Hypothalamic paraventricular nucleus lesions differentially affect serotonin-1A (5-HT1A) and 5-HT2 receptor agonist-induced oxytocin, prolactin, and corticosterone responses.
A number of receptor subtypes mediate hormonal responses to serotonin (5-HT). To test the hypothesis that the hypothalamic paraventricular nucleus (PVN) mediates 5-HT1A and 5-HT2 receptor-mediated oxytocin, PRL, and corticosterone responses, we studied the effects of the 5-HT1A agonist ipsapirone and the 5-HT2A/2C agonist 1-(2,5-dimethoxy-4-iodophenyl)2-aminopropane (DOI) after surgical PVN lesions or sham operations. Chronically cannulated, conscious, freely moving, male Wistar rats were injected iv (1 mg/kg) shortly after (3-4 days) and 5 weeks after (35-37 days) the operations. In sham-operated rats, ipsapirone caused marked elevations in plasma PRL and corticosterone, but not oxytocin concentrations, whereas DOI increased plasma concentrations of all three hormones. Short term PVN lesions prevented ipsapirone-induced corticosterone and DOI-induced oxytocin responses. DOI-induced PRL and corticosterone responses were also markedly inhibited 3-4 days after lesioning, although small rises over the baseline values were still observed. The ipsapirone-induced PRL response was unaffected by the lesioning. Five weeks after PVN lesioning, partial recoveries were observed in ipsapirone- and DOI-induced corticosterone and DOI-induced oxytocin responses, whereas DOI-induced PRL responses remained suppressed. The present findings suggest that the PVN or neural pathways close to it mediate oxytocin, PRL, and corticosterone responses to the 5-HT2 receptor agonist DOI as well as corticosterone, but not PRL, responses to the 5-HT1A receptor agonist ipsapirone. The results after long term PVN lesioning show that the oxytocin and corticosterone responses may be partially restored with time after lesioning.
Bagdy
G
G
Laboratory of Experimental Medicine, National Institute of Psychiatry and Neurology, Budapest, Hungary.
Makara
G B
GB
D000662:Amphetamines / Q000494:pharmacology; D000818:Animals; D003345:Corticosterone / Q000378:metabolism*; D008297:Male; D010121:Oxytocin / Q000378:metabolism*; D010286:Paraventricular Hypothalamic Nucleus / Q000502:physiology*; D011388:Prolactin / Q000378:metabolism*; D011743:Pyrimidines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011985:Receptors, Serotonin / Q000502:physiology*; D017366:Serotonin Receptor Agonists / Q000494:pharmacology*; D013997:Time Factors
D000662:Amphetamines; D011743:Pyrimidines; D011985:Receptors, Serotonin; D017366:Serotonin Receptor Agonists; D010121:Oxytocin; C043077:ipsapirone; D011388:Prolactin; C015952:4-iodo-2,5-dimethoxyphenylisopropylamine; D003345:Corticosterone