Drug-induced activation of the inferior olivary nucleus in young rabbits. Differential effects of harmaline and quipazine.
Ontogenic evolution of behavioural and electrophysiological responses to the serotonergic agents, quipazine and harmaline, was studied in the maturing rabbit in normal and pretreated conditions. As regards behavioural effects, tremor induced by quipazine was present from the first postnatal day and was antagonized by methysergide, but not by p-chlorophenylalanine (PCPA) or pretreatment with 5,7-dihydroxytryptamine (5,7-DHT). In contrast, tremor induced by harmaline could not be elicited before the second postnatal week and was partially antagonized by methysergide and 5,7-DHT, but not by PCPA. Electrophysiological studies of cell activity in the inferior olivary nucleus revealed a similar dependency on age since rhythmic activation of the inferior olivary nucleus could be registered from the first postnatal day with quipazine and only from the 8th postnatal day with harmaline; drug interactions with methysergide, PCPA and 5,7-DHT were the same as for the behavioural observations. It is suggested that quipazine directly activates serotonin receptors which are already present at birth, whereas harmaline requires the presence of serotonergic fibres for such activation.
Barragan
L A
LA
Delhaye-Bouchaud
N
N
Laget
P
P
D015116:5,7-Dihydroxytryptamine / Q000494:pharmacology; D000470:Alkaloids / Q000494:pharmacology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D005106:Exploratory Behavior / Q000187:drug effects; D010134:Fenclonine / Q000494:pharmacology; D006246:Harmaline / Q000494:pharmacology*; D008784:Methysergide / Q000494:pharmacology; D009043:Motor Activity / Q000187:drug effects; D009847:Olivary Nucleus / Q000187:drug effects*; D011804:Quinolines / Q000494:pharmacology*; D011814:Quipazine / Q000494:pharmacology*; D011817:Rabbits; D014202:Tremor / Q000139:chemically induced
D000470:Alkaloids; D011804:Quinolines; D015116:5,7-Dihydroxytryptamine; D011814:Quipazine; D006246:Harmaline; D010134:Fenclonine; D008784:Methysergide