Delayed and sustained effect of acetoxycycloheximide on memory in mice.

108

Mice were trained in an automated visualdiscrimination task. When injected with cycloheximide before training, mice showed: (a) some impairment of memory within minutes after the beginning of training, (b) gradual development of total amnesia in less than 3 hr or in more than 6 hr after training, depending on the extent of training, and (c) spontaneous recovery of memory within 3 days after training. The results are consistent with the operation of three processes of memory storage: (i) a short-term process that is independent of protein synthesis, (ii) a long-term process that is dependent on protein synthesis, and (iii) a slow-developing memory storage that becomes apparent during the days after training.Previous studies on effects of cycloheximide and acetoxycycloheximide on learning and memory in mice given brief training have repeatedly demonstrated normal acquisition in the presence of these potent inhibitors of cerebral protein synthesis, normal retention for about 3 hr, and then marked and permanent amnesia by 6 hr after training (1, 2). These experiments suggested a simple view of learning and memory in mice. Since acquisition and retention for at least 3 hr were normal during marked inhibition of cerebral protein synthesis, it seemed reasonable to postulate a "short-term" memory storage process that is independent of protein synthesis, with a fixed lifetime of 3-6 hr. Since long-term retention was impaired only if the drug were given shortly before or very shortly after training, a "long-term" memory storage process that is dependent on protein synthesis was also postulated that is normally initiated during training or within minutes there-FIG. 1. The Deutsch Carousel for training a discrimination habit in mice. Mice are placed in the apparatus while facing position A. The mouse is then rotated to position B for trial one, and then to adjacent positions for subsequent trials. At each position, the mouse must touch the small object to escape shock. Once the mouse has been secured in the apparatus, the entire training procedure is controlled by a PDP/8L computer.after. With decline of the proposed "short-term" process after 3 hr, absence of the "long-term" process is detectable and amnesia is observed.Recent experiments in a multiple-trial, automated discrimination task and the work of others suggest that the situation is somewhat more complex. In the present report, we describe studies indicating that (a) cycloheximide impairs the gradual acquisition of a discrimination task when training is continued beyond 20-30 trials, although it does not affect acquisition up to this point, (b) memory is detectable for less than 3 hr after training when cycloheximide-treated mice are given brief training, but considerable memory is detectable for more than 6 hr after training when cycloheximide-treated mice are given more extended training, and (c) once amnesia has developed, it may persist for only several days, followed by complete, spontaneous recovery of memory. We will present an interpretation of thes...

Section: Methodscontrasting

confidence: 55%

“…Mice given 15 trials were tested for retention by exposure to 15 additional trials after 10 see (these mice received 30 consecutive trials), 15 min, 1 hr, 3 hr, or 24 hr (Fig. 3A).…”

Section: Methodsmentioning

confidence: 99%

Variable Decay of Memory and Its Recovery in Cycloheximide-Treated Mice

Squire

Barondes

1972

108

“…We found support for involvement of these functional pools by observing that a large amnestic dose of AXM strikingly reduced the rate of accumulation of CAs from circulating tyrosine for at least 12 hr, greatly exceeding in degree and duration what might be anticipated from the loss of tyrosine hydroxylase activity in Vitro. We also found that the antibiotic, in spite of its inhibitory effect on the rate of accumulation of newly synthesized CAs, increased the endogenous levels of CAs for 4 hr after treatment, indicating that it interferes with aspects of CA metabolism in addition to biosynthesis (14).The present experiments extend this approach to CXM, Ani, puromycin, and to the smallest dose of intracerebrally injected AXM found to be amnestic in mice (15). We find all of these antibiotics to have substantial effects on central CAs.…”

mentioning

confidence: 51%

“…The present experiments extend this approach to CXM, Ani, puromycin, and to the smallest dose of intracerebrally injected AXM found to be amnestic in mice (15). We find all of these antibiotics to have substantial effects on central CAs.…”

mentioning

confidence: 71%

Studies on memory: inhibitors of protein synthesis also inhibit catecholamine synthesis.

