Wm. G. Drew

Dorsal hippocampal lesions: Effects of preconditioning CS exposure on flavor aversion

A learned aversion to a walnut solution paired with lithium carbonate was examined in rats with lesions of the dorsal hippocampus. While preconditioning CS exposure retarded conditioning in controls, this same manipulation did not affect suppression to the CS in animals with lesions and, in fact, resulted in greater stimulus control in these subjects. These results support the view that the hippocampus is involved in the modulation of attention.

Effects of δ9-THC, LSD-25 and scopolamine on continuous, spontaneous alternation in the Y-maze

The effects of δ9-THC, LSD-25 and scopolamine on continuous, spontaneous alternation of the hooded rat in the Y-maze were determined. LSD and scopolamine decreased the number of arm entries (responsivity) while concomitantly reducing percent alternation. THC however, reduced responsivity and percent alternation more at the lower dose (1 mg/kg) when compared to control than at the higher dose (3 mg/kg). Only scopolamine induced a significant increase in stimulus perseveration. The results are discussed in relation to the advantages afforded by the continuous spontaneous alternation procedure.

Lead-Induced Hyperactivity. Chronic Exposure during the Neonatal Period in the Rat

The effects of chronic exposure to low levels of lead via maternal milk during the neonatal period in the rat were evaluated by means of several activity measures, spontaneous alternation in the Y-maze, and weight data. Animals reared at the highest concentrations of lead showed retarded body growth. Lead-treated rats were found to be more active in the Y-maze and in the tilt-box, but not in the running wheel. Lead-treated rats showed lowered spontaneous alternation and increased squealing; results were dependent upon the concentration of lead on which the animals were reared. Activity and alternation data provide suggestive evidence of lead-induced damage of the hippocampus, a structure which undergoes much of its development during the stage in which the lead was administered. Behavioral parallels found between lead poisoning and childhood hyperactivity were discussed with respect to the utility of chronic low level lead administration as an animal model of minimal brain dysfunction hyperactivity.

Effect of 9 -THC on the open-field activity of the rat.

Using the open-field activity of the hooded rat as a model of overall activity, the dose-response and time-action effects of doses of Δ9-THC which did not adversely affect spontaneous activity or behavior on appetitively motivated tasks were studied. Subjects received two exposures to an open field one week apart. Prior to the first exposure subjects were treated with small doses of Tween 80-water. At 30 min or 3 h prior to the second exposure subjects were treated with Tween or Δ9-THC in doses which ranged from 0.5–5 mg/kg. Results indicated that Δ9-THC affected various indices of open-field activity such as grooming, sniffing and ambulation differently depending on the time after injection. Rearing and defecation were affected similarly by THC independent of post-injection intervals.

Effects of Neonatal Lead Exposure on Apomorphine-induced Aggression and Stereotypy in the Rat

Rats were exposed to lead via the maternal milk. At 90 days of age, lead-exposed pairs and control pairs were tested for aggression induced by 5.0 mg/kg apomorphine. The large increase in aggression in response to apomorphine seen in controls was markedly attenuated in lead-treated subjects. In contrast, apomorphine-induced stereotypy was not affected. These results provide a further demonstration of persistent behavioral abnormalities resulting from early exposure to lead at levels which do not affect weight gain or mortality.

Comparison of 9 -THC, LSD-25 and scopolamine on non-spatial single alternation performance in the runway

Rats were trained in a straight runway on a non-spatial single alternation (NSSA) which involved presentation of reward (R) and nonreward (N) in a fixed repeating sequence (i.e. R-N-R-N ...). Patterned running results since rats learned to run fast on R trials and slow on N trials. This task can be regarded as an animal analog of the goal directed serial alternation task employed with humans. After patterned running was well established the effects of graded doses of δ9-THC, LSD and scopolamine were delineated. Although all drugs modified alternation performance, each agent produced distinctly specific effects on the different components of NSSA. δ9-THC disrupted alternation by decreasing running speed on R trials and increasing running speed on N trials. Lower doses of LSD increased running speed on N trials while leaving R trial speeds unchanged. At the highest dose, LSD decreased running speed on R trials while leaving N trial speeds only slightly elevated from baseline. Scopolamine disrupted alternation solely by decreasing speed on R trials. The results were discussed with reference to the effects of these drugs on internal inhibition, registration and recall of internal cues and timing behavior.

Impairment of Latent Learning in the Rat by a Marihuana Component

NUMEROUS studies in both humans1–3 and animals4 indicate that marihuana and its chief psychoactive constituent, Δ9-tetrahydrocannabinol (Δ9-THC), may have disruptive effects on short term memory. It has been suggested, however, that the memory-disrupting qualities of marihuana in humans may actually be incidental to its effect on normal attentional processes5. Furthermore, interpretation of animal investigations in terms of drug-induced memory disruption may be difficult as Δ9-THC may alter appetitive motivation6. So it is unclear whether performance deficits are a consequence of impaired memory, attention, or motivation.

CONTINUOUS, SPONTANEOUS ALTERNATION IN THE RAT: INFLUENCE OF Y-MAZE ARM TIMES

Fifty-four male hooded rats were observed for two sessions, 8 min. each for continuous spontaneous alternation in a Y-maze. Subjects were found to alternate on 71% of all choices. Responsivity decreased during each session and a decided preference was shown for the initial placement arm regardless of its spatial position. Though arms per se did not affect alternation, the amount of time spent in previous arms differentially affected alternation depending on whether the subject was displaying alternation or non-alternation behavior during the preceding trials. Results are discussed in terms of their implications for stimulus satiation models of spontaneous alternation behavior.

Apomorphine-Induced Aggression: an Evaluation of Possible Sensitizing Factors in the Rat

The effects of prior experience with fighting and prior experience with both apomorphine and fighting were evaluated as possible sensitizing factors in rat intraspecific aggression induced by apomorphine. Results revealed that prior experience with the drug alone, or with fighting alone, had no effect on apomorphine-induced aggression. However, animals that had previously fought under the influence of apomorphine showed even higher levels of aggression suggesting that repeated experience with both the drug and fighting induces a type of sensitization.

Effects of Post-Trial Injections of Scopolamine and Eserine on Acquisition of a Simultaneous Brightness Discrimination

4 groups of rats were given injections of scopolamine, methylscopolamine, eserine or saline immediately following the completion of an acquisition trial on a brightness discrimination in a T-maze. Results indicated that eserine and scopolamine groups displayed little or no reduction in errors over 50 acquisition trials, while Ss treated with methylscopolamine or saline showed a marked reduction in errors over the last 15 trials. While the data can be interpreted in terms of a consolidation model of memory, a progressive increase in failures to eat on rewarded trials by groups receiving the centrally active drugs, indicates that side effects of these drugs probably played a role in learning impairments.