title: Pertussis toxin or 8-bromo-cAMP block inhibition of the acoustic startle response by the alpha 2-adrenergic agonist ST-91.
abstract: Stimulation of supraspinal alpha 2-adrenergic receptors by intraventricular infusion of the alpha 2-adrenergic agonist ST-91 depresses a simple vertebrate behavior, the acoustic startle response. Intraventricular pretreatment with pertussis toxin, an agent known to inactivate the inhibitory guanine nucleotide binding protein (Gi) which can inhibit adenylate cyclase, completely prevented the depressant behavioral effect of ST-91. In contrast, pertussis toxin did not alter the depressant effect of intraventricular infusion of the 5-HT 1B agonist 1-m-chlorophenylpiperazine (mCPP). Intraventricular infusion of the cyclic adenosine monophosphate (cAMP) analog 8-bromo-cAMP also reversed the depressant effect of ST-91 without altering the effect of mCPP. These data suggest that inhibition of adenylate cyclase may be involved in the effect of activation of central alpha 2-adrenergic receptors.
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D037361:Adenylate Cyclase Toxin; D000262:Adenylyl Cyclases / Q000502:physiology; D000818:Animals; D003000:Clonidine / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors; D000242:Cyclic AMP / Q000502:physiology*; D007276:Injections, Intraventricular; D008297:Male; D037342:Pertussis Toxin; D010879:Piperazines / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D013216:Reflex, Startle / Q000502:physiology*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D037361:Adenylate Cyclase Toxin; D010879:Piperazines; D011942:Receptors, Adrenergic, alpha; D010566:Virulence Factors, Bordetella; D015124:8-Bromo Cyclic Adenosine Monophosphate; C011266:ST 91; D000242:Cyclic AMP; D037342:Pertussis Toxin; D000262:Adenylyl Cyclases; D003000:Clonidine; C015068:1-(3-chlorophenyl)piperazine