The role of 5-HT(1A) receptors in control of lower urinary tract function in cats.
In the present study, the role of 5-HT(1A) receptors in control of lower urinary tract function in cats was examined using 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) and 5-methoxy-N,N-dimethyltryptamine (5-MeODMT) as agonists and WAY100635 and LY206130 as antagonists. Bladder function was assessed using cystometric infusion of saline or 0.5% acetic acid to produce bladder irritation. External urethral sphincter (EUS) function was assessed using electromyographic (EMG) recordings of activity recorded during cystometry or by recording electrically evoked pudendal reflexes. Both 5-HT(1A) receptor agonists caused dose-dependent decreases in bladder activity and increases in EUS EMG activity under conditions of acetic acid infusion. 5-HT(1A) receptor antagonists reversed both the bladder-inhibitory and sphincter-facilitatory effects. Thus, 5-HT(1A) receptor activation can have opposite effects on nociceptive afferent processing depending upon the efferent response being measured. During saline infusion of the bladder, 8-OH-DPAT produced moderate inhibition of bladder activity and had no significant effect on sphincter electromyographic (EMG) activity. 8-OH-DPAT either had no effect, or inhibited, low-threshold electrically evoked pudendal reflexes. These findings indicate that 5-HT(1A) receptor stimulation is inhibitory to bladder function in cats, especially under conditions where the bladder is hyperactive due to irritation. Furthermore, these bladder-inhibitory effects are the exact opposite of the bladder-excitatory effects of 8-OH-DPAT reported in rats. 5-HT(1A) receptor stimulation increases EUS motoneuron activity when driven by nociceptive bladder afferent inputs but not when driven by non-nociceptive afferent inputs. In summary, 5-HT(1A) receptor agonists facilitate a nociceptor-driven spinal reflex (sphincter activity) but inhibit a nociceptor-driven supraspinal reflex (micturition). This pattern of activity would facilitate urine storage and may be important under 'fight-or-flight' conditions when serotonergic activity is high.
Thor
Karl B
KB
Division of Nervous System Disorders, Eli Lilly and Co., Indianapolis, IN, USA. karlthor@aol.com
Katofiasc
Mary A
MA
Danuser
Hansjorg
H
Springer
Johannes
J
Schaus
John M
JM
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology; D019342:Acetic Acid; D000818:Animals; D002415:Cats; D003556:Cystitis / Q000503:physiopathology; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D004576:Electromyography; D005260:Female; D009119:Muscle Contraction / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects / Q000294:innervation; D010879:Piperazines / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D011985:Receptors, Serotonin / Q000187:drug effects*; D044263:Receptors, Serotonin, 5-HT1; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D014521:Urethra / Q000187:drug effects / Q000294:innervation / Q000502:physiology; D001743:Urinary Bladder / Q000187:drug effects / Q000294:innervation / Q000502:physiology; D014551:Urinary Tract / Q000187:drug effects* / Q000294:innervation
D010879:Piperazines; D011725:Pyridines; D011985:Receptors, Serotonin; D044263:Receptors, Serotonin, 5-HT1; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; C090413:N-(2-(4-(2-methoxyphenyl)-1-piperazinyl)ethyl)-N-(2-pyridinyl)cyclohexanecarboxamide; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D019342:Acetic Acid