The 5-HT1A receptor antagonist p-MPPI blocks 5-HT1A autoreceptors and increases dorsal raphe unit activity in awake cats.
The effects of the putative 5-HT1A receptor antagonist 4-iodo-N-[2-[4-(methoxyphenyl)-1-piperazinyl]ethyl]-N-2-pyridinyl-benzam ide (p-MPPI) were examined on the activity of serotonergic dorsal raphe nucleus neurons in freely moving cats. Systemic administration of p-MPPI produced a dose-dependent increase in firing rate. This stimulatory effect of p-MPPI was evident during wakefulness (when serotonergic neurons display a relatively high level of activity), but not during sleep (when serotonergic neurons display little or no spontaneous activity). p-MPPI also blocked the ability of the 5-HT1A receptor agonist 8-hydroxy-(2-di-n-propylamino)tetralin (8-OH-DPAT) to inhibit serotonergic neuronal activity. This antagonism was evident both as a reversal of the neuronal inhibition produced by prior injection of 8-OH-DPAT and as a shift in the potency of 8-OH-DPAT following p-MPPI pretreatment. Overall, these results in behaving animals indicate that p-MPPI acts as an effective 5-HT1A autoreceptor antagonist. The increase in firing rate produced by p-MPPI supports the hypothesis that autoreceptor-mediated feedback inhibition operates under physiological conditions.
Department of Psychology, Princeton University, NJ, USA. bjorn.bjorvatn@pki.uib.no
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B
Bjorvatn
C A
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Fornal
F J
FJ
Martín
C W
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Metzler
B L
BL
Jacobs
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects; D000631:Aminopyridines / Q000494:pharmacology*; D000818:Animals; D017660:Autoreceptors / Q000037:antagonists & inhibitors*; D002415:Cats; D004347:Drug Interactions; D004569:Electroencephalography / Q000187:drug effects; D004594:Electrophysiology; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D010879:Piperazines / Q000494:pharmacology*; D011903:Raphe Nuclei / Q000187:drug effects* / Q000502:physiology; D011985:Receptors, Serotonin / Q000187:drug effects*; D044263:Receptors, Serotonin, 5-HT1; D012702:Serotonin Antagonists / Q000494:pharmacology*; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D014851:Wakefulness
D000631:Aminopyridines; D017660:Autoreceptors; D010879:Piperazines; D011985:Receptors, Serotonin; D044263:Receptors, Serotonin, 5-HT1; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; C087205:4-(2'-methoxyphenyl)-1-(2'-(N-(2''-pyridinyl)-4-iodobenzamido)ethyl)piperazine; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin