Effects of preoptic warming on subretrofacial and cutaneous vasoconstrictor neurons in anaesthetized cats.
AUTOR(ES)
McAllen, R M
RESUMO
1. Sympathetic and subretrofacial neuron responses to preoptic warming were studied in chloralose- or Saffan-anaesthetized, paralysed cats. 2. Warming a thermode in the preoptic region inhibited the activity of cutaneous vasoconstrictor fibres supplying hairy skin. Muscle vasoconstrictor fibre activity recorded at the same time was either unaffected or raised. 3. Small injections of sodium glutamate (5 nl, 0.1 M) were made into the region of the subretrofacial nucleus in the ventrolateral medulla. The part of that region where glutamate injections evoked brisk increases in cutaneous vasoconstrictor fibre activity was chosen for further study. 4. Extracellular single unit recordings were made in that area from seventy-seven subretrofacial neurons, which were identified by their barosensitivity (inhibition by carotid blind sac inflation). Forty-seven of them were antidromically activated by stimulation in the spinal cord. 5. The activity of twenty subretrofacial neurons (twelve proven bulbospinal) was significantly reduced by periods of preoptic warming. Cutaneous vasoconstrictor activity recorded at the same time also fell. Forty-nine subretrofacial neurons (thirty-five proven bulbospinal) were unaffected or excited by periods of preoptic warming that inhibited cutaneous vasoconstrictor fibres. The response of eight neurons was unclear. 6. No difference in either mean firing rate or axonal conduction velocity was found between neurons inhibited by preoptic warming and other subretrofacial neurons. 7. The subretrofacial neurons inhibited by warming were found intermingled with those unaffected or excited. Marked recording sites of warm-inhibited neurons were clustered around the ventromedial border of the subretrofacial nucleus. 8. In two cats, bilateral inhibition of subretrofacial neurons by surface application of 1 M glycine reduced cutaneous vasoconstrictor fibre activity to 32 and 44% of control levels. 9. The results suggest that specific cutaneous vasoconstrictor premotor neurons exist in the subretrofacial nucleus. These apparently provide most of the background excitatory drive to cutaneous vasomotor neurons. Central warming stimuli may act, at least in part, by withdrawing that drive.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1155913Documentos Relacionados
- Effects of sympathetic activity and galanin on cardiac vagal action in anaesthetized cats.
- Effects of stimulation of nasal and superior laryngeal inputs on the hindlimb vasculature of anaesthetized cats.
- Effects of aerosol-applied capsaicin, histamine and prostaglandin E2 on airway sensory receptors of anaesthetized cats.
- Selective regional vasoconstriction underlying pressor effects of galanin in anaesthetized possums compared with cats.
- Lung C-fibre receptor activation and defensive reflexes in anaesthetized cats.