Neuropeptides in the posterodorsal medial amygdala modulate central cardiovascular reflex responses in awake male rats

The rat posterodorsal medial amygdala (MePD) links emotionally charged sensory stimuli to social behavior, and is part of the supramedullary control of the cardiovascular system. We studied the effects of microinjections of neuroactive peptides markedly found in the MePD, namely oxytocin (OT, 10 ng and 25 pg; n=6/group), somatostatin (SST, 1 and 0.05 μM; n=8 and 5, respectively), and angiotensin II (Ang II, 50 pmol and 50 fmol; n=7/group), on basal cardiovascular activity and on baroreflex- and chemoreflex-mediated responses in awake adult male rats. Power spectral and symbolic analyses were applied to pulse interval and systolic arterial pressure series to identify centrally mediated sympathetic/parasympathetic components in the heart rate variability (HRV) and arterial pressure variability (APV). No microinjected substance affected basal parameters. On the other hand, compared with the control data (saline, 0.3 µL; n=7), OT (10 ng) decreased mean AP (MAP50) after baroreflex stimulation and increased both the mean AP response after chemoreflex activation and the high-frequency component of the HRV. OT (25 pg) increased overall HRV but did not affect any parameter of the symbolic analysis. SST (1 μM) decreased MAP50, and SST (0.05 μM) enhanced the sympathovagal cardiac index. Both doses of SST increased HRV and its low-frequency component. Ang II (50 pmol) increased HRV and reduced the two unlike variations pattern of the symbolic analysis (P<0.05 in all cases). These results demonstrate neuropeptidergic actions in the MePD for both the increase in the range of the cardiovascular reflex responses and the involvement of the central sympathetic and parasympathetic systems on HRV and APV.

Autonomic evaluation of hepatitis C virus infected patients / Avaliacao autonomica de pacientes infectados pelo virus da hepatite C

There are few studies reporting the association between hepatitis C virus (HCV) infection and disautonomia. We have evaluated the autonomic cardiovascular function in 12 patients with sensory small-fiber polyneuropathy infected by HCV. The mean age was 49±13 years old. The mean infection time was 9.6 years in six (50%) patients. Thermal and pinprick hypoesthesia was observed in distal legs in all patients. Autonomic symptoms were referred by eight (66.7%) patients. Among patients with abnormal autonomic cardiovascular test, five (41.7%) showed abnormal results in two or more tests. Valsalva maneuver was abnormal in seven (58.3%) patients. We can consider that there is an association of both parasympathetic and sympathetic efferent cardiovascular dysfunction in this group of patients.

Existem poucos estudos que relatam a associação entre infecção pelo vírus da hepatite C (HCV) e disautonomia. Avaliamos a função autonômica cardiovascular em 12 pacientes com polineuropatia de fibras finas e infectados pelo HCV. A idade média foi de 49±13 anos. O tempo de infecção média foi de 9,6 anos em seis (50%) pacientes. Hipoestesia termoalgésica foi observada nos segmentos distais das pernas em todos os pacientes. Sintomas autonômicos foram relatados por oito (66,7%) pacientes. No teste autonômico cardiovascular, cinco (41,7%) apresentaram resultados anormais em dois ou mais testes. Manobra de Valsalva foi anormal em sete (58,3%) pacientes. Podemos considerar que há comprometimento de ambas as vias parassimpática e simpática cardiovasculares eferentes nesse grupo de pacientes.

