Central injections of noradrenaline and adrenaline differentially affect plasma free fatty acid and glucose in conscious pigeons (Columba livia)

The possible involvement of central noradrenergic and/or adrenergic circuits in central mechanisms controlling free fatty acids and glucose levels was investigated in conscious pigeons. The effects of intracerebroventricular injections of noradrenaline (80 nmol) or adrenaline (80 nmol) on plasma free fatty acids and glucose concentrations were examined. The possible role of the autonomic nervous system, of sympathetic terminals and of pituitary hormone release in the metabolic responses induced by intracerebroventricular injections of adrenaline and noradrenaline was investigated by systemic pretreatment with a ganglionic blocker (hexamethonium, 1 mg/100 g), guanethidine (5 mg/100 g), and somatostatin (15 μg/100 g), respectively, 15 min before intracerebroventricular administration of adrenaline, noradrenaline or vehicle. Intracerebroventricular noradrenaline injections strongly increased plasma free fatty acid concentration but evoked no change in blood glucose levels, while adrenaline treatment increased glycemia without affecting free fatty acid levels. Hexamethonium did not block the increase in plasma free fatty acids induced by noradrenaline, while somatostatin pretreatment abolished noradrenaline-induced lipolysis during the experimental period. Adrenaline-induced hyperglycemia was blocked by systemic injections of somatostatin, hexamethonium and guanethidine. The present results suggest that: (1) adrenergic and noradrenergic mechanisms may participate in central control of blood glucose and free fatty acids, respectively, as observed in mammals, (2) noradrenaline-induced lipolysis may be mediated by pituitary mechanisms, and (3) postganglionic sympathetic fibers, possibly innervating the endocrine pancreas, may be involved in adrenaline-induced hyperglycemia. Accepted: 14 April 2000     

急性低氧对大鼠血液中儿茶酚胺及血小板聚集性的影响

健康ＳＤ雄性大鼠,体重２５０－３００ｇ,麻醉、气管插管,用人工呼吸机经气袋供气,自发吸入氧浓度为９％的氧氮混合气,用高效液相色谱－电化学联合检测法及电阻法检测循环血液中儿茶酚胺及全血血小权聚集性的动态变化。结果：急性低氧１５ｍｉｎ时血液中肾肾上腺素（Ａ）浓度及全血血小板聚集性显著增加（Ｐ〈０．０１）,而去甲肾上腺素（ＮＡ）浓度虽有所增加,但无统计学意义（Ｐ〉０．０５）;复氧１５ｍｉｎ时血液中儿茶酚     

OCCURRENCE AND PROPERTIES OF MONOAMINE OXIDASE IN ADRENERGIC NEURONS

—Monoamine oxidase activity of peripheral organs of various species has been examined after surgical, chemical and immunological sympathectomy to assess the proportion of enzyme activity in adrenergic neurons and in extraneuronal cells. Significant falls in monoamine oxidase activity of vas deferens, submaxillary gland, iris and spleen were seen after sympathetic denervation although not in heart, small intestine and kidney. It was suggested that a correlation exists between the extent of the fall in monoamine oxidase activity after sympathectomy and the density of sympathetic innervation of the control organ. Studies of monoamine oxidase activity in vas deferens after inhibition with clorgyline suggested multiple forms of monoamine oxidase. Differences in inhibitor sensitivity, substrate specificity and thermal inactivation of monoamine oxidase in normal and denervated vas deferens were found and it was suggested that differences exist in the properties of the neuronal and extraneuronal monoamine oxidase.     

