Behavioral effects of 8-OH-DPAT injections into pontine and mesencephalic areas containing 5-HT-immunoreactive perikarya in the pigeon.
This study examined the distribution of 5-HT-immunoreactive perikarya (5-HT-IRp) and the effects of local injections of 8-OH-DPAT into 5-HT-IRp-containing pontine and mesencephalic regions on feeding and drinking behaviors in free-feeding pigeons. When infused into the midline 5-HT-IRp-containing areas, 8-OH-DPAT (6.1 nmol) reliably elicited drinking and, to a lesser extent, feeding responses during the first hour after injection. These responses were significantly higher than the ingestive indexes observed (1) after vehicle (ascorbic acid 0.1%, 200 nl) injections at the same sites and (2) after 8-OH-DPAT injections into adjacent sites devoid of 5-HT-IRp. Increases in drinking were proportionally higher than those observed in feeding and a significant negative correlation was observed between water and food after midline 8-OH-DPAT injections. Similar dipsogenic responses were observed after injections of different 8-OH-DPAT doses (0.6, 2.0, and 6.1 nmol). Pretreatment with local injections of p-MPPI (an antagonist of 5-HT1A receptors) attenuated the ingestive responses evoked by 8-OH-DPAT injections. Injections of 8-OH-DPAT into lateral 5-HT-IRp-containing sites evoked only inconsistent and weak ingestive responses. These results indicate that 5-HT1A receptor-mediated circuits located in the midline superior raphe system of the pigeon may play an important role in mechanisms controlling water intake, similar to that observed in mammals.
Häckl
Luciane P N
LP
Department of Physiological Sciences-CCB, Federal University of Santa Catarina, 88040-900 Florianópolis, SC, Brazil.
de Oliveira Richter
Graciela
G
Serralvo Faria
Moacir
M
Paschoalini
Marta A
MA
Marino-Neto
José
J
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000008:administration & dosage*; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D010856:Columbidae; D004305:Dose-Response Relationship, Drug; D004326:Drinking / Q000187:drug effects* / Q000502:physiology; D004435:Eating / Q000187:drug effects* / Q000502:physiology; D007150:Immunohistochemistry; D007276:Injections, Intraventricular; D008297:Male; D008636:Mesencephalon / Q000737:chemistry / Q000187:drug effects* / Q000502:physiology; D011149:Pons / Q000737:chemistry / Q000187:drug effects* / Q000502:physiology; D012701:Serotonin / Q000032:analysis* / Q000502:physiology
D012701:Serotonin; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin