Monoclonal antibodies specific for rat relaxin. VIII. Passive immunization with monoclonal antibodies throughout the second half of pregnancy reduces water consumption in rats.

Recent studies demonstrated that exogenous relaxin promoted drinking in nonpregnant rats. The purpose of this investigation was to determine the influence of endogenous relaxin on water consumption in pregnant rats. To that end, a monoclonal antibody specific for rat relaxin, designated MCA1, was used to passively neutralize endogenous relaxin throughout the second half of pregnancy in intact rats. Five milligrams of highly purified MCA1 were administrated iv to rats daily from days 12-22 of pregnancy. Controls received either a monoclonal antibody for fluorescein (monoclonal antibody control) or PBS (vehicle control). The amount of water consumed and both the total duration of water consumption and the total number of episodes when water was consumed were determined daily during both dark and light periods for all treatment groups. From days 13-22 of pregnancy, all three of these parameters of water consumption increased during the 10-h dark period (P < 0.01), but not during the 14-h light period. The mean daily water consumption in MCA1-treated rats was significantly less than that in controls (P < 0.05). Relaxin's effects on water consumption were limited to the 14-h light period (P < 0.01). No difference was found in daily water consumption between the MCA1-treated and control groups during the 10-h dark period. There was a tendency during the light period for both the total duration of water consumption (P = 0.06) and the total number of episodes when water was consumed (P = 0.13) to be less in MCA1-treated rats than in controls. Food consumption and body weight increased as pregnancy progressed, but no differences were found among the three treatment groups. We conclude that endogenous relaxin has effects on water consumption. It promotes water consumption during the daily light period in the second half of pregnancy in rats. Thus, relaxin may be a dipsogenic agent.

Modification of olfactory-related behavior in juvenile Atlantic salmon by changes in pH.

The hypothesis that low pH modifies the response of salmonids to certain olfactory stimuli was tested. An interactive video-computer system was used to monitor the behavior of juvenile Atlantic salmon (Salmo salar). At a pH of 7.6, animals were attracted to glycine and avoidedL-alanine. These effects were dose-dependent, with a threshold of 10(-7) M. The response of the fish to both amino acids changed when the pH of the test chamber was gradually lowered from 7.6 to 5.1; they became attracted toL-alanine and indifferent to glycine. These effects were reversible with a return to pH 7.6. Our findings suggest that acid rain may contribute to reductions in salmonid populations in acidified rivers by impairing the recognition of olfactory cues by salmon during their spawning migration.

An interactive video-computer tracking system for quantification of locomotor behavior.

We have developed a flexible, moderately priced, behavioral analysis system which has been used to determine the response of salmonids to certain olfactory stimulants. The system, which we call ITS for interactive computer-video tracking system, consists of a 128K Apple IIe computer with software, a video camera and videocassette recorder, and a special-effects generator. Experiments are video taped and then, during playback, the special effects generator is used to simultaneously display the video image and the graphics output of the computer on a monitor. The user tracks the animal of interest using an electronic pen, and the position of that animal in the test chamber, in the form ofx-y coordinates, is determined by the computer at user-defined time intervals. When tracking is complete, a plot of the track of the animal is printed within the outline of the test chamber. The following data can also be calculated: swimming velocity, distance from a predetermined point in the chamber (for example, olfactory stimulant source), and time spent in a given area. These variables can be calculated over any chosen time periods and/or for the entire experiment. ITS has numerous advantages over commercially available devices that perform similar tasks. First, it is relatively inexpensive, especially if one already owns video equipment and a computer. Second, it can analyze many types of experiments that can be stored on video tape, including field observations or manipulations. Third, because it is not automated, it is easy to track multiple objects, even if their tracks cross or are not easily located against a low-contrast background. Finally, because whole images do not have to be digitized, and data collection intervals can be adjusted by the user, it is possible to analyze very long experiments with a microcomputer. In this paper we describe ITS and then we demonstrate how we have used it to demonstrate that changes in ambient pH alter the behavioral response of juvenile Atlantic salmon to olfactory stimuli.