Cardiovascular, metabolic and endocrine effects of chemical sympathectomy and of adrenal demedullation in fetal sheep

A procedure in fetal sheep for causing peripheral sympathectomy by regular intravascular guanethidine sulphate administration and for causing adrenal demedullation by intragland injection of acid formalin is reported. Demedullation substantially removed adrenaline from the fetal circulation, but has a small effect only on noradrenaline. Plasma noradrenaline levels were depressed by 50% when demedullated fetuses were also subject to peripheral sympathectomy by guanethidine sulphate treatment. This provides some evidence that the paraganglia in the sheep fetus contributes to resting plasma catecholamines. Furthermore the ability of adrenal demedullation to increase markedly this pool of extra-adrenal chromaffin tissue indicates that in the fetus adrenal activity regulates the growth of these para-aortic bodies. In response to sympathectomy plasma vasopressin concentrations rose substantially, whilst adrenal demedullation caused a small rise. Demedullation and sympathectomy depressed fetal plasma glucose and elevated plasma cortisol. In both sympathectomised and adrenal demedullated fetuses resting heart rate and blood pressure was not depressed. However in those with a depleted peripheral nervous system periods of cardiovascular instability were apparent after 2-3 days of treatment with guanethidine sulphate. Hence there were regular episodes where fetal blood pressure and heart rate fell sharply followed 60-90s later by very large increases in blood pressure sustained for up to 10 min and associated with substantial production of plasma vasopressin and catecholamines. These results show that fine cardiovascular control in the fetus requires an intact sympathetic system as the endocrine system is too slow responding to effectively maintain reflex vascular control.     

Demonstration and partial characterization of cytosol receptors for testosterone.

Androgen uptake was investigated in several peripheral organs after administration of (1,2,6,7 minus -3H)testosterone to castrated male rats. The animals were killed after 30 min, the organs were taken out, and the radioactivity was determined after tissue combustion. A relatively high accumulation of androgen was found in pancreas, adrenals, spleen, thigh muscle, kidneys, and liver in addition to the classical androgen target organs coagulation glands, seminal vesicles, prostate, preputial glands, and harderian glands. In a second serier of experiments, nuclear and cytosol fractions were prepared from prostate, seminal vesicles, coagulation glands, preputial glands, spleen, submaxillary glands, kidneys, and pancreas from castrated male rats give (1,2,6,7 minus -3H)testosterone, and these fractions were then characterized by thin-layer and radio-gas chromatography with respect to their patterns of labeled steroids. Only prostate and seminal vesicles were found to contain significant amounts of nuclear 5alpha-(-3H)dihydrotestosterone. The major nuclear androgen was (-3H)testosterone that was the only detectable labeled steroid in coagulation glands, preputial glands, and spleen and that constituted 70% or more of the nuclear radioactivity in seminal vesicles, submaxillary glands, kidneys, and pancreas. These results indicate that testosterone itself may be the predominant active androgen principle in vivo in most androgen target organs and that conversion to 5alpha-dihydrotestosterone is generally not a prerequisite for androgen activity. Using an ultrasensitive micromodification of isoelectric focusing (cf. M. Katsumata and A. S. Goldman (1974), Biochem. Biophys. Acta 359, 112. It was possible to show that cytosol from kidney; submaxillary gland, thigh muscle, and levator ani muscle and nuclei from kidney and submaxillary gland contained androgen-binding proteins with pI's in the region 4.6-5.1 ("4.6 minus 5.1 Complex"). This complex also formed in vitro after incubation of (1,2,6,7 minus -3H)testosterone with cytosol from kidney and submaxillary gland. (1,2,6,7 minus -3H)Testosterone was bound with high affinity to receptor proteins in cytosol from both kidney, submaxillary gland, and thigh muscle with dissociation constants of 5.0 x 10 minus -12 M (kidney), 3.3 x 10 mi;nus -11 M and 4.1 x 10 minus -10 M (two types of binding sites, submaxillary gland), 2.4 x 10 minus -12 M (thigh muscle) and 1.9 x 10 minus -12 M (levator ani muscle). The number of binding sites was in all cases between 1 and 20 fmol/mg of protein. On the basis of these results the hypothesis is presented that a common class of testosterone receptors is present in most organs and that these receptors can be detected both in vivo and in vitro provided methods sensitive enough are utilized.     

