Roger E. Davis

Chemical studies on memory fixation in goldfish.

Summary Puromycin and acetoxycycloheximide, antibiotics known to block selectively protein synthesis, also block the formation of memory of shock avoidance in the goldfish.

Actinomycin D Blocks Formation of Memory of Shock-Avoidance in Goldfish

When 2 micrograms of antinomycin D was injected intracranially into goldfish immediately after a training session, the formation of long-term memory of a shock-avoidance was blocked. The results are discussed in relation to similar findings with acetoxycycloheximide and puromycin in the goldfish and with apparently conflicting results in the mouse.

Autoradiographic localization of sex steroid-concentrating cells in the brain of the teleost Macropodus opercularis (Osteichthyes: Belontiidae)

Tritiakd estradiol or testosterone was administered to gonadectomized male paradise fish, Macropodus opercularis, to investigate the neuroanatomical location of sex steroidretaining cells. Each male was sacrificed 2 hr following intraperitoneal injection of the labeled hormone. Autoradiograms were prepared, and sections were taken from the entire brain, the anterior spinal cord, and the pituitary. Following 4 to 12 months of exposure, the distribution of labeled cells was seen to be the same for males which had received the estradiol as those which received testosterone, but estradiol resulted in a greater number of labeled cells. Steroid-concentrating cells were located in the ventral telencephalon, preoptic area, lateral tuberal nucleus, nucleus of the lateral recess of the third ventricle, and caudal portion of the posterior periventricular nucleus. In addition, the

Time-co-ordinated prefeeding activity in fish

Abstract Fish fed daily at a regular time under controlled artificial illumination became active daily for a number of hours just before feeding time. Experiments with killifish ( Fundulus heteroclitus ) in constant light and under alternating 12-hour periods of bright and dim light showed that the timing of the pre-feeding activity is influenced by shifts in the light cycle and feeding time; when feeding time in constant light was shifted 6 hours, the pre-feeding activity shifted approximately 6 hours in 1 to 3 days. The conclusion was reached that the pre-feeding activity is a consequence of conditioning the act of feeding to an endogenous cue which itself is coordinated by the time of feeding or daily changes in light.

EFFECTS OF PUROMYCIN, ACETOXYCYCLOHEXIMIDE AND ACTINOMYCIN D ON PROTEIN SYNTHESIS IN GOLDFISH BRAIN*

EXPERIMENTS in our laboratory have demonstrated that memory fixation of a shockavoidance task in the goldfish can be blocked by puromycin or acetoxycycloheximide (AXM)

Environmental Control of Amnesic Effects of Various Agents in Goldfish

when administered within 1 hr after training, but not at later times (AGRANOFF and KLINGER, 1964; DAVIS, BRIGHT and AGRANOFF, 1965; AGRANOFF, DAVIS and BRINK, 1965, 1966). The present studies report the effects of these compounds as well as actinomycin D on the incorporation of [3H]leucine into goldfish brain protein.

Evidence for RNA transport in rat optic nerve

Abstract Fish given a single electroconvulsive shock or intracranial administration of puromycin, acetoxycycloheximide, or KCl immediately following shock avoidance training show amnesia on retraining days later. When the treatments are given 24 hr after training no amnesia develops. But amnesia can be obtained 24 hr after training with KCl, puromycin and acetoxycycloheximide, if the fish are replaced in the intertrial environment for a brief period just prior to injection. Implications of these results to the consolidation hypothesis of memory formation are discussed. Previously unreported results on the amnesic effects of intracranial KCl in goldfish are also described.

Telencephalic Lesions and Behavior in the Teleost, Macropodus opercularis: Reproduction, Startle Reaction, and Operant Behavior in the Male

A NUMBER of biochemical and autoradiographic studies have been made on the distribution and movement of labelled substances within the neuron. Proteins labelled after in duo administration of radioactive precursors have been shown to be conveyed from the original site of synthesis down the nerve fibres at an average daily rate of a few millimetres (GRAFSTEIN, 1967; LASEK, 1968; TAYLOR and WEISS, 1965 and WEIS and HOLLAND, 1967). Furthermore, recent studies on the uptake of radioactive amino acids from isolated axons have shown that the nerves can carry on a significant local protein synthesis (EDSTR~M, 1966; GIUDIITA, DETTBARN and BRZIN, 1968 and KOENIG, 1967). The discovery within axons of small amounts of RNA. mainly of the ribosomal type (EDSTROM, EICHNER and EDSTROM, 1962; KOENIG, 1965 and KOEMG, 1967), would indicate the presence of a protein-synthesizing machinery which operates independently from the cell body. At present the origin and form of this RNA are unknown. It may either be synthesized by the axon or by satellite cells, or perhaps be transported down from the neuronal perikaryon. In the present experiments the possibility of axonal flow of RNA from the cell body has been studied by measuring the distribution of radioactivity along the optic nerves at various times after injection into the eyeball of radioactive precursors. EXPERIMENTAL

Sexual behavior: social and ecological influences in the anabantoid fish, Trichogaster trichopterus

Bilateral ablation of the telecephalon at the level of the anterior commissure blocked reproduction in male paradise fish. Lesioned males performed species typical displays at the start of the spawning trial but thereafter avoided the female, and they did not build nests. All the sham-operated males spawned and built nests. The reaction of the male to a startle stimulus and the rate of operant responding for visual reinforcement were used as additional, independent measures of the behavioral effects of the ablation. Removal of the telencephalon greatly increased startle reactivity and decreased the rate of operant responding. Hyperreactivity could account for long response latencies, reduced mobility, and other reported effects of telencephalic ablation in teleosts which have previously been attributed to impaired nonspecific arousal.

Sex differences in aggressivity and the effects of social isolation in the anabantoid fish, Macropodus opercularis

The influence of behavioral and environmental variables on the initiation of spawning in Trichogaster trichopterus was investigated. The behavioral responses of isolated males and females to conspecific visual and chemical stimuli were also examined. Fish in divided aquaria were administered visual cues of a conspecific through a glass partition, chemical cues by an exchange of water between the two chambers, or both visual and chemical cues. Males and females differed in their response to stimuli from the opposite sex. In addition, responses differed with the sex of the stimulus fish. Chemical cues elicited nest building in males but not females. In the spawning experiments, when one member of a pair of fish was exchanged daily, the male spawned the first day without a nest. The female spawned only after several days. Two manipulations shortened spawning latency: Introducing a new male daily and isolating the female for 3 days in the spawning aquarium prior to union with a male. Spawning was delayed, or did not occur, when the female was exchanged each day during the mating period or when a second, smaller female was kept in the spawning aquarium for 3 days prior to introduction of a male. These results suggest that the induction of spawning readiness in females is more susceptible to social and environmental variables than it is in males.