Stella Y. Botelho

Myotonia in a Horse

Congenital myotonia, similar to that which has been reported in humans and in goats, is here reported for the first time in another species. Evidence is given to show (i) that the myotonic phenomenon is present despite complete block of neuromuscular transmission; (ii) prior to injection of curare, synchronous activity of muscle fibers may result not only from ephaptic stimulation of neighboring fibers but also from reflex firing; and (iii) water deprivation does not relieve the myotonia.

Effect of calcium antagonism or chelation on rabbit lacrimal gland secretion and membrane potentials

1. ACh‐induced secretion from the main excretory duct, as well as ACh‐induced hyperpolarizations and resting membrane potentials of superficial, probably acinar, cells were recorded from the rabbit lacrimal gland perfused in vivo with either control or test solutions.

Consensual intraocular pressure changes resulting from unilateral extraocular muscle contraction.

Direct stimulation of one lateral rectus muscle produced not only an increase in ipsilateral intraocular pressure but also changes in the contralateral intraocular pressure. These consensual intraocular pressure changes were independent of changes in respiration and systemic arterial pressure. The magnitude and type of consensual response varied and were not correlated with either the increase in ipsilateral muscle tension or the increase in ipsilateral intraocular pressure. Evidence has been given to support the hypothesis that the consensual response is neurogenic. The adequate stimulus for this reflex appeared to be increased tension produced by contraction of an extraocular muscle with an attendant increase in ipsilateral intraocular pressure, suggesting that the receptors lie at or near the junction of the muscle and sclera and respond more readily to changes in tension than to changes in length. The afferent pathway appeared to be other than the sixth cranial nerve and the efferent pathway was not somatic.