Electrical responses of homing pigeon and guinea pig Purkinje cells to pineal indoleamines applied by microelectrophoresis

Abstract

Summary. The effects of microelectrophoretically applied melatonin (aMT), 5-methoxytryptophol (ML), 5-hydroxytryptophol (HL) and noradrenaline (NA) on the electrical activity of cerebellar Purkinje and other cells during both day-and nighttime were studied in urethane-anesthetized intact and pinealectomized homing pigeons and guinea pigs.In the intact pigeon, equal numbers of Purkinje cells were excited and inhibited by aMT and ML, whilst the responses to HL were predominantly inhibitory. The responses varied significantly depending on whether the cells were tested during the day or at night (P < 0.001). Pinealectomy abolished the observed day/night differences. In intact pigeons most of the other cerebellar units were inhibited by aMT and ML, whilst HL elicited an excitation in about 50% of the units.In the guinea pig most of the Purkinje cells were inhibited by aMT and ML, whereas HL caused no response in most of the units. No significant 24-h rhythmicity in response to the indoles could be observed. The responses of the other cerebellar units were more complicated, aMT caused an excitation in most of the units, whilst the predominant response caused by ML was inhibition. Only 30% of these units responded to HL; the remainder showed no measurable responses.It is apparent from these studies that pineal indoleamines may play a modulatory role in the cerebellum.Abbreviations: ECG electrocardiogram; GABA gamma-aminobutyric acid; further abbreviations see Summary * Present address:

Weak electromagnetic fields attenuate tremor in multiple sclerosis

“…In view of the fact that EMFs alter pineal melatonin secretion (Welker et al, 1983;Demaine & Semm, 1983;Wilson et al, 1986;Rudolph et al, 1988) and the findings that the cerebellum and brainstem reticular formation contain and/or synthesize melatonin (Izumi et al, 1973;Pazo, 1979;Semm & Vollrath, 1982;Sallanon et al, 1982;Semm, 1983;Cardinali et al, 1979;Laudon et al, 1988) as well as the observation that melatonin increases 3',5'-adenosine monophosphate (CAMP) concentrations in the cerebellum (Anton-Tay, 1974) suggest that magnetically-induced alterations in melatonin functions modifies cerebellar functions (Anton-Tay, 1974;Semm, 1983;Demaine & Semm, 1986;Semm & Vollrath, 1984). In addition, melatonin has been shown to increase the multineuronal unit activity of the red nucleus (Anton-Tay, 1974), suggesting that it alters subcortical neuronal activity in part through a multineuronal pathway involving, among others, the cerebellorubro-dentate circuit (Anton-Tay, 1974).…”