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Intermediate and long-term memories of associative learning are differentially affected by transcription versus translation blockers inLymnaea

Susan Sangha, Andi Scheibenstock, Chloe McComb and Ken Lukowiak^*

Department of Medical Physiology and Biophysics, Neuroscience Research Group, 3330 Hospital Drive NW, University of Calgary, Calgary, Alberta T2N 4N1, Canada

View larger version (31K): [in a new window]   Fig. 1. The effect of protein synthesis blockers on transcription (Actinomycin D) and translation (Anisomycin) on spontaneous aerial respiratory behaviour in Lymnaea. (A) Breathing time observed during a 30 min session in hypoxic pondwater, at 2.5, 4.5, 8 and 24 h post-injection in (1) non-injected controls, (2) saline-injected controls, (3) Actinomycin D- and (4) Anisomycin-injected Lymnaea. All injections were into the foot of the snail. (B) Number of pneumostome openings observed using the above protocol. (N=20-25; see text).

View larger version (9K): [in a new window]   Fig. 2. A single 0.5 h training session is sufficient to produce a memory that persists for 3 h but not 4 h in Lymnaea. (A) 20 naïve snails were pre-injected with saline 2.5 h before receiving a single session of operant conditioning training of 0.5 h duration (1). When tested 3 h later (MT) memory was observed. That is, the number of attempted pneumostome openings in the memory test session was significantly less (P<0.01) than the number in the operant conditioning training session. (B) A second naïve cohort of snails (N=20) was trained as in A, except that memory was tested 4 h after the training session. No memory was observed. That is, the number of attempted openings in the memory test (0.5 h) session was not statistically different (NSD) from the number of attempted openings in the training session (P>0.05).

View larger version (11K): [in a new window]   Fig. 3. The differential effect of a transcription and a translation blocker on ITM formation in Lymnaea. (A) A naïve group of snails (N=20) was injected with the transcriptional protein synthesis inhibitor Actinomycin D 2.5 h before the training session. Following the 0.5 h training session (1) the snails were tested for memory 3 h later (MT). Memory was present. That is, the number of attempted pneumostome openings in the memory test session was significantly less than the number of attempted openings in the operant conditioning training session (P<0.01). To show that this was a case of memory and not a drug-induced side effect, we altered the context 1 h later. When challenged with the `carrot context' (see text) the snails attempted as many pneumostome openings as they did in the training session (P>0.05) and statistically more than in the memory test session (P<0.01). (B) As in A, except that snails were injected with the translational protein synthesis blocker Anisomycin. No ITM was observed when tested 3 h after the training session. That is, the number of attempted pneumostome openings in the memory test session was not statistically different (NSD) from the number in the training session (P>0.05).

View larger version (11K): [in a new window]   Fig. 4. A 1 h training session is sufficient to produce a memory in Lymnaea that persists for at least 24 h. A naïve cohort (N=20) of snails was injected with saline 2.5 h before operant conditioning training of 1 h duration (1). When tested for memory 24 h later (MT), memory was observed. That is, the number of attempted pneumostome openings in the memory test session was significantly less than the number of openings in the training session (P<0.01).

View larger version (9K): [in a new window]   Fig. 5. Both transcription and the translation blockers prevent LTM formation in Lymnaea. (A) A naïve group of snails (N=20) was injected with the transcriptional protein synthesis inhibitor Actinomycin D 2.5 h before the 1 h training session (1). Following the 1 h training session the snails were tested for memory 6 h later (MT). Memory was not present. That is, the number of attempted pneumostome openings in the memory test session was not statistically different from the number in the training session (P>0.05). (B) As above, except the translational blocker Anisomycin was injected. Again, no memory was observed. That is, the number of attempted pneumostome openings in the memory test session was not statistically different from the number in the training session (P>0.05).