+ boutons formed asymmetrical synapses with mainly dendrites, but also somata and spines of SI neurons. Dendrites which were postsynaptic to DBH+ boutons also formed synapses with many other unlabeled axon terminals. Since previous studies have shown that dendrites of SI cholinergic neurons formed few synapses, the present result suggests that the noradrenergic influence of SI cholinergic neurons may be mediated mainly by polysynaptic pathways.

Brainstem afferents to the tuberomammillary nucleus in the rat brain with special reference to monoaminergic innervation

Monoaminergic innervation of a histamine-producing cell group, the tuberomammillary nucleus in the posterior hypothalamus, was investigated in the rat by light and electron microscopic immunohistochemical techniques. Immunohistochemical staining of sections of the posterior hypothalamus was demonstrated afferent fibers immunoreactive to tyrosine hydroxylase in ventral and medial subgroups of the tuberomammillary nucleus afferent fibers immunoreactive to tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (DBH), phenyletanolamine-N-methyltransferase (PNMT), and serotonin (5-HT). TH- and DBH-immunoreactive fibers were similar and were evenly and densely distributed throughout the tuberomammillary nucleus. Fibers stained with 5-HT antibodies were also present throughout the tuberomammillary nucleus but exhibited the densest labeling in the dendritic layer adjacent to the glia limitans in the ventral subgroup. Innervation by PNMT-immunoreactive axons was sparse. Electron microscopic analysis of TH-, DBH-, and 5-HT-immunoreactive fibers in the tuberomammillary nucleus revealed vesicle-containing terminal boutons, which formed synapses with dendrites of varying size. Synaptic contacts with nerve cell bodies were not found. Retrograde transport of the fluorescent dye Fast Blue injected into the tuberomammillary nucleus, combined with immunofluorescent staining with anti-TH, anti-DBH, anti-PNMT, and anti-5-HT antibodies, showed that monoaminergic input to the tuberomammillary nucleus originated mainly from the adrenergic and noradrenergic cell groups C1-C3 and A1-A2, respectively, and from the serotoninergic cell groups B5-B9 as designated by Dahlström and Fuxe ('65). Few double-labeled neurons were found in the nucleus locus coeruleus and the dopaminergic cell groups of the rostral brain stem. The present findings suggest that the activity of the histamine-producing neurons of the tuberomammillary nucleus is influenced by monoaminergic neurons in the ventrolateral and dorsomedial medulla oblongata and the raphe nuclei of the rostral brainstem.

Purifications of rat adrenal dopamine-beta-hydroxylase: immunological analysis of its soluble and membrane-bound forms with the use of an antibody raised against the soluble form

Soluble and membrane-bound dopamine-beta-hydroxylases (sDBH and mDBH, respectively) from rat adrenal glands have been purified through concanavalin A-Sepharose chromatography, gel filtration, and ion-exchange high-performance chromatographies. Both sDBH and mDBH were composed by four subunits of apparent molecular weight of 75,000 and showed a native molecular weight of 300,000. This procedure has not allowed us to obtain a sufficient amount of enzyme to immunize a rabbit. A second, more rapid procedure was designed to isolate sDBH, including concanavalin A-Sepharose chromatography and preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A rabbit antiserum was raised against this purified protein. The specificity of the antiserum was demonstrated by neutralization of rat adrenal gland DBH activity, labeling of rat adrenal medulla on histological sections, and, after Western blot, labeling of the 75,000-molecular-weight band in the different fractions associated with DBH activity during purification. The antiserum had a higher affinity for the sDBH denatured by sodium dodecyl sulfate than for the native protein. It had a higher affinity for sDBH than for mDBH. These results strongly suggest the presence of specific hydrophilic epitopes on the sDBH, revealing structural differences between the two hydroxylase forms. Two protein bands were stained on Western blots of crude rat adrenal gland extract. One band had an apparent molecular weight of 75,000, and the other of 82,000. Our results showed that the two proteins contained similar epitopes, an observation suggesting a close structural relationship. The higher-molecular-weight protein could be the 75,000 protein before covalent modifications and cleavage.

Neuropeptide distribution in the cervico-thoracic paravertebral ganglia of the cat with particular reference to calcitonin gene-related peptide immunoreactivity

Paraffin sections of cervical and upper thoracic paravertebral ganglia of the cat were investigated by immunohistochemistry using antisera directed against calcitonin gene-related peptide (CGRP). The relationships of CGRP-immunoreactive structures to those exhibiting immunoreactivity to antisera against other regulatory peptides and dopamine-beta-hydroxylase (DBH), respectively, were studied in consecutive sections. Singly scattered CGRP-immunoreactive neuronal perikarya were observed in the superior and middle cervical ganglia as well as in the stellate ganglion. These neurons also displayed immunoreactivity to vasoactive intestinal polypeptide (VIP), and some additionally exhibited faint substance-P immunoreactivity. DBH- and neuropeptide Y-immunoreactive ganglion cells were not identical with CGRP-immunoreactive neuronal cell bodies. According to the immunoreactive properties of varicosities, which abut on CGRP/VIP-immunoreactive perikarya, three types of CGRP/VIP-immunoreactive ganglion cells could be distinguished: (1) CGRP/VIP-immunoreactive neurons being surrounded by somatostatin-immunoreactive nerve fibers, (2) neurons being approached by both DBH- and met-enkephalin-immunoreactive varicosities, and (3) neurons receiving both DBH- and neurotensin-immunoreactive fibers. The stellate and upper thoracic ganglia harbored clusters of intensely VIP-immunoreactive somata, which lacked CGRP-immunoreactivity. Fine somatostatin-immunoreactive and coarse CGRP-immunoreactive fibers were distributed within these clusters, whereas patches of neurotensin-immunoreactive fibers were complementarily arranged. At all segmental levels investigated, a few postganglionic neurons were approached by both CGRP-immunoreactive and substance P-immunoreactive varicosities, but lacked a VIP-immunoreactive innervation. Therefore, CGRP/substance P-immunoreactive fiber baskets appeared rather to be of extraganglionic origin than to emerge from intraganglionic CGRP/VIP/SP neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Noradrenaline and neuropeptide Y innervation of the rat hypothalamus are differentially affected by 6-hydroxydopamine

