Local differences in calretinin immunoreactivity in the optic tectum of the ocellated dragonet.

The optic tectum of the ocellated dragonet (Synchiropus ocellatus) was studied with immunohistochemistry. Antibodies raised against the calcium binding protein calretinin (CR) revealed a lamination similar to that already reported for other ray finned fish. Most immunoreactive fibers could be observed in those layers receiving retinal afferents and most immunoreactive cells occur in the stratum periventriculare. However, there are marked differences in the presence of other calretinin-positive cell types and immunoreactive lamina between the dorsomedial and ventrolateral parts of the tectum. Synchiropus is a bottom dwelling fish with strong functional subdivisions of the visual system into dorsal and lateral visual fields. The differences in calretinin-positive cell bodies and fibers may be a sensitive indicator of functional differences of tectal circuitry.

Gustatory feedback affects feeding related motor pattern generation in starved 3rd instar larvae of Calliphora vicina.

Gustatory feedback allows animals to distinguish between edible and noxious food and adapts centrally generated feeding motor patterns to environmental demands. In reduced preparations obtained from starved Calliphora larvae, putatively appetitive (ethanol), aversive (sodium acetate) and neutral (glucose) gustatory stimuli were applied to the anterior sense organs. The resulting sensory response was recorded from the maxillary and antennal nerves. All three stimuli increased the neural activity in both nerves. Recordings obtained from the antennal nerve to monitor the activation pattern of the cibarial dilator muscles, demonstrated an effect of gustatory input on the central pattern generator for feeding. Ethanol consistently enhanced the rhythmic activity of the CDM motor neurons either by speeding up the rhythm or by increasing the burst duration. Ethanol also had an enhancing effect on the motor patterns of a protractor muscle which moves the cephalopharyngeal skeleton relative to the body. Sodium acetate showed a state dependent effect: in preparations without spontaneous CDM activity it initiated rhythmic motor patterns, while an ongoing CDM rhythm was inhibited. Surprisingly glucose had an enhancing effect which was less pronounced than that of ethanol. Gustatory feedback therefore can modify and adapt the motor output of the multifunctional central pattern generator for feeding.