Effects of hippocampal brain damage on auditory and visual recent memory: comparison with marijuana-intoxicated subjects.

A battery of tests clinically employed for the estimation of auditory and visual recent memory dysfunction was administered to eight subjects having circumscribed damage to the temporal lobe. It was hypothesized that the performance of subjects with temporal lobe lesions would qualitatively resemble that of subjects intoxicated with marijuana. Where comparisons could be made, the performance of these "temporal lobe" patients paralleled the performance of subjects acutely intoxicated with known doses of delta 9-THC. Results are discussed in terms of cannabinoid actions on hippocampal functioning and, in general, support the hypothesis that the action of marijuana in the brain may focus in the hippocampal region and produce behavioral changes similar to that resulting from traumatic injury or removal of the region.

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.

Lead-induced behavioral disorders in the rat: effects of amphetamine.

The effects of d-amphetamine on several measures of activity and spontaneous alternation were evaluated in rats chronically exposed to a low level of lead acetate via maternal milk during the neonatal period. Alterations in the amphetamine responses of lead-treated rats were observed with some measures of activity and exploration but not with others. 'Paradoxical' responses were observed with postural rearing and spontaneous alternation. No drug response was seen in lead-treated animals with respect to center field activity in contrast to a large increase seen in controls. Normally, amphetamine reduces grooming behavior, but since this reduction was greater in lead-reared than in control rats, the data suggest that for this measure the lead-reared rat may posses an increased sensitivity to amphetamines. These results were discussed in terms of the behavioral parallels found between lead poisoning and childhood hyperactivity, and the potential of this model as an animal analog of minimal brain dysfunction hyperactivity.

Marijuana: effects on storage and retrieval of prose material.

In a two phase design, an attempt was made to differentiate the effect of marijuana on the storage and retrieval of prose material. In the first phase, 40 male subjects were administered a single 500 mg marijuana cigarette containing 2.1%delta9-THC or a placebo cigarette. Fifteen minutes after smoking, they listened to and at the same time read a narrative passage of approximately 200 words in length. Subsequently, an immediate free recall test was given in which subjects were required to write down as much of the story as they could remember. The second phase was conducted 24h later. Marijuana and placebo subjects were randomly subdivided into four groups with half of the subjects participating in the same drug condition as occurred on day one while the others switched drug state. Fifteen minutes after smoking, all subjects recalled the passage presented on day one and then were given 24 questions concerning facts and events in the story which could be answered in a few words. These questions served as retrieval cues. Following this, a new passage was presented in the same manner as occurred on day one. After an immediate free recall test, another cued recall test was administered. Results indicated that marijuana reduced immediate recall under both cued and uncued conditions incomparison to placebo. No relative cued recall advantage was found in the marijuana groups for the old or new story and marijuana produced only a moderate decrement in recall of the old story on day two. However, marijuana given in the second phase significantly reduced memory for items recalled in the initial phase irrespective of drug or cueing condition in phase one, suggesting that retrieval was also affected. Some decrement in recall of the new story did occur as a function of drug state change in group M-P. This effect was related to the serial position of input items. Serial position did not interact with drug state under any other recall condition.

Marijuana and memory impairment: the effect of retrieval cues on free recall.

In an attempt to ascertain the effect of retrieval cues on recall deficits which occur following intoxication with marijuana, 40 male volunteers were presented with word lists following the smoking of a single one gram marijuana (0.94% delta 9 -THC) or placebo cigarette and then were required to recall these words immediately after presentation. Recall occurred under a condition in which cues representative of to-be-remembered words were present or in an uncued condition. Results indicated that recall was depressed following marijuana administration under both cued and uncued conditions with cues being only mildly effective in reversing the recall deficit. There was no increase in the number of internal intrusions under marijuana, but the number of external intrusions was significantly elevated under the cued conditions.

Lead-inducing 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.

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.