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Monoaminergic modulation of the ionic channels in Kenyon cells isolated from the mushroom body of the cricket brain
454
Abstracts
The direction of wind-evoked escape in the cricket, Gryllus bimaculatus, became incorrect just after the ablation of one of a pair of cerci. When the cricket was reared under the condition that permitting free walking, however, the escape direction showed a compensational recovery almost 2 weeks after the ablation. In our previous study, it was revealed that an artificial air puff applied from the opposite to the stationary walking was effective for the behavioral compensation when it was synchronized with the walking. It was hard evidence that a self-stimulation of the wind-sensory system during walking is essential for the behavioral compensation. Our next question was how long was the time-window that a cricket CNS recognizes an artificial air puff as a self-generated wind. To explore this, we changed the time delay from the start of walking to the onset of the artificial air puff for a cricket during a stationary walking. Escape direction of the cricket to an air puff stimulus was investigated after 14-day's training. Crickets those were trained by the air puff with the time delay shorter than one-second showed compensational recovery in their escape direction.
be monitored by activities of salivary neurons. Here, I locally injected mecamylamine (MEC), an antagonist of acetylcholine receptors, into three distinct olfactory centers to investigate its effects on conditioning. By injecting MEC into the antennal lobes (ALs), calyces of the mushroom bodies (MBs) or lateral protocerebrums (LPRs), olfactory responses of salivary neurons were partially abolished, suggesting that MEC-sensitive neurons in these brain areas participate in olfactory pathways. When MEC was injected into the ALs or MB calyces before conditioning, no conditioning effects were observed during conditioning trials and in tests 2.5 h after conditioning, at which time olfactory responses are recovered. This suggests that MEC-sensitive MB intrinsic neurons (Kenyon cells), or neurons in downstream pathways, participate in olfactory conditioning. When MEC was injected into the LPR, conditioning effects were not detected during conditioning trials but were detected in tests at 2.5 h after conditioning. This suggests that an association of CS and US occurs in neurons upstream of the MEC-sensitive LPR neurons. Taken together, the results suggest that MEC-sensitive Kenyon cells play critical roles in olfactory conditioning.
doi:10.1016/j.cbpb.2008.09.026 doi:10.1016/j.cbpb.2008.09.028 26. Cognitive process underlying insect classical conditioning Makoto Mizunami, Sae Unoki, Yasuhiro Mori, Daisuke Hirashima, Ai Hatano, Yukihisa Matsumoto, Grad. School Life Sci. Tohoku Univ. Sendai, 980-8577, Japan Classical conditioning is the most extensively studied form of associative learning and is widespread among vertebrates and invertebrates, but its underlying neural processes remain controversial. In insects, classical conditioning is regarded as the formation of a new reflex pathway for the conditioning stimulus (CS) to evoke a conditioned response. In mammals, however, formation of internal representations of external sensory events, which is often referred to as a cognitive process, is thought to underlie classical conditioning. Here we show that the latter cognitive account is applicable to insects. In insect classical conditioning, octopaminergic (OAergic) or dopaminergic (DAergic) neurons convey appetitive or aversive unconditioned stimulus (US), respectively. We show that pharmacological blockade of OA or DA receptors impairs aversive or appetitive memory recall, respectively, in crickets, thereby suggesting that activation of OA or DAergic neurons is needed for appetitive or aversive memory recall, respectively. On the basis of this finding, we propose a model of insect classical conditioning, in which new synaptic connections from neurons representing CS to OA or DAergic neurons representing US are formed during conditioning, and activation of this pathway underlies memory recall. This model was supported by pharmacological analysis combined with a second-order conditioning procedure.
