Histamine receptors in mammalian retinas

Abstract

Mammalian retinas are innervated by histaminergic axons that originate from perikarya in the posterior hypothalamus. To identify the targets of these retinopetal axons, we localized histamine receptors (HR) in monkey and rat retinas by light and electron microscopy. In monkeys, puncta containing HR3 were found at the tips of ON-bipolar cell dendrites in cone pedicles and rod spherules, closer to the photoreceptors than the other neurotransmitter receptors. This is the first ultrastructural localization of any histamine receptor and the first direct evidence that HR3 is present on postsynaptic membranes in the central nervous system. In rat retinas, most HR1 were localized to dopaminergic amacrine cells. The differences in histamine receptor localization may reflect the differences in the activity patterns of the two species. Indexing termsretinopetal; centrifugal; bipolar; amacrine; primate; dopamine Vertebrate retinas receive input from the brain via retinopetal axons, and this pathway has important modulatory effects on retinal neurons in birds and fish, the groups that have been studied most intensively. The functions of retinopetal axons in mammalian retinas are not well understood, however (Uchiyama, 1989). Histamine has been localized to retinopetal axons in the guinea pig (Airaksinen and Panula, 1988), monkey (Gastinger et al., 1999), and rat (Gastinger et al., 2001) retinas. These axons originate from perikarya in the tuberomammillary nucleus of the posterior hypothalamus (Manning et al., 1996;Panula et al., 1989). Mast cells, another possible source of histamine, are not present in the retina (Smelser and Silver, 1963). With the identification of the neurotransmitter of these retinopetal axons, it is now possible to predict how these inputs contribute to information processing in mammalian retinas.These retinopetal axons are expected to be active at night in rats and during the day in monkeys. Histaminergic neurons play an important role in the ascending arousal system (Saper et al., 2001), firing at a steady rate during waking and becoming silent during sleep (Steininger et al., 1999;Vanni-Mercier et al., 2003). In rats, a nocturnal species, histaminergic neurons are most active at night, and the rate of histamine release in the posterior hypothalamus is higher at night than during the day (Prast et al., 1992). In macaques, a diurnal species, levels of histamine metabolites in the third ventricular cerebral spinal fluid are higher during the day than at night (Prell et al., 1989).In the central nervous system, histamine acts on three types of G-protein-coupled receptors: histamine receptor 1 (HR1), histamine receptor 2 (HR2) and histamine receptor 3 (HR3). Among these, only HR1 has been characterized previously in mammalian retinas (Nowak, 1993;Sawai et al., 1988). However, there is indirect evidence that HR2 and HR3 are also present in mammalian retinas. Histamine inhibits a forskolin-induced increase in cAMP in the rabbit retina via HR2 (Nowak, 1991;Nowak et al., 1989). Histamine also increa...

Functional Heterogeneity of Retinal Dopaminergic Neurons Underlying Their Multiple Roles in Vision

“…These procedures would have also blocked any input to DA neurons from cholin- ergic amacrine cells, which is indirectly mediated through GABA (Neal et al, 2001). DA cells also receive histaminergic input from centrifugal fibers in monkey and rat retinas (Gastinger et al, 2006), but this extraretinal input, if it exists in the mouse, was interrupted in our isolated retinas. The retinal neurohormone melatonin is a modulator of dopamine release (Dubocovich, 1983), but the mouse strain we used (C57BL/6J) lacks the ability to synthesize melatonin because of genetic mutations (Ebihara et al, 1986).…”

Retinopetal Axons in Mammals: Emphasis on Histamine and Serotonin

“…Because histamine has no effect when synaptic transmission is blocked, this effect on ganglion cells must be indirect. 70 In monkeys, HR3 are found on the tips of the dendrites of ON-bipolar cells 64 (Fig. 7), but the effects of histamine on primate bipolar cells have not yet been studied.…”

“…56 The binding of ligands to HR1 has been characterized in membrane preparations from mammalian retinas, 41,57 and HR1 have been localized to the IPL in macaque retinas. 58 There is indirect evidence suggesting that histamine acting at HR1 enables humans to respond to light stimuli at higher temporal frequencies. HR1 antagonists decrease the critical flicker fusion frequency.…”

“…In rats, dopaminergic neurons express HR1 (Fig. 6), 64 and these receptors would be activated by tonic release of histamine at night. Histamine strongly inhibits the release of dopamine from guinea pig retinas.…”

Histamine Involvement in Visual Development and Adaptation

“…3,7 Retinopetal axons have been suggested to play a role in light adaptation through histamine receptors in the retina. 2,7,8 Following the visual information, histamine was reported to influence the neocortical synaptic plasticity in vivo, while cortical histaminergic activation increases the degree of plasticity in the mature thalamocortical communication suggesting that the central histaminergic system plays an important role in regulating synaptic plasticity. 9 Until now, no studies have exposed the effect of environmental stimuli on the histaminergic circuit of the brain pertaining to the visual system.…”