Effects of remifentanil infusion regimens on cardiovascular function and responses to noxious stimulation in propofol-anesthetized cats

Objective-To evaluate the effects of 2 remifentanil infusion regimens on cardiovascular function and responses to nociceptive stimulation in propofol-anesthetized cats.Animals-8 adult cats.Procedures-On 2 occasions, cats received acepromazine followed by propofol (6 mg/kg then 0.3 mg/kg/min, IV) and a constant rate infusion (CRI) of remifentanil (0.2 or 0.3 mu g/kg/min,IV) for 90 minutes and underwent mechanical ventilation (phase I). After recording physiologic variables, an electrical stimulus (50 V; 50 Hz; 10 milliseconds) was applied to a forelimb to assess motor responses to nociceptive stimulation. After an interval (>= 10 days), the same cats were anesthetized via administration of acepromazine and a similar infusion regimen of propofol; the remifentanil infusion rate adjustments that were required to inhibit cardiovascular responses to ovariohysterectomy were recorded (phase II).Results-In phase I, heart rate and arterial pressure did not differ between remifentanil-treated groups. From 30 to 90 minutes, cats receiving 0.3 mu g of remifentanil/kg/min had no response to noxious stimulation. Purposeful movement was detected more frequently in cats receiving 0.2 mu g of remifentanil/kg/min. In phase II, the highest dosage (mean +/- SEM) of remifentanil that prevented cardiovascular responses was 0.23 +/- 0.01 mu g/kg/min. For all experiments, mean time from infusion cessation until standing ranged from 115 to 140 minutes.Conclusions and Clinical Relevance-Although the lower infusion rate of remifentanil allowed ovariohysterectomy to be performed, a CRI of 0.3 mu g/kg/min was necessary to prevent motor response to electrical stimulation in propofol-anesthetized cats. Recovery from anesthesia was prolonged with this technique.

Morphological characterization of the venom secretory epidermal cells in the stinger of marine and freshwater stingrays

Marine and freshwater stingrays are characterized by the presence of one to three mineralized serrated stingers on the tail, which are covered by epidermal cells secreting venom. When these animals are dorsally touched, the stinger can be introduced into the aggressor by a whip reflex mechanism of the tail, causing severe mechanical injuries and inoculating the venom. Accidents in humans are frequent causing intense local pain, oedema and erythema. Bacterial secondary infection is also common. In addition, injuries involving freshwater stingrays frequently cause a persistent cutaneous necrosis. The exact localization of the venom secretory epidermal cells in the stinger is controversial, but it is known that it is preferentially located in the ventrolateral grooves. A comparative morphological analysis of the stinger epidermal tissue of different marine and freshwater Brazilian stingray species was carried out. The results indicate that in freshwater species there is a larger number of protein secretory cells, of two different types, spread over the whole stinger epidermis, while in marine species the protein secretory cells are located only around or inside the stinger ventrolateral grooves. These differences between the stingers of the two groups can justify the more severe envenomation accidents with the freshwater species when compared with the marine species. (c) 2007 Elsevier Ltd. All rights reserved.

MASSETERIC ELECTROMYOGRAPHIC SILENT PERIOD DURATION IN PATIENTS WITH TEMPOROMANDIBULAR-JOINT DYSFUNCTION

1. The present study compared the duration of the electromyographic silent period (SP) of the masseter muscles elicited by chin-tapping in normal asymptomatic adults (N = 39) and in a group with symptoms of temporomandibular joint dysfunction (TMJD) (N = 31).2. EMG activity was recorded from right (RM) and left (LM) masseter muscles using bipolar surface electrodes coupled to a DISA 1500 EMG-System. During maximal clenching, ten taps were applied downwards to the chin with a reflex hammer.3. The mean SP durations obtained for the normal group were 25.45 +/- 4.20 ms (RM) and 25.33 +/- 4.18 ms (LM), whereas the TMJD group presented significantly greater values (P < 0.01, Student t-test) of 41.89 +/- 12.94 ms (RM) and 42.40 +/- 12.99 ms (LM). The upper limits of normality calculated for RM and LM were 32.36 ms and 31.21 ms, respectively. Eighty-four percent of patients with TMJD showed SP durations above these limits.4. The results indicate that the measurement of masseteric SP duration may be used as an objective diagnostic method of TMJ disorders, provided that borderline values are interpreted with caution along with clinical impressions.

