Histamine actions on activity of cultured hypothalamic neurons: evidence for mediation by H1- and H2-histamine receptors.
Tuberal hypothalamic tissue cultures were used to investigate the actions of histaminergic agents on neuronal activity using extracellular glass micropipettes. Histamine and H1- and H2-agonists were applied locally onto single active neurons by iontophoresis, while histaminergic antagonists were perfused through the bathing medium. Peri-event histogram and ratemeter analysis showed histamine to both excite and depress unit activity. Excitations were only antagonized by putative H1- and not H2-histamine antagonists, whereas inhibitions were antagonized by H2- and H2-antagonists. Dimaprit, a specific H2-agonist, elicited inhibitions of activity, while 2-(2-pyridyl)ethylamine, a putative H1-agonist, elicited both excitations and inhibitions. Two pharmacologically distinct populations of histamine receptors may exit in the hypothalamus: excitatory H2-receptors and inhibitory H2-receptors.
D000818:Animals; D046508:Culture Techniques; D004305:Dose-Response Relationship, Drug; D005071:Evoked Potentials / Q000187:drug effects; D006632:Histamine / Q000494:pharmacology*; D007031:Hypothalamus / Q000187:drug effects*; D009433:Neural Inhibition / Q000187:drug effects; D009474:Neurons / Q000187:drug effects; D051381:Rats; D011968:Receptors, Histamine / Q000187:drug effects*; D011969:Receptors, Histamine H1 / Q000187:drug effects*; D011970:Receptors, Histamine H2 / Q000187:drug effects*; D009435:Synaptic Transmission / Q000187:drug effects
D011968:Receptors, Histamine; D011969:Receptors, Histamine H1; D011970:Receptors, Histamine H2; D006632:Histamine