OCCURRENCE AND PROPERTIES OF CATECHOL-O-METHYL TRANSFERASE IN ADRENERGIC NEURONS

—A study has been made of the catechol-O-methyl transferase activity of some peripheral tissues after sympathetic denervation. A fall in catechol-O-methyl transferase activity was found in some organs, e.g. rat and rabbit vas deferens, cat nictitating membrane and rabbit submaxillary gland but not in mouse heart and spleen. It was found that suboptimal concentrations of S-adenosylmethionine did not reveal a significant difference between normal and denervated organs but at optimal concentrations a fall was seen in some organs. Catechol-O-methyl transferase activity was present in bovine splenic nerve and in adrenal medulla. It is suggested that the fall in enzyme activity after denervation indicates a neuronal cellular localization. A kinetic study of catechol-O-methyl transferase from normal and denervated rat vas deferens suggested that the neuronal and extraneuronal catechol-O-methyl transferase had different kinetic properties and an estimation of the kinetic constants of the neuronal enzyme was made.     

Histochemical and chemical studies on pre- and postnatal development of the different systems of “short” and “long” adrenergic neurons in peripheral organs of the rat

Summary The adrenergic innervation in the submaxillary gland, heart, kidney, small intestine, and accessory male genital organs and the development of the adrenal chromaffin cells and the sympathetic ganglia were studied in the rat from 15 days post coitum to 16 days post partum using the fluorescence histochemical method of Falck and Hillarp. The postnatal development of the noradrenaline concentrations in the heart and vas deferens was followed by fluorometric determinations.At about 15 days post coitum, the anlagen of the sympathetic chains were well visible in the form of two dorsal segmented columns of small branching sympathicoblasts exhibiting an intense catecholamine fluorescence. In the midline, ventrally to these two anlagen, another column of sympathicoblasts developed; this seemed to give rise to the prevertebral ganglia and to the short adrenergic neurons supplying the internal genital organs. At the level of the adrenal anlagen, small intensely fluorescent chromaffin cells were collected in two bilateral groups which became enclosed by adreno-cortical cells. This enclosure was, however, not complete even at two weeks post partum.Bundles of growing sympathetic nerves were visible in the periphery of the various organs studied at 19–21 days post coitum. A terminal innervation of the organs suggestive of a functional transmitter mechanism did not start to establish until at or immediately after birth. The final pattern of innervation was usually reached at about one week post partum, and the following development proceeded largely in the form of a quantitative increase in the number of nerves participating in the innervation apparatus. The adult level of noradrenaline in the heart and vas deferens was reached three to five weeks after birth. The small intestine was an exception in that the final pattern of innervation in the wall was attained immediately after birth.There was no overt difference in the rate of development of the terminal sympathetic innervation in organs supplied by short adrenergic neurons (accessory male genital organs) compared to the innervation of the submaxillary gland, heart and kidney, which receive classical long adrenergic neurons.The work was supported by a grant from the Association for the Aid of Crippled Children, New York, and was carried out within a research organization sponsored by the Swedish Medical Research Council (grants No. B71-14X-56-07A and B71-14X-712-06A).     

Similar poststimulatory pressor responses with different mechanisms in response to excitation of the locus coeruleus before and after acute adrenalectomy