The neuropeptide Y (NPY) innervation of the hypothalamus is thought to arise largely from noradrenaline (NA) neurons of the medullary tegmentum in the rat. This view was tested in this study by analyzing the effects of intraventricular injections of 6-hydroxydopamine (6-OHDA) on hypothalamic NA and NPY innervation. 6-OHDA markedly depletes or eliminates the NA innervation of the hypothalamus, as demonstrated by dopamine-beta-hydroxylase immunohistochemistry, but does not affect the NPY innervation of the hypothalamus. These results indicate that the hypothalamic NPY innervation arises in large part from intrinsic NPY-producing neurons rather than from medullary neurons in which NA and NPY coexist.

Increased dopamine-beta-hydroxylase-like immunoreactivity in non-noradrenergic axons supplying the guinea-pig uterine artery after 6-hydroxydopamine treatment

We have reinvestigated the immunohistochemistry of autonomic axons supplying the guinea-pig uterine artery to determine whether non-noradrenergic paracervical ganglion neurons projecting to the artery contain immunoreactivity to dopamine-beta-hydroxylase (DBH) or somatostatin (SOM) in addition to neuropeptide Y (NPY) and vasoactive intestinal peptide (VIP). In untreated arteries no VIP axons had immunoreactivity to tyrosine hydroxylase (TH), although 9% had immunoreactivity to DBH. Somatostatin immunoreactivity was detected in 25% of non-noradrenergic axons containing NPY and VIP. After in vivo treatment with 6-hydroxydopamine (6-OHDA), noradrenergic axons containing immunoreactivity to NPY, DBH and TH were absent from the adventitia-medial junction. However, 65-70% of the non-noradrenergic axons with NPY and VIP showed DBH immunoreactivity after 6-OHDA. These axons did not show catecholamine fluorescence after incubation with pargyline together with noradrenaline, dopamine or L-DOPA. The number of axons with SOM immunoreactivity increased by 44% after 6-OHDA treatment, but only 24% of SOM axons had DBH immunoreactivity. Surgical destruction of the non-noradrenergic autonomic axons in 6-OHDA-treated animals led to the loss of all DBH immunoreactivity. These results demonstrate that DBH immunoreactivity can be detected in a small proportion of non-noradrenergic axons supplying uterine arteries from untreated animals. After chemical sympathectomy with 6-OHDA, the levels of DBH immunoreactivity in axons of non-noradrenergic neurons increased, and more axons with DBH immunoreactivity were detected. DBH immunoreactivity seemed to increase preferentially in axons with NPY and VIP, but not SOM. The number of NPY, VIP axons containing SOM also increased after 6-OHDA. These findings demonstrate that peripheral neurons containing several different potential neurotransmitters can change their levels of neuropeptides and transmitter-synthesizing enzymes in response to local environmental changes.

Immunoelectron microscopic localization of dopamine beta-hydroxylase and chromogranin A in adrenomedullary chromaffin cells

Dopamine beta-hydroxylase (DBH) was purified from bovine adrenal medullae. Rabbit IgG raised against DBH inhibited its activity by 80%. In an immunoblot analysis, the IgG specifically recognized two subunits of DBH the 72 and 75 KD components. Chromogranin A (CGA) also was purified from bovine adrenal medullae, and rabbit IgG against CGA recognized this chromogranin A in the immunoblot analysis. The intracellular distribution of DBH and CGA in bovine chromaffin cells was determined quantitatively by immunoelectron microscopy using post-embedding protein A-gold technique. DBH and CGA were localized exclusively on chromaffin granules. The binding of gold particles to these granules was saturable. The maximum number of gold particles bound to the granules roughly corresponded to the number of DBH or CGA molecules in the granules estimated biochemically. DBH was observed evenly in the periphery and in the dense matrix of the chromaffin granules.

Immuno cross-reactivity suggests that catecholamine biosynthesis enzymes and beta-adrenergic receptors may be related

Turkey red blood cell, beta 1-adrenergic receptors (BARs) were prepared to electrophoretic homogeneity by affinity chromatography, size exclusion high performance liquid chromatography, and preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis and used to prepare rabbit polyclonal anti-BAR antibodies. Anti-BAR activity was confirmed by immunoadsorption of [125I]cyanopindolol-labeled BAR to a protein A affinity column using the anti-BAR antibodies. BAR was compared to the catecholamine biosynthetic enzyme dopamine B-hydroxylase (DBH) by anti-BAR antibody cross-reactivity. DBH was purified from bovine adrenal medullae chromaffin vesicles by ion exchange, size exclusion, and concanavalin A-Sepharose chromatography. Final DBH specific activities were 42 +/- 4 units/mg of protein. Homogeneity was confirmed by nondenaturing polyacrylamide gel electrophoresis. Both DBH and BAR were recognized by the anti-BAR antibodies on Western transfer and immunoblotting. No interactions were observed with preimmune controls. Similar results were obtained with glycosylated and deglycosylated DBH, suggesting that the anti-BAR antibodies recognize specific portions of DBH amino acid sequence and not associated carbohydrate. DBH-cross-reactive antibodies were also purified by affinity chromatography using immobilized DBH and shown to immunoadsorb [125I]cyanopindolol-labeled BAR by protein A affinity chromatography. These results suggest that the catecholamine biosynthetic enzyme DBH and BAR may be related in structure.

