Quantum Mechanics/Molecular mechanics calculations predict A1, not A2, is present in melanopsin (Opn4m) of red-eared slider turtles (Trachemys scripta elegans).

Melanopsin is a photopigment that plays a role in non-visual, light-driven, cellular processes such as modulation of circadian rhythms, retinal vascular development, and the pupillary light reflex (PLR). In this study, computational methods were used to understand which chromophore is harbored by melanopsin in red-eared slider turtles (Trachemys scripta elegans). In mammals, the vitamin A derivative 11-cis-retinal (A1) is the chromophore, which provides functionality for melanopsin.

Ocular Kinematics Measured by In Vitro Stimulation of the Cranial Nerves in the Turtle.

After animals are euthanized, their tissues begin to die. Turtles offer an advantage because of a longer survival time of their tissues, especially when compared to warm-blooded vertebrates. Because of this, in vitro experiments in turtles can be performed for extended periods of time to investigate the neural signals and control of their target actions.

Extracellular Recording of Light Responses from Optic Nerve Fibers and the Caudal Photoreceptor in the Crayfish.

Few laboratory exercises have been developed using the crayfish as a model for teaching how neural processing is done by sensory organs that detect light stimuli. This article describes the dissection procedures and methods for conducting extracellular recording from light responses of both the optic nerve fibers found in the animal's eyestalk and from the caudal photoreceptor located in the ventral nerve cord. Instruction for ADInstruments' data acquisition system is also featured for the data collection and analysis of responses.

A mammalian melanopsin in the retina of a fresh water turtle, the red-eared slider (Trachemys scripta elegans).

A mammalian-like melanopsin (Opn4m) has been found in all major vertebrate classes except reptile. Since the pupillary light reflex (PLR) of the fresh water turtle takes between 5 and 10 min to achieve maximum constriction, and since photosensitive retinal ganglion cells (ipRGCs) in mammals use Opn4m to control their slow sustained pupil responses, we hypothesized that a Opn4m homolog exists in the retina of the turtle. To identify its presence, retinal tissue was dissected from seven turtles, and total RNA extracted.

Spectral sensitivity of the photointrinsic iris in the red-eared slider turtle (Trachemys scripta elegans).

Our goal in this study was to examine the red-eared slider turtle for a photomechanical response (PMR) and define its spectral sensitivity. Pupils of enucleated eyes constricted to light by ∼11%, which was one-third the response measured in alert behaving turtles at ∼33%. Rates of constriction in enucleated eyes that were measured by time constants (1.

Consensual pupillary light response in the red-eared slider turtle (Trachemys scripta elegans).

Purpose of this study was to determine if the turtle has a consensual pupillary light response (cPLR), and if so, to compare it to its direct pupillary light response (dPLR). One eye was illuminated with different intensities of light over a four log range while keeping the other eye in darkness. In the eye directly illuminated, pupil diameter was reduced by as much as approximately 31%.

Pupil constriction evoked in vitro by stimulation of the oculomotor nerve in the turtle (Trachemys scripta elegans).

The pond turtle (Trachemys scripta elegans) exhibits a notably sluggish pupillary light reflex (PLR), with pupil constriction developing over several minutes following light onset. In the present study, we examined the dynamics of the efferent branch of the reflex in vitro using preparations consisting of either the isolated head or the enucleated eye. Stimulation of the oculomotor nerve (nIII) using 100-Hz current trains resulted in a maximal pupil constriction of 17.

Sympathetic influence on the pupillary light response in three red-eared slider turtles (Trachemys scripta elegans).

Objective: We investigated the effects of phenylephrine and its combination with vecuronium bromide on the iris of turtles to determine if the pupillary light response is affected by sympathetic innervation.

Animal Studied: Three red-eared slider turtles, Trachemys scripta elegans.

Procedure: Diameters of light-adapted pupils were tracked before and after topical application of drugs to eyes.

Vergence target selection in rhesus monkeys: behavior and modeling.

Previous studies have shown that a LATER (Linear Approach to Threshold with Ergodic Rate) race model can be used to explain saccadic target selection and latencies. The goal of the present study was to determine whether a comparable model could be applied to the underlying decision-making processes involved in target selection for transient vergence eye movements in rhesus monkeys. Luminance contrast of near and far Gabor pair stimuli were manipulated in a forced-choice paradigm to investigate their influence on vergence target selection.

Multiplied functions unify shapes of ganglion-cell receptive fields in retina of turtle.

Retinal ganglion cells in the turtle were extracellularly recorded to define the shapes of their receptive fields by small moving light spots. To better define the geometries, spectral-light adaptations and vitreal injections of 2-amino-4-phosphonobutyric acid (APB) were used to disrupt balances in field organization along dimensions of wavelength, ON and OFF responses, and center/surround areas. Three-dimensional data plots were fit by Gaussian, Gabor, and cardioid functions to show that the shapes of receptive fields are predicted by combinations of these multiplied functions.