Electrical stimulation of the locus coeruleus in anesthetized rats evoked a biphasic pressor response consisting of an initial sharp rise in blood pressure at the onset of stimulation, followed by a second elevation after cessation of the stimulus. This response, which was accompanied by an increase in plasma noradrenaline and adrenaline levels, was stable and could be easily reproduced over time. Sympathectomy by administration of guanethidine selectively abolished the primary pressor response. beta-Adrenergic blockade by intravenous administration of sotalol enhanced the secondary pressor response without affecting the primary component. Adrenal demedullation performed 24-48 h before the experiments selectively prevented the secondary pressor component. In contrast, acute adrenalectomy carried out during the experiment to impair the adrenomedullary secretions eliminated the secondary pressor response to stimulation of the locus coeruleus only in sympathectomized or in sotalol-treated rats but not in intact rats in which the response persisted. The latter, however, could be abolished by the administration of either guanethidine or sotalol, and it disappeared following repeated stimulation of the locus coeruleus. The study demonstrates that similar poststimulatory pressor responses with different underlying mechanisms can be elicited on excitation of the locus coeruleus before and after acute adrenalectomy in the rat. The results also suggest that intraneuronal adrenaline may be involved in the response evoked in acutely adrenalectomized animals.     

Annual variations of adrenal gland hormones in the lizard <Emphasis Type="Italic">Podarcis sicula</Emphasis>

The adrenal gland regulates metabolism and maintains normal electrolyte balance. Adrenal hormones are equivalent in all vertebrates; the chromaffin tissue produces adrenaline and noradrenaline and the steroidogenic tissue produces most of the steroid hormones present in mammals. Podarcis sicula belongs to the Squamata family of lizards and it is the most abundant lizard species in southern Italy. This species shows a reproductive annual cycle and the presence of seasonal variations in the activity of the hypothalamus-hypophyseal-thyroid axis. To investigate the existence of an annual cycle of lizard adrenal gland, we have measured plasma concentrations of corticosterone, ACTH, noradrenaline and adrenaline. We have shown that corticosterone rapidly increased from January to March to reach a peak value that persisted until July, then, it slowly decreased until December. ACTH levels increased from January to May and slowly decreased from July to December. Noradrenaline levels were higher in March and then decreased until December. On the contrary, adrenaline levels increased from March to July and slowly decreased until December. Our results demonstrate the existence of an annual cycle of the lizard adrenal gland activity. This is very interesting because its activity is important to rightly regulate the reproductive status of the Podarcis sicula lizard.     

Excitation-secretion coupling in exocrine glands. Properties of cyclic AMP phosphodiesterase and adenylate cyclase from the submaxillary gland and pancreas.

1. The cyclic AMP phosphodiesterase in homogenates of the submaxillary gland and pancreas was found to be associated mainly with the 300,000 times g supernatant fraction. A Lineweaver-Burk plot showed a high-affinity (Km app. = 1.6 muM) and a low-affinity (Km app. greater than 100muM) component for the cyclic AMP substrate. The enzyme was magnesium dependent, and strongly inhibited by papaverine, theophylline and caffeine. Cyclic GMP inhibited cyclic AMP phosphodiesterase, but only in concentrations greatly exceeding that of the cyclic AMP. Calcium did not alter the activity of the enzyme. The activity of the submaxillary cyclic AMP phosphodiesterase was not influenced by noradrenaline, dopamine, histamine, 5-hydroxytryptamine or gamma-amino butyric acid, and that of the pancreatic enzyme by acetylcholine, pancreozymin or secretin. 2. Adenylate cyclases from guinea-pig submaxillary gland and cat pancreas are particulate enzymes. The highest specific activity was recovered from the 1500 times g pellet. Guineo-pig submaxillary adenylate cyclase was activated by fluoride, noradrenaline, isoprenaline and adrenaline. The noradrenaline activation was blocked by the beta-adrenoceptor blocker, propranolol, but not by the alphs-adrenoceptor blocker, phentolamine. Neither acetylcholine nor carbachol had any effect on the adenylate cyclase activity. The apparent Km value for the 10- minus 4 M noradrenaline activated adenylate cyclase activity was completely aboliched by 5 mM calcium. Cat pancreatic adenylate cyclase was clearly and consistently activated by secretin, but not by pancreozymin or carbachol.     

