Behavioral performance effects of nifedipine in normotensive and renovascular hypertensive baboons

Nifedipine-morphine interaction: a further investigation on nociception and locomotor activity in mice

Nociception and locomotor activity were tested in mice (C57BL/6 and DBA/2 strains), receiving the dihydropyridine calcium-channel blocker nifedipine, alone or combined with morphine. The calcium antagonist did not change the reaction time to thermal stimulation (tail-flick test), when administered alone, but combinations of nifedipine and morphine prolonged tail-flick latencies less than did the opiate alone. Nifedipine decreased locomotion in both strains, reduced the hypermotility induced by morphine in C57 mice, and enhanced the locomotor depression induced by the opiate in DBA mice. A comparison of the effects of nifedipine with those of the non-calcium antagonist vasodilator, hydralazine, suggests that the interactions with morphine were not exclusively related to neuronal changes produced by calcium channel blockade, but also to haemodynamic factors. In fact, except for the lack of interference with morphine-induced hypermotility in C57 mice, hydralazine, given alone or in combination with morphine, produced effects similar to those of nifedipine.

Similar effects of nifedipine and hydralazine on anaesthesia and hypermotility induced by pentobarbitone in mice

Nifedipine, a dihydropyridine calcium channel blocker, and hydralazine, a non-calcium channel antagonist vasodilatator, enhanced pentobarbitone-induced sleeping time and reversed locomotor hyperactivity induced by a subhypnotic dose of the barbiturate in mice. The similarity of the behavioural effects, exerted by nifedipine and hydralazine, suggest that haemodynamic factors may play an important role in the interaction of calcium channel antagonists with barbiturates.

Exposure of baboons to combined 60 Hz electric and magnetic fields does not produce work stoppage or affect operant performance on a match-to-sample task

We examined the effects of combined 60 Hz electric and magnetic field (EMF) exposure on performance of delayed match-to-sample (MTS) procedure involving the flash rate of a light as the stimulus. Six baboons (Papio cynocephalus) fully acquired the task; four others functioned accurately only when cued. All ten subjects were assigned to EMF-exposed or sham-exposed groups of five and were used to test for a work-stoppage effect that was previously observed with initial exposure to electric fields (EF) of 30 or 60 kV/m. Here, we report the results of two experiments, each consisting of 6 week preexposure, exposure, and postexposure periods. We found no evidence of work stoppage with fields of 6 kV/m and 50 microT (0.5 G) or with 30 kV/m and 100 microT (1.0 G). In neither experiment was there evidence of an adverse effect of 60 Hz EMF exposure on MTS performance.

Behavioral performance effects of verapamil in normotensive and renovascular hypertensive baboons

Behavioral performances of normotensive and hypertensive adult male baboons were tested before, during, and following chronic oral dosing with verapamil. Performances during a five-color simultaneous match-to-sample task were measured for two doses (2.0, and 3.2 mg/kg/day) and vehicle. Each dose was administered for 21 consecutive days preceded and followed by 14-day baseline and recovery periods, respectively. Choice reaction times increased by 9% during the lower dose of verapamil, compared to vehicle; choice reaction times were unchanged at the higher dose. At baseline and during vehicle administration, the yellow and white stimuli were the most difficult to discriminate correctly; discrimination of these colors was slightly impaired by the lower, but not the higher dose of verapamil. Verapamil's behavioral effects were not modulated by blood pressure changes since both baboon groups showed equivalent changes in behavioral performance, but only renovascular hypertensive baboons showed blood pressure decreases. Verapamil appears to be an effective hypotensive and does not produce profound psychomotor impairment at clinically used doses during the first weeks of treatment.

Chronic hydrochlorothiazide and verapamil effects on motor activity in hypertensive baboons

Spontaneous motor activity was measured in six baboons during chronic oral dosing with a diuretic (hydrochlorothiazide/triamterene), a calcium channel blocker (verapamil), and a combination of the two drugs. Piezoelectric monitors sensitive to movement were attached to leather collars and were worn continuously by the baboons throughout the protocol. Baboons were made hypertensive during a preexperimental period by either 1) chronic administration of deoxycorticosterone acetate (DOCA)-salt or 2) surgical renal artery stenosis. Total inactive periods/day increased over baseline levels during diuretic alone and increased further during diuretic + verapamil combined. The total number of inactive periods/day returned toward baseline levels in the subsequent conditions of verapamil alone and baseline recovery. Activity levels decreased during combination dosing mainly during morning hours (0700-1100 h). Overall changes in activity occurred in the second week of dosing; this time period was found earlier to maximally decrease blood pressure and to impair behavioral performances.