Tonic and reflex cardiovascular autonomic control in trained-female rats

The effects of exercise training on cardiovascular and autonomic functions were investigated in female rats. After an aerobic exercise training period (treadmill: 5 days/week for 8 weeks), conscious female Wistar (2 to 3 months) sedentary (S, N = 7) or trained rats (T, N = 7) were cannulated for direct arterial pressure (AP) recording in the non-ovulatory phases. Vagal (VT) and sympathetic tonus (ST) were evaluated by vagal (atropine) and sympathetic (propranolol) blockade. Baroreflex sensitivity was evaluated by the heart rate responses induced by AP changes. Cardiopulmonary reflex was measured by the bradycardic and hypotensive responses to serotonin. Resting bradycardia was observed in T (332 ± 7 bpm) compared with S animals (357 ± 10 bpm), whereas AP did not differ between groups. T animals exhibited depressed VT and ST (32 ± 7 and 15 ± 4 bpm) compared to S animals (55 ± 5 and 39 ± 10 bpm). The baroreflex and cardiopulmonary bradycardic responses were lower in T (-1.01 ± 0.27 bpm/mmHg and -17 ± 6 bpm) than in the S group (-1.47 ± 0.3 bpm/mmHg and -41 ± 9 bpm). Significant correlations were observed between VT and baroreflex (r = -0.72) and cardiopulmonary (r = -0.76) bradycardic responses. These data show that exercise training in healthy female rats induced resting bradycardia that was probably due to a reduced cardiac ST. Additionally, trained female rats presented attenuated bradycardic responses to baro- and cardiopulmonary receptor stimulation that were associated, at least in part, with exercise training-induced cardiac vagal reduction.

Ocular and cardiovascular autonomic function in diabetic patients with varying severity of retinopathy.

The study was conducted to assess the ocular and cardiovascular autonomic function in diabetic patients with varying severity of diabetic retinopathy. Ocular and cardiovascular autonomic function tests were performed in 30 patients with type 2 Diabetes Mellitus (10 in each group of proliferative retinopathy, non-proliferative retinopathy and no retinopathy) of more than 5 years duration and 10 normal controls. Ocular autonomic function tests were done by measuring pupil cycle time and denervation hypersensitivity with 0.125% pilocarpine and 0.5% phenylephrine. Cardiovascular autonomic function was measured by a battery of standard tests. Denervation hypersensitivity to 0.125% pilocarpine and to 0.5% phenylephrine and pupil cycle time showed statistically significant differences (P value < 0.001) between controls and patients with proliferative retinopathy (PDR) and also between no retinopathy and PDR (P < 0.001). Systemic autonomic function tests namely expiration--inspiration ratio, difference in heart rate, 30th beat and 15th beat ratio in head up tilt and difference in diastolic blood pressure in head up tilt test also showed significant difference (P < 0.01) between controls and all 3 groups of diabetics. There was statistically significant difference found in para-sympathetic ocular autonomic dysfunction between NPDR and controls. Ocular and systemic autonomic dysfunctions are related to the severity of diabetic retinopathy.

Sympathetic skin response and cardiovascular autonomic function tests in Parkinson's disease

Autonomic dysfunction commonly occurs in Parkinson's disease, but the pathogenesis of autonomic dysregulation remains uncertain. Autonomic functions regulating the cardiovascular system have been investigated in Parkinson's disease, but those involving the extremities has not been well demonstrated. To compare autonomic dysfunctions of the cardiovascular system with those of the extremities, we performed sympathetic skin response (SSR) and cardiovascular autonomic function tests (CAFT) - 30:15 ratio, E:I ratio, Valsalva ratio, isometric exercise test (IET) - in 37 patients with Parkinson's disease and 33 age- and sex-matched healthy controls. The patients were asked to stop antiparkinsonian medications for at least 12 hours prior to the tests. SSR was measured at the right hand and foot after electrical stimulation of the right median and posterior tibial nerves. Absent SSR at either one or both extremities and CAFT beyond normal ranges were regarded as abnormal. Abnormal SSR was observed in 59% of patients, while abnormal CAFT were found in the range of 32%-81%. Patients with abnormal SSR showed more frequent and severe CAFT abnormalities than did patients with normal SSR. Among the CAFT, IET was well correlated with the SSR. The results suggest that parkinsonian sympathetic dysfunction involving either the cardiovascular system or the extremities may have the same pathophysiology.