Unmasking of a neonatal somatovesical reflex in adult cats by the serotonin autoreceptor agonist 5-methoxy-N,N-dimethyltryptamine.
K B Thor, T Hisamitsu, W C De Groat
Brain research. Developmental brain research June 1, 1990 DOI: 10.1016/0165-3806(90)90062-4
Summary
In a striking finding, low doses of 5-methoxy-N,N-dimethyltryptamine (5-MeODMT) successfully reversed bladder inhibition in 90% of adult cats tested. Specifically, in a sample of 10 cats, 9 exhibited abolished inhibition from perigenital stimulation, while 8 displayed enhanced bladder activity. This suggests that the somatovesical reflex can be acutely activated in adults when the serotonergic system is suppressed. Interestingly, higher doses halted spontaneous bladder activity but did not impede reflexive contractions, highlighting complex interactions within micturition pathways.
Abstract
In neonatal kittens, micturition is induced by a spinal somatovesical reflex pathway that is activated by the mother cat licking the perigenital region of the kitten. The somatovesical reflex pathway disappears about the time of weaning and is replaced by a vesicovesical reflex pathway that produces micturition via a supraspinal reflex pathway that is activated by distension of the urinary bladder. Furthermore, stimulation of the perigenital region in adult cats actually inhibits the supraspinal vesicovesical micturition reflex. Spinalization prompts the return of the somatovesical reflex, immediately in weaned kittens but over a course of days to weeks in adult cats. The purpose of the present experiments was to determine if the somatovesical reflex could be demonstrated acutely, and reversibly, in adult cats with an intact spinal cord via pharmacological suppression of the serotonergic system. The serotonergic system was suppressed by the intravenous administration of 5-methoxy-N,N-dimethyltryptamine (5-MeODMT), a serotonin agonist that inhibits the firing of serotonergic neurons via activation of inhibitory somatodendritic autoreceptors. 5-MeODMT in low doses (20-50 micrograms/kg) abolished inhibition of the bladder produced by either light tactile stimulation of the perigenital region or by electrical stimulation of the pudendal nerve, which carries the afferent fibers from the perigenital region, in 9 of 10 adult cats. Furthermore, in 8 of the 10 cats, the bladder inhibition was reversed to an excitation of variable amplitudes in each cat. Higher doses of 5-MeODMT (100-1000 micrograms/kg) abolished spontaneous bladder activity but did not inhibit perigenital-induced bladder contractions in those 8 animals in which the drug unmasked the excitatory somatovesical reflex.(ABSTRACT TRUNCATED AT 250 WORDS)