EFFECT OF TESTOSTERONE ON THE PRESSOR-RESPONSE TO COMMON CAROTID OCCLUSION IN GONADECTOMIZED CONSCIOUS MALE-RATS WITH LESION OF THE MEDIAN-EMINENCE

The influence of testosterone on the development of the pressor response to common carotid occlusion was investigated in control and median eminence-lesioned male rats. In control rats (N = 9), gonadectomy performed 21 days before the experiments reduced by 22% (from 51 +/- 2 to 40 +/- 2 mmHg) and treatment with testosterone (300-mu-g for 4 days before the measurements) increased the initial peak pressor response (from 51 +/- 2 to 57 +/- 2 mmHg) which depends on carotid innervation. The maintained response which is of central origin (probably ischemic) was less affected. In nongonadectomized rats (N = 6), lesions of the median eminence (6 days) decreased the initial peak by 19% (from 52 +/- 2 to 42 +/- 3 mmHg) and the maintained response by 56% (from 32 +/- 2 to 14 +/- 1 mmHg). Sham-operated rats served as controls. In gonadectomized animals (N = 6) the lesion reduced only the maintained response (from 23 +/- 2 to 11 +/- 1 mmHg). Testosterone supplementation restored the maintained response but did not alter the initial peak. These results indicate that the pressor response to common carotid occlusion in male rats is modulated by testosterone and that the depression in the maintained response caused by median eminence lesion can be reversed by steroid supplementation.

THE EFFECTS OF FOREBRAIN MULTIPLE LESIONS ON THE PRESSOR-RESPONSE INDUCED BY BILATERAL CAROTID OCCLUSION IN CONSCIOUS RATS

In the present study, the effects of electrolytic lesions of the anteroventral third ventricle (AV3V) region and of the medial forebrain bundle (MFB) on the pressor response induced by bilateral carotid occlusion (BCO) in conscious intact and aortic baroreceptor-denervated (AD) rats were investigated. In intact control rats, BCO during 60 s produced a pressor response that could be divided into an early response (ER = 50 +/- 3 mmHg) that reachs a peak during the first 20 s and a sustained late response (LR), smaller than ER (32 +/- 2 mmHg), observed during the last 30 s. In intact-innervated rats, AV3V lesion (2 days) reduced ER (22 +/- 3 mmHg) and LR (16 +/- 2 mmHg), whereas the bilateral MFB lesions (6 days) mainly reduced LR (9 +/- 1 mmHg). Rats with simultaneous lesion of both the AV3V region and the MFB showed additional reduction of the ER (15 +/- 3 mmHg), but not LR (11 +/- 1 mmHg) when compared to the effect of MFB lesions alone. Compared to the AV3V lesion alone, LR but not ER was reduced in rats with a double lesion. In sham-lesioned rats, AD induced a significant increase in the pressor response to BCO (ER = 75 +/- 4 mmHg and LR = 65 +/- 3 mmHg) when compared to intact controls. A similar reduction in ER and LR was observed in AD rats after AV3V (ER = 35 +/- 3 mmHg and LR = 40 +/- 2 mmHg) and MFB (ER = 49 +/- 6 mmHg and LR = 41 +/- 5 mmHg) lesions alone or combined (ER = 40 +/- 6 mmHg and LR = 35 +/- 7 mmHg). The results showed that simultaneous lesions of both the AV3V region and the MFB practically abolished the pressor response to BCO. They also suggested that aortic baroreceptor activity plays a significant role in the effects of AV3V and MFB lesions on the pressor response to BCO.