Noradrenergic innervation of the pineal gland--histochemical basis of scintigraphic imaging?

There is first evidence that the adult human pineal gland may be equipped with noradrenergic fibers as is the case in a variety of mammalian species. It therefore appears worthwhile to investigate the capacity of pineal noradrenergic nerves to take up 123I-MIBG, a prerequisite for scintigraphic imaging.

An immunological characterization of five common antigens of chromaffin granules and of large dense-cored vesicles of sympathetic nerve

Bovine chromaffin granules and large dense-cored vesicles of bovine splenic nerve were compared by one- and two-dimensional immunoblotting. Both types of vesicles contain chromogranin A, B and C. However, the proteolytic processing of these chromogranins within these vesicles is apparently different. Chromogranin B in chromaffin granules is processed by more than 80% whereas in nerve vesicles only 15% has been broken down to smaller proteins. In addition both types of vesicles contain dopamine beta-hydroxylase and cytochrome b-561.

Specific lysis of noradrenergic synaptosomes by an antiserum to dopamine-beta-hydroxylase

An antiserum to dopamine-beta-hydroxylase purified from bovine adrenal medulla, acting in the presence of complement, caused the release of 12% of lactate dehydrogenase, 20% of tyrosine hydroxylase activity, and 40% of noradrenaline (NA) content from synaptosomes prepared from rat brain cerebral cortex. Uptake of [3H]NA was reduced by 54%. Anti-serum alone or complement alone were without action. The antiserum plus complement had no effect on choline uptake and did not release choline acetyltransferase, glutamate decarboxylase, dopamine or 5-hydroxytryptamine. These results suggest selective lysis of noradrenergic terminals had occurred. An enhancement of lysis was not observed when synaptosomes were stimulated with 75 mequiv./lK+ and exposed to a sub-maximal dose of antiserum, plus complement.

Immunohistochemical study of catecholaminergic cell bodies in the rat spinal cord

Immunohistochemistry of three specific synthesizing catecholamine enzymes was used in the rat spinal cord to determine precisely the distribution of catecholaminergic perikarya and the nature of the neurotransmitter they contain. Single and double labeling experiments were performed on cryostat sections from perfused rats. The peroxidase anti-peroxidase (PAP) and the indirect fluorescence techniques were used for labeling spinal catecholaminergic somata and separated into two completely different populations. The first is located in the upper cervical cord and includes three apparently distinct groups: a lateral cluster, of probably a noradrenergic nature, and two central subgroups where noradrenergic and dopaminergic neurons are intermingled. It is likely that these cervical cells represent caudal extensions of the medullary catecholaminergic cell groups. In the remaining cord, only tyrosine hydroxylase immunoreactive cell bodies have been found. Accordingly, this second population is probably dopaminergic. It is present almost exclusively in the first sacral segments, where it is located in the commissural (mostly lateral) grey matter and in the marginal dorsal horn.

Immunohistochemical and biochemical study on the development of the noradrenaline- and adrenaline-storing cells of the adrenal medulla of the rat

The pre- and postnatal development of the adrenal medulla was examined in the rat by immunohistochemistry and by assay of catecholamines. Immunohistochemistry involved the use of antibodies to noradrenaline (NA), adrenaline (A) and the biosynthesizing enzymes dopamine beta-hydroxylase (DBH) and phenylethanolamine N-methyltransferase (PNMT). Adrenal glands were obtained from animals from the 16th day of gestation to the 7th postnatal day at daily intervals, and at the 14th postnatal day, and from adult rats. Tissues were fixed in ice-cold, 4% paraformaldehyde, buffered at pH 7.3. Cryostat sections (7 microns) were stained with the indirect immunofluorescence technique. Adrenals from the same developmental stages were assayed for the presence of DA (dopamine), NA and A by ion-pair reversed-phase liquid chromatography with electrochemical detection. In adult adrenals the majority of the medullary cells (approximately 80%) were highly immunoreactive to A and moderately immunoreactive to NA. They also showed immunoreactivity to both DBH and PNMT, i.e., they are synthesizing and storing A. The remaining cell clusters were only stained by antibodies to DBH and NA (NA-synthesizing and -storing cells). These findings correlate well with the relative concentrations of A and NA as determined by assay. Three developmental phases could be distinguished. In the first phase, the 16th and 17th prenatal day, medullary cells were only immunoreactive to DBH and NA, and only very small amounts of A as compared to NA were found. During the second period, from the 18th prenatal day to 2 or 3 days after birth, all medullary cells were immunoreactive to DBH, NA, PNMT and A, and during this phase the adrenaline concentration increased daily and became the predominant amine on the 20th day of gestation. Adrenaline represented 75% of total catecholamine on the 1st to 3rd day after birth. The third phase started at the 2nd or 3rd postnatal day and was characterized by the presence of an increasing number of medullary cells solely immunoreactive to DBH and NA, hence synthesizing and storing NA. The remaining cells were immunoreactive to DBH, NA, PNMT and A. Postnatally, the relative concentration of A continued to rise reaching 79% by the 4th postnatal day. These results indicate that initially the adrenal medullary cells are synthesizing and storing almost exclusively NA.(ABSTRACT TRUNCATED AT 400 WORDS)

