Ultrastructural localization of sympathetic axons in experimental rat sciatic nerve neuromas.

The ultrastructural localization of sympathetic axons was investigated in normal rat sciatic nerves and experimental sciatic nerve neuromas. The best ultrastructural localization of noradrenaline in the dense-cored vesicles of sympathetic axons was accomplished following pretreatment of rats with nialamide and 5-hydroxy dopamine, followed by fixation according to the modified chromaffin technique of Tranzer and Richards (1976). After such preparation, sympathetic axons containing 5-hydroxy dopamine-labelled dense-cored vesicles could be identified in normal sciatic nerve. Large accumulations of labelled dense-cored vesicles were also found in acute neuromas, up to 1 week after nerve section. Much smaller numbers of dense-cored vesicles could be identified in chronic neuromas from 2 to 3 weeks following nerve section. Sympathetic axons could also be identified following electron probe X-ray microanalysis of the tissue sections, using chromium detection as the marker for the noradrenaline-containing dense-cored vesicles. Unusual configurations of Schwann cell subunits, which enclosed myelinated fibres and sympathetic axon sprouts within the same basal lamina, were identified in the acute neuromas, 3-7 days after nerve section. Such configurations may be of relevance to the pathophysiological interaction which develops between sympathetic efferent and sensory fibres in peripheral nerve neuromas.

The determination of biogenic amines in four strains of the fruit fly Drosophila melanogaster.

A range of biogenic amines were measured in the heads from four strains of Drosophila melanogaster. Quantitation was carried out using gas chromatography-negative ion chemical ionization mass spectrometry (GC-NICIMS) with stable isotope dilution. The principal amines detected in the heads were dopamine, noradrenaline and 5 HT with small amounts of p- and m-tyramine; p-octopamine could not be detected in samples of 25 heads with a limit of detection of 10 pg per sample. In addition to conventional neurotransmitters or putative neurotransmitters the amines 5- and 6-hydroxydopamine were detected in the heads in substantial amounts.

Ultrastructure of monoaminergic terminals in the intermediolateral nucleus of the cat spinal cord.

Monoaminergic innervation of the intermediolateral nucleus of the cat spinal cord was investigated by fluorescence histochemistry and electron microscopy. Large numbers of monoaminergic terminals were labeled by prior administration of the false neurotransmitter 5-hydroxydopamine (5-OHDA). Ultrastructurally, 5-OHDA-labeled terminals fell into three types. Type I, which made up 55% of the labeled terminals, contained abundant, large and densely labeled vesicles and only a few small and unlabeled vesicles. This type was "bouton de passage". Type II, which made up 40% of the terminals, made asymmetrical synaptic contacts with typical postsynaptic structures. This type contained many small vesicles, some of which were labeled, and a few large dense-core vesicles. Type III, which made up 5% of the terminals, made close contact with presynaptic nerve endings containing abundant small unlabeled clear vesicles. The type III terminals contained many large and densely labeled vesicles and a few small flattened vesicles, most of which were unlabeled.

Endogenous dopamine functionally activates D-1 and D-2 receptors in striatum.

Rat striatal slices incubated with the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine at 1 mM were exposed to different concentrations (1-100 microM) of the catecholamine-releasing drug amphetamine. This produced both a concentration-dependent release of endogenous dopamine and accumulation of cyclic AMP in the slices. The cyclic AMP accumulation due to amphetamine was greatly increased when slices were coincubated with the selective dopamine D-2 antagonist (-)-sulpiride (30 microM), but the amphetamine-induced release of dopamine from the slices was the same in the presence or absence of (-)-sulpiride. Pretreatment of animals with reserpine (5 mg/kg s.c., 18 h before death) and in vitro incubation with alpha-methyl-p-tyrosine (50 microM for 90 min), respectively, reduced the ability of amphetamine (1-100 microM) [in the presence of 30 microM (-)-sulpiride] to induce release of dopamine and to elevate cyclic AMP accumulation in striatal slices. A similar reduction in amphetamine-induced dopamine release and cyclic AMP accumulation in striatal slices was observed 7 days following unilateral 6-OHDA lesions of the medial forebrain bundle of rats. These results suggest that amphetamine induces release of endogenous dopamine from the terminals of nigrostriatal dopamine neurones. Released dopamine is then able functionally and concomitantly to activate D-1 and D-2 receptors, seen as stimulation and inhibition of cyclic AMP accumulation, respectively.

[The response of monoamines in the rat brain to local vibration exposure].

An experimental study was performed to investigate the effects of local vibration on the brain monoamines of rats. The rats' hind limbs were exposed to vertical sinusoidal vibration at frequencies of 20-960 Hz under constant acceleration of 50 m/S2 for 240 min. Rats were decapitated immediately after the exposure, the brains were quickly removed from the cranium and blood was collected in a heparinized beaker. The brain was divided into seven regions on an ice plate, and the changes of norepinephrine (NE), dopamine (DA) and serotonin (5-HT) in the whole brain or regional brains were examined. Furthermore, to investigate the mechanism of the appearance of peripheral effects induced by local vibration, the response of plasma dopamine-beta-hydroxylase (DBH) activity was observed with and without pretreatment by 6-hydroxydopamine (6-OHDA), known as a drug for chemical sympathectomy. The amines were determined by fluorometry and DBH activity was by radioimmunoassay. The results obtained were as follows: NE level in the whole brain showed a tendency to decrease compared with the controls at a frequency of 120 Hz and an acceleration of 50 m/S2. Levels of DA and 5-HT in the whole brain showed no particular changes at any frequencies used in the present study. In the study of regional brains, NE showed a tendency to decrease at a frequency of 60 Hz and a significant decrease at a frequency of 120 Hz in the hypothalamus. In the hippocampus, NE showed significant decreases at frequencies of 60 Hz, 120 Hz and 240 Hz, especially at 120 Hz. DA showed a tendency to decrease in the striatum at a frequency of 20 Hz and a significant increase at a frequency of 60 Hz in the medulla oblongata and pons. 5-HT showed a significant increase in the hypothalamus at frequencies of 20 Hz and 120 Hz. The changes in brain amines induced by local vibration were compared with those by whole body vibration. By exposure to local vibration at a frequency of 20 Hz and acceleration of 50 m/S2, the amines in the whole brain were not meaningfully affected, whereas in whole body vibration at the same frequency and acceleration significant effects were observed. NE level was decreased significantly to 57% of that of the control in whole body vibration (20 Hz, 50 m/S2) and showed a tendency to decrease to 79% of that of the control in local vibration (120 Hz, 50 m/S2). Thus the effect of whole body vibration was much greater than that by local vibration.(ABSTRACT TRUNCATED AT 400 WORDS)

The stability of 6-hydroxydopamine under minipump conditions.

A number of investigators have recently used osmotic minipumps to continuously deliver the neurotoxin 6-hydroxydopamine (6-OHDA) to kitten cerebral cortex for periods up to 7 days. Because this compound is known to be particularly labile, we studied the stability of 6-OHDA stored under conditions similar to those found in an osmotic minipump. In 0.4% ascorbic acid, 4 mM 6-OHDA-HBr was found to be stable for at least one week as determined by (1) assay of the drug by high performance liquid chromatography and electrochemical detection and (2) test of the drug's ability to deplete mouse heart norepinephrine.

Chronic degeneration of aminergic nerve endings and blood-aqueous barrier.

Chemical sympathectomy of the anterior segment of the eye was performed in rabbits with 6-hydroxydopamine (6-OHDA) intravitreously injected. The response of the pupillary diameter (PD) and intraocular pressure (IOP) to NE, E and Isoproterenol was determined through instillation of the drugs in the pretreated and control eyes. The results were as follows: 1) Both PD and IOP at different intervals of time from the injection show a sharp decrease in the treated eye. 2) About four weeks after the injection, the instillation of NE and E increases the PD only in the 6-OHDA pretreated eyes, while IP administration is not effective on both control and pretreated eyes. 3) The instillation of the three drugs, while decreasing IOP in the control eyes, does not modify the already low IOP in the pretreated eyes. The authors suggest the presence of a postdenervation supersensitivity affecting only the alpha receptors, since the beta stimulant IP is inactive in both treated and untreated eyes.

Modification and characterization of the permanent sympathectomy produced by the administration of guanethidine to newborn rats.

The administration of guanethidine to newborn rats has been shown to produce a permanent sympathectomy with potential advantages over immunosympathectomy and 6-hydroxydopamine-induced chemical sympathectomy. In this paper, we report on a revised treatment regimen involving initiation of treatment (50 mg/kg/day) on day 7 after birth and continuing for 3 weeks. Animals treated by this protocol have a low mortality rate (approx. 10% above saline-treated controls) and no permanent growth deficit. Analysis of tyrosine hydroxylase activity in and light microscopic examination of superior cervical ganglia of the guanethidine-treated animals indicate complete destruction of sympathetic neurons by the end of the second week of treatment. During and after treatment there are no decreases in norepinephrine in whole brain of the treated animals. Norepinephrine levels in peripheral tissues are markedly reduced at both 9 and 16 weeks of age. Stimulation of vasomotor outflow produces no increase in blood pressure in guanethidine-treated rats at 9 or 26 weeks of age, indicating a complete and permanent functional denervation of the vasculature. The adrenal glands of the guanethidine-treated animals are not destroyed, but rather respond, apparently by transsynaptic induction, with increases in tyrosine hydroxylase and epinephrine content. Interestingly, despite the continued deprivation of a peripheral sympathetic nervous system in these animals. adrenal tyrosine hydroxylase and epinephrine levels return to control levels by 10 weeks of age. These data indicate that administration of guanethidine to newborn rats produces a very complete and permanent sympathectomy with significant advantages over immunosympathectomy and 6-hydroxydopamine-induced chemical sympathectomy.

The aminergic innervation of the pituitary gland in the roach Leuciscus rutilus.

Fluorescent (aminergic) fibers were demonstrated by the Falck-Hillarp technique in all parts of the neurohypophysis (NH) in the roach (Leuciscus rutilus). The fibers are very thin and few in number in the rostral (RNH) and proximal neurohypophysis (PNH) but slightly more numerous in the NH adjacent to the pars intermedia (PI). The fibers occur in normal fish as well as in specimens pre-treated with gamma-methyl-noradrenaline. It is proposed that all parts of the adenohypophysis have a very sparse aminergic innervation. There is no correlation between the number of type "B' fibers and fluorescent fibers in the roach NH. The technical difficulties in obtaining good and reliable results in teleost material are discussed.