Caudate unit activity and somal diameters in intact and nigral lesioned cats.
In a search for morphofunctional relationships in the head of the caudate nucleus (CN), we recorded extracellular unit activity in intact cats and in cats that had received bilateral injections of 6-OHDA into the substantia nigra (SN) 30 days previously. Only units firing spontaneously and continuously for 2 min were studied. In dorsal regions, potentials were small and iterative at almost constant intervals; the somal diameters were relatively small. In the ventrolateral region, potentials were bigger and appeared in bursts; somal diameters were significantly larger (p less than 0.05). For the centromedial region a histogram of numbers of neurons as a function of diameters revealed a Gaussian distribution extending from small to large neurons. Most dorsal neurons increased their firing rate to radial nerve, visual, SN, and/or nucleus centralis medialis (NCM) stimulation. Ventral neurons usually responded with excitation followed by long lasting inhibition, particularly to SN and NCM stimulation. A few neurons responded to all four inputs and some showed long-lasting potentiation in response to low frequency stimulation, suggesting a more general function. Greatest convergence (65%) was found for NCM and SN inputs. In lesioned cats, there was no SN driving, NCM's inhibitory actions almost disappeared, and the excitatory action of the other stimuli was reduced.
D000818:Animals; D002415:Cats; D002421:Caudate Nucleus / Q000187:drug effects / Q000502:physiology*; D004553:Electric Conductivity; D004558:Electric Stimulation; D005260:Female; D006892:Hydroxydopamines / Q000633:toxicity; D008297:Male; D008839:Microelectrodes; D009474:Neurons / Q000502:physiology*; D016627:Oxidopamine; D013378:Substantia Nigra / Q000502:physiology*
D006892:Hydroxydopamines; D016627:Oxidopamine