Karl Baettig

Selection for two-way avoidance deficit inhibits shock-induced fighting in the rat

Abstract Matched pairs of male and female, Roman high- and low-avoidance (RHA/Verh and RLA/Verh) rats were tested for shock-induced fighting, and single rats were tested for comparative sensitivity to footshocks. The main finding was that the RLA/Verh rats showed a total absence of shock-induced fighting or posturing. The females of both selected lines showed lower flinch-, shuffle- and jump-shock thresholds than did the males. Although the RHA/Verh rats had lower shuffle and jump thresholds than did the RLA/Verh rats, there was no significant difference in the initial detection of foot-shocks by either group (flinch threshold), and all 3 levels of threshold values for both were well below the 3 mA shock level used in the shock-induced fighting experiment. It was concluded that the genetically-based response suppression (freezing behavior) seen with RLA/Verh rats under these and all shock-stress conditions played a greater role in the inhibition of shock-induced fighting than did sensitivity to footshocks per se.

Maze patrolling, open-field behavior and runway activity following experimental portacaval anastomosis in rats

Abstract Surgical construction of a portacaval shunt in patients with debilitating liver cirrhosis is frequently followed by the development of hepatic encephalopathy, characterized by severe cognitive and neuromuscular abnormalities. The rat with a portacaval anastomosis provides a heuristic animal model for the biochemical consequences of the portosystemic diversion of the circulation; the behavioral effects of such shunting were studied in the present investigation. The spontaneous behavior of male Sprague-Dawley rats with a chronic experimental portacaval anastomosis (end-to-side) was evaluated in a complex enclosed maze, an illuminated open field and an enclosed hexagonal runway. There was little evidence that portacaval shunted rats differed from sham operated rats in total activity, explored area, maze-center entry, or in either of two indexes of the efficiency of patrolling within a complex Dashiell-type maze over 13 successive days with three different maze configurations. Similarly, experimental and control rats did not differ in any of several responses assessed in an illuminated open field. However, rats with a portacaval shunt were hypoactive in a runway test given two months postsurgery. All experimental subjects were verified to have an open portacaval shunt and to have sustained significant liver atrophy. These results emphasize the subtle nature of the behavioral effects resulting from the surgical construction of a portacaval anastomosis in rats.

Regional 5-HT analysis in roman high- and low-avoidance rats following MAO inhibition

5-HT and 5-HIAA levels were investigated in three brain regions of Roman high- and low-avoidance rats, following 10, 30 and 60 min of MAO inhibition (pargyline injection). Higher levels of 5-HT in the cortex at 30 and 60 min, as well as a higher disappearance rate of 5-HIAA in the midbrain/medulla region were exhibited by Roman high-avoidance rats, thus further characterizing the differences previously observed in whole brain 5-HT synthesis between these selected rat lines.

Effects of Nicotine on the Visual Evoked Response

The effects of smoking cigarettes differing in nicotine content (0.14 vs 1.34 mg/cigarette) on the peak-to-peak amplitude and peak latency of the human averaged visual evoked response (AVER) were measured in 10 male smokers after a 2-hr smoking deprivation period. The AVER was obtained under five different flash intensities. Eight different peaks were involved in the amplitude and latency measurements. The nicotine dosage and flash intensity factors both had significant effects on peak-to-peak amplitudes while only the flash intensity factor affected peak latencies. The general enhancement of peak-to-peak amplitudes by the 1.34 mg cigarette, relative to the 0.14 mg cigarette, indicates that the effects of cigarette smoking on the AVER are predominantly due to nicotines psychopharmacologic action, as opposed to other elements in tobacco smoke or as opposed to nonpharmacologic mechanisms involving learning processes. Past research, on an electrophysiological and behavioral level, indicating that nicotine, as administered via cigarette smoking, may have enhancing and/or restorative effects on visual attentional processes in the quiescent smoker was supported.

Acquisition and extinction of gustatory aversion in two lines of rats selectively bred for differential shuttlebox avoidance performance

Consumption of a palatable saccharin-glucose (SG) solution was compared in Roman High Avoidance (RHA/Verh) and Roman Low Avoidance (RLA/Verh) lines of rats in a taste aversion acquisition and extinction paradigm. Prior to treatment, SG-intake in a 1 -h drinking test by RHA/Verh rats was much greater than that by RLA/Verh rats. Both psychogenetic lines increased SG-intake over a series of exposures when each presentation was followed by saline injection, but decreased SG-intake when each presentation was followed by apomorphine injection. At the end of the acquisition phase, RHA/Verh rats treated with a toxic dose of apomorphine drank 36% less SG than RHA/Verh rats that were injected with saline, whereas RLA/Verh rats treated with apomorphine consumed 54% less SG than RLA/Verh rats injected with saline. Following 16 daily presentations of SG but no injections, extinction of the conditioned gustatory aversion was complete in the RHA/Verh group previously treated with apomorphine, but it remained incomplete in the RLA/Verh rats previously treated with apomorphine. This stronger taste aversion exhibited by RLA/Verh rats is in marked contrast to their extremely inferior performance in a shuttlebox active avoidance task. The basis of the behavioral differences in these two psychogenetically selected lines of rats is discussed.

