Histaminergic neurons in the sheep diencephalon

Abstract

The distribution of histaminergic neurons in the sheep brain was studied by immunohistochemistry by using antibodies raised against histamine. For the first time in this species, the presence of histamine-immunoreactive neurons was described in the caudal diencephalon, around the mammillary bodies, and in the tuberomammillary area. The general pattern of distribution of these neurons was similar to that described previously in other species, i.e., rodents and humans. The distribution in the five neuronal groups described in rodents was not easy to demonstrate in sheep, because the boundaries between each group were not clear. The labeled neurons appeared to form a continuous cell system, as in humans. Numerous histamine-immunoreactive mast cells were found in the habenula and the thalamus. Histamine-immunoreactive fibers were found in almost all of the structures studied. The highest density of fibers was seen in the tuberomammillary area, from which dense bundles of fibers ran rostrally and dorsally along the third ventricle in a parasagittal plane. Numerous immunostained fibers were found close to the wall of the ventricles; some of them appeared to reach the cerebrospinal fluid through the ependymal cell layer. Some fibers were also observed in the optic tract, and the lowest density was found in the supraoptic and paraventricular nuclei. These results should be useful for developing further physiological studies on the role of histaminergic neuronal systems in sheep.

Day–night differences in neural activation in histaminergic and serotonergic areas with putative projections to the cerebrospinal fluid in a diurnal brain

“…The CP, located at different sites of the third (3V), fourth (4V) and lateral ventricles (LV; Wolburg and Paulus, 2010), is the site of production of the cerebrospinal fluid (CSF), which transports essential molecules throughout the nervous system. The CP contains receptors for 5HT (Watson et al, 1995) and HA (Crook et al, 1986), and both neurotransmitters influence metabolism in this area (Crook et al, 1984, Watson et al, 1995); the route may be through their direct release into the CSF as suggested by studies that report the presence of histaminergic (Ericson et al, 1987, Tillet et al, 1998) and serotonergic (Lorez and Richards, 1973, Chan-Palay, 1976) axons or dendrites in close proximity to the ventricles.…”

The histaminergic system in human thalamus: correlation of innervation to receptor expression

“…The role of thalamus as the ‘cross of multiple brain circuits’ and ‘the central switchboard’ in conjunction with the fundamental modulating role of histamine and the involvement of both in various brain functions raise interesting questions on the relationship between these two. Histaminergic neurons are located exclusively in the posterior hypothalamic tuberomamillary nucleus in all mammals studied so far (Panula et al ., 1984; Steinbusch & Mulder, 1984; Watanabe et al ., 1984; Airaksinen & Panula, 1988; Airaksinen et al ., 1989, 1991; Tillet et al ., 1998; Sallmén et al ., 1999), and the efferent fibres reach almost all parts of the brain (Wahlestedt et al ., 1986; Airaksinen & Panula, 1988; Panula et al ., 1989; Inagaki et al ., 1990). A small group of histaminergic fibres was found to enter the thalamus and terminate selectively in some thalamic nuclei of rodents (Airaksinen & Panula, 1988; Airaksinen et al ., 1989; Panula et al ., 1989) and cats (Uhlrich et al ., 1993).…”

Distribution of Histamine-Containing Neurons in the Laboratory Shrew (Suncus murinus) Brain.

“…An immunohistochemical method using an anti-HIS antibody or an anti-L-histidine decarboxylase antibody enabled the morphological identification of HIS neurons [17,25] which have been previously reported in various mammals [4,11,15,18,21,22,27]. From a comparative morphological viewpoint, we have reported the intracerebral distribution of monoaminergic neurons in vertebrates, including the shrew (Suncus murinus) of the Insectivora order [6].…”