Distribution of dopamine-beta-hydroxylase-like immunoreactivity in the rat pineal organ

The aim of the present investigation was to study the distribution in the rat pineal gland of dopamine-beta-hydroxylase (DBH) which is essential for the formation of the melatonin synthesis-regulating substance noradrenaline (NA). In 5- and 8-month-old male Sprague-Dawley rats DBH-like immunoreactivity (DBH-LI) was studied using polyclonal antibodies against DBH and the indirect immunofluorescent technique. DBH-LI was mainly located in pineal nerve fibres coming from the superior cervical ganglia. The intensity of the staining reaction was considerably lower than in non-pineal noradrenergic nerve fibres and the impression was gained by comparison of DBH-LI specimens with glyoxylic acid-treated sections that only approximately one third of the NA-containing intrapineal nerve fibres exhibited DBH-LI. There were no detectable differences in DBH-LI with regard to time of day and age of the animals. These results suggest that NA synthesis may be relatively low in intrapineal sympathetic nerve fibers and that the NA required for the regulation of pineal melatonin synthesis may, to a large degree, stem from the circulation. In addition to nerve fibres, some rare intrapineal cell bodies exhibited DBH-LI; in 5-month-old rats their numbers did not reveal significant differences between day and night. These cells do not appear to represent pinealocytes. They may be a special population of noradrenergic nerve cells perhaps belonging to an as yet unknown intrapineal regulatory system.

Cytochemical relationships in the paracervical ganglion (Frankenhäuser) of rat studied by immunocytochemistry

Vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY) and calcitonin gene-related peptide (CGRP) immunoreactivities have been demonstrated in the paracervical ganglion of the rat using immunocytochemistry. Dopamine beta-hydroxylase (D beta H) and neurofilament protein triplet immunoreactivities have also been demonstrated in this region. The VIP, NPY, D beta H and neurofilament immunoreactivities were located in ganglion cells and nerve fibres, while CGRP immunoreactivity was localized only in nerve fibres. Many cells immunoreactive with D beta H antiserum were also immunoreactive with NPY antiserum. A small number of cells immunoreactive with VIP antiserum were also immunoreactive with NPY antiserum. CGRP-immunoreactive nerve fibres were distributed in certain regions of the ganglion only.

Characteristic distribution of noradrenergic terminals on the anterior horn motoneurons innervating the perineal striated muscles in the rat. An immuno-electromicroscopic study

Dopamine-beta-hydroxylase (DBH) immunohistochemistry was used to demonstrate the noradrenergic fibers and terminals in the anterior column of the rat lumbosacral spinal segments. PAP-positive varicose fibers were widely distributed in the gray matter with preferential accumulation in the nuclear regions containing motoneurons involved in the contraction of perineal striated muscles. Unmyelinated DBH fibers were composed of nodular enlargements (varicosities, 0.4-3.0 microns in diameter) and very fine, short intervals (intervaricose segments, 0.1-0.2 micron in diameter and 1.0-4.0 microns in length). DBH-positive dense products were electron microscopically often confined within small granular particles and less frequently within large granules. Additionally, in order to characterize the innervation pattern of noradrenergic fibers on dendritic bundles organized in the motoneuronal pools innervating the pelvic small muscles, semi-quantitative analysis was done in the area of the dorsolateral nucleus endowed with especially well-developed dendritic bundles. DBH terminals contacting with unreactive dendrites were more common (67.9%) than those with neuronal somata (15.1%), and the remainder (17%) had no contacts with surrounding neuronal elements. Furthermore, specialized synaptic formations were observed in only 20.1% of these nodules. The results suggest that bulbospinal descending noradrenergic neuron systems influence the functioning of pelvic muscles principally via the neuronal contacts with dendritic bundles in the spinal cord.

Dopamine beta-hydroxylase-like immunoreactivity in the rat and cat carotid body: a light and electron microscopic study

Immunocytochemical localization of dopamine beta-hydroxylase (DBH) was used to study the synthesis and storage sites of norepinephrine (noradrenaline) in the rat and cat carotid bodies. In the rat carotid body some parenchymal cells exhibited strong DBH-like immunoreactivity (DBH-I), while others displayed only faint DBH-I. In a typical parenchymal cell cluster, most cells with strong DBH-I were irregular in shape and appeared to partially surround those with weak DBH-I which usually were rounded in contour. In the cat carotid body most parenchymal cells showed a strong to moderate DBH-I. In both the rat and cat carotid bodies varicose nerve fibres with DBH-I were associated primarily with blood vessels. All autonomic ganglion cells examined, which were associated with the rat carotid body, showed DBH-I. Electron microscopy revealed that most DBH-I in the strongly positive cells of the rat carotid body was associated with dense granules (possibly corresponding to dense-cored vesicles of various sizes), although some was found in other sites. In oval cells with less DBH-I, reactivity resided in some of the large granules. In the cat carotid body the glomus cells contained more granules of various sizes and shapes than did those of the rat carotid body. Most of the cat glomus cell granules exhibited DBH-I activity. Our results indicate that some of glomus cells in the rat and most of the glomus cells in the cat contain DBH and therefore may be sites of norepinephrine synthesis.

