The influence of the frequency and pattern of sympathetic nerve activity on serotonin N-acetyltransferase in the rat pineal gland (original) (raw)
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Journal of the autonomic nervous system, 1985
In order to elucidate the role of sympathetic innervation for pineal function, the influence of both unilateral and bilateral electrical stimulation of the superior cervical ganglia on the electrical activity of single cells in the rat pineal gland was investigated. These experiments revealed a clear influence on spontaneous electrical activity of single pinealocytes. About half of the units tested by unilateral stimulation exhibited either a graded continuous augmentation or inhibitions of different magnitude. In addition, 'silent' cells without spontaneous activity could be activated by sympathetic stimulation. Sequential and simultaneous bilateral stimulations showed that only a few cells could be influenced by both ganglia and in these cases the influence seemed to be additive. Some pineal cells do not appear to be under the control of the sympathetic nervous system.
Anatomy and Embryology, 1989
Melatonin metabolism in the mammalian pineal gland is under the clear influence of sympathetic fibers originating in the superior cervical ganglia (SCG). Previous studies suggested that pineal "synaptic" ribbons (SR) as well are regulated by the gland's sympathetic innervation. To gain more insight into the mechanisms involved, we examined the effects of sympathetic stimulation on SR number and on the activity of melatonin forming enzymes, serotonin N-acetyltransferase (NAT) and hydoxyindole-Omethyltransferase (HIOMT). The SCG in adult male rats were stimulated electrically during daytime for either 15 or 120 rain. Immediately following stimulation, the glands were removed and processed for electron microscopy and for the determination of NAT and HIOMT activities. No differences in pineal SR number, size or location were found in rats stimulated with either parameters when compared with sham-stimulated or control animals. While the activity of HIOMT remained unchanged, the activity of NAT was also unaltered following 15 min of stimulation, but was augmented approximately three-fold in animals stimulated for 120 min. It is concluded that if SR in the rat pineal gland are under sympathetic control, the regulation is different from that involved in melatonin formation.
Cell and Tissue Research, 1980
The pineal gland of the rat receives a rich nervous supply originating from the superior cervical ganglia. These fibers contain serotonin in addition to their neurotransmitter, noradrenaline. Cytochemical studies at the ultrastructural level have shown that both amines are present in the cores of the granular vesicles that are characteristic of these nerves. It is presently shown that the bilateral electrical stimulation of the preganglionic fibers innervating the ganglia markedly reduces the number of small sites reacting cytochemically for both noradrenaline and serotonin, these sites corresponding to the cores of small granular vesicles, while the larger reactive sites (cores of large vesicles) remain unaltered. The vesicles are retained in nerve terminals after stimulation, as observed in conventionally processed tissues, although with altered sizes and shapes. Apart from these cytochemical and structural changes, nerve stimulation also reduces the endogenous noradrenaline content of the pineal gland. Thus, both noradrenaline and serotonin are released from their storage sites in pineal sympathetic nerves after electrical stimulation in vivo. This suggests the possibility that several substances with presumed transmitter or modulatory functions might be simultaneously released by nerve impulses from a given nerve terminal.
Effects of pineal factors on the action potentials of sympathetic neurons
Cellular and Molecular Neurobiology, 1986
1.Neurons from rat superior cervical ganglia were grown in coculture with pineal cells. Action potentials of neurons in cocultures were 25% longer and were 25% greater in amplitude than those recorded from neurons grown in the presence of ganglionic nonneuronal cells alone.2.Neurons showed an increase in action potential duration with increasing time in culture. This may have been related to
Journal of Pineal Research, 1986
In order to elucidate further the role of sympathetic innervation for pineal function, the influence of sympathectomy on the spontaneous electrical activity of single cells in the pineal gland of adult male rats was investigated. Extracellular single-unit recordings were made during nighttime in the pineal gland of urethaneanesthetized, blinded adult male rats that had been treated neonatally with 6hydroxydopamine, or that were ganglionectomized either during, or 12-16 h or 36-40 h, prior to the recording experiment. These experiments revealed that the excitatory influence of the sympathetic system on pineal nocturnal electrical activity can be abolished by either chemical sympathectomy of neonatal rats or surgical superior cervical ganglionectomy in adult animals.
Day-night rhythm of acetylcholine in the rat pineal gland
Neuroscience Letters, 1997
Using high-performance-liquid-chromatography (HPLC) measurement of acetylcholine, choline acetyltransferase (ChAT) enzyme assay and anti-ChAT immunohistochemistry, we have investigated the expression of the cholinergic system in pineal glands of male rats. Glands procured during the day period (1200 h) contained significant amounts of acetylcholine (0.5 pmol/gland). A similar content was found in pineal glands after a 48 h culture period, i.e. when the intrapineal nerve fibres have degenerated. This strongly indicates that the pinealocytes are the cells which contain acetylcholine. To confirm this conclusion we demonstrate substantial ChAT-like immunoreactivity in pinealocytes. ChAT enzyme activity measured in homogenized glands (day period) was 7 ± 3 nmol/mg per h. Acetylcholine content as well as ChAT enzyme activity increased about 10-fold in pineal glands during the night period (2400 h). The present study demonstrates for the first time the presence of a day-night rhythm of ChAT and acetylcholine in rat pinealocytes. The function of pineal acetylcholine is not clear, but there are indications that acetylcholine may depress noradrenaline release from intrapineal sympathetic fibres and hence melatonin synthesis.
Naunyn-schmiedebergs Archives of Pharmacology, 1977
The injection of p-chlorophenylalanine (PCPA) acutely reduced serotonin in the pineal gland of the rat and selectively elevated the noradrenaline (NA) content during the subsequent 24 h. The activity of tyrosine hydroxylase (TH) also increased in intact glands during the first 6 h after PCPA injection but returned to normal at 24 h. This enhancement of enzyme activity was only observed in the presence of a non-saturating concentration of the cofactor. Serotonin depletion by PCPA cannot directly account for the increased enzyme activity, because the amine does not modify TH activity. Moreover, this increase is restricted to the pineal, since in other sympathetically innervated organs, such as the atria, PCPA produced an acute but transient reduction in TH activity. The elevation described here is not due to a net increase in the amount of enzymatic protein, because TH activity is similar in pineal homogenates from treated and control rats when a saturating concentration of the cofactor was used. The availability of storage sites in pineal nerve vesicles due to serotonin depletion, seems to release TH activity from the negative control exerted by cytoplasmic catecholamines. Enzyme activity in the pineal is acutely enhanced until a new steady state is reached at a higher concentration of endogenous NA.
Archives of Biochemistry and Biophysics, 1974
Norepinephrine added in vitro to cultured rat pineal glands produced a severalfold increase in the concentration of cyclic AMP. Chronically decreasing the sympathetic input to the pineal gland by any one of a variety of procedures, such as superior cervical ganglio~ectomy, decentralization of these g~nglia, or chemical sympathectoomy with 6-hydroxydopamine, results in a several-fold enhancement of this norepinephrine-induced elevation in the levels of cyclic AMP in pineal glands cultured in vitro. The development of the increased sensitivity of the cyclic AMP system can be prevented by administering norepinephrine in vivo during the period of reduced sympathetic input. Ganglionectomy also caused an increase in the isoproterenolinduced elevation of cyclic AMP in pineal glands in vivo. These results support the concept that the increased pharmacologic response to catecholamines in some chronically denervated adrenergic structures may be due to an increase in the catechol~mine-sensitive adenylate cyclase system of these structures.