Uptake of3H-adrenaline and14C-noradrenaline into neuronal and extraneuronal tissue compartments in the perfused gas gland of the swimbladder of the Atlantic cod,Gadus morhua

Summary The neuronal and extraneuronal accumulation of radiolabelledl-adrenaline andl-noradrenaline was studied in the gas gland of the swimbladder of the Atlantic cod,Gadus morhua. Both amines are taken up into the tissue compartments, and a preference for noradrenaline for both uptake processes was demonstrated. A relatively high neuronal accumulation compared to earlier results (cod spleen; Ungell and Nilsson 1984) was seen and this is probably due to the more dense innervation of the swimbladder gas gland. A higher extraneuronal accumulation may be due to the presence of arterial smooth muscle.It is concluded that the adrenergic nerves of the swimbladder gas gland of the cod preferentially accumulate noradrenaline, a situation similar to that in mammals.Abbreviations A/NA adrenaline/noradrenaline ratio - PBA phenoxybenzamine - PNMT phenylethanolamine-N-methyl tranferase     

Biorhythms and pineal gland

Endocrine biorhythms are classified according to the period time, as one of the most characteristic properties of biorhythms. Each endocrine organ has parallel more than one biorhythms with different period time (e. g. circadian and circannual rhythms). The time of acrophase of the biorhythms at the different endocrine organs is fairly variant. This review summarizes the rhythmic function of the THS-thyroid, gonadotrophic-gonadal and ACTH-adrenocortical systems. Pineal gland plays an integrative role in the regulation of rhythmic function of the endocrine system. The melatonin secretion of this gland also reveals conspicuous circadian and circannual rhythms both in mammals and in birds. Mammalian pineal is functional only if its peripheral sympathetic innervation from the superior cervical ganglion is intact. In contrast, melatonin secretion and its circadian rhythm is also maintained in birds under isolated conditions (explanted into an in vitro superfusion system). The 24 hours period time of melatonin circadian rhythm can not be changed by light impulses. The phases of the circadian rhythm, however, can be turned by changing the time of environmental light-dark phases. The wavelength of the artificial light used for reversal of circadian rhythm is an important factor. The development of the entrainment and synchronization of the circadian melatonin rhythm in birds is independent of the rhythmic day-night changes in environmental lighting condition. The differences in the main elements of the biological clock between mammals and birds are discussed.     

Dependence of the cytotoxic effect of guanethidine on the degree of sympathetic activity

Young rats aged 15-29 days received a subcutaneous injection of guanethidine sulphate (5 mg/kg body weight) every day. Owing to damage to the postganglionic sympathetic neurones, on about the 60th day of life we observed a significant decrease in the noradrenaline concentration in these animals' hearts compared with the controls. If every guanethidine injection was followed immediately by intensive physical exercise, there was no drop in the heart noradrenaline concentration. Physical exercise of the same intensity performed a few hours before injecting guanethidine did not prevent the drop in the noradrenaline concentration in the heart. The results show that an exercise-induced increase in sympathetic activity, at a time when guanethidine is circulating in the blood and accumulating in the adrenergic neurones, inhibits the cytotoxic effect of guanethidine. Isolated physical exercise performed between the 15th and 29th day of life leads to an increase in the noradrenaline content of the heart of rats aged 60 days.     

Alteration of neonatal rat parotid gland acinar cell proliferation by guandethidine-induced sympathectomy.

Newborn rats were injected with guanethidine-sulfate (20 micrograms/g body weight) every 48 hr from 12 hr after birth until day 14 (eight injections per animal). The guanethidine treatment resulted in an 86% absolute reduction in cell number in the superior cervical ganglia of 15 day old rats. The cells which remained after guanethidine treatment showed destruction of mitochondria and an extensive decrease in endoplasmic reticulum. Chemical sympathectomy with guanethidine induced a 3.1 hr lengthening of the acinar cell generation cycle time (17.4 hr to 20.5 hr), resulting from a longer G1 period (6.9 hr in the control group as compared to 10.5 hr in the guanethidine-treated group), as well as a cecrease in the mean percentage of [3H]thymidine-labeled acinar cells (22.3 +/- 0.5% to 19.3 +/- 0.5%) and mean acinar cell mitotic index (2.6 +/- 0.2% to 2.1 +/- 0.1%). A circadian rhythm was found to exist in parotid gland acinar cell mitotic activity of 15 day old rats and the amplitude of the rhythm was reduced from 26.5% to 14.9% in guanethidine-treated rats. This study indicates that the diminution of sympathetic influence on the developing parotid gland results in a slight, but significant alteration in acnar cell proliferation.     

