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ABSTRACT
Activation of central serotonergic receptors are involved in the genesis of
cardiovascular and respiratory responses to various stimuli. Various
publications have demonstrated that intracerebroventricular (i.c.v) serotonin
(5HT) administration induces pressor responses, due to 5HT
1A, 1D
and 5HT
2A,
2B
activation. Nevertheless, information concerning the participation of the renal
nerve in the responses is lacking. The same applies to the cardiovascular and
respiratory responses to intracisternaly (i.c) 5HT administration. Therefore, the
present work was designed to evaluate the participation of 5HT
1
and 5HT
2
receptors on the cardio respiratory responses due to i.c.v and i.c 5HT
administration. Serotonin was administered in doses of 4, 40,120 nmol/kg.
Methiotepin (MT-0.44 µmol/kg) antagonist of 5HT
1
and 5HT
2
was employed 15
min before 5HT to evaluate the participation of the receptors in the
cardiovascular and respiratory responses . Male rats (Wistar, 250g) were used,
initially anesthetized with ether and later kept under intravenous anesthesia
(Uretana, 1,2 g/kg). The following variables were registered: MAP (mean arterial
pressure), HR (heart rate), RR (respiratory rate), IRNA (integrated activity of
renal nerve) and area of the renal nerve (aRNA). The statistic significance was
act at p < 0,05 and the results had been expressed as mean ± EPM (ANOVA).
The administration of 5HT i.c and i.c.v, promoted rise in MAP (4 nmol/kg: i.c.:
77,86 ± 1,56 to 84,43 ± 2,05; i.c.v.: 76,57 ± 2,59 to 83,00 ± 2,56; 40 nmol/kg;
i.c: 74,00 ± 1,53 to 87,57 ± 1,51; i.c.v.: 78,86 ± 3,27 to 96,57 ± 2,42; 120
nmol/kg; i.c.: 75,00 ± 5.81 to 84,29± 5,53; i.c.v.: 98,14 ± 8,10 to 118,43 ± 5,00)
mmHg and in aRNA (4 nmol/kg; i.c.: 1,99 ± 0,16 to 3,10 ± 0,25. ; i.c.v.: 2,11 ±
0,13 to 3,56 ± 0,11. ; 40 nmol/kg; i.c.: 1,75 ± 0,08 to 3,29 ± 0,22. ; i.c.v.: 1,66 ±
0,05 to 3,88 ± 0,05. ; 120 nmol/kg; i.c.: 1,92 ± 0,06 to 3,56 ± 0,09. ; i.c.v.: 1,87±
0,08 to 4,94 ± 0,22) U.A, not occurring significant alterations RR . Regarding
HR, the low dose of 5-HT i.c caused tachycardia (373,29 ± 7,78 to 388,14 ±
9,67; i.c.v.: 370,71 ± 8,36 to 404,14 ± 9,37) beats/min, whilst bradycardia was
observed in the higher doses (i.c.: 40 nmol/kg: 369,29 ± 7,93 to 355,29 ± 8,25;
i.c.v: 382,43 ± 12,36 to 332,86 ± 13,09; 120 nmol/kg ic: 364,57 ± 12,46 to
349,86 ± 12,78; i.c.v.: 396,14 ± 16,58 to 328,00 ± 16,12) beats/min. Methiotepin
attenuated i.c.v and i.c 5-HT effects (i.c.: PAM: 77,29 ± 3.91 to 46,43 ± 2.91