Effect of inadequate frequency response of direct writing electrocardiograph on rat electrocardiogram.

Fairly good electrocardiograms of rats can be recorded by using a band width of 0.5 to 75 Hz. Change in low frequency did not alter the wave pattern or duration. Change in high frequency altered the durations and wave pattern grossly. 50 Hz filter is useful in avoiding AC interference but creates artificial notches in all the waves.

Effect of hippocampal lesion on acquisition of conditioned avoidance behaviour in albino rats.

Control, hippocampal and Sham control male albino rats weighing 150-200 gms were trained for acquisition of conditioned avoidance behavioural response using escape avoidance apparatus. Parameters like rate of performance, error scores, conditioned stimulus latency and unconditioned stimulus latency were studied. It was observed that there was a facilitation in the behavioural response with less error scores in hippocampal animals as compared to Sham control and control groups. Our observations are similar to those of Douglas and Pribram and Douglas and it is concluded that the hippocampus acts as a gate restricting the range of stimuli to which an intact animal attends.

Effect of change in limb position on mean electrical axis and amplitudes of QRS complex of rat electrocardiogram.

The effect of altered fore limb alignment to trunk on mean electrical axis (MEA) and on amplitude of the QRS complex of frontal plane leads was studied in both prone and supine postures in 32 albino rats. It was found that in both postures bilateral extension of fore limbs caused a significant change in MEA to right. Unilateral change in the fore limb alignment caused a shift in MEA to right only in supine position, but was ineffective in prone position. The amplitudes of QRS complexes also changed with change in MEA. The changes in MEA with change in limb alignment and subsequent alteration in amplitude of QRS complexes can be attributed to the alteration in anatomical orientation of the heart in the chest cavity.

Sensory nerve conduction in diabetes mellitus and diabetic neuropathy.

Electrophysiological evaluation of conduction in sensory fibres of right ulnar and median nerves were carried out in normal subjects and diabetics with and without neuropathy. The sensory conduction velocities of ulnar as well as median nerves are significantly depressed in both groups of diabetics, particularly in those with neuropathy. The diabetics with or without neuropathy require a higher strength of stimulus for conduction in both median and ulnar nerves as compared to the normal subjects. The amplitude of action potentials is also lowered in both ulnar and median nerves of the two groups of diabetics. Estimation of conduction velocities of sensory fibres can be considered as a more useful parameter than the measurement of amplitude of action potentials in the diagnosis and evaluation of neuropathy in diabetics. It is concluded that assessment of sensory nerve conduction in median nerve is a better indicator than that of ulnar nerve for this purpose.

Production of myocardial lesions in a graded fashion by noninvasive technique in albino rats.

Systematic study of producing graded lesions of myocardium with the use of Isoproterenol (IPT) reveals that mild to severe degree of infarction can be induced by administering the compound for one to four consecutive days in the dose of 85 mg/kg body weight in rats. These findings differ slightly from those of Rona et al. where they have not attempted to produce the lesions in a graded fashion. The experimental period can be reduced to two days by using high dose (170 mg/kg), but such procedure increases significantly the mortality in these animals and lesions are not produced in graded fashion.

Cardiovascular effects of acetaldehyde in guinea pigs.

The hemodynamic effects of intravenous administration of acetaldehyde were determined in anesthetized control (group I), propranolol pretreated (group II) and phentolamine pretreated (group III) guinea pigs. Acetaldehyde produced an immediate and significant increase in mean arterial pressure followed by its progressive decrease resulting in hypotension. Heart rate increased significantly. In propranolol treated animals, acetaldehyde-induced tachycardia was not produced whereas in phentolamine treated animals, the initial pressor response was converted into a depressor one. Hence the increase in mean arterial pressure and heart rate produced by acetaldehyde are likely to be due to catecholamine release from adrenergic nerve endings.

Production of reinfarction in rat heart.

An experimental mode of producing reinfarction in rat heart by Isoproterenol administration is described. Such preparation can be helpful in evaluation of drugs in chronic myocardial infarction, which is commonly encountered in clinical practice.

E.C.G. findings in normal rats and after administration of isoproterenol.

Electrocardiograms of normal rats were studied and compared with those of the rats receiving parenteral IPT. The rat E.C.G. resembles essentially human E.C.G. IPT administration brought about E.C.G. changes suggesting myocardial infarction. Appearance of Q wave in aVL was a consistent feature of E.C.G. after 24 hr of IPT injection. With additional doses of IPT the ECG in these rats showed a well marked Q wave and increase in the amplitudes of R and T waves in limb and increase in the amplitudes of R and T waves in limb and chest leads.