28. Monoaminergic modulation of the ionic channels in Kenyon cells isolated from the mushroom body of the cricket brain Kumiko Kosakai, Kozue Aoki, Kaori Satoh, Masami Yoshino, Department Biol., Tokyo Gakugei Univ., Tokyo 184-8501, Japan It has been revealed that octopamine (OA) mediates unconditioning stimulus (US) or reward (appetitive) signals, whereas dopamine (DA) mediates punishment (aversive) signals in insect olfactory learning. However, their target molecules and signaling mechanisms are not fully understood. In this study, we investigated the effects of OA and DA on ionic channels identified in Kenyon cells isolated from the mushroom body of the cricket (Gryllus bimaculatus) brain. Two different ionic channels were identified: one is the voltage dependent L-type Ca2+ channels and the other is the Na+-activated K+ (KNa) channels. The results clearly showed that OA and DA respectively increased and decreased the Po of KNa channels. It was also revealed that OA and DA respectively decreased and increased the Po of L-type Ca2+ channels. Possible involvement of cAMP and cGMP signal cascades was also investigated. Application of 8-Br-cAMP increased the PO of KNa channels and decreased the Po of Ca2+ channels. On the other hand, 8-Br-cGMP increased the Po of Ca2+ channel and decreased the Po of KNa channels. These results indicate that modulation of KNa channels and voltage-dependent L-type Ca2+ channels are involved in the process of olfactory learning.
doi:10.1016/j.cbpb.2008.09.027 doi:10.1016/j.cbpb.2008.09.029 27. Roles of mecamylamine-sensitive Kenyon cells in olfactory salivary conditioning of cockroaches Hidehiro Watanabe a, Makoto Mizunami b, a Department Earth System Sci., Fac. Sci., Fukuoka Univ., Fukuoka 814-0180, Japan; b Grad. Sch. Life Sci., Tohoku Univ., Sendai 980-8577, Japan Cockroaches, Periplaneta americana, exhibit salivary conditioning in which olfactory conditioning stimulus (CS) is associated with gustatory unconditioned stimulus (US), and this conditioning can
29. Neurotransmitter modulation of the action potentials and net membrane currents in Kenyon cell isolated from the mushroom body of the cricket brain Rie Terazima, Masami Yoshino, Department Biol., Tokyo Gakugei Univ., Tokyo 184-8501, Japan Acetylcholine (Ach) and octopamine (OA) have been implicated to be neurotransmitters mediating the conditioning and appetitive
Abstracts
The direction of wind-evoked escape in the cricket, Gryllus bimaculatus, became incorrect just after the ablation of one of a pair of cerci. When the cricket was reared under the condition that permitting free walking, however, the escape direction showed a compensational recovery almost 2 weeks after the ablation. In our previous study, it was revealed that an artificial air puff applied from the opposite to the stationary walking was effective for the behavioral compensation when it was synchronized with the walking. It was hard evidence that a self-stimulation of the wind-sensory system during walking is essential for the behavioral compensation. Our next question was how long was the time-window that a cricket CNS recognizes an artificial air puff as a self-generated wind. To explore this, we changed the time delay from the start of walking to the onset of the artificial air puff for a cricket during a stationary walking. Escape direction of the cricket to an air puff stimulus was investigated after 14-day's training. Crickets those were trained by the air puff with the time delay shorter than one-second showed compensational recovery in their escape direction.
be monitored by activities of salivary neurons. Here, I locally injected mecamylamine (MEC), an antagonist of acetylcholine receptors, into three distinct olfactory centers to investigate its effects on conditioning. By injecting MEC into the antennal lobes (ALs), calyces of the mushroom bodies (MBs) or lateral protocerebrums (LPRs), olfactory responses of salivary neurons were partially abolished, suggesting that MEC-sensitive neurons in these brain areas participate in olfactory pathways. When MEC was injected into the ALs or MB calyces before conditioning, no conditioning effects were observed during conditioning trials and in tests 2.5 h after conditioning, at which time olfactory responses are recovered. This suggests that MEC-sensitive MB intrinsic neurons (Kenyon cells), or neurons in downstream pathways, participate in olfactory conditioning. When MEC was injected into the LPR, conditioning effects were not detected during conditioning trials but were detected in tests at 2.5 h after conditioning. This suggests that an association of CS and US occurs in neurons upstream of the MEC-sensitive LPR neurons. Taken together, the results suggest that MEC-sensitive Kenyon cells play critical roles in olfactory conditioning.
