Removal Of Superior Cervical Ganglion Research Articles

Sympathetic regulation of circadian rhythm of serotonin N-acetyltransferase activity in pineal gland of infant rat.

The circadian rhythms of serotonin N-acetyltransferase activity in the pineal glands of infant and adult rats were compared. The nighttime increase of N-acetyltransferase activity in the pineals of infant rats was blocked by removal of superior cervical ganglion or by pretreatment with reserpine, l-propranolol, and cycloheximide. Injection of isoproterenol to infant rats markedly elevated pineal N-acetyltransferase activity. When the pineal glands of infant rats were organ-cultured, N-acetyltransferase activity spontaneously increased 7--12 h after the rats were killed. When infant rats were previously denervated or pretreated with reserpine and their pineals were cultured, this spontaneous elevation of N-acetyltransferase activity was abolished, indicating that the transient increase of the enzyme activity in organ culture was due to a liberation of catecholamine from degenerating nerve endings. Additional illumination until midnight prevented the nighttime increase of N-acetyltransferase activity in intact infant rats but not in blinded infant rats. These observations are taken to indicate that N-acetyltransferase rhythm in immature rat pineals is regulated by the sympathetic nerves in the same manner as in adult rat pineals, that the immature rat pineal does not contain a time-keeping system, and that there is no extraretinal light perception in infant rats as far as N-acetyltransferase rhythm is concerned.

The sympathetic superior cervical ganglia as peripheral neuroendocrine centers.

The superior cervical ganglia (SCG) provide sympathetic innervation to the pineal gland, cephalic blood vessels, the choroid plexus, the eye, carotid body and the salivary and thyroid glands. Removal of the ganglia brings about several neuroendocrine changes in mammals, including the disruption of water balance in pituitary stalk-sectioned rats, and the alteration of normal photoperiodic control of reproduction in hamsters, ferrets, voles, rams and goats. These effects are commonly attributed to pineal denervation. However pinealectomy does not always mimic ganglionectomy in its neuroendocrine sequelae. This paper discusses several examples illustrating the lack of homology of ganglia and pineal removal, including the prolactin release brought about by gonadal steroids in spayed rats, the changes in drinking behaviour caused by ganglionectomy and the control of goitrogenic response to methylmercaptoimidazole in rats. All these examples indicate that SCG removal, at least as far as for neuroendocrinologists and pineal experimenters are concerned, should not be considered simply as "pineal denervation". A functionally relevant link between SCG and the hypothalamus may occur in rats inasmuch as ganglionectomy depresses norepinephrine uptake and increases the number and responses of alpha-adrenoceptors in medial basal hypothalamus. Lastly the SCG are active points of concurrency for hormone signals, as revealed by the metabolic changes induced by steroid and anterior pituitary hormones in these structures even in the absence of intact preganglionic connections, as well as by the existence of putative receptors for some of the hormones, namely, estradiol, testosterone and corticosteroids. The SCG appear to constitute a peripheral neuroendocrine center.

Hippocampal lesions, superior cervical ganglia removal, and behavior in rats

Rats were subjected to either bilateral removal of the superior cervical ganglia (SCG) or to a sham operation of the neck. Subsequently, these rats received either bilateral neopallial lesions, bilateral dorsal hippocampal lesions or no further operation. The SCG removal prevented the anomalous noradrenergic innervation of remaining hippocampal tissue. This anomalous innervation, as reported by Loy and Moore [19], originates from neurons in the SCG. All animals were then evaluated on behaviors previously shown to be sensitive to hippocampal destruction: open field activity, spontaneous alternation and spatial maze learning, in order to determine if any behavioral consequences could be related to the anomalous hippocampal innervation. No statistically significant differences appeared which could be unambiguously related to the anomalous innervation.

Comparative Biochemistry of the Pineal Gland

The pineal gland is biochemically very active. In mammals, it has the unique capacity to synthesize the hormone melatonin (N-acetyl-5-methoxy-tryptamine). Although the synthesis of melatonin is confined mainly to the pineal gland of all vertebrates, the eyes and brains of amphibians and fish also can form melatonin. Melatonin is synthesized in the pineal as follows: tryptophan → 5-hydroxy-tryptophan → serotonin → N-acetylserotonin → melatonin. The final step is catalyzed by the enzyme, hydroxyindole-O-methyl transferase (HIOMT), which is highly localized in the pineal of all vertebrate species examined. The activity of HIOMT is changed when animals are kept in constant darkness or light. In rats, highest HIOMT activity is present in constant darkness, while the reverse occurs in avian species. In mammals, information about lighting reaches the pineal via the retina → inferior accessory optic tract → preganglionic sympathetic fibers → superior cervical ganglia → postganglionic fibers → pineal parenchymal cells. Lighting messages reach the hen's pineal via a nonretinal pathway. Studies with tissue culture indicate that noradrenaline liberated from sympathetic nerves stimulates synthesis of melatonin. There are circadian rhythms in pineal serotonin content which are endogenous and abolished by removal of superior cervical ganglia or by decentralization. There is also a 24-hour rhythm in pineal noradrenaline. This rhythm is exogenous and is abolished by blinding or cutting the inferior accessory optic tract.