Development of beta-adrenergic receptors and the in vitro accumulation of cyclic AMP in the chick spinal cord

Effects of 6-hydroxydopamine on the development of the immune system in chickens

It has been suggested that the sympathetic nervous system communicates with lymphocytes expressing cell surface receptors for neurotransmitters such as norepinephrine (NE), on the basis of the finding that neurotransmitters modify immune responses in mammalian species. We confirmed that chicken lymphocytes in the brusa of Fabricius, thymus and spleen expressed beta-adrenergic receptor (beta-AR) mRNA from embryonic day (E) 10 and that intracellular cAMP level was elevated by NE, suggesting that lymphocytes express functional beta-AR on their surface at an early embryonal stage. To clarify whether the nervous system is involved in the development of the immune system, the effects of 6-hydroxydopamine (6-OHDA), one of sympathectomizing agents, on chicken lymphocytes was investigated. A single injection of 6-OHDA at a dose of 400 microg into a chicken embryo was carried out at E7 or 14 (as referred to E7 group and E14 group, respectively). NE level and the relative proportion of Bu-1a(+), CD4(+) and CD8(+) cells in the spleen of 3-week-old chickens were not altered by 6-OHDA treatment. However, the proliferative responses and expression of IL-2 mRNA in spleen cells cultured with pokeweed mitogen were reduced in E7 group compared with those of control. Furthermore, in CD8(+) spleen cells of E14 group of 3-week-old chickens, the expression of beta-AR mRNA and the relative increase of intracellular cAMP stimulated with NE were significantly decreased. These results suggest that the sympathetic nervous system affects the development of the immune system.

The postnatal development of norepinephrine-stimulated cyclic AMP accumulation in rat spinal cord

Norepinephrine (NE) stimulated cyclic adenosine 3',5'-monophosphate (cyclic AMP) accumulation in regional spinal cord and cortical tissue slices from postnatal rats demonstrated distinct developmental patterns. NE-concentration-response studies using a 10-min incubation period demonstrated minimal NE-stimulated cyclic AMP accumulation in whole spinal cord at PD 1-5 with maximal sensitivity on PD 12. Thereafter, sensitivity decreased to adult values at PD 30. Sensitivity changes were reflected in alterations in maximal response only since NE EC50s all averaged 10(-6) M. This agrees with no change in calculated Kd for NE with increased Vmax to PD 12 and a reduction thereafter. Studies on regional spinal cord and cerebral cortical cyclic AMP accumulation indicated peak NE sensitivity in cervical and thoracic cord occurred at PD 10, in lumbar cord at PD 15, and in cerebral cortex at PD 20. The fact that inhibition of phosphodiesterase (PPDE) produced the same percentage alteration in peak accumulation in spinal cord slices regardless of postnatal age suggests that PPDE is not the primary determinant of the ontogenic changes. The results indicate that the postnatal development of spinal NE receptors may be reflected in an increase in the responsiveness of the cyclic AMP system to NE.

Synthesis of catecholamines in the developing spinal cord of the rat

Using mass fragmentographic techniques, the synthesis of dopamine (DA) and norepinephrine (NE) was studied in five functional regions in the spinal cord of the developing rat. Norepinephrine was first detectable in the whole cord on fetal day (FD) 16. Thereafter, there was a rapid increase in synthesis. The fastest rate occurred in the ventral horn. The peak concentration was recorded in the latter half of neonatal life, followed by a decline back to the levels found in the adult cord. The capacity of the developing cord to synthesize NE from injected L-dihydroxyphenylalanine (L-DOPA) increased in concert with its normal synthetic capacity. There was no clear consistent pattern in the development of DA synthesis, with two exceptions: (1) in the cervical dorsal horn (CDH), cervical ventral horn ( CVH ), and thoracic zona intermedia ( TZI ), there was a peak of DA on the day of birth; (2) in all regions there was a peak of DA on neonatal day (ND) 20. At FD 16 (the earliest time studied) the developing cord was capable of considerable synthesis (6.0 nmol/g) of DA from injected L-DOPA. This synthetic capacity developed rapidly, peaked at ND 4, and declined back to the adult levels by ND 20. Control experiments indicate that only about 10% (at best) of the DA synthesized from injected L-DOPA occurs in monoaminergic nerve terminals. Norepinephrine is synthesized exclusively in noradrenergic nerve terminals. The newly synthesized DA and NE are both extensively metabolized in the cord. The results are discussed in relationship to current attempts to understand the functional importance of spinal monoaminergic nerves.(ABSTRACT TRUNCATED AT 250 WORDS)

