PubMed · 207039
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A Schömig, R Dietz, F Kaden, J B Lüth, W Mäurer. 1977. [Sympathetic vascular tonus in beta blockade].. https://pubmed.ncbi.nlm.nih.gov/207039/
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(1) In chloralose-anesthetized cats, elevation of carotid sinus pressure caused blood pressure, sweat gland potentials and nictitating membrane tension to decrease. (2) The onset and recovery of the sweat gland and nictitating membrane responses usually preceded the respective phases of the blood pressure (depressor) response; the latencies of the sweat gland and nictitating membrane responses agreed with the latencies predicted for neural reflex pathways. (3) The sweat gland and nictitating membrane responses were evoked less consistently than the depressor response. (4) In experiments where only the sweat gland potentials and blood pressure were studied: (a) the sinus pressure threshold for inhibition of sweat gland activity was similar to the threshold for the depressor response; (b) cutting the sinus nerves, or blocking the efferent neural activity to the sweat glands, eliminated the effects of sinus pressure elevation on the sweat gland potentials; (c) with carotid sinus pressure held constant, decreases in blood pressure, produced by stimulating the peripheral end of the vagus nerve, did not affect the sweat gland potentials. (5) These results indicate that baroreceptors can reflexly modulate activity in sympathetic neurons whose target organs are not fundamentally involved in blood pressure regulation.
Chronically implanted moveable electrodes were used to map the pontine tegmentum and caudal midbrain for intracranial self-stimulation in relation to the ascending noradrenergic systems as revealed by fluorescence histochemistry. In no area tested was there a consistent correlation between the quality or the presence of self-stimulation and the degree of noradrenergic fiber density or cellular aggregation. Of particular importance was the failure to obtain self-stimulation from the locus coeruleus, despite repeated testing and extensive attempts at behavioral shaping. Those areas supporting self-stimulation included the dorsal raphe nucleus, the superior cerebellar peduncle and the mesencephalic and motor nuclei of the trigeminal nerve. These data appear to rule out activation of the ascending noradrenergic systems as an explanation of the rewarding effects of stimulation in these areas. A gustatory-visceral fiber system is suggested as an alternative possible substrate.