Flexner

Goodman

1975

The rates of accumulation of newly synthesized catecholamines and endogenous catecholamine levels in mice were determined after treatment with cycloheximide, acetoxycycloheximide, puromycin, and anisomycin. The rates of accumulation were found to be decreased by all antibiotics tested, weakening the assumption that their amnestic effects are due solely to inhibition of protein synthesis. The hypothesis that protein synthesis is essential for longterm memory has developed from the observation in several species that treatment with an inhibitor of protein synthesis before or shortly after training leads to amnesia of the training experience (1-6). There is evidence, however, that important side-effects on the central adrenergic system may be common to all inhibitors of protein synthesis and that these side-effects may contribute to the amnesia. For example, in mice and rats the amnesia caused by puromycin, acetoxycycloheximide (AXM), and cycloheximide (CXM) is attenuated by adrenergic stimulants or monoamine oxidase inhibitors (7-9). Also consistent with this possibility are the reports that AXM, CXM, and anisomycin (Ani) cause a reduction of tyrosine hydroxylase activity (10,11). This further suggests that the amnestic effects of the antibiotics may depend in part on a reduction of the functional pools of newly synthesized catecholamines (CAs) (12, 13). We found support for involvement of these functional pools by observing that a large amnestic dose of AXM strikingly reduced the rate of accumulation of CAs from circulating tyrosine for at least 12 hr, greatly exceeding in degree and duration what might be anticipated from the loss of tyrosine hydroxylase activity in Vitro. We also found that the antibiotic, in spite of its inhibitory effect on the rate of accumulation of newly synthesized CAs, increased the endogenous levels of CAs for 4 hr after treatment, indicating that it interferes with aspects of CA metabolism in addition to biosynthesis (14).The present experiments extend this approach to CXM, Ani, puromycin, and to the smallest dose of intracerebrally injected AXM found to be amnestic in mice (15). We find all of these antibiotics to have substantial effects on central CAs. In some ways, these effects resemble those produced by inhibitors of tyrosine hydroxylase and dopamine f3-hydroxylase, agents reported to have the same amnestic properties as those of CXM in active or passive avoidance (16, 17) and food-motivated discrimination tasks (18).Male Swiss-Webster and ICR mice (28-32 g) were housed as previously described (14). CXM (120 mg/kg) and Ani (25-30 mg/kg; gift of Pfizer Inc.) were injected subcutaneously in 0.2 ml of water. AXM (10,ug/injection site; gift of the National Cancer Institute) or puromycin (90 gg/injection site; neutralized with NaOH) were injected bitemporally in 12 ,ul of water under light Evipal (150 mg/kg) anesthesia. Controls were injected in the same way with 12 gl of water per injection site. The inhibitor of tyrosine hydroxylase, a-methyl-para-tyrosine (methyl ester-HCl...

“…Barondes and Cohen have found a long-lasting amnesia that is induced in minimally trained mice when AXM or cycloheximide is injected before or immediately after training (7). A transient amnesia has been observed in mice both by Flexner and Flexner (8) and by Quartermain et at.…”

mentioning

confidence: 85%

Acetoxycycloheximide-Induced Transient Amnesia: Protective Effects of Adrenergic Stimulants

Serota

Roberts

Flexner

1972

It has previously been shown that rats trained 5 hr after intracerebral injection of acetoxycycloheximide show a transient amnesia at 24 hr after training. We have tested the possibility that adrenergic stimulants might provide protection from the amnesia. Metaraminol, given either before or after training or before testing, prevents the drug-induced amnesia. D-Amphetamine, injected soon after training, also prevents the amnesia. A model is presented to explain the drug-induced amnesia in terms of both the assumed effect of acetoxycycloheximide on the adrenergic system and prevention of the amnesia by metaraminol and D-amphetamine.The protein synthesis inhibitors, puromycin and acetoxycycloheximide (AXM), have been used in a number of experiments designed to determine whether protein synthesis is necessary for the formation of a long-term memory (1, 2). Although puromycin does indeed act to produce a reliable and long-lasting amnesia, it has become clear that the amnesia can be attributed to factors other than the temporary cessation of protein synthesis. Thus, a mixture of puromycin and AXM, which produces a more profound inhibition of protein synthesis than puromycin alone, has no amnesic effect (3).Furthermore, the puromycin-induced amnesia can be reversed by various treatments, including the injection of drugs acting on the adrenergic system. It appears that the puromycin-induced amnesia may be the result of puromycinpeptides that block norepinephrine receptor sites at synapses (4). This hypothesis is in accord with the apparent need for adequate concentrations of norepinephrine both at the time of testing (5) and at the time of consolidation immediately after training (6).Various amnesic effects of AXM (or cycloheximide) have been reported. Barondes and Cohen have found a long-lasting amnesia that is induced in minimally trained mice when AXM or cycloheximide is injected before or immediately after training (7). A transient amnesia has been observed in mice both by Flexner and Flexner (8) and by Quartermain et at. (9). Rats trained 5 hrs after intracerebral injections of AXM develop a transient amnesia at 24 hrs after training (10).Possibly AXM, like puromycin, has effects on the norepinephrine system that are responsible for the amnesic effects of the drug. If this were the case, adrenergic simulants might provide protection from amnesia. We have found that the temporary amnesia induced in rats by injection of AXM is prevented by an injection of metaraminol given either before or after training or before testing. D-Amphetamine injected soon after training also prevents the AXM-induced amnesia. These results with D-amphetamine are similar to those reported by Barondes and Cohen (11). MATERIALS AND METHODSMale Buffalo or Fisher rats (Microbiological Ass., 250-300 g) were used. Rats were trained in a shock-avoidance, brightness-discrimination task in a Y-maze to a criterion of six out of seven correct responses, under described conditions (10). 30 Min before training or at various times between train...