The influence of the frequency and pattern of sympathetic nerve activity on serotonin N‐acetyltransferase in the rat pineal gland.

Abstract

SUMMARYThe activity of the pineal enzyme arylamine: N-acetyltransferase (NAT) was determined following direct stimulation ofthe preganglionic or post-ganglionic nerves of the superior cervical ganglia.1. Stimulation of the preganglionic trunks at 10 c/sec during the day or night was sufficient to increase NAT activity approximately 50-fold, to levels comparable to those observed at night in the intact animal. The time course of this effect of nerve stimulation differed between day and night.2. The responses of pineal NAT to certain frequencies of stimulation were similar for preganglionic and post-ganglionic stimulation. In both cases the responses to stimulation at 5 c/sec appeared to be maximal, 10 c/sec causing no further increase. However, at 1-0 c/sec, stimulation was more effective post-ganglionically than preganglionically.3. Various patterns of preganglionic stimulation, having the same average frequency, differed in their ability to increase the activity of NAT. Some, though not all, of these differences between patterns were observed during post-ganglionic stimulation.4. Unilateral stimulation of the preganglionic nerves produced an increase in NAT activity that was less than half the increase produced by bilateral stimulation, suggesting that the innervation from the two ganglia interact within the pineal gland.5. These data indicate that changes in the firing rates of sympathetic nerves innervating the pineal gland, within the range of frequencies typically observed for sympathetic neurones, would be sufficient to account for the circadian rhythm in NAT activity observed in the intact rat. Changes in the over-all pattern of sympathetic activity, in addition to changes in the total number of stimuli, could play a significant role in the pineal response.

Imitations of the circadian changes in rabbit photic responses, elicited by stimulation of the cervical sympathetic nerves and mediated by means of intraocular adrenergic alpha receptors

“…The results of unilateral stimulation with identical pulses, on the other hand, suggest that the same transition may be induced by a rise of the discharge rate in 50 pet of all of these -most probably specific-preganglionic fibers from practically zero, again, towards 2.0 cps or less. These very low discharge frequencies of nearly 0.0 cps, 0.7 cps and 2.0 cps, are in full accordance with data in literature on the discharge levels of pre-and postganglionic sympathetic fibers (mainly towards the head) under physiological circumstances (Adrian et al, 1932;Bronk et al, 1936;Folkow, 1952;1960;Iggo and Vogt, 1960;Polosa, 1968;Jänig and Schmidt, 1970;Large, 1975;Koss and Rieger, 1976;Passatore and Pettorossi, 1976;Gebber and Barman, 1980;Bowers and Zigmond, 1982). The results of the type I-experiments show further that the postganglionic sympathetic fibers in question, which may well be quite separate from the other sympathetic fibers ending in the eyes and the head, exert their influence mainly or exclusively by the activation of adrenergic alpha receptors.…”

Classification of preganglionic neurones projecting into the cat cervical sympathetic trunk.

“…Neurones supplying these organs are probably small in number. They are expected to be depressed in their activity by light (Bowers & Zigmond, 1982). Pupillary motoneurones are likely to show little resting activity under our experimental conditions (Passatore & Pettorossi, 1976) and possibly exhibit an activation during inspiration; it has been demonstrated in humans that the pupils dilate during inspiration (Ohtsuka, Asakura, Kawasaki & Sawa, 1988); Borgdorff (1975) showed in the cat that pupils dilate with a latency of 200-1000 ms after onset of the phrenic nerve discharge.…”

Rhythmic Release Pattern of Pineal Melatonin in Rodents

“…One input comes from brain areas such as the habenular nuclei or the posterior commissure [Dafny, 1980;Korf and Moller, 1984]. The other input which is extensively studied consists of sympathetic nerves originating bilaterally from the superior cervical ganglia relaying information from the retina to the pineal gland [Axelrod, 1974], In rats, electrical stimulations applied to the cervical sym pathetic ganglion and its postganglionic nerves activated the bioelectrical activities of pinealocytes [Reuss et al 1985] as well as elevated the activities of pineal N-acetyltransferase, the rate-limiting enzyme in the melatonin synthesis pathway [Volkman and Heller, 1971;Bowers and Zigmond, 1982], In rats, the sympathetic innervation of the pineal gland is believed to be adrenergic in nature. Norepinephrine has been suggested to be the transmitter released from the postganglionic sympa thetic fibres of the superior cervical ganglia onto the pinealo cytes within the pineal gland [Ebadi, 1984].…”