Central effects of the calcium antagonist, nifedipine

1. Central effects of the calcium antagonist, nifedipine retard (10, 20 and 40 mg) and nifedipine capsules (10 mg) were studied in 14 healthy male subjects. Two placebos and an active control drug, oxazepam (15 mg), were included. Medication was administered double-blind at 10.00 h. The effects of drugs on performance and subjective feelings were assessed before and from 1.5-2.5 h and 3.5-4.5 h after ingestion, and recordings of the electrical activity of the brain (EEG) and body sway carried out. 2. Performance was assessed using digit symbol substitution, continuous attention, letter cancellation, choice reaction time, finger tapping, immediate and short-term memory, together with critical flicker fusion and two flash fusion. The EEG was recorded with eyes open while the subjects carried out a mental arithmetic task, and with eyes closed, when they were required to relax. Body sway was recorded with eyes open and with eyes closed. Subjects assessed their mood and well-being on a series of 12 visual analogue scales. 3. Nifedipine did not alter performance levels on any of the skills tested, while oxazepam (15 mg) increased the number of errors (P less than 0.01) and reduced accuracy at continuous attention (P less than 0.01). 4. Nifedipine (10 mg) reduced total power of the EEG in the frequency range (0.5-30 Hz), and nifedipine (20 mg) increased total alpha power (7.5-13 Hz) (P less than 0.05). Oxazepam reduced alpha and increased beta 1 power (13.5-21 Hz).(ABSTRACT TRUNCATED AT 250 WORDS)

Behavioral effects of chronic, orally administered diuretic and verapamil in baboons

Behavioral performances of six baboons were tested during chronic oral dosing with diuretic (hydrochlorothiazide/triamterene), a calcium channel blocker (verapamil), and a combination of the two drugs. Reaction times and color matching-to-sample performances as well as physiological measures were obtained in deoxycorticosterone acetate (DOCA)-salt baboons and in renovascular hypertensive baboons. Combined diuretic and verapamil impaired color matching to a small degree in comparison to baseline performance, while drug administered alone had no effect. Weekly systolic and diastolic blood pressures decreased maximally from baseline during the drug combination period, and were accompanied by maximal increases in serum sodium. The largest behavioral impairments during combination dosing were observed for colors that were most difficult to discriminate during baseline. Significant positive correlations were found between systolic blood pressure and color matching accuracy. No differences between the animal hypertension groups were found as a function of drug condition either in physiological or behavioral responses. Only the combination of diuretic and verapamil produced a deleterious effect on color discrimination, which suggests further study of commonly administered drug combination therapies in hypertension.

Matching to sample, blood pressure and hormonal effects of chronic enalapril in baboons

Sensory and behavioral performance of three normotensive and one renovascular hypertensive baboon was tested before, during and following chronic oral dosing with the angiotensin converting enzyme (ACE) inhibitor enalapril. Performance measurements during a five-color simultaneous matching to sample task were obtained during enalapril dosing of 0.18 and 0.61 mg/kg/day, and vehicle. Each dose was administered for 21 consecutive days preceded and followed by 14 baseline and recovery periods, respectively. BP from awake animals as well as serum ACE activity were measured. Systolic BPs decreased by a maximum of 6-8% (8 mmHg). ACE activity was decreased in a dose-dependent fashion by 54.01% and 81.63% for 0.18 mg/kg and 0.61 mg/kg doses, respectively. At 0.61 mg/kg, the duration of simple key-press motor behavior increased by 15% in the first week and then progressively returned to baseline levels. Systematic changes in choice reaction times or color discrimination accuracy were not observed. Although the renovascular hypertensive baboon displayed greater hypotension and ACE inhibition, behavioral effects were not significantly different from normotensive baboons. The present study extends to sensory functions the lack of adverse behavioral side-effects of enalapril.