Schedule induced ethanol polydipsia in psychogenetically selected lines of rats

Schedule induced ethanol polydipsia was established in 28 male and female rats of two psychogenetically selected lines bred for extremes in active avoidance performance. These rats were maintained at 80% normal body weight and given 36 consecutive daily 45-min sessions with 3% (w/w) ethanol available. During the acquisition phase, food pellets were delivered intermittently on a FT-1 min schedule. Baseline tests preceded and followed the acquisition phase and involved presentation of 45 food pellets together at the start of a test. Roman High Avoidance (RHA/Verh) rats exhibited greater ethanol intake than Roman Low Avoidance (RLA/Verh) rats and female rats drank more ethanol (adjusted for body weight differences) than male rats during baseline and acquisition phases. Furthermore, baseline ethanol intake increased significantly from the initial block to the final block of sessions following acquisition testing, but remained significantly lower than ethanol intake during the final block of acquisition tests. In a second experiment, naive female rats of the two psychogenetic lines were given baseline tests or sessions with food intermittently delivered on a FT-2 min schedule following a period of free feeding or a 20-hr session 3% ethanol was continuously available. In the initial phase of acquisition, fasted RHA/Verh rats drank more ethanol than RLA/Verh rats. In the second phase, undeprived rats of these two lines did not differ in ethanol intake. In a final acquisition phase, fasted RHA/Verh and RLA/Verh rats did not differ significantly in ethanol consumption. Under both deprivation regimens, baseline ethanol intake increased from the initial to the final baseline test. The ethanol consumption of fasted rats in the final acquisition test was significantly greater than that in the final baseline test. Thus, although pronounced and relatively enduring differences in the schedule induced ethanol intake of these two rat lines were observed under the condition of chronically reduced body weight, this strain difference was relatively weak and observed only in the initial phase of acquisition when 20-hr fasted rats were tested.

Environmental and genetic effects on food-deprivation induced stomach lesions in male rats

When Roman high- and low-avoidance (RHA/Verh and RLA/Verh) rats were individually housed in plastic cages with sawdust bedding and food-deprived (F-D) for 4-5 days, it was found that F-D RHA/Verh rats had more lesions than their unfasted controls and more lesions than F-D RLA/Verh rats. The lesions were mostly petechial in nature and located in the glandular portion of the stomach. Also, F-D RHA/Verh rats which were housed in the same room as the controls, as well as F-D RHA/Verh rats which were housed in a separate room with a strong food odor present, had more lesions than F-D RHA/Verh rats housed in the same separate room when there was no food odor, and when none of the rats present had access to food. When F-D RHA/Verh and F-D RLA/Verh rats were individually housed in metal cages with grid floors, however, a general increase in lesion scores resulted and differences between the two rat lines disappeared, as did differences among the room conditions. Also, many lesions were of an ulcerative nature and were located in the rumenal portion of the stomach. It was concluded that sensory (in this case olfactory, at least) and genetic factors are capable of playing roles in the induction of stomach lesions in rats, and that the type, extent and location of the lesions can depend upon whether or not the animals have access to sawdust bedding.

Exaggerated consumption of saccharide solutions following experimental portacaval anastomosis in rats.

Male Sprague-Dawley rats were subjected to end-to-side portacaval anastomosis and permitted to recover from the acute effects of this surgical procedure. Subsequently, portacaval-shunted rats consistently drank abnormally large quantities of 5% (W/V) solutions of glucose, fructose, and sucrose in 24-hr two-bottle tests with water present as the second fluid. The volume of glucose consumed was not altered when the concentration was increased from 5 to 10%. The pattern of preferences exhibited by the portacaval-shunted rats was similar to that of the sham-operated rats, even in three- to five-choice preference tests with several palatable fluids available simultaneously. However, no abnormally high consumption of either water- or quinine-adulterated sucrose solution was noted. Although exaggerated consumption of 0.1% sodium saccharin was not observed in the present study, subsequent unpublished research indicates that when portacaval-shunted rats are given a 0.06% sodium saccharin solution in a preference test, overconsumption relative to control rats occurs. Portacaval shunts were verified both by anatomical examination and by determination of hepatic and testicular atrophy at the conclusion of the investigation. The evidence suggests that over-responsiveness to a palatable taste underlies this phenomenon of exaggerated saccharide consumption.