Purification and characterization of rat dopamine beta-monooxygenase and monoclonal antibodies to the enzyme

Dopamine beta-monooxygenase was extensively purified from rat adrenal. The specific activity of the final preparation was approx. 1500 nmol/min per mg protein, which was much higher than the highest yet reported. As judged by gel filtration on Ultrogel AcA22, SDS-polyacrylamide gel electrophoresis, and cross-linking studies, the enzyme appeared to be composed of four identical subunits, each possessing a molecular weight of 88 000. The isoelectric point of the enzyme was estimated to be pH 6.6 in the presence of 8 M urea. Spleen cells from BALB/c mice immunized with rat dopamine beta-monooxygenase were fused to P3-X63-Ag8-653 mouse myeloma cells. From 55 hybrid cells, 10 stable clones secreting anti-dopamine beta-monooxygenase antibody were obtained. Antibody from one clone was coupled to CNBr-activated Sepharose 4B and the monoclonal antibody-Sepharose was shown to be very useful to isolate rat dopamine beta-monooxygenase from crude preparations.

Retrograde transport of dopamine beta-hydroxylase antibodies in sympathetic neurons: effects of drugs modifying noradrenergic transmission

Antibodies to dopamine beta-hydroxylase (anti-D beta H) were taken up by noradrenergic nerve terminals in the iris following attachment to D beta H, and were transported back to, and accumulated in, the superior cervical ganglion (SCG). Concurrent, or prior destruction of noradrenergic terminals with 6-hydroxydopamine, injected intraocularly, blocked the retrograde transport of anti-D beta H. However, recovery was rapid, reaching 50% of control values within 1 day. Such transport was characterized by a shorter time period before accumulation could be detected in the SCG and by a slower rate of accumulation. These results suggest that noradrenergic neurons recover their ability to turn over synaptic vesicles by exocytosis and transport these back to the ganglion early during the period of axonal regeneration when the axonal length is shorter than normal. The uptake and transport of anti-D beta H was regulated by alpha-adrenergic agents administered locally in the vicinity of noradrenergic nerve terminals. Thus intraocular injection of phentolamine resulted in an increased accumulation of anti-D beta H in the SCG, while amphetamine and the postsynaptic alpha-receptor antagonist, phenylephrine, decreased accumulation. Clonidine and desipramine, which have a predominant presynaptic action, failed to influence the transport of anti-D beta H. These results suggest that in vivo the uptake of anti-D beta H can be increased more by local postsynaptic reflex actions than by a mechanism depending on the inhibition of presynaptic alpha-receptors.

A new methodological approach for studying axonal transport: cytofluorometric scanning of nerves

A new technique for studying axonal transport has been developed. The technique, which is based on histofluorescence techniques, enables the measurement of several different accumulated substances and parameters within a single nerve in relation to a nerve crush or local cooling. Any substance that can be made to fluoresce can be measured. The tissue is treated according to the formaldehyde-induced fluorescence method of Hillarp and Falck for visualization of monoamines, or according to the indirect immunofluorescence method. For immunofluorescence the nerve is cryostat-sectioned and various sections can be incubated with primary antisera against different antigens. After incubation and mounting the sections are placed in a cytofluorimeter (Leitz MPV II). They are passed under a measuring slit at a steady speed by a motor driven cross-table. The fluorescence intensity passing through the measuring slit is continuously registered by a recording unit with an integrator. This recorder produces a graphical nerve accumulation profile, and the area under the profile, relating to the fluorescence, is expressed in arbitrary units. This article presents data on the accumulation of noradrenaline, dopamine beta-hydroxylase, and tyrosine hydroxylase in crush-operated rat sciatic nerve. The time-course accumulations for noradrenaline (visualized by the Falck and Hillarp method) and dopamine beta-hydroxylase (visualized by immunofluorescence) demonstrated a striking similarity, which is to be expected since the two substances are stored in the same organelle. Tyrosine hydroxylase (visualized by immunofluorescence) showed a slower accumulation with time, but faster than would be expected had the enzyme been 100% soluble. Colchicine but not lumi-colchicine blocked the transport of noradrenaline organelles. With the new scanning technique we have the potential to study accumulation profiles of several different substances within a single nerve. Morphometric data, morphological observations, and photograph documentation of the same nerve section are also available.

Genomic and phenotypic expression of autonomic neurons

We found that catecholamine biosynthetic enzymes, tyrosine hydroxylase, dopamine B-hydroxylase and phenylethanolamine N-methyl-transferase share similar protein domains in their primary structures, and therefore are coded for by a single gene or a family of genes. In a recent report, we also demonstrated that antisera directed against tyrosine hydroxylase, choline acetyltransferase and glutamate decarboxylase cause specific complement-mediated lysis of dopaminergic, cholinergic and GABA-ergic subpopulation of synaptosomes, respectively. This implies that the neurotransmitter biosynthetic enzyme and the specific nerve ending protein(s) also share similar protein domain(s). Therefore, we postulate that the specific neurotransmitter biosynthetic enzyme and a certain membrane protein of the nerve endings probably share similar gene coding sequences and that coordinate expression of these proteins may determine the phenotype of the neuron.