doi:10.1016/j.cbpb.2008.09.026 doi:10.1016/j.cbpb.2008.09.028 26. Cognitive process underlying insect classical conditioning Makoto Mizunami, Sae Unoki, Yasuhiro Mori, Daisuke Hirashima, Ai Hatano, Yukihisa Matsumoto, Grad. School Life Sci. Tohoku Univ. Sendai, 980-8577, Japan Classical conditioning is the most extensively studied form of associative learning and is widespread among vertebrates and invertebrates, but its underlying neural processes remain controversial. In insects, classical conditioning is regarded as the formation of a new reflex pathway for the conditioning stimulus (CS) to evoke a conditioned response. In mammals, however, formation of internal representations of external sensory events, which is often referred to as a cognitive process, is thought to underlie classical conditioning. Here we show that the latter cognitive account is applicable to insects. In insect classical conditioning, octopaminergic (OAergic) or dopaminergic (DAergic) neurons convey appetitive or aversive unconditioned stimulus (US), respectively. We show that pharmacological blockade of OA or DA receptors impairs aversive or appetitive memory recall, respectively, in crickets, thereby suggesting that activation of OA or DAergic neurons is needed for appetitive or aversive memory recall, respectively. On the basis of this finding, we propose a model of insect classical conditioning, in which new synaptic connections from neurons representing CS to OA or DAergic neurons representing US are formed during conditioning, and activation of this pathway underlies memory recall. This model was supported by pharmacological analysis combined with a second-order conditioning procedure.
28. Monoaminergic modulation of the ionic channels in Kenyon cells isolated from the mushroom body of the cricket brain Kumiko Kosakai, Kozue Aoki, Kaori Satoh, Masami Yoshino, Department Biol., Tokyo Gakugei Univ., Tokyo 184-8501, Japan It has been revealed that octopamine (OA) mediates unconditioning stimulus (US) or reward (appetitive) signals, whereas dopamine (DA) mediates punishment (aversive) signals in insect olfactory learning. However, their target molecules and signaling mechanisms are not fully understood. In this study, we investigated the effects of OA and DA on ionic channels identified in Kenyon cells isolated from the mushroom body of the cricket (Gryllus bimaculatus) brain. Two different ionic channels were identified: one is the voltage dependent L-type Ca2+ channels and the other is the Na+-activated K+ (KNa) channels. The results clearly showed that OA and DA respectively increased and decreased the Po of KNa channels. It was also revealed that OA and DA respectively decreased and increased the Po of L-type Ca2+ channels. Possible involvement of cAMP and cGMP signal cascades was also investigated. Application of 8-Br-cAMP increased the PO of KNa channels and decreased the Po of Ca2+ channels. On the other hand, 8-Br-cGMP increased the Po of Ca2+ channel and decreased the Po of KNa channels. These results indicate that modulation of KNa channels and voltage-dependent L-type Ca2+ channels are involved in the process of olfactory learning.
doi:10.1016/j.cbpb.2008.09.027 doi:10.1016/j.cbpb.2008.09.029 27. Roles of mecamylamine-sensitive Kenyon cells in olfactory salivary conditioning of cockroaches Hidehiro Watanabe a, Makoto Mizunami b, a Department Earth System Sci., Fac. Sci., Fukuoka Univ., Fukuoka 814-0180, Japan; b Grad. Sch. Life Sci., Tohoku Univ., Sendai 980-8577, Japan Cockroaches, Periplaneta americana, exhibit salivary conditioning in which olfactory conditioning stimulus (CS) is associated with gustatory unconditioned stimulus (US), and this conditioning can
29. Neurotransmitter modulation of the action potentials and net membrane currents in Kenyon cell isolated from the mushroom body of the cricket brain Rie Terazima, Masami Yoshino, Department Biol., Tokyo Gakugei Univ., Tokyo 184-8501, Japan Acetylcholine (Ach) and octopamine (OA) have been implicated to be neurotransmitters mediating the conditioning and appetitive