The behavioral toxicity of a tributyltin ester in the rat.

The behavioral toxicity of an organic tin compound under consideration for use in marine antifouling paint was assessed using a Sidman avoidance paradigm. The assessed compound, an organometallic polymer (tributyltin [methacrylic-CO-methylmethacrylate] ester), is from a group of alkyltin compounds of which triethyl and tributyltin are known to be toxic. Rats were tested under a free-operant avoidance procedure for 6 months while ingesting the polymer in their drinking water. At the beginning of the 5th month significant behavioral changes became evident, reflected in increases in shock rate, decreased responding, and a shifting of the interresponse time distribution. Performance improved upon withdrawal of the contaminant suggesting that limited exposure to the polymer may not result in permanent behavioral dysfunction.

Behavioral effects of morphine on free-operant avoidance under hyperbaric pressure.

Morphine sulfate was tested under hyperbaric pressure to assess its effects on behavior. Four male hooded rats were trained to avoid brief electric shocks under a free-operant unsignalled avoidance procedure. Using an individual organism design, we injected each rat subcutaneously with morphine sulfate (2.0, 4.0, 6.0, 8.0 mg/kg body wt.) or saline (0.1 ml/100 g body wt.). Rats were tested at 1.0 and 7.1 atmospheres absolute (ATA) in a dry hyperbaric chamber while breathing a mixture of helium and oxygen. Each session lasted 60 min. Overall, the analgesic effects of morphine at 1.0 and 7.1 ATA were found to be similar. Shock avoidance by a rat was found to be a monotonic function of the drug dose; the fewest shocks were associated with the 2.0 mg/kg dose. Increased pressure did not significantly affect the number of shocks received by a rat across doses. Total responding remained stable throughout the study, but the temporal pattern of responding was differentially influenced by drug dose.

Microwave radiation and chlordiazepoxide: synergistic effects on fixed-interval behavior.

In the presence of low-intensity pulsed microwave radiation, at an average power density of 1 milliwatt per square centimeter, the response-rate-increasing effects of chlordiazepoxide were potentiated in rats. The behavioral effects of a drug can be modified by brief exposure to a low-level microwave field even when the radiation level alone has no apparent effects on the behavior.

Reduction of the behavioral effects of delta9-tetrahydrocannabinol by hyperbaric pressure.

Delta9-tetrahydrocannabinol in doses of 0.5, 1.0, 2.0 and 4.0 mg/kg was administered to rats under normal (1 ATA) and increased (3, 5 and 7 times normal) atmospheric pressure. Behavior was maintained by a food-reinforced differential-reinforcemnet-of-low-rate (DRL) schedule. Dose-dependent decrements in performance was observed at the 1 ATA conditions, in which response rates increased and the well-established temporal discrimination disintegrated. Under the elevated pressure conditions, however, a reversal of behavioral toxicity occurred during which performance improved as a function of pressure. The behavioral disruptions occurring at the 5- and 7-ATA pressures were minimal compared with those occurring at 1 ATA under equivalent doses of the drug. The present experiment has demonstrated that delta9-tetrahydrocannabinol produces significant behavioral changes at 1 ATA pressure, but when atmospheric pressure is increased the drug effects are reduced.

Interaction of hyperbaric nitrogen and oxygen effects on behavior.

Breathing elevated environmental pressures of nitrogen and oxygen produced changes in behavior of rats that evidenced an interaction between the two gases. Rates of responding generated by a fixed-interval schedule of reinforcement systematically changed as partial pressures of nitrogen were elevated from 0.8 to 10.4 ATA. Response rates increased above baseline followed by a decline in rates as a function of increasing nitrogen pressure. Concurrent increases in partial pressures of oxygen from 0.2 to 2.2 ATA potentiated the rate-increasing effects of nitrogen at low to moderate nitrogen pressures and enhanced rate-decreasing effects at higher nitrogen pressures. Raised oxygen pressures modulated and interacted with the narcotic effects of nitrogen on behavior.

Helium pressure effects on avoidance behavior in rats breathing high nitrogen pressures.

3 rats given avoidance training and then exposed to 7, 13, and 19 ATA breathing nitrogen, then to 25, 31, and 37 ATA breathing helium, showed increased avoidance response rates above established baselines to 19 ATA followed by a decline. Narcotic effects of nitrogen were not reduced differentially by addition of helium.

Free operant avoidance in rats under increased nitrogen pressures.

Rats performed on a free operant avoidance schedule with a response-shock interval of 20 sec. and a shock-shock interval of 2 sec. Avoidance response rates increased and shock frequency decreased when the rats were exposed to elevated pressures of both air and a nitrogen-oxygen mixture in a hyperbaric chamber. Increases in response rates were related to raised partial pressures of nitrogen at 89.0 psi and 111.3 psi. Conditional probabilities of interresponse times indicated that increases in response rates were not due to disruption of temporal discrimination. Increased avoidance rates under pressure suggested direct excitatory effects of high pressures of nitrogen.