Commissural NTS contributes to pressor responses to glutamate injected into the medial NTS of awake rats

In the present study we investigated whether interruption of the chemoreceptor reflex by an electrolytic lesion of the commissural subnucleus of the nucleus tractus solitarii (commNTS) influenced presser and bradycardic responses induced by microinjection of L-glutamate (L-Glu) into the medial NTS (mNTS) of conscious rats. Seven days after sham lesions, seven rats demonstrated significant presser [change in mean arterial pressure (MAP) = +33 +/- 3 mmHg] and bradycardic [change in heart rate (HR) = -74 +/- 8 beats/min (bpm)] responses to chemoreceptor reflex activation by intravenous injection of KCN. Likewise, L-Glu (1 nmol in 100 nl) injected into the mNTS in sham rats induced presser (+29 +/- 2 mmHg) and bradycardic responses (-90 +/- 8 bpm). However, in 11 rats with lesions in commNTS, presser and bradycardic chemoreceptor reflex responses were abolished, and injection of L-Glu into the mNTS decreased MAP (-14 +/- 6 mmHg) and HR (-59 +/- 16 bpm) as is reported in anesthetized control rats. We conclude that presser responses induced by L-Glu microinjected into the baroreceptor reflex region of mNTS in conscious rats depend on the integrity of the commNTS, which plays an important role in central chemoreceptor reflex pathways.

Effects of buprenorphine on nociception and spontaneous locomotor activity in horses

Objective-To investigate spontaneous locomotor activity (SLA) and antinociceptive effects of buprenorphine in horses.Animals-6 healthy adult horses.Procedures-Horses received each of 3 treatments (10 mL of saline [0.9% NaCl] solution, 5 mu g of buprenorphine/kg, or 10 mu g of buprenorphine/kg). Treatments were administered IV Order of treatments was randomized, and there was a 10-day interval between subsequent treatments. Spontaneous locomotor activity was investigated in a behavioral box by use of infrared photoelectric sensors connected to a computer, which detected movement of each horse. Antinociceptive effect was investigated by hoof-withdrawal reflex latency (HWRL) and skin-twitching reflex latency (STBL) after painful stimulation with a heat lamp.Results-Moderate excitement was observed in all horses from 5 to 10 minutes after the administration of both dosages of buprenorphine. The SLA increased significantly for 6 and 14 hours after IV administration of 5 and 10 mu g of buprenorphine/kg, respectively. Values for HWRL increased significantly only at 30 minutes after injection of 5 mu g of buprenorphine/kg, whereas STRL and HWRL each increased significantly from 1 to 6 hours (except at 2 and 4 hours) and 11 hours, respectively, after injection of 10 mu g of buprenorphine/kg.Conclusions and Clinical Relevance-IV injection of buprenorphine caused a dose-dependent increase in SLA, but only the dose of 10 mu g/kg induced analgesia on the basis of results for the experimental method used.

SEX-RELATED DIFFERENCES IN CARDIOVASCULAR-RESPONSES TO COMMON CAROTID OCCLUSION IN CONSCIOUS RATS

Mean arterial pressure and heart rate were determined in conscious, unrestrained groups of 10 male, female and androgenized female Wistar rats 20 s (early pressor response) and 1 min (late sustained response) after bilateral carotid artery occlusion. The early pressor response, which is of carotid reflex origin, was 40% greater in female than in male rats (45 +/- 2 vs 63 +/- 3 mmHg, respectively). The late sustained response, which is of central origin (probably ischemic), did not differ between male and female rats (32 +/- 2 vs 37 +/- 4 mmHg, respectively). The magnitude of the early pressor response of androgenized female tats (50 +/- 2 mmHg) was similar to that of male rats (45 +/- 2 mmHg) but the late sustained response was 19% smaller (26 +/- 2 mmHg). Common carotid occlusion caused increases in heart rate which were greater in female (51 +/- 9 and 34 +/- 9 beats/min in the early pressor response and late sustained response, respectively) than in male rats (31 +/- 5 and 8 +/- 4 beats/min, respectively). In androgenized female rats, heart rate decreased during common carotid occlusion (34 +/- 7 and 35 +/- 8 beats/min after 20 s and 1 min, respectively). These data provide evidence that there are substantial sex-related differences in the cardiovascular responses to common carotid occlusion in conscious rats and indicate that administration of androgens to newborn female rats affects the baroreceptor reflex control of their arterial pressure.

