Antagonistic effects of somatostatin and substance P on respiratory regulation in the rat ventrolateral medulla oblongata.
Substance P (SP) in the dose range 0.75-1.5 nmol exerts a potent stimulatory effect on ventilation after microinjection into the rat ventrolateral medulla oblongata (VLM; n. reticularis lateralis, n. paragigantocellularis lateralis). A significant but less pronounced effect is also seen in the dorsal medulla (DM; n. tractus solitarius). Somatostatin (0.6-1.8 nmol) inhibited ventilation and induced apnoea after microinjection into the VLM but not the DM. Serial microinjections of the two peptides showed a reciprocal antagonistic action in the VLM but not in the DM. The apnoea-inducing effect of SOM was blunted by SP while SOM reduced the ventilatory stimulation induced by SP. Extracellular single unit recordings were performed following the microiontophoretic application of SP and/or SOM to respiratory-related and non-respiratory-related neurons in the VLM and DM. Although a heterogeneous population of neurons were recorded from, the majority of respiratory-related units in the VLM responded with excitation to SP and inhibitory to SOM. A direct interaction between the peptides was seen in some respiratory-related units. The neurons not responding to either of the peptides were usually non-respiratory. Dorsal to the VLM, the type of response to the two peptides was less likely to be antagonistic and a wider distribution of response types were recorded. The results indicate a direct physiological antagonism between SP and SOM regarding their effects on respiratory regulation elicited in the VLM.
Chen
Z B
ZB
Department of Pharmacology, University of Göteborg, Sweden.
Engberg
G
G
Hedner
T
T
Hedner
J
J
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D004347:Drug Interactions; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects / Q000502:physiology*; D008845:Microinjections; D051381:Rats; D011919:Rats, Inbred Strains; D012119:Respiration / Q000187:drug effects / Q000502:physiology*; D013004:Somatostatin / Q000008:administration & dosage / Q000494:pharmacology*; D013373:Substance P / Q000008:administration & dosage / Q000494:pharmacology*; D013990:Tidal Volume; D013997:Time Factors
D013373:Substance P; D013004:Somatostatin