Physiological aspects on catecholamine sampling

Catecholamine (CA) determinations are valuable tools in studies of sympatho-adrenal activity. However, several methodological problems should be considered when designing experiments and interpreting plasma CA results. The commonly assessed antecubital venous noradrenaline (NA) concentrations reflect local nerve activity, since about half of this NA is derived from the forearm tissues. Sympathetic nerve activity is not uniform, but may vary considerably between organs. Overall sympathetic activity is best assessed by measurements of NA in arterial or mixed venous blood. Venous adrenaline (ADR) levels may also be unrepresentative due to marked and variable extraction in the peripheral tissues. Urinary NA and ADR excretion studies still provide valuable information. Regional studies of NA overflow from individual organs give good estimates of local nerve activity and will increase the understanding of the functional organization of the sympathetic nervous system.     

ALTERATION OF NEONATAL RAT PAROTID GLAND ACINAR CELL PROLIFERATION BY GUANETHIDINE-INDUCED SYMPATHECTOMY

Newborn rats were injected with guanethidine-sulfate (20 μg/g body weight) every 48 hr from 12 hr after birth until day 14 (eight injections per animal). The guanethidine treatment resulted in an 86% absolute reduction in cell number in the superior cervical ganglia of 15 day old rats. The cells which remained after guanethidine treatment showed destruction of mitochondria and an extensive decrease in endoplasmic reticulum. Chemical sympathectomy with guanethidine induced a 3.1 hr lengthening of the acinar cell generation cycle time (17.4 hr to 20.5 hr), resulting from a longer G₁ period (6.9 hr in the control group as compared to 10.5 hr in the guanethidine-treated group), as well as a decrease in the mean percentage of [³H]thymidine-labeled acinar cells (22.3 ± 0.5% to 19.3 ± 0.5%) and mean acinar cell mitotic index (2.6 ± 0.2% to 2.1 ± 0.1%). A circadian rhythm was found to exist in parotid gland acinar cell mitotic activity of 15 day old rats and the amplitude of the rhythm was reduced from 26.5% to 14.9% in guanethidine-treated rats. This study indicates that the diminution of sympathetic influence on the developing parotid gland results in a slight, but significant alteration in acinar cell proliferation.     

Guanethidine and Pupillary Reaction

Local application of guanethidine to the eye results in miosis. The sympathicolytic action of guanethidine on the pupil was proved by the consistent appearance of a Horner''s syndrome after instillation of a 10% solution into the conjunctival sac. Lack of cocaine mydriasis and unimpaired adrenaline mydriasis after guanethidine application are further evidence of this mode of action. Guanethidine is the first drug that can be consistently relied upon to produce miosis by inhibiting sympathetic impulses to the intraocular pupillary muscles; it also inhibits sympathetic impulses to Horner''s muscle of the upper lid. It is a reliable sympathicolytic agent for testing the reaction of abnormal pupils.     

