5-Hydroxytryptamine (5-HT) agonists: effects on neocortical slow wave activity after combined muscarinic and serotonergic blockade.
In freely-moving rats treated with a combination of reserpine (10 mg/kg, i.p.) and scopolamine (5 mg/kg, i.p.), neocortical low voltage fast activity (LVFA) associated with continuous multiunit activity (MUA) was abolished and replaced by 2-6 Hz large irregular slow activity (LISA) above 1.5 mV associated with a burst-suppression pattern of MUA. Administration of the monoamine oxidase inhibitor pargyline (50-100 mg/kg, i.p.) completely suppressed 2-6 Hz LISA and restored normal-appearing LVFA and continuous MUA. The 5-hydroxytryptamine (5-HT) receptor agonists quipazine (0.5-20 mg/kg, i.p.), (+/-)-DOI (0.1-5 mg/kg, s.c.), and buspirone (0.1-10 mg/kg, i.p.), but not 8-hydroxy-2-(di-n-propylamine) tetraline (8-OH-DPAT, 0.05-0.8 mg/kg, s.c.) and RU 24969 (1-30 mg/kg, i.p.), produced a partial suppression of 2-6 Hz LISA and restored some lower voltage activity (< 1 mV) above 6 Hz associated with continuous MUA. However, as opposed to pargyline, no receptor agonist tested restored continuous, normal-appearing LVFA. Even though agonists at 5-HT receptors can produce some activation of neocortical slow wave activity after combined cholinergic and serotonergic blockade, this effect is not equivalent to that observed after restoration of endogenous 5-HT transmission.
Dringenberg
H C
HC
Neuroscience Program, Siebens-Drake Research Institute, University of Western Ontario, London, Canada.
Vanderwolf
C H
CH
D000818:Animals; D002540:Cerebral Cortex / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D008297:Male; D010293:Pargyline / Q000494:pharmacology; D051381:Rats; D012110:Reserpine / Q000494:pharmacology*; D012601:Scopolamine / Q000494:pharmacology*; D017366:Serotonin Receptor Agonists / Q000494:pharmacology*
D017366:Serotonin Receptor Agonists; D012110:Reserpine; D010293:Pargyline; D012601:Scopolamine