Histamine operates Cl -gated channels in crayfish neurosecretory cells.
We describe a histamine-activated Cl(-) conductance in the X-organ neurons from crayfish Cherax quadricarinatus, which has comparable properties to the homomultimeric histamine-gated ion channels described in Drosophila. Topical application of histamine inhibited spontaneous neuronal firing in the X-organ sinus gland tract, concomitant with an increase in the membrane conductance. In X-organ neurons in culture and under voltage-clamp conditions, histamine evoked outward currents at -40 mV that reversed at the Cl(-) equilibrium potential. Histamine sensitivity in these neurons had a half-maximal response (EC(50))=3.3+/-1 micromol l(-1), with a Hill number of 2.6+/-0.4. The histamine-evoked current was blocked by tiotidine, cimetidine, ranitidine and 256+/-11 and 483+/-11 micromol l(-1), respectively) and d-tubocurarine (IC(50)=21+/-2 micromol l(-1)), but was insensitive to picrotoxin, bicuculline and strychnine. Neither GABA nor glutamate was capable of desensitizing the histamine response, indicating that histamine activates a particular Cl(-) conductance. The presence of immunoreactive neurons to histamine in the medulla terminalis with axonal projections to the neuropile suggests a possible histaminergic modulation of the X-organ sinus gland system.
Cebada
Jorge
J
Department of Physiology, Biophysics and Neuroscience, Centro de Investigación y de Estudios Avanzados del IPN (CINVESTAV-IPN), Av. Instituto Politécnico Nacional 2508, San Pedro Zacatenco, 07360 México City, México.
García
Ubaldo
U
D000818:Animals; D003400:Astacoidea / Q000033:anatomy & histology / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D018118:Chloride Channels / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005123:Eye / Q000033:anatomy & histology / Q000166:cytology / Q000187:drug effects; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism; D006632:Histamine / Q000276:immunology / Q000494:pharmacology*; D006633:Histamine Antagonists / Q000494:pharmacology; D015640:Ion Channel Gating / Q000187:drug effects*; D008297:Male; D009474:Neurons / Q000166:cytology / Q000187:drug effects; D009490:Neurosecretory Systems / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D011968:Receptors, Histamine / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D018118:Chloride Channels; D006633:Histamine Antagonists; D011968:Receptors, Histamine; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D006632:Histamine