Interactions between Sympathomimetic Amines and Antidepressant Agents in Man

Intravenous infusions of phenylephrine, noradrenaline, adrenaline, and isoprenaline were given to healthy human volunteers after five to seven days on phenelzine, tranylcypromine, or imipramine, and cardiovascular responses were compared with those observed under control conditions. With monoamine oxidase inhibitors there was a 2-2½ fold potentiation of the pressor effect of phenylephrine, but no clinically significant potentiation of cardiovascular effects of noradrenaline, adrenaline, or isoprenaline. With imipramine there was potentiation of the pressor effects of phenylephrine (2-3 fold), noradrenaline (4-8 fold), and adrenaline (2-4 fold); there were dysrhythmias during adrenaline infusions, but no noticeable or consistent changes in response to isoprenaline.Noradrenaline and adrenaline in amounts contained in local anaesthetics used in dentistry are not likely to be significantly potentiated in otherwise healthy patients receiving monoamine oxidase inhibitors. Hazardous potentiation of their cardiovascular effects might occur in patients receiving tricyclic antidepressants.Our observations do not indicate that the hazards associated with isoprenaline inhalation by bronchial asthmatics would be increased by coincident therapy with a monoamine oxidase inhibitor or tricyclic antidepressant.     

Effects of Peptides of the Secretin-Glucagon Family and Cyclic Nucleotides on Tyrosine Hydroxylase Activity in Sympathetic Nerve Endings

Previous studies have shown that certain peptides of the secretin-glucagon family stimulate tyrosine hydroxylase activity in sympathetic neurons of the superior cervical ganglion and three of its end organs, i.e., the iris, pineal gland, and submaxillary gland. To determine whether a similar regulation occurs in other sympathetic neurons, the effects of two of these peptides, secretin and vasoactive intestinal peptide, were examined in the right cardiac ventricle of the rat, a tissue innervated primarily by the middle and inferior cervical ganglia. Both peptides stimulated tyrosine hydroxylase activity, measured in situ, in this tissue. In addition, several second messenger systems were investigated as possible mediators of this peptidergic stimulation of tyrosine hydroxylase activity in autonomic end organs. 8-Bromoadenosine 3',5'-cyclic monophosphate and forskolin elevated tyrosine hydroxylase activity in slices of both the right ventricle and the submaxillary gland. 8-Bromoguanosine 3',5'-cyclic monophosphate also stimulated tyrosine hydroxylase activity in both tissues, whereas nitroprusside stimulated activity only in the submaxillary slices. Furthermore, the phosphodiesterase inhibitors 3-isobutyl-1-methylxanthine and/or Ro 20-1724 potentiated the stimulation by secretin, as well as the stimulations by forskolin and nitroprusside. Phorbol 12,13-dibutyrate also stimulated tyrosine hydroxylase activity in cardiac and submaxillary slices; however, no potentiation of these effects was seen following addition of either phosphodiesterase inhibitor. These data, taken together with those of previous studies, suggest a role for a cyclic nucleotide, probably adenosine 3',5'-cyclic monophosphate, in the peptidergic stimulation of tyrosine hydroxylase activity in sympathetic nerve terminals.     

A SENSITIVE RADIOIMMUNOASSAY FOR 7S NERVE GROWTH FACTOR ANTIGENS IN SERUM AND TISSUES

A radioimmunoassay was developed which can measure accurately concentrations of mouse 7S nerve growth factor antigens (NGFA) as low as 3·0 ng/ml in serum or tissue homogenates. Extremely large amounts of presumed nerve growth factor were found in the submaxillary gland; but considerable quantities were also present in mouse serum, kidney, adrenal gland and vas deferens. Heart, spleen, liver and muscle contained less of the presumed nerve growth factor, and only small amounts were recovered from brain. Rat adrenal gland and serum from rats, guinea pigs and man contained much less immunologically reactive material. The level of presumed nerve growth factor in the mouse heart was highest at birth and decreased slowly during maturation. In the mouse submaxillary gland the content of presumed nerve growth factor increased rapidly after 2 weeks of postnatal age, with higher levels found in male animals. Destruction with 6-hydroxydopamine of the sympathetic nerves in the hearts of newborn or adult mice did not significantly alter the amount of presumed nerve growth factor recovered in the heart.