Neurochemical mediators of anxiety have inconsistent effects on hypothalamic self-stimulation in rats.
We studied effects of anxiogenic and anxiolytic compounds on the electric self-stimulation of the medial fore-brain bundle in male rats to find out if there is a link between reward and anxiety-related behaviours. The cholecystokinin agonist, caerulein (25-100 micrograms/kg) and the 5-HT agonist 1-(3-chlorophenyl)piperazine (0.2-1 mg/kg) dose-dependently inhibited the electric self-stimulation. The 5-HT2A antagonist, ketanserin, at 2.5 mg/kg, increased the self-stimulation at high currents but not at threshold current. The 5-HT3 antagonist ondansetron (10 and 100 micrograms/kg). The alpha 1-adrenergic antagonist, prazosin (0.125 and 0.5 mg/kg), the beta-adrenergic antagonist, propranolol (5 and 10 mg/kg) and the alpha 2-adreno-receptor antagonist, atipamezole (4 mg/kg), did not affect the self-stimulation. Nor did the benzodiazepine agonist, diazepam (5-15 mg/kg), a benzodiazepine receptor antagonist flumazenil (at 10 and 25 mg/kg) or the inverse agonist of benzodiazepine receptors, N-methyl-beta-carboline-3-carboxamide (10 and 20 mg/kg), cause any substantial changes of the self-stimulation. We conclude that only two anxiolytic drugs (caerulein and 1-(3-chlorophenyl)piperazine) suppress the electric self-stimulation. These findings indicate that anxiogenicity as such is not able to weaken the hypothalamic electric self-stimulation. Anxiety and reward are apparently mediated through separate neural pathways.
Borisenko
S A
SA
Department of Pharmacology and Toxicology, University of Helsinki, Finland.
Meng
Q H
QH
Rauhala
P
P
Männistö
P T
PT
D000661:Amphetamine / Q000494:pharmacology; D000818:Animals; D014150:Antipsychotic Agents / Q000494:pharmacology; D001007:Anxiety / Q000503:physiopathology*; D001143:Arousal / Q000187:drug effects*; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D002108:Ceruletide / Q000494:pharmacology; D007031:Hypothalamus / Q000187:drug effects*; D008297:Male; D010868:Pimozide / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012653:Self Stimulation / Q000187:drug effects*
D014150:Antipsychotic Agents; D000697:Central Nervous System Stimulants; D010868:Pimozide; D002108:Ceruletide; D000661:Amphetamine