Biomaterial Database

Augmentation of bursting pacemaker activity by egg-laying hormone in Aplysia neuron R15 is mediated by a cyclic AMP-dependent increase in Ca2+ and K+ currents. 1987

E S Levitan, and R H Kramer, and I B Levitan

Release of the neuropeptide egg-laying hormone (ELH) from Aplysia bag cell neurons augments the endogenous bursting pacemaker activity of neuron R15. We have studied the ionic mechanisms underlying the effect of ELH in voltage-clamped R15 neurons. Both electrical discharge of the bag cells, which releases endogenous ELH, and application of synthetic ELH on cell R15 result in an increase in two discrete ionic currents. One of these currents activates with hyperpolarization, reverses near the K+ equilibrium potential, is sensitive to the external K+ concentration, and is blocked by addition of 5 mM Rb+ or 1 mM Ba2+ to the bathing medium. This current appears to be identical to the inwardly rectifying K+ current IR. The other current activates with depolarization and is blocked by replacement of external Ca2+ with Co2+ or Mn2+. This current appears to be a voltage-gated Ca2+ current ICa. Both ICa and IR in R15 have previously been shown to be enhanced by the neurotransmitter serotonin, acting via intracellular cyclic AMP. We now report that increasing cyclic AMP in R15, by applying either serotonin or the adenylate cyclase activator forskolin together with a phosphodiesterase inhibitor, mimics and occludes the action of ELH on neuron R15. Furthermore, application of ELH increases the cyclic AMP content of single R15 neurons, as measured by radioimmunoassay. Finally, the effects of ELH are potentiated by a phosphodiesterase inhibitor. These results suggest that ELH augments bursting activity in R15 by causing cyclic AMP-mediated increases in IR and ICa.

UI	MeSH Term	Description	Entries
D007447	Invertebrate Hormones	Hormones produced by invertebrates, usually insects, mollusks, annelids, and helminths.	Hormones, Invertebrate
D009474	Neurons	The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM.	Nerve Cells,Cell, Nerve,Cells, Nerve,Nerve Cell,Neuron
D011188	Potassium	An element in the alkali group of metals with an atomic symbol K, atomic number 19, and atomic weight 39.10. It is the chief cation in the intracellular fluid of muscle and other cells. Potassium ion is a strong electrolyte that plays a significant role in the regulation of fluid volume and maintenance of the WATER-ELECTROLYTE BALANCE.
D002118	Calcium	A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.	Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D004594	Electrophysiology	The study of the generation and behavior of electrical charges in living organisms particularly the nervous system and the effects of electricity on living organisms.
D000242	Cyclic AMP	An adenine nucleotide containing one phosphate group which is esterified to both the 3'- and 5'-positions of the sugar moiety. It is a second messenger and a key intracellular regulator, functioning as a mediator of activity for a number of hormones, including epinephrine, glucagon, and ACTH.	Adenosine Cyclic 3',5'-Monophosphate,Adenosine Cyclic 3,5 Monophosphate,Adenosine Cyclic Monophosphate,Adenosine Cyclic-3',5'-Monophosphate,Cyclic AMP, (R)-Isomer,Cyclic AMP, Disodium Salt,Cyclic AMP, Monoammonium Salt,Cyclic AMP, Monopotassium Salt,Cyclic AMP, Monosodium Salt,Cyclic AMP, Sodium Salt,3',5'-Monophosphate, Adenosine Cyclic,AMP, Cyclic,Adenosine Cyclic 3',5' Monophosphate,Cyclic 3',5'-Monophosphate, Adenosine,Cyclic Monophosphate, Adenosine,Cyclic-3',5'-Monophosphate, Adenosine,Monophosphate, Adenosine Cyclic
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D001048	Aplysia	An opisthobranch mollusk of the order Anaspidea. It is used frequently in studies of nervous system development because of its large identifiable neurons. Aplysiatoxin and its derivatives are not biosynthesized by Aplysia, but acquired by ingestion of Lyngbya (seaweed) species.	Aplysias