Immunofluorescent evidence for exocytosis and internalization of secretory granule membrane in isolated chromaffin cells

Cultured bovine adrenal medullary chromaffin cells were stimulated with the secretogogues Ba2+ or carbamyl choline plus Ca2+ in the presence of a monospecific rabbit IgG fraction directed against bovine dopamine beta-hydroxylase. The anti-dopamine beta-hydroxylase was labeled either with fluorescent protein A or with a fluorescent second antibody to rabbit IgG. Stimulation produced a patchy cell surface distribution of fluorescence. There was no noticeable internalization of the fluorescence for up to 2 h. In similar experiments using fluorescent monovalent fragments (Fab) of the same monospecificidopamine-beta-hydroxylase IgG, a more uniform distribution of the fluorescence was observed. A few min after a 5 min period of stimulation with Ba2+, the fluorescence appeared to be on or near the cell surface; however, after 20 min or more it was distributed throughout the cytoplasm except that the cell nuclei were not labeled. Thus, dopamine beta-hydroxylase which appeared on the cell surface as a consequence of exocytosis was internalized in the presence of monovalent antibody fragments, but not in the presence of the divalent (polyclonal) antibody, presumably because endocytosis of dopamine beta-hydroxylase was inhibited by crosslinking of the dopamine beta-hydroxylase molecules. The internalized anti-dopamine beta-hydroxylase Fab fragments were found to reappear on the cell surface during a second secretory response. It is concluded that the interior of the chromaffin granule membrane, for which dopamine beta-hydroxylase is a marker, becomes exposed on the surface of the cell during secretion and that the membrane is then retrieved back into the cell where it can be re-used in a further secretory cycle.

Enkephalins are associated with adrenergic granules in bovine adrenal medulla

The subcellular localization of enkephalins was studied in the bovine adrenal medulla. In the adrenal medulla enkephalins (Met-enkephalin, Leu-enkephalin, Met-enkephalin-Arg6-Phe7 and Met-enkephalin-Arg6-Gly7-Leu8) are found free and in the form of cryptic peptides included in larger precursors. Total Met-enkephalin immunoreactivity, which includes free and cryptic peptides, was determined after a sequential enzymatic treatment with trypsin and carboxypeptidase B. Total Met-enkephalin immunoreactivity, dopamine beta-hydroxylase and catecholamines were found to have a parallel distribution in the various subcellular fractions. The bulk of the total Met-enkephalin immunoreactivity (42%) was recovered in the large granule fraction. The large granule fraction also contained 38% of the total dopamine beta-hydroxylase activity, and 42% of the total catecholamines. Enkephalins are thus concentrated in the chromaffin granules. Chromaffin granules were also separated according to the method of Terland & coworkers into two fractions: one containing the dense noradrenergic vesicles and the other containing lighter adrenergic vesicles. Total Met-enkephalin immunoreactivity was restricted to the fractions containing the lighter adrenergic vesicles. In these fractions the molar ratio of adrenaline to total Met-enkephalin immunoreactivity was 97. This study is in accord with immunocytochemical observations which have indicated that enkephalins are located in adrenergic and not in the noradrenergic cells in the bovine adrenal medulla.

Tetanus toxin binding to different morphological phenotypes of cultured rat and bovine adrenal medullary cells

Tetanus toxin (TT) binding to cultured rat and bovine adrenal medullary cells has been investigated using indirect immunofluorescence and anti-dopamine-beta-hydroxylase (DBH) antibodies as a probe to identify catecholaminergic cells. TT binds to all rat adrenal medullary cells which display a neuronal phenotype induced by treatment with nerve growth factor and/or medium conditioned by C6 glioma cells. In contrast, 90-95% of the rounded DBH-positive cells are TT-negative, suggesting that in vitro-transdifferentiation of rat chromaffin cells alternates the expression of membrane properties. Cultured bovine chromaffin cells have no TT binding sites independent of their morphological phenotype.

Origins of spinal noradrenergic pathways demonstrated by retrograde transport of antibody to dopamine-beta-hydroxylase

Retrograde transport of antibody to dopamine-beta-hydroxylase (DBH) was used to locate the cells of origin of descending noradrenergic (and possibly adrenergic) pathways to the spinal cord. Following injections of DBH antibody into various spinal cord levels, cell bodies were immunocytochemically localized in brainstem nuclei known to contain noradrenergic neurons. These cell groups included the nucleus locus coeruleus, the nucleus subcoeruleus, the medial and lateral parabrachial nuclei, the Kölliker-Fuse nucleus, and the region dorsal and lateral to the superior olivary nucleus. Caudally, none of the noradrenergic cell groups of the medulla contained retrogradely labeled neurons. These findings indicate that the sources of spinal cord noradrenergic input are derived exclusively from the cells of the pons.

Immunochemical evidence for exocytosis in isolated chromaffin cells after stimulation with depolarizing agents

After chemical stimulation with depolarizing agents (Ba2+ or Ca2+/carbachol) isolated living chromaffin cells display a drastically increased binding capacity for anti-DBH, distributed spotwise on or near the outer cell membrane. This effect is inhibited by noradrenaline; it is not evoked by the non-exocytotically releasing agents tyramine and reserpine. the effect of apparent externalization of DBH is paralleled by the observation of a DBH-dependent binding of 125I-labelled protein A upon the same depolarizing stimuli. These observations are discussed as possible evidence for exocytotic activities.

Effect of nerve activity on transport of nerve growth factor and dopamine beta-hydroxylase antibodies in sympathetic neurones

The effect of nerve activity on the uptake and retrograde transport of nerve growth factor (NGF) and dopamine beta-hydroxylase (DBH) antibodies was studied by injecting 125I-labelled NGF and anti-DBH into the anterior eye chamber of guinea-pigs. Decentralization of the ipsilateral superior cervical ganglion (SCG) had no significant effect on the retrograde transport of either NGF or anti-DBH. Phenoxybenzamine produced a 50% increase in anti-DBH but not NGF accumulation and this effect was prevented by prior decentralization. This demonstrates that NGF is taken up independently of the retrieval of synaptic vesicle components.

