動物生理学 III

Handout No. 7①②Fig. Neuronal pathway regulating pineal melatonin
synthesis in the rodent.
Photic information is transmitted to the pineal through thesuprachiasmatic nucleus (SCN) and the superior cervical
ganglion (SCG). Abbreviation: IML, intermediolateral cellcolumn.
Fig. 1. Functional and structural properties of intrinsicallyphotosensitive retinal ganglion cells (ipRGCs) in relation to
those of conventional rod and cone photoreceptors. (a)Schematic representation of contrasting voltage responses ofan ipRGC (red) and a cone (green) to a step increase inillumination (black). In the ipRGC, the light response isdelayed, depo- larizing and includes fast action potentials. Inthe cone, the response is rapid, hyperpolarizing and lacks
spikes. (b) Comparison of action spectra for photoreceptors of the rat retina. The similarity in the forms of the curves indicates that each is based on a photopigment using avitamin A derivative as the chromophore. Relative displacements of the curves on the wavelength axis reflect differences in the protein (opsin) component of thephotopigment. Optimal wavelengths: ipRGC (red), 484 nm; green cone (green), 510 nm; ultraviolet cone (purple), 359 nm; rod (blue), 500 nm. (c) Tracing of a rat ipRGC asviewed in the flat-mounted retina; the axon is shown in gray. The inset shows a rod photoreceptor drawn to scale. (d) Schematic vertical section of retina showing interrelationships between ipRGCs and other photo- receptors (shown in color), other retinal cells (shown in gray or black) and retinal layers. The ipRGC (red) has a cell body inthe ganglion cell layer (GCL), whereas rods (blue) and cones (green) have cell bodies in the outer nuclear layer (ONL). The ipRGC has an axon that leaves the eye tocommunicate with the brain, whereas rods and cones communicate only with other retinal cells through synapses in the outer plexiform layer (OPL). Rods and cones drive
conventional ganglion cells (black) by way of bipolar cells (gray), which have their cell bodies in the inner nuclear layer (INL). For clarity, only the cone pathway is shown. Thisvertical pathway might also influence ipRGCs. Dendrites of ipRGCs stratify in the upper part ( ‘off sublayer’ ) of the inner plexiform layer (IPL). This is surprising because it istypical of retinal ganglion cells that are hyperpolarized by light but not of those, such as the ipRGCs, that are depolarized by light. The dendrites of ipRGCs are photosensitiveand spread far more widely in the plane of the retina than do the outer segments (OS) of the classical photoreceptors, permitting greater spatial integration. (e)Photo-micrograph of a rat ipRGC, filled by intracellular dye during recording and viewed in the flat-mounted retina after histochemical processing. The axon is indicated by thearrow.

③Fig. 2. Schematic summary of brain regions and circuits influenced by intrinsicallyphotosensitive retinal ganglion cells (ipRGCs). The ipRGCs and their axons areshown in dark blue, their principal targets in red. Projections of ipRGCs to thesuprachiasmatic nucleus (SCN) form the bulk of the retino-hypothalamic tract
and contribute to photic entrainment of the circadian clock. The orange pathwaywith green nuclei shows a polysynaptic circuit that originates in the SCN andphotically regulates melatonin release by the pineal gland (P) through its
sympathetic innervation. Synaptic links in this pathway include theparaventricular nucleus (PVN) of the hypothalamus, the intermediolateral nucleus(IML) of the spinal cord and the superior cervical ganglion (SCG). Another directtarget of ipRGCs is the olivary pretectal nucleus (OPN), a crucial link in the circuitunderlying the pupillary light reflex, shown in light blue (fibers) and purple(nuclei). Synapses in this parasympathetic circuit are found at theEdinger–Westphal nucleus (EW), the ciliary ganglion (CG) and the iris muscles(I). Other targets of ipRGCs include two components of the lateral geniculate
nucleus of the thalamus, the ventral division (LGNv) and the intergeniculate
leaflet (IGL).

④Figure 32-1 Olfactory sensory neurons are embedded in a small area of specialized epithelium in thedorsal posterior recess of the nasal cavity. These neurons project axons to the olfactory bulb of thebrain, a small ovoid structure that rests on the cribriform plate of the ethmoid bone.

⑤Figure 32-3 Individual olfactory sensory neurons respond todifferent odorants. The records are from patch clamp recordings ofthe responses of three neurons (A, B, C) to three odorants, eachat a concentration of 5 x 10-4 M. One cell responded only to one ofthe odorants while another responded to two odorants; the thirdcell was stimulated by all three odorants, (Adapted from Firestein
et al. 1993.)