Involvement of Serotonin in the Mechanisms Establishing the Motor Nucleus of the Trigeminal Nerve

Abstract

The establishment of the motor nucleus of the trigeminal nerve (MNTN) was studied during the early postnatal period in 21 female Wistar rats given the serotonin synthesis inhibitor parachlorophenylalanine on day 16 of intrauterine development (before the formation of the serotoninergic system). These experiments showed that serotonin deficiency during the prenatal period in rats led to changes in the structural organization of the MNTN. During the early stages of postnatal development, there was a delay in the development of the neuropil, with decreases in neuron body sizes and, in some cells, partial loss of chromatophilic substance, along with the presence of dead cells with signs of hyperchromatosis in all parts of the MNTN and especially its ventrolateral part. Neuron death then slowed, though some cells had morphological abnormalities. With increasing postnatal age (by day 20), there was a reduction in the number of motoneurons, evidently due to a gradual increase in cell death. Motoneuron degeneration in the areas of the MNTN studied was accompanied by astrocyte gliosis.