Immune lesions of central noradrenergic neurons produced by antibodies to dopamine-beta-hydroxylase

(1) Intraventricular injection of antibodies to dopamine-beta-hydroxylase (DBH) caused degeneration of central noradrenergic nerve terminals in rats and guinea-pigs. In rats it was necessary to infuse exogenous complement in the form of guinea-pig serum together with the anti-DBH, whereas in guinea-pigs the anti-DBH was effective on its own. Control animals were infused with equivalent amounts of non-immune serum and complement and showed no signs of degeneration other than in the region of the needle tract. (2) There was a loss of varicosities in most terminal fields of the noradrenergic projections and swollen distorted axons were seen in both ascending and descending noradrenergic pathways. Noradrenergic cell bodies in the locus coeruleus and subcoeruleus appeared unaffected. No histochemical changes were observed in dopaminergic neurons. (3) The ultrastructural changes in degenerating axons that were first identifided by fluorescence histochemistry included swelling, vacuolation, accumulation of dense cored vesicles, lysosome-like bodies and smooth membranous sacs. The surrounding neuropil appeared normal. (4) There was a significant depletion of noradrenaline in all regions of the rat brain ranging from 20% in the hypothalamus to 80% in the neocortex. Dopamine concentrations were unaffected. (5) These observations provide a new approach to the production of selective lesions in specific neurotransmitter pathways that could be extended to non-adrenergic neurones. They may also be useful as a model for the study of autoimmune diseases of the nervous system.

Immunochemically identical hydrophilic and amphiphilic forms of the bovine adrenomedullary dopamine beta-hydroxylase

By means of a monospecific antibody, dopamine beta-hydroxylase was monitored immunoelectrophoretically in various extracts of chromaffin granules. Approximately one-third of the dopamine beta-hydroxylase present was located in the membrane fraction and could only be liberated with detergent. The dopamine beta-hydroxylases of the buffer and membrane fractions were antigenically identical, but differed in their amphiphilicity, as demonstrated by the change in precipitation patterns on removal of Triton X-100 from the gel, on charge-shift crossed immunoelectrophoresis and on crossed hydrophobic interaction immunoelectrophoresis with phenyl-Sepharose. Furthermore, immunoelectrophoretic analysis in the presence of Triton X-100 plus the cationic detergent cetyltrimethylammonium bromide indicates additional heterogeneity of the membrane-bound dopamine-beta-hydroxylase. By limited proteolysis with chymotrypsin and thermolysin the amphiphilic form could be convered into its hydrophilic counterpart.

Specific uptake and retrograde flow of antibody to dopamine-beta-hydroxylase by central nervous system noradrenergic neurons in vivo

This study sought to determine whether the administration in vivo of antibody to dopamine-beta-hydroxylase (AD beta H) is taken up by central noradrenergic neurons and transported by retrograde flow to the cell bodies of origin. AD beta H serum or preimmune serum (control) in volumes of 1--20 microliter were stereotaxically injected into the lateral ventricle. Rats were sacrificed at times ranging from 1 h to 8 days. Cryostat sections were stained with fluorescein conjugated IgG. After 24 h, a bilateral granular fluorescence was seen only in neuronal cell bodies corresponding to noradrenergic cell groups A1--A7 with the most intense fluorescence localized within perikarya and processes of the locus coeruleus (A6) and subcoeruleus. This technique also permitted the visualization of the ascending dorsal and ventral noradrenergic bundles as well as varicose fibers and terminals in a pattern identical to that reported with histofluorescence, autoradiographic, biochemical and classical immunofluorescence techniques for the identification of noradrenergic fiber distributions. At 3 and 6 h, the first detectable fluorescence was observed in forebrain noradrenergic terminals and in fibers of the dorsal and ventral noradrenergic bundles. At 10 h fluorescent varicosities were first visualized within the caudal dorsal bundle and some cytoplasmic fluorescent particles were seen within locus coeruleus cell bodies. After 18 h locus coeruleus and subcoeruleus cell bodies were heavily stained, whereas medullary noradrenergic cell groups and nerve fibers were not labeled until after 24 h. An intense locus coeruleus fluorescence remained for 3 days and was completely absent after 6 days. Bilateral transection of the dorsal noradrenergic bundle in the rostral mesencephalon, at the time of injection, effectively blocked the retrograde transport of fluorescing material to the locus coeruleus. The overall staining pattern suggests that, in vivo, central noradrenergic fibers are capable of taking up antibody to dopamine-beta-hydroxylase. The ability of a dorsal bundle transection to abolish locus coeruleus staining, as well as the time course of AD beta H staining in noradrenergic neurons, suggests that AD beta H is transported via a rapid retrograde flow process. This technique combines retrograde transport of a marker protein with the sensitivity and specificity of immunocytochemical procedures to provide a new tool for the neuroanatomical study of neurotransmitter systems.

Noradrenergic transmission in isolated guinea-pig intestine following in vivo administration of antibodies to dopamine beta-hydroxylase

The effectiveness of transmission from noradrenergic nerves supplying the guinea-pig ileum was evaluated in normal preparations and in preparations taken from animals injected 18 h to 4 days previously with antiserum to dopamine beta-hydroxylase. Degeneration of the nerves following the antiserum was monitored histochemically in the same preparations. A decline in the effectiveness of transmission, which paralleled the degeneration of the nerves, was observed. The earliest effects were detected at 18 h and the greatest effect was found at 2-4 days following the administration of antiserum. Binding of the antibodies has been detected as early as 6 h after injection. It is therefore concluded that binding of the antibodies to the nerves, per se, does not significantly compromise transmission, and that histochemical evidence of degeneration can be used to indicate the onset of functional deterioration of noradrenergic nerves following their exposure to antibodies to dopamine beta-hydroxylase.