The development of catecholaminergic nerves in the spinal cord of rat. II. Regional development

The development of noradrenergic and dopaminergic nerves in 5 regions of the developing spinal cord of rat, from fetal day (FD) 16, to the young adult stage was studied. The normal synthetic capacity of adrenergic nerves in the ventral horn of the cervical and lumbar regions developed at the same time, and at the same rate, despite their spatial separation, and before similar development of the noradrenergic nerves in the dorsal horn and zona intermedia. In the ventral horn, the synthesis of NE from injected L-DOPA, as well as the release and metabolism of NE are well-established at 12 h (ND 0.5) after birth. In the dorsal horn these developments occur later at ND 4. Except in the dorsal horn of the cervical region, there was no easily observable, consistent pattern in the development of regional spinal dopaminergic innervation. The capacity of the developing cord to synthesize dopamine (DA) from injected DOPA is significantly developed at FD 16 (the earliest time studied), and peaked in all regions as early as ND 4. Control experiments indicate that 100%, and only 10% respectively of NE and DA synthetized from injected DOPA, occurred in descending monoaminergic fibers. Norepinephrine is synthesized exclusively in noradrenergic nerves. Cells appear transiently in the developing cord at FD 18, that are capable of synthesizing catecholamines (probably mainly DA) from injected DOPA. During postnatal development of the cord, and to a less extent in the adult, the network of catecholaminergic nerves actually present, is more extensive than that normally revealed during routine fluorescence microscopy. The results are discussed in the context of current attempts to understand the functional importance of catecholaminergic nerves in the mammalian spinal cord, and elsewhere in the CNS.

An epinephrine-containing pathway in avian spinal cord: development and localization

We have studied the uptake mechanism, biochemistry and autoradiographic localization of a descending epinephrine-containing pathway in the chick spinal cord. This epinephrine (E) projection has a developmental timetable (appears at 14 days in ovo) that is different from those of the serotonin (5-HT) and norepinephrine (NE) projections which appear at 8 and 12 days respectively. E possesses its own uptake mechanism with different pharmacological specificities from those of the NE and 5-HT uptake mechanisms. Phenylethanolamine-N-methyltransferase (PNMT), the enzyme that converts NE to E, is present in the cord at 14 days in ovo which is the same time that the uptake mechanism is detectable. Transection of the spinal cord at upper thoracic levels almost completely eliminates the uptake mechanism and PNMT activity below the transection, indicating a supraspinal origin of this pathway. E can first be detected fluorimetrically at 12 days in ovo but at this age E appears not to be of supraspinal origin since transmission at 5 days in ovo does not deplete the spinal cord of E. However, transection of the spinal cord at 3 days post-hatching does markedly reduce the E content by 12 days. Autoradiographic analysis after uptake with [3H]E shows a circumscribed localization of the uptake of E to the neuropil of the preganglionic sympathetic nucleus (nucleus of Terni). These observations demonstrate the presence of a separate descending epinephrine-containing projection in the avian spinal cord which terminates predominantly on preganglionic sympathetic neurons. This pathway may be the major central autonomic pathway in the avian spinal cord.

Evidence for the existence of alpha- and beta-adrenoceptors on neurones and glial cells of cultured rat central nervous system--an autoradiographic study

The cellular localization of the binding of radioactive noradrenaline and alpha- and beta-adrenoceptor antagonists was studied in organotypic cultures of rat cerebellum, brain stem and spinal cord using autoradiography. In cerebellar cultures, many neurones, which appeared to be Purkinje cells, were labelled by [3H]noradrenaline and by the beta-antagonists [3H]dihydroalprenolol and [3H]carazolol, whereas no binding of the alpha-antagonists [3H]prazosin and [3H]rauwolscine was detected. In cultures of spinal cord and brain stem, [3H]noradrenaline and the beta-antagonists were bound to many large neurones. Binding of [3H] alpha-antagonists was observed to a small number of brain stem and spinal neurones, the labelling being much weaker than that produced by the [3H] beta-antagonists. The antidepressant [3H]desmethylimipramine was bound to many neurones and glial cells in cerebellar, brain stem and spinal cord cultures. Glial cells also possessed binding sites for [3H]noradrenaline and alpha- and beta-adrenoceptor antagonists, findings that are consistent with recent electrophysiological observations which indicate the existence of alpha- and beta-adrenoceptors on cultured astrocytes.