Effects of vasoactive intestinal polypeptide on the response properties of cells in area 17 of the cat visual cortex

Abstract

1. Vasoactive intestinal polypeptide (VIP) was iontophoretically applied to a population of 90 single cells in the primary visual cortex (area 17) of the cat. Response magnitude, response selectivity, spontaneous activity, and the ratio between the visual response and spontaneous activity (signal-to-noise ratio) of the cells were assessed quantitatively before and during drug application. 2. VIP had little effect in the absence of visual stimulation, with only 29/90 (32%) of the cells showing a change of even 1 sp/s in their spontaneous activity. In contrast it had a clear effect on the visual responses of the majority (73/90, 81%) of the cells tested. 3. VIP produced a substantial change (i.e., > or = 40%) in optimal response magnitude for 57 of the affected cells. Of these 65% were facilitated, usually with no change or an improvement in signal-to-noise ratio and direction selectivity. The remaining cells were inhibited, with more variable effects on their visual response characteristics, and were found predominantly in the superficial laminae. 4. The effects of VIP bore a remarkable resemblance to those reported previously for the muscarinic action of acetylcholine (ACh). VIP and a muscarinic cholinergic agonist, either ACh or acetyl-beta-methacholine (MeCh), were therefore applied in turn to a group of 40 cells. In 23 cases VIP and the muscarinic agonist were also applied simultaneously. 5. The effects of VIP and the cholinergic agonist matched in 92% of the cases where both drugs were effective. That is to say, cells that were facilitated by VIP were facilitated also by ACh or MeCh, and vice versa. In many instances there was a clear similarity in the pattern as well as the direction of the effects produced by the two substances. The result of simultaneous application was generally additive. 6. These data suggest that VIP and ACh activate very similar postsynaptic mechanisms, and share a closely related function at the level of individual cortical cells. Thus VIP may facilitate the responses of both the excitatory and the inhibitory components of the cortical circuit, leading to an overall increase in responsiveness and selectivity. In contrast to the cholinergic input from the basal forebrain, however, the VIP-positive cortical cells are likely to exert a very localized influence, over a circumscribed region of the cortex, in response to the presence of an effective visual stimulus.

Broad characterization of endogenous peptides in the tree shrew visual system

“…VIP is present in many GABAergic neurons, and is thought to be co-released with GABA during interneuron activation. It has been shown that VIP can exert substantial changes in activity of V1 neurons in the cat [62], with effects depending on cortical layer. Thus, in addition to being useful for labeling a specific kind of GABAergic interneuron, VIP can also act as a neurotransmitter in V1 and modify cortical computations.…”

Revisiting enigmatic cortical calretinin-expressing interneurons

“…For instance in the cat visual cortex, exogenously applied VIP had little or no effect on recorded neurons in the absence of visual stimulation, but enhanced their visual responses (Murphy et al, 1993; Fu et al, 2014). Consistently, by activating VPAC1 receptors and cAMP/PKA signaling, VIP reduced the slow AHP current and the tonic potassium current which regulates the excitability of hippocampal and cortical pyramidal neurons (Haug and Storm, 2000; Hu et al, 2011).…”

Vasoactive Intestinal Peptide Selectively Depolarizes Thalamic Relay Neurons and Attenuates Intrathalamic Rhythmic Activity

“…Although neurophysiological studies regarding the actions of VIP are few, this peptide has been found to produce a number of different actions within the CNS. VIP has been found to depolarize brain stem neurons and increase the excitability of hippocampal and neocortical neurons (Haas and Gahwiler 1992;Kohlmeier and Reiner 1999;Murphy et al 1993;Pawelzik et al 1992). This peptide has also been shown to enhance GABAergic synaptic transmission in cultured hippocampal neurons presumably through a presynaptic site of action (Wang et al 1997).…”

“…VIP is also widely distributed throughout the central and peripheral nervous system where it may serve as a putative neuromodulator (Gozes and Brenneman 1989). VIP has been found to produce a variety of actions including alterations in intrinsic properties of neurons or synaptic transmission in the CNS (Gozes and Brenneman 1989;Kohlmeier and Reiner 1999;Murphy et al 1993;Wang et al 1997). This peptide has been localized within TRN neurons (Burgunder et al 1999b), and VIP receptors are distributed within primary relay thalamic nuclei such as VB and the dorsal lateral geniculate nucleus (Sheward et al 1995;Usdin et al 1994;Vertongen et al 1997).…”