[Preparations of human dopamine beta hydroxylase subunits and antibodies against these subunits (author's transl)]

The present study deals with the dissociation of human dopamine beta hydroxylase (DBH) in subunits with a mol. wt of 79,500, and the preparation of specific antibodies in rabbits. No cross-reactivity was observed between human DBH and antibodies against human DBH subunits.

Visualization of central noradrenergic neurons in thick sections by the unlabeled antibody method: a transmitter-specific Golgi image

The unlabeled peroxidase-antiperoxidase method has been used with an antiserum against rat dopamine-beta-hydroxylase (DBH) to obtain a three-dimensional image of noradrenergic cell bodies and their processes in thick Vibratome sections of rat brain. This method stains DBH-positive neurons exclusively with a result similar to that of the Golgi method, which makes it possible to analyze the geometric plan of these neurons and their projections in the central nervous system. In 100-micron sections, DBH-positive axons can be followed over long distances, and the results indicate that their distribution in cerebral and cerebellar cortex is not diffuse but has a strict geometric order.

Properties of partially purified bovine brain dopamine beta-hydroxylase

Dopamine beta-hydroxylase has been partially purified from bovine brain. A 140-fold purification factor was achieved using solubilization with Triton X-100, ammonium sulphate fractionation between 20-50 per cent saturation, affinity chromatography on concanavalin A-Sepharose 4 B and then filtration through Sephadex G200. The specific activity at the end was 51 nmoles/h/mg protein. The majority of endogenous inhibitors were lost. Immunological studies, kinetic studies, studies on the interaction with lectins and the effect of carboxylic acids on enzyme activity were carried out. Our data are in favour of the close similarity between the bovine brain and adrenal enzymes. No major differences could be found, at least with the characterization experiments using in the present study.

Involvement of complement in degeneration of sympathetic nerves after administration of antiserum to dopamine beta-hydroxylase

The involvement of complement in the degeneration of noradrenergic nerves in the guinea-pig iris produced by administration of antibody to dopamine beta-hydroxylase (DBH) in vivo was investigated histochemically. When 500 microliter of antiserum to DBH was injected systemically, no evidence of degeneration was observed in the iris although the noradrenergic supply of the myenteric plexus of the ileum degenerated within 2 days. However, injection of 20 microliter of complement (C) into the anterior chamber of one eye within 2 days of the systemic administration of anti-DBH produced a degeneration of 50--90% of noradrenergic terminals in the iris, the nerves of the iris of the contralateral uninjected eye being unaffected. Electron microscopy confirmed the presence of degenerating nerve terminals in the iris. The extent of degeneration produced by addition of C decreased when C was injected at increasing intervals after the antiserum. Intraocular injection of 5 microliter of anti-DBH together with 20 microliter of C caused a substantial degeneration of noradrenergic nerves in the iris. In contrast, intraocular injection of the Fab'2 fragment of anti-DBH (which did not bind C, but still bound DBH in vitro and in vivo) failed to cause degeneration in the presence of 20 microliter of C. The degeneration of guinea-pig sympathetic nerves caused by antibodies to DBH thus appears to be due to a complement mediated lysis of sympathetic axon membranes. The relative susceptibilities of the noradrenergic fibres in different tissues probably depend on the local concentrations of anti-DBH and C.

Inheritance of low immunoreactive human plasma dopamine-beta-hydroxylase. Radioimmunoassay studies

Inheritance plays an important role in the determination of human plasma dopamine-beta-hydroxylase (DBH) enzymatic activity. It has been demonstrated that an allele (d) for very low enzymatic plasma DBH is inherited as an autosomal recessive trait. A radioimmunoassay for human DBH was developed to test the hypothesis that the presence of this allele results in a decrease in plasma DBH protein levels. The mean immunoreactive DBH (IDBH) in blood from a randomly selected population of adolescents was 824+/-38 ng/ml (mean+/-SEM, n = 134). The correlation coefficient of enzymatic DBH with IDBH for this group of 134 adolescents was 0.84 (P < 0.001). Of these subjects, 3.7% had values of < 100 ng/ml and appeared to compose a separate subgroup analogous to the 3-4% of the population that is homozygous for the allele for low enzymatic activity. There was a significant sibling-sibling correlation of IDBH values in the 14 sibling pairs included among the 134 subjects studied (r = 0.60, P < 0.025). IDBH was also measured in blood from 56 subjects homozygous (dd) for the allele for low enzymatic DBH (enzymatic activity < 50 U/ml) and in blood of 80 first-degree relatives of homozygous probands. All but two dd subjects had IDBH levels of <100 ng/ml. Results of family studies were compatible with the autosomal recessive inheritance of an allele for IDBH levels of less than 100 ng/ml which segregates with the allele for very low enzymatic activity. Average IDBH in blood of 37 obligate heterozygotes as determined by family studies (Dd) was 599+/-53 ng/ml (mean +/- SEM), significantly lower than the IDBH values found in a randomly selected population (P < 0.005). These results are compatible with the conclusion that the presence of the allele for low plasma enzymatic DBH results in a decrease in the quantity of DBH protein in human plasma.