Effects of prenatal exposure to deltamethrin on forced swimming behavior, motor activity, and striatal dopamine levels in male and female rats

The effects of prenatal exposure of rat pups to 0.08 mg/kg deltamethrin (DTM) on physical, reflex and behavioral developmental parameters, on forced swimming and open-field behaviors, and on striatal monoamine levels at 60 days of age were observed. Maternal and offspring body weight, physical and reflex development were unaffected by the exposure to the pesticide. At 21 days of age, open-field locomotion frequency and immobility duration of male and female offspring were not different between control and exposed animals. However, male rearing frequency was increased in experimental animals. A decreased immobility latency to float and in general activity after the swimming test in male offspring was observed at adult age; no interference was detected in the float duration during the swimming test. In addition, these animals presented higher striatal 3,4-dihydroxyphenylacetic acid (DOPAC) levels without modification in dopamine (DA) levels and an increased DOPAC/DA ratio. These data indicate a higher activity of the dopaminergic system in these animals. Noradrenaline (NA) levels were increased, while MHPG levels were not detectable in the system studied. Serotonin (5-HT) and 5-hydroxyindolacetic acid (5-HIAA) levels, as well as the homovanillic acid (HVA)/DA ratio, were not modified by the exposure to the pesticide. No changes were observed in swimming and open-field behaviors nor were there any changes in striatal monoamines or their metabolites in the female experimental group. In relation to the pesticide formula, the present data showing that prenatal exposure to DTM alters latency to float and the activity of striatal dopaminergic system might reflect a persistent effect of the pesticide on animal motor activity, mainly in males. on the other hand, the decrease in general activity observed in experimental male rats suggests higher levels of emotionality induced by previous exposure to the swimming behavior test in relation to control animals. Data gathered in the present study may be important for the assessment of the safety of pyrethroid insecticides. (C) 2001 Elsevier B.V. All rights reserved.

Plant derived alkaloid (-)-cassine induces anti-inflammatory and anti-hyperalgesics effects in both acute and chronic inflammatory and neuropathic pain models

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Central control of cardiorespiratory interactions in fish

Fish control the relative flow rates of water and blood over the gills in order to optimise respiratory gas exchange. As both flows are markedly pulsatile, close beat-to-beat relationships can be predicted. Cardiorespiratory interactions in fish are controlled primarily by activity in the parasympathetic nervous system that has its origin in cardiac vagal. preganglionic neurons. Recordings of efferent activity in the cardiac vagus include units firing in respiration-related bursts. Bursts of electrical stimuli delivered peripherally to the cardiac vagus or centrally to respiratory branches of cranial, nerves can recruit the heart over a range of frequencies. So, phasic, efferent activity in cardiac vagi, that in the intact fish are respiration-related, can cause heart rate to be modulated by the respiratory rhythm. In elasmobranch fishes this phasic activity seems to arise primarily from central feed-forward interactions with respiratory motor neurones that have overlapping distributions with cardiac neurons in the brainstem. In teleost fish, they arise from increased levels of efferent vagal activity arising from reflex stimulation of chemoreceptors and mechanoreceptors in the orobranchial, cavity. However, these differences are largely a matter of emphasis as both groups show elements of feed-forward and feed-back control of cardiorespiratory interactions. (C) 2008 Elsevier GmbH. All rights reserved.

Dose-related antinociceptive effects of intravenous buprenorphine in cats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Ventrolateral periaqueductal gray lesion attenuates nociception but does not change anxiety-like indices or fear-induced antinociception in mice

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Corticosterone does not change open elevated plus maze-induced antinociception in mice

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Contribution of the rostral ventromedial medulla to post-anxiety induced hyperalgesia

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)